Design of an Atypical Construction of Equipment for Additive Manufacturing with a Conceptual Solution of a Printhead Intended Fo

applied sciences

Article Design of an Atypical Construction of Equipment for Additive Manufacturing with a Conceptual Solution of a Printhead Intended for the Use of Recycled Plastic Materials

Jakub Kašˇcak 1 , Štefan Gašpár 2,Ján Paško 2, Lucia Knapˇcíková 3,* , Jozef Husár 3 , Petr Baron 1 and Jozef Török 1

1 Department of Computer Aided Manufacturing Technologies, Faculty of Manufacturing Technologies with a Seat in Prešov, Technical University of Košice, Štúrova 31, 08001 Prešov, Slovakia; [email protected] (J.K.); [email protected] (P.B.); [email protected] (J.T.) 2 Department of Technical Systems Design and Monitoring, Faculty of Manufacturing Technologies with a Seat in Prešov, Technical University of Košice, Štúrova 31, 08001 Prešov, Slovakia; [email protected] (Š.G.); [email protected] (J.P.) 3 Department of Industrial Engineering and Informatics, Faculty of Manufacturing Technologies with a Seat in Prešov, Technical University of Košice, Bayerova 1, 08001 Prešov, Slovakia; [email protected] * Correspondence: [email protected]; Tel.: +421-55-602-6407

Abstract: This article presents the variability of Fused deposition modelling (FDM) technology and the possibilities of its use in the design and implementation of a prototype atypical device. The assumptions of the behaviour of individual components and subsystems of the design result from an extensive application of the finite element method and motion analysis of subsystems and various Citation: Kašˇcak,J.; Gašpár, Š.; parts of the structure. The use of this method to such an extent accelerated the design process and its Paško, J.; Knapˇcíková,L.; Husár, J.; implementation. The proposal itself reflects the current state of this technology and its focus is on Baron, P.; Török, J. Design of an Atypical Construction of Equipment improving sustainable development. As is generally known, great efforts are currently being made for Additive Manufacturing with a to reduce plastic waste volume and its environmental burden. The proposed concept is modified to Conceptual Solution of a Printhead replace the final treatment of the top layers of the models, called “ironing” by non-planar layering Intended for the Use of Recycled of material. At the same time, it points out the advantages of this method in reducing energy Plastic Materials. Appl. Sci. 2021, 11, requirements and the time required to produce models. The conclusion is a conceptual design of 2928. https://doi.org/10.3390/ a printhead for a proposed prototype, designed to use recycled FDM, intending to streamline the app11072928 possibility of recycling with little serial and piece production. This process thus closes the circle of opportunities published by us, which in the future can contribute to the optimisation of this Academic Editor: Francesco Ciardelli technology towards increasing the efficiency of resource use, reduction of energy demands and environmental burden. Received: 27 February 2021 Accepted: 23 March 2021 Keywords: fused deposition modelling; fused filament fabrication; non-planar printing; plastic Published: 25 March 2021 waste; recycling; alternative design

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional afﬁl- iations. 1. Introduction According to previous surveys and trends for the ﬁrst quarter of 2019, Fused deposition modelling (FDM) technology still accounts for most additive manufacturing technologies, up to 46%. Despite the development of new technologies and designs, FDM

Copyright: © 2021 by the authors. technology increased compared to 2018. Excessive production of plastic waste is currently Licensee MDPI, Basel, Switzerland. a global problem. There are now 12 different basic types of additive devices on the market This article is an open access article (Figure1). As a result, this technology’s demand, despite its now common occurrence, is distributed under the terms and growing in schools or households and various industries [1]. For this reason, the technology conditions of the Creative Commons can also be considered as a significant producer of plastic waste, to which its “hobby” use Attribution (CC BY) license (https:// also makes a significant contribution, which makes it difficult to monitor in this respect [2]. creativecommons.org/licenses/by/ 4.0/).

Appl. Sci. 2021, 11, 2928. https://doi.org/10.3390/app11072928 https://www.mdpi.com/journal/applsci Appl.Appl. Sci. Sci. 20212021,, 1111,, x 2928 FOR PEER REVIEW 2 2of of 26 25

50% 0.46

40% 0.36 0.38 0.33 0.33 30% 0.25 0.21 20% 0.13 0.13 0.1 0.07 0.1 0.08 0.15 0.04 10% 0.12 0.04 0.060.04 0.02 0.02 0.02 00.02 0% FDM SLS SLA DMLS/ Polyjet Multi DLP Binder EBM CLIP/ SDL LOM SLM jet jetting CDLP fusion

2018 2019

Figure 1. Additive manufacturing technologies and their share in the industry [1]. Figure 1. Additive manufacturing technologies and their share in the industry [1]. This article closes the imaginary circle of reducing the impact of the environmental loadThis produced article bycloses FDM the technology, imaginary addressed circle of reducing in the publication the impact Polylactic of the environmental Acid and Its loadCellulose produced Based by Composite FDM technology, as a Significant addressed Tool in for the the publication Production Polylactic of Optimized Acid Modelsand Its CelluloseModified Based for Additive Composite Manufacturing as a Significant [3]. ThisTool publicationfor the Production presented of Optimized the possibilities Models of Modifiedusing topological for Additive optimisation Manufacturing of models [3]. for This FDM publication production presented and composite the possibilities biodegradable of usingplastics. topological Another optimisation phase aimed of at models improving for FDM the state production of sustainable and composite development biodegrada- in FDM bletechnology plastics. isAnother the modification phase aimed of the at process improving characteristic the state ofof thissustainable type of model development production in FDMand thetechnology recycling is of the plastic modification waste associated of the process with production characteristic [4,5]. of We this consider type of creating model productionan alternative and type the recycling of construction of plastic with wast thee possibilityassociated ofwith integrating production a combined [4,5]. We printcon- siderhead creating to be the an mainalternative benefit type of theof construc ongoingtion research. with the As possibility presented of inintegrating the publication, a com- binedFDM print technology head to works be the with main 3D benefit objects of dividedthe ongoing into research. planes or As layers. presented These in then the servepub- lication,as perimeters FDM technology for creating works 3D objects. with 3D This object researchs divided aims into to createplanes aor prototype layers. These device then to servefinish as FDM perimeters technology for creating items by 3D applying objects. Th non-planaris research layers. aims to Due create to the a prototype use, recycling device of tofilaments finish FDM and technology failures from items FDM by production,applying non-planar we intend layers. that this Due device to the allowsuse, recycling the use ofof filaments recycled plasticand failures in various from forms.FDM production, The integration we intend of the that printhead, this device which, allows by the its veryuse ofnature, recycled can plastic process in such various material, forms. has The a significant integration impact of the on printhead, the recycling which, process by its itself very in nature,the industry. can process such material, has a significant impact on the recycling process itself in theOne industry. of the current trends and at the same time a way to reduce the time required for the productionOne of the current of the model trends is and the at so-called the same non-planar time a way method to reduce of layeringthe time required the material. for theWe production currently encounter of the model this methodis the so-called especially non-planar in its application method toof robotic layering arms. the Thesematerial. are Wedifficult currently to compare encounter with this conventional method especially commercial in its FDMs. application However, to robotic their high arms. accuracy, These arespeed, difficult rigidity to compare of the entire with system conventional and other commercial properties FDMs. that make However, them at their the forefronthigh accu- in racy,many speed, fields, rigidity are also of directly the entire proportional system and to theirother price. properties The article that make presents them the at process the fore- of design and presentation of partial results achieved by the created prototype of the device, front in many fields, are also directly proportional to their price. The article presents the the main benefit of which is to make this method of model production available to a wider process of design and presentation of partial results achieved by the created prototype of group of users. the device, the main benefit of which is to make this method of model production availa- ble1.1. to Non-Planar a wider group Layering of users. of Material In connection with FDM technology application to robotic arms or other atypical 1.1. Non-Planar Layering of Material structures, whose structures are inspired by these arms, a simple question arises: whether, in theIn currentconnection state, with accuracy, FDM method technology of production application and to implementation robotic arms or of other new materials, atypical structures,it is necessary whose or structures not to approach are inspired the production by these arms, of models a simple differently. question arises: Due to whether, current intrends the current and developments state, accuracy, in method this technology, of production improvement and implementation of operating of parameters new materi- of als,production it is necessary and its or application not to approach to sophisticated the production equipment of models types, differently. innovation Due is to necessary current trendsfor the and production developments process in itself this [ 6technology,,7]. improvement of operating parameters of productionOne of and the its directions application FDM to technology sophisticated is taking equipment is the changetypes, innovation in the same is approach necessary to forgenerating the production printhead process paths itself or changing [6,7]. the material method. The current way of generating toolpathsOne of consists the directions of dividing FDM the technology object to beis ta createdking is intothe change planes thatin the correspond same approach to the tolayer’s generating height. printhead This means paths that or each changing of the the perimeters material ismethod. formed The first current in the X way and of Y gen- axes, eratingand only toolpaths after its consists completion of dividing will there the beobject a shift to be in thecreated Z-axis. into This planes method that correspond of layering Appl. Sci. 2021, 11, x FOR PEER REVIEW 3 of 26

Appl. Sci. 2021, 11, 2928 3 of 25

to the layer’s height. This means that each of the perimeters is formed first in the X and Y axes, and only after its completion will there be a shift in the Z-axis. This method of layeringthe material the material has been has usedbeen fromused thefrom beginning the beginning of FDM of technologyFDM technology development development until untiltoday. today. This process This process indicates indicates that FDM that devices, FDM de invices, slang in referred slang referred to as 3D to printers, as 3D printers, operate operaterealistically realistically in the 2.5 in axes the during2.5 axes their during operation. their operation. Such a method Such a ofmethod layering of thelayering material the materialis associated is associated with the with print the surface print surface characteristic characteristic state and state their and different their different properties proper- for tiestheir for orientation their orientation to the device to the coordinationdevice coordination system duringsystem printingduring printing [8,9]. [8,9]. Nowadays, narrow groups of researchers specialising in FDM technology deal withwith this issue withinwithin institutionsinstitutions andand companies.companies. Autodesk is oneone ofof thesethese companies.companies. ThisThis company, whichwhich isis oneone ofof thethe leadersleaders andand pioneerspioneers inin CADCAD // CAM and CAE software, has since July 2018 ofﬁciallyofficially registeredregistered patentpatent no.no. US10005126B2.US10005126B2. [[10].10]. ThisThis patentpatent describesdescribes the so-calledso-called “Systems“Systems and and methods methods for for enhanced enhanced 3D 3D printing”. printing”. One One of these of these methods methods uses usesa non-planar a non-planar layering layering of the of material the material shown shown in Figure in Figure2[8]. 2 [8].

Figure 2. Method of generating individual layers in a planar process of layering [[8].8].

This method of printingprinting involvesinvolves modifyingmodifying thethe SlicerSlicer program.program. Since, as already mentioned, the the generation generation of of paths paths for for the the printhead printhead takes takes place place in planar in planar layers, layers, it is nec- it is essarynecessary to implement to implement the the Z-axis’s Z-axis’s active active part participationicipation during during the the printing printing process. This function is only involved in G-code generation in a few situations, such as e.g.,e.g., approachapproach to reference points by rapidly moving the device or printing in a special mode for creating thin-walled models through spiralisation continuous printing of one edge perimeter. TheThe necessary function is already implemented within the Slicer program, but it is inactive in the production of models in the usual way. Due to their previous research and knowledge in non-planar layering of materials materials to to verify verify the the theory, theory, the program Slic3r was was modified. modified. The software modificationmodification itself consisted of several steps related to emulating the Linux system, compiling the already existing Slic3r softwaresoftware andand addingadding newnew functions.functions. AfterAfter these steps, they were able to process the firstfirst models and test theirtheir implementation using available FDM FDM devices. devices. After After the the software software wa wass successfully successfully modified modified andand the G-code the G-code was wasgenerated, generated, it was it time was to time implement to implement them. them.However, However, the performance the performance itself was itself accom- was paniedaccompanied by several by several technical technical problems. problems. These These largely largely resulted resulted from from the very the very design design of the of FDMthe FDM device device and andits printhead its printhead [11–13]. [11–13 ]. The firstfirst device used was Ender 3 from Creality. This device is a specific specific and currently very widespread Cartesian-type device. Due to its shape and construction, several rently very widespread Cartesian-type device. Due to its shape and construction, several modifications were necessary at the outset. Since the printhead and its cooling are not modifications were necessary at the outset. Since the printhead and its cooling are not adapted to the Z-axis’s active use, it was required to disassemble all the printhead’s cooling adapted to the Z-axis’s active use, it was required to disassemble all the printhead’s cool- elements. The resulting model did not meet the required quality. The main reason was the ing elements. The resulting model did not meet the required quality. The main reason was fact that the Z-axis of this device is controlled only unilaterally. This fact caused significant the fact that the Z-axis of this device is controlled only unilaterally. This fact caused sig- geometric inaccuracies and poor adhesion of non-planar layers in the region of the model, nificant geometric inaccuracies and poor adhesion of non-planar layers in the region of which is farthest from the X-axis’s initial position. Due to this fact, a more compact device the model, which is farthest from the X-axis’s initial position. Due to this fact, a more com- of the same type was used in the solution. The Anet device, type-designated E12, has pact device of the same type was used in the solution. The Anet device, type-designated two guide screws and a sufficient printing volume to carry out non-planar printing. The E12, has two guide screws and a sufficient printing volume to carry out non-planar print- successfully created model can be seen in Figures2 and3. ing. The successfully created model can be seen in Figures 2 and 3. Appl.Appl. Sci.Sci. 20212021,, 1111,, 2928x FOR PEER REVIEW 44 of 2526 Appl.Appl. Sci. Sci. 2021 2021, ,11 11, ,x x FOR FOR PEER PEER REVIEW REVIEW 44 ofof 2626

FigureFigure 3. 3. Method Method of of generating generating individual individual layers layers in in a a non-planar non-planar method method of of layering layering [8]. [8]. FigureFigure 3. 3. MethodMethod of of generating generating individual individual layers layers in in a anon-planar non-planar method method of of layering layering [8]. [8]. During the model manufacturing process, both methods were used to shape the test DuringDuringDuring thethe the modelmodel model manufacturinmanufacturin manufacturinggg process,process, process, bothboth both methodsmethods methods werewere were usedused used toto to shapeshape shape thethe the testtest test specimen used. Due to the heating pad and its shape, the model’s production began as a specimenspecimenspecimen used.used. used. DueDue Due toto to thethe the heatingheating heating padpad pad andand and ititss its shape,shape, shape, thethe the model’smodel’s model’s productionproduction production beganbegan began asas asaa standard planar print. It created the planar basis of the model up to 50% of its height. standardstandarda standard planarplanar planar print.print. print. ItIt createdcreated It created thethe the planarplanar planar basisbasis basis ofof ofthethe the modelmodel model upup up toto to 50%50% 50% ofof of itsits its height.height. height. Subsequently, these planar surfaces were used as support for non-planar perimeters, Subsequently,Subsequently,Subsequently, thesethese these planarplanar planar surfacessurfaces surfaces werewere were usus usededed asas as supportsupport support forfor for non-planarnon-planar non-planar perimeters,perimeters, perimeters, formed in the higher layers of the model, as shown in Figure 4. An interesting feature of formedformedformed inin in thethe the higherhigher higher layerslayers layers ofof of thethe the model,model, model, asas as shownshown shown inin inFigureFigure Figure 4.4. 4 AnAn. An interestinginteresting interesting featurefeature feature ofof this type of material layering was the significant saving of time required to create test thisthisof this typetype type ofof material ofmaterial material layeringlayering layering waswas was thethe the significsignific signiﬁcantantant savingsaving saving ofof of timetime time requiredrequired required toto to createcreate create testtest test models. With the same operating parameters and material consumption differing by only models.models.models. WithWith With thethe the samesame same operatingoperating operating parametersparameters parameters andand and materialmaterial material consumptionconsumption consumption differingdiffering differing byby by onlyonly only 5%, there was a 30% time saving for a model created using the non-planar method. 5%,5%,5%, therethere there waswas was aa a 30%30% 30% timetime time savingsaving saving forfor for aa a modelmodel model createdcreated created usingusing using thethe the non-planarnon-planar non-planar method.method. method.

Figure 4. Display a combination of of planar planar and and non-plan non-planarar material material layering layering (1—non-planar (1—non-planar layer, layer, FigureFigure 4.4. DisplayDisplay aa combinationcombination ofof planarplanar andand non-plannon-planarar materialmaterial layeringlayering (1—non-planar(1—non-planar layer,layer, 2—layer height, 3—step length, 4—extrusion width, 5—planar layers, 6—print/object surface) [8]. 2—layer2—layer2—layer height,height, height, 3—step3—step 3—step length,length, length, 4—ext4—ext 4—extrusionrusionrusion width,width, width, 5—planar5—planar 5—planar layers,layers, layers, 6—print/object6—print/object 6—print/object surface)surface) surface) [8].[8]. [8 ]. The nature ofof thethe resultingresulting surfacesurface obtainedobtained byby thethe non-planarnon-planar methodmethod ofof layeringlayering TheThe naturenature ofof thethe resultingresulting surfacesurface obtainedobtained byby thethe non-planarnon-planar methodmethod ofof layeringlayering thethe material allowed betterbetter prediction ofof mechanicalmechanical properties ofof thesethese models compared thethe material material allowed allowed better better prediction prediction of of mech mechanicalanical properties properties of of these these models models compared compared toto conventionalconventional planarplanar models.models. This obtainedobtained resultsresults fromfrom thethe variablevariable orientationorientation ofof thethe toto conventionalconventional planarplanar models.models. ThisThis obtainedobtained resultsresults fromfrom thethe variablevariable orientationorientation ofof thethe surfaces’ contact surfaces, which can lead to a changechange inin thethe distributiondistribution ofof forcesforces inin thethe surfaces’surfaces’ contactcontact surfaces,surfaces, whichwhich cancan leadlead toto aa changechange inin thethe distributiondistribution ofof forcesforces inin thethe layers,layers, e.g.,e.g., underunder tensiletensile stress.stress. Planar regions created usingusing FDMFDM technologytechnology areare usuallyusually layers,layers, e.g.,e.g., underunder tensiletensile stress.stress. PlanarPlanar regionsregions createdcreated usingusing FDMFDM technologytechnology areare usuallyusually lessless resistantresistant toto tensiletensile stress.stress. ItIt followsfollows fromfrom thethe samesame wayway ofof assemblingassembling thethe modelmodel fromfrom lessless resistantresistant toto tensiletensile stress.stress. ItIt followsfollows frfromom thethe samesame wayway ofof assemblingassembling thethe modelmodel fromfrom planarplanar surfaces.surfaces. This resistance isis lowestlowest inin thethe directiondirection ofof thethe Z-axis.Z-axis. DivideDivide themthem intointo aa planarplanar surfaces.surfaces. ThisThis resistanceresistance isis lowestlowest inin thethe directiondirection ofof thethe Z-axis.Z-axis. DivideDivide themthem intointo aa mixture of tensiletensile andand shearshear forces,forces, andand thethe theoreticaltheoretical assumptionassumption ofof thethe distributiondistribution ofof mixturemixture ofof tensiletensile andand shearshear forces,forces, andand thethe ththeoreticaleoretical assumptionassumption ofof thethe distributiondistribution ofof thesethese forcesforces dependingdepending on on the the increased increased displacement displacement of of the the layers layers caused caused by by stress stress can can be thesethese forcesforces dependingdepending onon thethe increasedincreased displacementdisplacement ofof thethe layerslayers causedcaused byby stressstress cancan seenbe seen in Figurein Figure5[14 5,15 [14,15].]. bebe seenseen inin FigureFigure 55 [14,15].[14,15].

Figure 5. Illustration ofof thethe assumptionassumption ofof thethe changechange inin thethe shearshear forceforce componentcomponent FSFS asas aa functionfunc- FigureFigure 5.5. IllustrationIllustration ofof thethe asassumptionsumption ofof thethe changechange inin thethe shshearear forceforce componentcomponent FSFS asas aa func-func- oftion the of displacement the displacement of the of layers the layers induced induce byd the by forces the forces during during the tensile the tensile test [ 15test]. [15]. tiontion ofof thethe displacementdisplacement ofof thethe layerslayers induceinducedd byby thethe forcesforces duringduring thethe tensiletensile testtest [15].[15].

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1.2. Problems in the Field of Non-Planar Layering of Material by Commercial Equipment 1.2.1.2.During ProblemsProblems the inin closure thethe FieldField of ofof the Non-PlanarNon-Planar model using LayeringLayering this method, ofof MaterialMaterial several byby CommercialCommercial problems Equipment Equipmentarise due to the constructionDuringDuring of thethe the closureclosure FDM device ofof thethe modelandmodel the usingusing printhea thisthisd. method,method, This is due severalseveral to the problems problems shape and arise arise individual due due to to the the componentsconstructionconstruction forming of of the the FDM FDMthe FDM device device device’s and and the the printhea printhead. printhead, andd. This This several is is duedue issues toto thethe arise shapeshape connected andand individualindividual with thecomponentscomponents formation formingof forming non-planar the the FDM FDM layers. device’sdevice’s The most printhead, printhea importantd, and and severalis several the shape issues issues of arise arisethe head connected connected itself and with with thethethe individual formationformation components ofof non-planarnon-planar involved layers. layers. The Thein cooling mostmost important im theportant layers. isis theSincethe shapeshape the ofprintof thethe head head itselfactively itself and and engagesthethe individualindividual the Z-axis componentscomponents in this process involvedinvolved in the inin coolingcasecooling of thenon-planarthe layers.layers. Since Sincelayers, thethe it printprintreturns headhead to activelyplacesactively whereengagesengages individual, the the Z-axis Z-axis either in in this thisplanar process process or innon-planar, thein casethe case of non-planarperimeters of non-planar layers,of a particular layers, it returns it heightreturns to places have to whereplaces al- readyindividual,where been individual, formed. either planar Thiseither process or planar non-planar, oftenor non-planar, causes perimeters the perimeters printhead of a particular ofcomponents a particular height have to height collide already have with been al- theformed.ready surface been This of formed.the process created This often model, process causes as theoften shown printhead causes in Figure the components printhead 6. The Anet to components collide E12 printhead with to the collide surfaceand thewith of basicthethecreated geometrysurface model,of of the the created as print shown nozzle model, in Figure are as shownshown6. The [16].in Anet Figure E12 printhead6. The Anet and E12 the printhead basic geometry and the ofbasic the geometry print nozzle of arethe shownprint nozzle [16]. are shown [16].

Figure 6. The shape of the head and nozzle of the device Anet E12 (a) 42° both sides, (b) 45 and 34°, (c) 12 and 23°. FigureFigure 6.6.The The shapeshape ofof thethe headhead and and nozzle nozzle of of the the device device Anet Anet E12 E12 ( a(a)) 42 42°◦ both both sides, sides, ( b(b)) 45 45 and and 34 ◦, (c34°,) 12 (c and) 12 23and◦. 23°. Depending on the print head’s shape, we can observe several shortcomings directly relatedDependingDepending to its non-planar onon thethe printprintingprint head’shead’s application. shape,shape, wewe Given cancan observe observethe condition severalseveral of shortcomingsshortcomings the heat block, directlydirectly the nozzle,relatedrelated and toto itsitsthe non-planarnon-planar cooling location, printingprinting it application.isapplication. clear that GivenGivenits use the thein conditionthecondition production ofof thethe of heatheat non-planar block,block, thethe surfacesnozzle,nozzle, will andand be thethe significantly coolingcooling location,location, limited itit [17]. isis clearclear As thatalreadythat itsits usementioned,use inin thethe productionproduction in terms of of ofcooling non-planarnon-planar the layer’ssurfacessurfaces material, willwill bebe this significantlysignificantly problem is limitedlimited easily [eliminated.[17].17]. AsAs alreadyalready By a mentioned, mentioned,simple disassembly inin termsterms oforof coolingchangingcooling thethe thelayer’slayer’s blower’s material,material, shape, thisthis we problemproblem increase isis the easilyeasily print eliminated.eliminated. head’s reach ByBy a ain simple simple the Z-axis, disassembly disassembly exceeding or or changing changing larger heightthethe blower’sblower’s differences. shape,shape, wewe increaseincrease thethe printprint head’shead’s reachreach inin thethe Z-axis,Z-axis, exceedingexceeding largerlarger heightheightAnother differences.differences. problem is the shape of the print nozzle itself. Unlike blowers and other printheadAnotherAnother components, problemproblem they isis thethe cannot shapeshape be ofof theremovethe print printd nozzle ornozzle moved. itself. itself. As Unlike Unlikeshown blowers blowersin Figure andand 7, otherotherthe shapeprintheadprinthead of the components, components,nozzle itself they theyis also cannot cannot limiting be removedbe inremove creating ord moved. or non-planar moved. As shown As surfaces. shown in Figure inOne Figure7, thepossible shape 7, the solutionofshape the nozzle ofis the itselfusenozzle of is alsotheitself so-called limiting is also in limiting“Airbrush” creating in non-planar creating nozzle, non-planarwhich surfaces. consists One surfaces. possibleof a sharp One solution possibletip. It is increasesthesolution use ofthe is the overhangthe so-called use of angles the “Airbrush” so-called that the nozzle, “Airbrush”print he whichad can nozzle, consists copy. which With of a sharptheseconsists modifications, tip. of It a increases sharp tip.it theis It possibleoverhangincreases to achieve anglesthe overhang that a significant the angles print thatincrease head the can print in copy. FDM head With devices’ can these copy. efficiency modifications, With these when modifications, itprinting is possible non- it to is planarachievepossible surfaces. a to significant achieve However, increasea significant these in FDMadjustments increase devices’ in haveFDM efficiency their devices’ whenlimits. efficiency printing This limit non-planarwhen is the printing very surfaces. fact non- thatHowever,planar the print surfaces. these nozzle’s adjustmentsHowever, ideal position these have adjustments during their limits. the extrusionhave This their limit of limits. the is the material This very limit factis perpendicular is that the the very print fact tonozzle’s thatthe surfacethe idealprint of positionnozzle’s the model duringideal being position the created, extrusion during with of thein the the extrusion material solution of is of the perpendicular this material problem is describedperpendicular to the surface in theofto thealreadythe modelsurface mentioned being of the created, model in patent being within application created, the solution with No.in of theUS10005126B2. this solution problem of this described A problemcritical in limit described the alreadyis the in statedmentionedthe alreadyvalue in in mentioned the patent range application of in 22.5°–45° patent No. application depend US10005126B2.ing No.on the US10005126B2. direction A critical of limit the A print iscritical the head stated limit move- valueis the ◦ ◦ mentinstated the [10]. range value It follows ofin 22.5the that,range–45 in dependingof order 22.5°–45° further on depend theto increase directioning on the the of efficiency thedirection print of headof non-planar the movement print head layering [ 10move-]. It offollows mentmaterial, [10]. that, aIt device infollows order is that, furtherrequired in order to increasewhose further design the to efficiency increase allows the ofthe non-planar printheadefficiency of layeringto non-planarbe tilted of material,partially layering a [18].deviceof material, is required a device whose is required design allowswhose the design printhead allows to the be printhead tilted partially to be [ 18tilted]. partially [18].

(a) (b) Figure 7. The shape of print nozzles and their influence on non-planar printing efficiency (a) stand- Figure 7. The shape of(a print) nozzles and their inﬂuence on non-planar(b printing) efﬁciency (a) standard ardFigure print nozzle,7. The shape (b) Airbrush of print nozzle.nozzles and their influence on non-planar printing efficiency (a) stand- print nozzle, (b) Airbrush nozzle. ard print nozzle, (b) Airbrush nozzle. Appl. Sci. 2021, 11, x FOR PEER REVIEW 6 of 26 Appl.Appl. Sci. Sci. 20212021,, 1111,, x 2928 FOR PEER REVIEW 6 6of of 26 25

1.3. Current State in the Field of the Use of Non-Planar Layering of Material 1.3.1.3. Current Current State State in in the the Field Field of of the the Us Usee of of Non-Planar Non-Planar Layering Layering of of Material Material As already mentioned, each FDM device can perform the simultaneous movement AsAs already already mentioned, eacheach FDMFDM devicedevice can can perform perform the the simultaneous simultaneous movement movement in in all three axes. However, due to the shape and nature of FDM devices’ control, it is active inall all three three axes. axes. However, However, due due to to the the shape shape and andnature nature ofof FDMFDM devices’devices’ control, it is active active only in specific situations. At present, however, non-planar layering of material is receiv- onlyonly in in specific speciﬁc situations. At present, however,however, non-planar non-planar layering layering of of material material is is receiving receiving increasing attention in conventional embodiments of plant constructions and connect- ingincreasing increasing attention attention in conventionalin conventional embodiments embodiments of plantof plant constructions constructions and and connecting connecting with the application of this technology to industrial robotic arms (Figure 8). These ingwith with the applicationthe application of this of technologythis technology to industrial to industrial robotic robotic arms (Figurearms (Figure8). These 8). createThese create ideal conditions for the application of this technology. createideal conditionsideal conditions for the for application the application of this of technology. this technology.

Figure 8. Application of non-planar 3D printing on a robotic arm [19]. FigureFigure 8. 8. ApplicationApplication of of non-planar non-planar 3D 3D pr printinginting on on a a robotic robotic arm arm [19]. [19]. In the research presented in the publication “Development of a three-nozzle extru- InIn the the research presentedpresented inin the the publication publication “Development “Development of of a three-nozzlea three-nozzle extrusion extrusion system for conformal multi-resolution 3D printing with a robotic manipulator” [19], sionsystem system for conformalfor conformal multi-resolution multi-resolution 3D printing3D printing with with a robotic a robotic manipulator” manipulator” [19 ],[19], we we can see the application of this technology to the robotic arm. To achieve ideal condi- wecan can see see the the application application of thisof this technology technology to the to the robotic robotic arm. arm. To achieveTo achieve ideal ideal conditions conditions for non-planar printing, a separate reversible print head has been designed. The tionsfor non-planar for non-planar printing, printing, a separate a separate reversible reversible print print head head has been has designed.been designed. The basicThe basic principle of operation is to save the maximum time, which is achieved by different basicprinciple principle of operation of operation is to saveis to thesave maximum the maximum time, time, which wh isich achieved is achieved by different by different layer layer heights in the printing process and a combination of non-planar and planar layers. layerheights heights in the in printing the printing process process and and a combination a combination of non-planar of non-planar and and planar planar layers. layers. In In essence, thisessence, means this that means the individual that the individual printheads printheads have nozzles have of different nozzlesof diameters. different diameters. In essence, this means that the individual printheads have nozzles of different diameters. These are activelyThese areinterchanged actively interchanged during the production during the productionprocess [19]. process [19]. These are actively interchanged during the production process [19]. Figure 9 showsFigure different9 shows types different of non-planar types of non-planar surfaces formed surfaces by formeda robotic by arm. a robotic Their arm. Their Figure 9 shows different types of non-planar surfaces formed by a robotic arm. Their basic idea isbasic to create idea a is non-planar to create a non-planarbase copying base the copying surface theof the surface support of the model. support Instead model. Instead basic idea is to create a non-planar base copying the surface of the support model. Instead of the usualof Infill, the usuali.e., the Inﬁll, percentage i.e., the percentagevalue of the value filling of known the ﬁlling from known the creation from the of creation mod- of models of the usual Infill, i.e., the percentage value of the filling known from the creation of models by FDMby devices, FDM devices,a planar a laminated planar laminated plastic plasticis used isin used this incase. this The case. one The already one already men- mentioned els by FDM devices, a planar laminated plastic is used in this case. The one already mentioned servesserves as a support as a support for the for upper the upper non-planar non-planar surfaces. surfaces. tioned serves as a support for the upper non-planar surfaces.

Figure 9. Demonstration of non-planar models printed by this method [19]. FigureFigure 9. Demonstration 9. Demonstration of non-planar of non-planar models models printed printed by this by methodthis method [19]. [19]. The applicationThe applicationof FDM technology of FDM technologyto robotic arms to robotic and other arms atypical and other structures atypical is structures a is a The application of FDM technology to robotic arms and other atypical structures is a current topiccurrent that significantly topic that significantly supports the supports development the development in this area in of this technology. area of technology. Sim- Similar current topic that significantly supports the development in this area of technology. Sim- ilar studies studiesand conceptual and conceptual solutions solutions significantl significantlyy contribute contribute to the increase to the increase of interest of interestin in the ilar studies and conceptual solutions significantly contribute to the increase of interest in the field of non-planarfield of non-planar printing. printing. It has an It integral has an place integral in continuous place in continuous research researchin the field in the field of the field of non-planar printing. It has an integral place in continuous research in the field of materials,materials, mechanical mechanical properties properties of mode ofls, models, development development of structures of structures and software and software [20]. of materials, mechanical properties of models, development of structures and software [20]. [20].2. Methodology 2. Methodology Within the methodology of design of the FDM device design, it is necessary to deter- 2. Methodology Withinmine the methodology and define its of required design of parameters the FDM device and purpose. design, it Since is necessary the work to aims deter- to design the structureWithin focused the methodology on innovations of design and currentof the FD trendsM device in the design, industry, it is onenecessary of its prioritiesto determine and define its required parameters and purpose. Since the work aims to design the mineis its and use. define It is wellits required known parameters that recent trendsand purpose. in the Since use of the FDM work devices aims to are design different. the Appl. Sci. 2021, 11, 2928 7 of 25

Whether it is the use of printheads installed on robotic arms, or oversized printing used, for example, in construction, the creation of tissue through the layering of biological material, or new materials in this area, the devices used in these areas have one thing in common. They all work on the same principle of layering thermoplastic or other materials in planar layers [21]. This is based on theoretical assumptions, which form a partial solution related to the design of an atypical structure for FDM technology. Within the publication, we focus on a specific construction type, which we consider to be ideal in several ways. It is well known that compared to serial robots used in conjunction with FDM technology and conventional 3D printer designs, devices based on the principle of parallel manipulators are dominant. Due to their availability, it is relatively simple compared to robotic arms, as well as in regard to speed and dynamic movement. The disadvantage of these devices is their somewhat complicated operation compared to conventional Cartesian-type constructions and the lower achieved accuracy of component production. In the field of parallel manipulators, we know several types of constructions, such as tripod-type manipulators, also used in FDM technology devices, and various other types of constructions based on the parallel motion [22]. As part of the device’s design, i.e., developing an atypical device, we encounter a combined Cartesian-type construction with an effector characteristic of delta devices. This type of device offers new possibilities in terms of system control and the possibilities of its application. Due to the design and application of the solution to a specific type of atypical production of models, it is necessary to determine the proposed equipment’s basic requirements. Given the knowledge already gained related to structures, control, kinematics and data processing for FDM technology, we can create a list of basic requirements for creating an atypical structure [23]. These requirements are completed to develop an atypical device designed for non-planar 3D printing. Partial goals are presented, as follows: • Creating a conceptual design. • Modification of the design based on theoretical knowledge. • Design of key components of the structure. • Application of the finite element method to optimise the design of key components. • Design of construction subsystems. • Construction assembly and verification. • Conceptual design of an integrated extrusion system for processing and printing from recycled material.

2.1. Construction Design Based on Acquired Knowledge Due to the previous research in types of additive devices, types of their constructions and application solutions, we have arrived at a possible conceptual design of the structure. This construction is to be adapted to the models’ production conditions through non-planar layering of the material. As part of a partial solution, we initially considered a simple alternative to the Tripteron-type construction, which forms a kind of basis for atypical devices with untapped potential. From our perspective, this could be used in the printing of non-planar surfaces [24]. As shown in Figure 10, constructions of this type are designed to combine Cartesian- type FDM devices. Instead of a standard printhead attached to the X-axis, they have an effector similar to delta-type devices. Given the theoretical knowledge in the ﬁeld of non-planar layering of material, the key is using an effector connected separately to each of the device axes [25–27]. Appl. Sci. 2021, 11, 2928 8 of 25 Appl. Sci. 2021, 11, x FOR PEER REVIEW 8 of 26

Figure 10. The Tripteron structure used for the initial model for evaluation and design [28]. Figure 10. The Tripteron structure used for the initial model for evaluation and design [28].

However,However, duringduring the the implementation implementation of of this th construction,is construction, we we encountered encountered significant signifi- shortcomings.cant shortcomings. The FDMThe FDM technology technology used used in the in production the production of key of componentskey components does does not achievenot achieve the requiredthe required accuracy, accuracy, which which would woul notd ensurenot ensure the system’sthe system’s sufficient sufficient accuracy accu- andracy rigidity and rigidity in the in case the ofcase the of used the used transformation transformation mechanism mechanism combining combining linear linear guidance guid- andance timing and timing belt. Thebelt. simple The simple forked forked joints joints ingested ingested in the in joints the joints of the of individual the individual arms arms did notdid havenot have sufficient sufficient rigidity, rigidity, which which in the in Z-axis the Z- causedaxis caused the deflection the deflection of the of entire the entire arm andarm theand subsequent the subsequent crossing crossing of the of linear the linear mechanism. mechanism. Based Based on these on facts,these itfacts, was it necessary was neces- to modifysary to modify the proposal, the proposal, which will which ensure: will ensure: •• SufficientSufficient rigidity rigidity of of the the system system in in the the Z-axis. Z-axis. •• ProperProper placement placement of of linear linear guides, guides, guide guide rods rods and and transformation transformation mechanisms. mechanisms. •• CorrectCorrect position position of of the the effector effector for for the the device device guides guides and and the the printing printing pad. pad. •• ProperProper placement placement of of sufficient sufficient print print pads. pads. •• PlentyPlenty of of space space for for arm arm movement movement to to prevent prevent collision collision with with the the frame frame when when lifting lifting in thein Z-axis.the Z-axis. •• DesignDesign of of thethe arms to to not not collide collide with with the the machine machine frame, frame, the printing the printing pad or pad other or othercomponents. components. DuringDuring thethe FDMFDM device’sdevice’s designdesign forfor thethe productionproduction ofof modelsmodels byby non-planarnon-planar layeringlayering ofof material, we we relied relied on on theoretical theoretical knowledg knowledgee and and an anoverview overview of the of thecurrent current state. state. The Theknowledge knowledge was wassubsequently subsequently applied applied to an to existing an existing kinematic kinematic model model of the of theTripteron Tripteron de- device.vice. With With the the help help of of various various types types and and modi modificationsfications necessary necessary for realising 3D3D printingprinting onon suchsuch aa device,device, thisthis processprocess achievedachieved itsits designdesign ofof anan atypicalatypical constructionconstruction ofof anan FDMFDM device.device. As As already already mentioned, mentioned, the the proposed proposed de devicevice has has all all the the characteristic characteristic elements elements of ofthe the construction construction used used by additi by additiveve production production devices devices FDM. FDM. Its base Its is base an open is an “L” open shaped “L” shapedframe. It frame. has sufficient It has sufficient space to spaceplace tothe place printing the printingplate, lines, plate, drives lines, and drives other and elements other elements[26–28]. [26–28]. 2.2. Layout Design of the Construction Frame 2.2. Layout Design of the Construction Frame The resulting device concept is designed for non-planar 3D printing, because the The resulting device concept is designed for non-planar 3D printing, because the con- conventional design of the FDM device, controlled in three axes, is unsatisfactory in non- ventional design of the FDM device, controlled in three axes, is unsatisfactory in non- planar printing due to insufficient extrusion of the material at an elevation of more than planar printing due to insufficient extrusion of the material at an elevation of more than 22.5◦. A new concept is proposed for the possible extension, which will allow it to work in 22.5°. A new concept is proposed for the possible extension, which will allow it to work more than three axes. It is, therefore, a matter of connecting two types of devices in series. Thisin more fact than harms three the stabilityaxes. It is, of therefore, the system, a matter as well of as connecting other parameters. two types For of this devices reason, in aseries. frame This of a fact smaller harms height the stab (Figureility 11of ),the and system, a larger as base,well as was other chosen, parameters. which partially For this eliminatesreason, a frame the negative of a smaller vibrations height in (Figure the frame 11), causedand a larger by the base, movement was chosen, of the which arms. partially eliminates the negative vibrations in the frame caused by the movement of the arms. Appl. Sci. 2021, 11, 2928 9 of 25 Appl. Sci. 2021, 11Appl., x FOR Sci. PEER 2021, REVIEW11, x FOR PEER REVIEW 9 of 26 9 of 26

Figure 11. LayoutFigureFigure design 11.11. LayoutLayoutof the frame designdesign structur ofof thethe frameeframe with structurestructura descriptione withwith of aa description thedescription axes. ofof thethe axes.axes.

The device’s TheframeThe device’sdevice’s is made frame frame of aluminium is is made made of of profiles aluminium aluminium measuring profiles profiles 20 measuring measuring × 20 and 20 20 × 40×20 20 mm. and and 20 20× × 4040 mmmm.. The orientationTheThe of orientationorientation these profiles ofof thesethese is adapted profilesprofiles so isis that, adaptedadapted due to soso the that,that, device’s duedue toto complicated thethe device’sdevice’s complicatedkine-complicated kine-kinematic, there arematic,matic, no therecollisionsthere areare no noof collisionsthecollisions arms an ofofd thethe carriages armsarms andan ind carriagesthecarriages individual inin thethe axes, individualindividual with the axes,axes, withwith thethe frame of the structureframeframe of the(Table structure structure 1). Another (Table (Table influence 1)1).. Another Another on theinfluence influence orientation on on the theof orientation the orientation profiles of is ofthe also the profiles profiles is also is used by the usedalsoused usedconnecting by the by used the parts, used connecting connectingi.e., clamps parts,, parts, which i.e., clamps i.e., ensure clamps,, which the mutual which ensure ensure position the mutual the of mutual indi- position position of indi- of vidual shapesindividualvidual and ensure shapes shapes th ande whole and ensure ensure frame’s the thewhole stability. whole frame’s frame’s stability. stability.

Table 1. DimensionalTableTable 1. 1. characteristicsBasic Dimensional dimensions characteristicsof the of theproposed frame. of frame. the proposed frame.

Basic DimensionsBasicBasic ofDimensions Dimensions the Frame of of the the Frame Frame Frame lengthFrame inFrame the lengthY-axis length inin thethe Y-axis Y-axis 570 [mm] 570 [mm][mm] Frame lengthFrame inFrame the lengthX-axis inin the the X-axis X-axis 500 [mm] 500 [mm][mm] Maximum sizeMaximumMaximum of the base size area ofof the the base base area area 285 × 103 [mm285 2852] × × 103 [mm[mm2]2] Maximum frameMaximumMaximum height frameframe height height 390 [mm] 390 [mm][mm]

The constructionTheThe constructionofconstruction FDM devices ofof FDMFDM is relatively devicesdevices undemanding. isis relativelyrelatively undemanding.undemanding. The models have TheThe modelsmodelsbeen havehave beenbeen adapted to beadaptedadapted fixed using toto be be simple ﬁxed fixed using usingconnections simple simple connections of connections M3 screws of ofM3and M3 screws “T” screws matrix. and and “T” Various “T” matrix. matrix. vari- Various Various variants variants of cornerofants brackets corner of corner bracketsserved brackets as served setting served as elem setting asents setting elements for the elem frame forents the forof framethe the structure. frame of the of structure. theThe structure. device The device The device was was designeddesignedwas so thatdesigned its so assembly that so itsthat assembly requiresits assembly requiresminimal requires minimalinterventions minimal interventions interventions in the frame in the structure.in framethe frame structure. structure. In In connectionconnectionIn with connection the assignment’s with with the the assignment’s assignment’ssolution, a solution, virtual solution, model a virtual a virtual of the model modelwhole of the assemblyof the whole whole assemblyand assembly and and all all componentscomponentsall wascomponents created. was Thewas created. bodycreated. Theof theThe body system body of theof itself the system wassystem itselfrelatively itself was was relativelysimple. relatively The simple. use simple. The The use use of of fasteners andfastenersof fasteners individual and and individual elements individual in elements a elementspredetermined in ain predetermined a pr edeterminedlocation on location the location frame on theonwas the frame seam- frame was was seamless. seamless. The negativeTheless. negative Thefactors negative factorswere thefactors were assembly thewere assembly theof plasticassembly of plastic parts of withplastic parts the with parts help the with of help screw the of screwhelp con- of connections, screw connections, the themechanicalnections, mechanical the properties mechanical properties of propertiesthe of thema materialsterials of theused usedma andterials and the the useddeviations deviations and the of deviationsthe of the equip- equipment of the equip- used ment used totoment produce produce used components. components.to produce components.When mountedmounted When onon amounteda metal metal frame, frame, on a they metalthey caused causedframe, the thethey plastic caused element the plastic elementtoplastic deform.to deform. element Other Other to negative deform. negative effects Other effects were negative were shown shown effects during duringwere the shown commissioning the commissioning during the of individualcommissioning axes. of individualThese ofaxes. individual These negative negative axes. factors, These factors, extremely negative extremely complicatingfactors, complicating extremely the design complicatingthe design of the of structure the designstruc- itself, of the caused structure itself, causedtheture accumulation itself,the accumulation caused of the large accumulation of amountslarge amounts of of plastic large of plastic waste,amounts waste, which of plastic which resulted waste, resulted in the which needin resulted to recycle in the need to recyclethethe failures.need the to failur Therecycle criticales. Thethe components failurcriticales. componentsThe were critical the bearingswecomponentsre the of bearings motors, were theof drives motors,bearings and lead of screws,motors, drives and leadwhichdrives screws, canand be whichlead seen screws, can in Figures be whichseen 12 in can and Figures be 13 seen. Modifying 12 inand Figures 13. theseModifying 12 and designs 13. these Modifying using designs the ﬁnite these element designs using the finitemethodusing element the greatly finite method acceleratedelement greatly method thisacce processlerated greatly andthis acce reducedprocesslerated and the thisamount reduced process of theand plastic amount reduced waste the generated, amount of plastic wasteresultingof plasticgenerated, fromwaste resulting the generated, high failure.from resulting the high from failure. the high failure.

Figure 12.Figure DetailFigure 12. ofDetail the 12. key ofDetail thecomponents keyof the components key of components the X-axis of the guide X-axisof the and guideX-axis drive andguide housing. drive and housing. drive housing.

Due to these Duedeformations, to these deformations, e.g., to offset e.g.,the guideto offset bar the and guide guide bar screw. and guideThis misa- screw. This misalignment waslignment measurable was in measurable millimetres, in whichmillimetres, is unacceptable which is unacceptablefor the smooth for running the smooth running Appl. Sci. 2021, 11, x FOR PEER REVIEW 10 of 26

of the drives and the trolley’s movement with the arm. The misalignment of the lead screw or rod caused an extreme deflection of the flexible coupling, which could not compensate for this deformation. As a result of these shortcomings, the engines overheated, and the truck stopped unintentionally at a greater distance. Due to the dispositional solution of the device frame and the lack of space for alternative possibilities of mutual storage of Appl. Sci. 2021, 11, 2928these subsystems, the need arose on the device to create models common for the storage 10 of 25 of components in both axes. As shown in Figure 13, the Y-axis drive mount is also the opposite component for the X-axis bearing, guide screw and guide rod mount.

FigureFigure 13. Detail 13. ofDetail key ofcomponents key components of bearings of bearings guided guided and drives and drivesin the Y-axis. in the Y-axis.

These defectsDue arose to theseon all deformations, key components e.g., used to offset to mount the guide drives bar and and linear guide technol- screw. This misalign- ogy on the device.ment was As a measurable solution to inthis millimetres, situation in which commercially is unacceptable used FDM for the devices, smooth ap- running of the plying the so-calleddrives and free the end trolley’s of lead movement screws. It withmeans the that arm. the The end misalignment of the lead screw of the is lead screw or housed in clearancerod caused housing. an extreme This play deflection subsequently of the allows flexible compensation coupling, which in non-coaxial could not compensate movement offor the this lead deformation. screw and linear As a resulttechnology, of these and shortcomings, there is no bending the engines and negative overheated, and the forces. Such trucka solution stopped is unacceptable unintentionally due to at athe greater nature distance. of our constr Dueuction. to the dispositionalIn this case, solution of the loose endsthe of device the guide frame screws and would the lack caus ofe space other forunwanted alternative vibrations possibilities and vibrations of mutual storage of of the system,these which subsystems, would negatively the need aroseaffect onthe the prints’ device quality. to create As modelsa solution common to these for the storage problems, weof used components the so-called in both application axes. As of shownthe finite in element Figure 13 method, the Y-axis before drive the model mount is also the production process.opposite This component solution forconsisted the X-axis of analyses bearing, of guide the model’s screw and location guide within rod mount. the virtual subsystemThese and subsequent defects arose simulation on all key componentsof the effects used acting to mounton individual drives and compo- linear technology nents [27,28].on Individual the device. values As a of solution deviations to this from situation the initial in commercially position can be used seen FDM in Tables devices, applying 2 and 3. Repeatedthe so-called measurements free end of of real lead models, screws. modifications It means that theof CAD end of models the lead and screw cor- is housed in rection of dimensionsclearance and housing. geometry This playof compon subsequentlyents were allows done. compensation In essence, it inwas non-coaxial a matter movement of measuringof the the magnitude lead screw of and the linear angular technology, deformation andthere of the is drive no bending bearing and after negative fixing forces. Such the plastic componenta solution to is unacceptablethe metal frame due and to thecomparing natureof it ourwith construction. the simulation. In thisSubse- case, the loose quent deformationends of was the implemented guide screws in would a CAD cause model, other which unwanted served vibrations as a template and for vibrations a of the new part. Thissystem, process which was would applied negatively to each bearing affect the of prints’the drive quality. and Asthe alead solution screw to end these problems, element. Gradualwe used measurements the so-called and application adjustment of thes have finite succeeded element method in reducing before this the nega- model production tive factor toprocess. a minimum, This solutionthus ensuring consisted smooth of analyses movements of the in model’s all axes. location within the virtual subsystem and subsequent simulation of the effects acting on individual components [27,28]. Table 2. The resultIndividual of the X values and Y axes of deviations drive displacement. from the initial position can be seen in Tables2 and3. Repeated measurements of real models, modifications of CAD models and correction Placementof dimensions and geometry X of[mm] components were done. Y In [mm] essence, it was a matter of Nema 17 (holdingmeasuring screw the 1) magnitude of the 2.907 angular deformation of the 2.583 drive bearing after fixing the Nema 17 (holdingplastic componentscrew 2) to the metal 1.13 frame and comparing it with 1.066 the simulation. Subsequent Z axis deformationdeformation was implemented 0.054 in a CAD model, which served 0.048 as a template for a new Combinedpart. deformation This process was applied 0.018 to each bearing of the drive and 0.008 the lead screw end element. Gradual measurements and(torque, adjustments force) have succeeded in reducing this negative factor to a minimum, thus ensuring smooth movements in all axes.

Table 2. The result of the X and Y axes drive displacement.

Placement X [mm] Y [mm] Nema 17 (holding screw 1) 2.907 2.583 Nema 17 (holding screw 2) 1.13 1.066 Z axis deformation 0.054 0.048 Combined deformation 0.018 0.008 (torque, force) Appl. Sci. 2021, 11, Appl.x FOR Sci. PEER 2021 REVIEW, 11, x FOR PEER REVIEW 11 of 26 11 of 26

Appl. Sci. 2021, 11, 2928 11 of 25

Table 3. DimensionalTable characteristics 3. Dimensional of characteristics the proposed offrame. the proposed frame.

PlacementTable 3. DimensionalPlacement characteristics Z [mm] of the proposedZ [mm] frame. Z′ [mm] Z′ [mm] Nema 17 (holdingNema screw 17 (holding 1) Placement screw 1) 1.650 1.650 Z [mm] 1.940 1.940 Z0 [mm] Nema 17 (holding screw 2) 0.761 0.667 Nema 17 (holding screwNema 2) 17 (holding screw0.761 1) 1.650 0.667 1.940 X axis deformationX axis Nema deformation 17 (holding screw 0.004 2) 0.004 0.761 0.008 0.008 0.667 Y axis deformationY axis deformationX axis deformation 0.013 0.013 0.004 0.009 0.009 0.008 Combined deformationCombined Ydeformation axis deformation 0.013 0.009 Combined deformation (torque,0.018 force)0.018 0.0180.008 0.008 0.008 (torque, force) (torque, force)

The second problemTheThe secondsecond was the problemproblem implementation waswas thethe implementationimplementation of the shapes ofof theotherthe shapesshapes components ofof otherother in componentscomponents inin the design of thenewthe design designmodels. ofof Asnewnew shown models.models. in Figu AsAs shownshownre 14, the inin FigureFigumountingre 1414,, thetheof motors mountingmounting and of oflinear motorsmotors andand linearlinear technology oftentechnologytechnology interfered oftenoften with interferedinterfered the proposed with with models, the the proposed proposed not excluding models, models, notthe not excludingfact excluding that all the thethese fact fact that that all all these these models had tomodels modelscorrelate hadhad with toto correlatethecorrelate aluminium withwith thethe profiles aluminiumaluminium and their profilesprofiles grooves’ andand theirdimensions.their grooves’ grooves’ This dimensions. dimensions. ThisThis fact required afact factspecific requiredrequired set of aa the specificspecific parameters setset ofof thethe of parameters printingparameters andof of extrusionprinting printing and ofand the extrusion extrusion equipment’s of of the the equipment’s equipment’s material on whichmaterialmaterial the production onon which which the the of production modelsproduction was of ofcarried models models out. was was We carried carried achieved out. out. We an We achievedideal achieved mate- an an ideal ideal material material extrusion withextrusionrial extrusionthe right with settings,with the the right whichright settings, settings, allowed which which us to allowed createallowed components us us to to create create with components components a non- with with aa non-non- conflicting shapeconflictingconflicting and the shape correctshape andand dimensions. thethe correctcorrect Th dimensions.dimensions.ese components TheseThese then componentscomponents easily landed thenthen in easilyeasily the landedlanded inin thethe specified place,specifiedspecified in correlation place,place, with inin correlationcorrelation the developed withwith the theCAD developeddeveloped model. CAD CAD model. model.

FigureFigure 14. Detail 14. FigureDetail of the of14.key the Detail components key of components the key of the components ofgu theide guideand of drive andthe gu drivebearingside bearingsand in drive the inZ-axis. bearings the Z-axis. in the Z-axis.

During the structure’sDuringDuring the thedesign structure’sstructure’s process, designdesign we did process,process, not work wewe didonlydid not notwith workwork static onlyonly models, withwith staticasstatic models,models, asas was interpretedwaswas in interpretedtheinterpreted deformation in in thethe shown deformationdeformation in Figures shown shown 12–14, in in Figures Fibutgures we 12also 12–14,–14 used, but but the we we so-called also also usedused thethe so-calledso-called motion analysis.motionmotion Due analysis.toanalysis. the arms’ DueDue arrangemen toto thethe arms’arms’t, arrangement,thearrangemen types of linest, thethe typesusedtypes and ofof lineslines the possible usedused andand thethepossible possible negative phenomenanegativenegative resulting phenomenaphenomena from resulting resultingthe individual fromfrom the thesubsystems, individualindividual the subsystems,subsystems, static analysis thethe staticstaticalone analysis analysis alonealone was insufficient.waswas The insufﬁcient.insufficient. device is ThedividedThe devicedevice into isis several divideddivided smaller intointo severalseveral subsystems, smallersmaller which subsystems,subsystems, reduced whichwhich reducedreduced the time requiredthethe timetimefor each requiredrequired analysis forfor eachrun.each analysisOnanalysise of these run.run. subsystems OneOne ofof thesethese was subsystemssubsystems also the already waswas alsoalso thethe alreadyalready mentioned X-axismentionedmentioned line, together X-axis X-axis line,with line, together itstogether key component. with with its its key key component.The component. whole pa Thert The of whole thewhole construc- part pa ofrt theof the construction construction was used wasfortion the usedwas simulation used for the for simulation theitself, simulation as shown itself, itself, asin shownFigure as shown in15. Figure in Figure 15. 15.

Figure 15. IllustrationFigureFigure of 15.15. the IllustrationIllustration subsystem ofof used thethe subsystem subsystemby the motion usedused analysis. byby thethe motionmotion analysis.analysis.

After definingAfter Afterall the deﬁningdefining connections all the and connections supplementing and and supplem supplementingthe structuralenting elements the the structural structural such aselements elements such such as screw connectionsasscrew screw and connections connectionsbearings fromand and bearingsthe bearings library from from of thethe the usedlibrary library program, of of the the used the location program, and thethe locationlocation andand type of electric motor used were deﬁned. The advantage of this type of analysis is that it Appl. Sci. 2021, 11, x FOR PEER REVIEW 12 of 26

type of electric motor used were defined. The advantage of this type of analysis is that it is not necessary to explain all the factors operating on the subsystem. The definition of these factors results from the CAD model itself, the relationships between the individual components, the selected types of materials, etc. The starting curve of the electric motor (Figure 16) during the analysed load is decisive for us. This was adjusted according to the assumed operating parameters of the proposed FDM device. In Table 4, we can see the individual parameters defining the course of simulation of the subsystem motion and its analysis.

Table 4. Definitions used in the X-axis motion analysis subsystem.

Detail of Analysis Ground Aluminium Frame (Profiles 20 × 20, 20 × 40) Element size [mm] 1.4 Appl. Sci. 2021, 11, 2928 12 of 25 Motor speed [mm/s] 60 Material of analysed part Polylactic acid (PLA) Elastic modulus [MPa] 3500 is not necessary toPoisson’s explain ratio all the factors operating on the subsystem. 0.300 The deﬁnition of these factors resultsDensity from [g/cm3] the CAD model itself, the relationships between 1252 the individual components, theYield selected stress types [MPa] of materials, etc. The starting curve 59 of the electric motor (Figure 16) during the analysed load is decisive for us. This was adjusted according to the assumedThese operating operating parameters parameters of are the unsatisfactory proposed FDM due device. to the design. In Table An4, intense we can increase see the individualin the carriage parameters speed in deﬁning the X-axis the coursecauses ofundesired simulation oscillations of the subsystem between motion the lead and screw its analysis.and the lead bar, transmitted by the carriage’s work with the arm attached (Figure 16).

FigureFigure 16. 16. DescriptionDescription of of the the starting starting curve curve of of the the el electricectric motor motor determined determined according according to the standard printing speed. the standard printing speed. Due to the motion analysis result, we assumed this negative phenomenon at each Table 4. Deﬁnitions used in the X-axis motion analysis subsystem. acceleration, deacceleration or change of the orientation of the print head movement in the X and Y axes. In extreme cases,Detail for of example, Analysis it manifests itself only by breaking the contact of the print head with the printout. The solution to eliminating this problem was Ground Aluminium Frame (Proﬁles 20 × 20, 20 × 40) to activate the so-called jerk settings. This function is one of the options related to controlling the speedElement of sizethe [mm]production process implemented in the 1.4 used software for model Motor speed [mm/s] 60 preparation.Material This of analysedparameter part is also known from the field Polylactic of machine acid (PLA) tools. By activating it, we partiallyElastic modulus limit the [MPa] starting speeds to a specific value, from 3500 which the speed subsequently increasesPoisson’s until ratio it reaches the required operating value. 0.300 The use of the “jerk setting” functionDensity could [g/cm3] be explained as follows. If the device has 1252 a set maximum speed v = 60 mm/s, andYield an stress acceleration [MPa] a = 20 mm/s2, the device reaches this 59 speed in three jumps in

These operating parameters are unsatisfactory due to the design. An intense increase in the carriage speed in the X-axis causes undesired oscillations between the lead screw and the lead bar, transmitted by the carriage’s work with the arm attached (Figure 16). Due to the motion analysis result, we assumed this negative phenomenon at each acceleration, deacceleration or change of the orientation of the print head movement in the X and Y axes. In extreme cases, for example, it manifests itself only by breaking the contact of the print head with the printout. The solution to eliminating this problem was to activate the so-called jerk settings. This function is one of the options related to controlling the speed of the production process implemented in the used software for model preparation. This parameter is also known from the field of machine tools. By activating it, we partially limit the starting speeds to a specific value, from which the speed subsequently increases until it reaches the required operating value. The use of the “jerk setting” function could be explained as follows. If the device has a set maximum speed v = 60 mm/s, and an acceleration a = 20 mm/s2, the device reaches this speed in three jumps in 3 s after start-up. If we set the value “jerk”, or jerks to j = 10 mm/s, we spread the first jump at acceleration and the last at de-acceleration to 2 s. It means a rise from speed from 0 to 10 mm/s and a Appl. Sci. 2021, 11, x FOR PEER REVIEW 13 of 26

3 s after start-up. If we set the value “jerk”, or jerks to j = 10 mm/s, we spread the first jump at acceleration and the last at de-acceleration to 2 s. It means a rise from speed from 0 to Appl. Sci. 2021, 1110, 2928 mm/s and a subsequent increase by leaps according to the corresponding acceleration 13 of 25 value up to the required value v = 60 mm/s. This method of eliminating undesired oscillations is suitable as a temporary solution for the production of test specimens. Due to thesubsequent excessive increasescope of by applying leaps according this method to the correspondingto all components acceleration of the valuedevice, up to the we list only a fewrequired of the value most v critical = 60 mm/s. ones. This By methodrepeatedly of eliminating combining undesired FEM, measurements oscillations is suitable and correctionsas of a temporaryCAD models, solution we have for the achieved production the of correct test specimens. placement of each axis and Due to the excessive scope of applying this method to all components of the device, the components stored on it. This correlated with the standard deviation of the equipment we list only a few of the most critical ones. By repeatedly combining FEM, measurements on which they andwere corrections manufactured, of CAD i.e., models, ± 0.01 we mm. have The achieved finite theelement correct method placement allowed of each us axis and to reduce the plasticthe components waste produced stored on it.signific This correlatedantly, but with dozens the standard of defective deviation pieces of the were equipment produced despiteon which this reduction. they were manufactured,As a result of i.e.,the± increased0.01 mm. Thevolume ﬁnite of element failures, method it was allowed necessary to recycleus to reduce the waste the plastic thus produced. waste produced signiﬁcantly, but dozens of defective pieces were produced despite this reduction. As a result of the increased volume of failures, it was 2.3. Recycling ofnecessary Plastic Waste to recycle from theDesign waste thus produced.

Due to the2.3. accumulation Recycling of Plastic of plastic Waste waste from Design and its inherent negative impact on the environment, the recyclingDue to of the plastics accumulation in addi oftive plastic production waste and isits necessary. inherent negativeThere are impact cur- on the rently many studiesenvironment, and publications the recycling dealing of plastics with in this additive issue. production We most often is necessary. encounter There are material recyclingcurrently with manyconventional studies and FDM publications equipment. dealing Their with simple this issue. versions, We most which often have encounter only one print materialhead, produce recycling a relatively with conventional large am FDMount equipment. of plastic waste, Their simple not just versions, in the area which have of failures. Becauseonly onethe printdevices head, use produce only one a relatively type of largematerial amount in their of plastic operation, waste, not the just mate- in the area rial used to supportof failures. the printing Because theof individu devices useal onlymodels one typehas a of majority material inshare their in operation, the produc- the material tion of waste. Equallyused to supportproblema thetic printing are the of filament individual residues, models wh hasich, a majority due to sharethe insufficient in the production of waste. Equally problematic are the filament residues, which, due to the insufficient volume, have no use in larger components. Due to the waste produced in this way, several volume, have no use in larger components. Due to the waste produced in this way, several devices are useddevices in this are technology, used in this which technology, enable which the enablerecycling the recyclingand reuse and of reusematerial. of material. In a In a relatively simplerelatively cycle, simplethe material cycle, the is materialcrushed is into crushed granules into granules of a specific of a specific size, size,and and then then this this granulate isgranulate introduced is introduced into a specialised into a specialised extruder. extruder. It works It on works the onprinciple the principle of a plas- of a plastic tic injection chamber,injection with chamber, the difference with the difference that the that melt the is melt not isinjected not injected into intothe themould. mould. The The melt melt passes throughpasses througha nozzle a nozzleof a specific of a specific diameter diameter and and is then is then cooled cooled and and wound wound onon a a roll. We roll. We schematicallyschematically see this see process this process shown shown in inFigure Figure 17. 17 .

Figure 17.Figure Equipment 17. Equipment for the forproduction the production of fila ofment ﬁlament from from recycled recycled granulate granulate [29]. [29 ].

Due to deficiencies,Due to inaccura deficiencies,cies inaccuraciesand various and types various of ex typesternal of influences, external influences, which can which can significantly affectsignificantly the production affect the of production models using of models FDM using technology, FDM technology, the presentation the presentation will will always contain a certain percentage of failures. This failure, which is characteristic in always contain a certain percentage of failures. This failure, which is characteristic in par- particular of the initial stages of prototype production and the changes resulting from there, ticular of the initialis predominant stages of inprototype plastic waste prod generation.uction and Given the changes that this articleresulting presents from the there, design and is predominantmanufacture in plastic waste of atypical generation. FDM equipment, Given that it is this obvious article that pr itesents was necessary the design to addressand this manufacture ofissue atypical during FDM its production. equipment, The it application is obvious of thethat finite it was element necessary method to (FEM) address technology this issue duringin designingits production. key components The applicat hasion partially of the reduced finite element this failure. method Nevertheless, (FEM) tech- due to the nology in designinginaccuracies key components and deviations has of partially the FDM reduced devices, the this problem failure. of Nevertheless, storing the different due types to the inaccuraciesof materials and deviations used, and of thethe mechanicalFDM devices, properties the problem of the of prints storing themselves, the different this design types of materialsdid notused, go withoutand the plasticmechanical waste accumulation.properties of Duethe prints to this factthemselves, and the amount this de- of waste produced, the recycling of the produced plastic waste was implemented in this activity. sign did not go without plastic waste accumulation. Due to this fact and the amount of The design has also been extended to include a separate printhead concept, designed to waste produced,work the directly recycling with of recycled the produced granulate. plastic The recyclingwaste was of wasteimplemented from FDM in production this ac- and tivity. The designindustry has asalso such been is of extended interest to manyto include studies. a separate The issue ofprinthead partial recovery concept, of wastede- from individual sectors is also addressed in the publication “Evaluation of the Circularity of Appl.Appl. Sci. Sci. 2021 2021, 11, 11, x, xFOR FOR PEER PEER REVIEW REVIEW 1414 of of 26 26

signed to work directly with recycled granulate. The recycling of waste from FDM pro- Appl. Sci. 2021, 11, 2928signed to work directly with recycled granulate. The recycling of waste from FDM pro- 14 of 25 ductionduction and and industry industry as as such such is is of of interest interest to to many many studies. studies. The The issue issue of of partial partial recovery recovery ofof waste waste from from individual individual sectors sectors is is also also addressed addressed in in the the publication publication “Evaluation “Evaluation of of the the CircularityCircularity of of Recycled Recycled PLA PLA Filaments Filaments for for 3D 3D Printers” Printers” [30]. [30]. The The subject subject of of this this publication publication isis the the use use of of Recycledplastic plastic impact impact PLA from Filaments from various various for industries 3Dindustries Printers” in in a [a 30predef predef]. Theinedined subject ratio. ratio. of At At this the the publication same same time, time, is the use of itit points points out outplastic the the importance importance impact from and and various method method industries of of circulation circulation in a predeﬁned of of these these materials ratio.materials At the in in sameproduction production time,it points out (Figure(Figure 18). 18). the importance and method of circulation of these materials in production (Figure 18).

Figure 18. Demonstration of FDM production waste before processing into granulate form. FigureFigure 18.18. Demonstration ofof FDMFDM productionproduction wastewaste beforebefore processingprocessing intointo granulategranulate form.form.

TheThe overall overall recyclingThe recycling overall process process recycling is is not not process complicated. complicated. is not complicated. Essentially, Essentially, plastic Essentially,plastic failures, failures, plastic filament filament failures, filament residuesresidues and andresidues supporting supporting and supportingmaterial material are are material crushed crushed are into into crushed granules. granules. into It granules. It is is then then processed Itprocessed is then processed by by a a de- de- by a device vicevice working workingworking on on the the principle principle on the principle of of plastic plastic of injection. injection. plastic injection.The The difference difference The differenceis is that that instead instead is that of of injecting insteadinjecting of injecting thethe melt melt into intothe the the melt mold, mold, into the the the filament filament mold, theis is extrud extrud filamenteded through isthrough extruded a a nozzle nozzle through of of the athe nozzle desired desired of diameter, thediameter, desired diameter, thethe filament filamentthe is is cooled filamentcooled and and is then cooled then wound wound and then on on a wounda roll roll. .Thanks Thanks on a roll. to to this this Thanks process, process, to this it it is process,is possible possible it to isto possible to recyclerecycle most mostrecycle of of the the plastic mostplastic of waste waste the plastic produced. produced. waste At At produced. present, present, however, however, At present, this this however,step step is is beginning beginning this step to to is beginning seemseem redundant, redundant,to seem especially especially redundant, in in the the especially piece piece or or sm in sm theallall series pieceseries production orproduction small series area. area. production Implementing Implementing area. the Implementingthe granulategranulate processing processingthe granulate mechanism mechanism processing into into mechanism the the printh printh intoeadead theitself itself printhead will will allow allow itself us us willto to reduce allowreduce usthese these to reduce these stepssteps with with a stepsa low low degree withdegree a lowof of production production degree of productionload. load. As As can can load. be be seen seen As canin in the the be publication seenpublication in the publication“Towards “Towards “Towards DistributedDistributed DistributedRecycling Recycling with with Recycling Additive Additive with Manufa Manufa Additivecturingcturing Manufacturing of of PET PET Flake Flake of Feedstocks” PETFeedstocks” Flake Feedstocks” [31]. [31]. The The [31]. The extrusionextrusion system systemextrusion works works system on on the worksthe principle principle on the principleofof two two differently differently of two differently oriented oriented oriented screws, screws, screws,which which are whichare are used usedused to to move moveto the movethe granulate granulate the granulate through through through the the print print the head. head. print By head.By applying applying By applying heat heat and and heat pressure pressure and pressure in in dif- dif- in different ferentferent areas, areas,areas, the the melt melt the reaches meltreaches reaches a a state state a that statethat is is that identical identical is identical to to the the tofibre fibre the st fibrestateate during stateduring during the the extrusion extrusion the extrusion of the ofof the the filament filamentfilament by by a a byconventional conventional a conventional printhead. printhead. printhead. As As already Asalready already mentioned, mentioned, mentioned, the the thecombination combination combination of of of the finite thethe finite finite element elementelement method method method used, used, used, measurements, measurements, measurements, repeated repeated repeated correction correction of ofof CAD CADCAD models modelsmodels and and subsequent subsequentsubsequent printingprinting printing caused caused the the accumulation accumulation of of unnecessary unnecessary waste waste during during the the atypical atypical structure’s structure’sstructure’s prototyping. prototyping.prototyping. In InIn combination combinationcombination with withwith the the so-called so-called common common waste waste fromfrom from FDMFDM FDM production,pro- pro- such duction,duction, such suchas as excessas excess excess support, support, support, cuttings cuttings cuttings and and and ends ends ends of of of filaments filaments filaments significantly significantly significantly affect affect affect the the the direction di- di- of the rectionrection of of the thedesign design design of of theof the the structure structure structure (Figure (Figure (Figure 19 19 ).19). In). In In the the the beginning, beginning, beginning, the the the excess excess excess and and and non-gift non-gift non-gift material was recycled and processed into a filament. This process has proven efficient but relatively materialmaterial was was recycled recycled and and processed processed into into a a fi filament.lament. This This process process has has proven proven efficient efficient but but lengthy and inefficient due to the production batch [32,33]. relativelyrelatively lengthy lengthy and and inefficient inefficient due due to to the the production production batch batch [32,33]. [32,33].

Figure 19. Demonstration of the cycle of recycling plastic models from the design of the structure. FigureFigure 19. 19. Demonstration Demonstration of of the the cycle cycle of of recycling recycling plasti plastic cmodels models from from the the design design of of the the structure. structure. Due to this fact, the design was extended by the creation of an effector with a separate DueDue to to this this fact, fact, the the design design was was extended extended by by the the creation creation of of an an effector effector with with a a separate separate extrusion mechanism integrated directly into it. The print head designed in this way will extrusionextrusion mechanism mechanism integrated integrated directly directly into into it. it. The The print print head head designed designed in in this this way way will will then allow us to skip some of the steps necessarily associated with recycling. We also consider it another of the necessary steps to improving the state of long-term sustainable development in connection with this type of technology. Appl. Sci. 2021, 11, x FOR PEER REVIEW 15 of 26

then allow us to skip some of the steps necessarily associated with recycling. We also consider it another of the necessary steps to improving the state of long-term sustainable development in connection with this type of technology.

Appl. Sci. 2021, 112.4., 2928 Guide Design in Y and X Axes 15 of 25 Each functional structure must have suitable lines, drives and transformation mechanisms. Due to the creation of the system, which is formed by the series connection of two instruments, the2.4. work Guide pays Design increased in Y and Xattent Axesion to lines and transformation mechanisms. It is known that most commonly available FDM devices work with extreme clearances Each functional structure must have suitable lines, drives and transformation mecha- [34]. This includesnisms. e.g., Due free to theends creation of the of lead the system,screws whichin the isZ-axis, formed which by the are series also connection visible, of two e.g., on Zmorphinstruments, SX or Creality the work CR-Max pays increaseddevices. attentionThese are to considered lines and transformation upper and middle mechanisms. It class in terms ofis price known and that quality most commonly of available available FDM equipment. FDM devices A work frequent with extreme recommenda- clearances [34]. tion of these devices’This includes intermediaries e.g., free ends is not of theto tighten lead screws the inscrew the Z-axis,connections which areto the also stop. visible, e.g., This fact, combinedon Zmorph with SXthe or mechanisms’ Creality CR-Max seri devices.al involvement, These are played considered an important upper and middlerole class in the design. in terms of price and quality of available FDM equipment. A frequent recommendation By successiveof these selection, devices’ we intermediaries have eliminat is noted tothe tighten conventional the screw mechanisms connections toused the stop.to This fact, combined with the mechanisms’ serial involvement, played an important role in move the FDM device’s components. Due to previous experience and the device’s con- the design. ceptual design, instrumentsBy successive with selection, V-shaped we wh haveeels eliminated and timing the belts conventional have been mechanisms excluded. used to When moving,move the mechanism the FDM device’s controlled components. by the Due timing to previous belts was experience unsatisfactory. and the device’s They concep- often wear out tualand design,loosen, instruments resulting in with inaccurate V-shaped movement wheels and timingof the beltsarms. have This been can excluded. lead to When a collision or damagemoving, to the the mechanism effector. controlledThe mechanism by the timing moving belts using was unsatisfactory.rubber wheels They in the often wear shape of a “V” outhas andbeen loosen, eliminated resulting due in inaccurateto the frequent movement loosening of the arms. of eccentric This can nuts, lead towhich a collision or subsequently causedamage a change to the effector. in the components The mechanism’ position. moving In using the rubbercase of wheels the series in the connec- shape of a “V” tion of the newlyhas designed been eliminated structure’s due to arms, the frequent this fact loosening would lead of eccentric to the nuts,accumulation which subsequently of negative forcescause caused a change by the intruck’s the components’ incorrect position position. relative In the caseto the of themachine series coordina- connection of the newly designed structure’s arms, this fact would lead to the accumulation of negative tion system. The deflection of these arms would subsequently cause the linear guide and forces caused by the truck’s incorrect position relative to the machine coordination system. the lead screwThe to deflectioncross, thus of thesepreventing arms would the carriage subsequently from cause moving the linear and guide damaging and the the lead screw drive. As part toof cross,our proposal, thus preventing we chose the carriage two variants from moving of the and solution damaging applied the drive. to the As XY part of our and ZZ′- axes. Theproposal, first variant we chose is two a combination variants of the ofsolution a guide applied rod and to a the guide XY and screw. ZZ0- axes. The first The lines ofvariant the devices is a combination in the X ofand a guide Y axes rod are and essentially a guide screw. identical (Figure 20). The drive of the entire lineThe linesis provided of the devices by the in Nema the X and17 motor Y axes are(3), essentiallywhich is connected identical (Figure to the 20 ). The lead screw (5) usingdrive offlexible the entire coupling line is (4). provided The carriage by the Nema movement 17 motor (10) (3), is whichensured is connectedthrough to the a guide screw andlead a screw nut (9) (5) usingwhich flexible drives coupling the carriage (4). The in carriagethe Z-axis. movement A guide (10) rod’s is ensured combi- through a guide screw and a nut (9) which drives the carriage in the Z-axis. A guide rod’s combination nation provides its exact position with a diameter of 8 mm (6) with a linear ball bearing provides its exact position with a diameter of 8 mm (6) with a linear ball bearing (8). The (8). The linear bearinglinear bearing and guide and guide nut are nut housed are housed in the in carriage, the carriage, ensuring ensuring the the transmission transmission of the of the guide movementsguide movements to the first to thestage first of stage the arm of the in armthe Y-axis in the Y-axis and its and correct its correct orientation orientation for for the device’sthe coordination device’s coordination system. system.

Figure 20. FigureDrive, 20.transformationDrive, transformation mechanism mechanism and device and device guidance guidance in the in Y-axis. the Y-axis.

The line used in the X-axis is similar to the ﬁrst line. The elements of its construction The line used in the X-axis is similar to the first line. The elements of its construction and the principle of operation remain unchanged. The only change is component No. 2. and the principleThis of key operation component, remain which unchanged. is common to The the X-axisonly andchange Y-axis, is securescomponent the motor’s No. 2. position This key component,in the Y-axis. which These is common components to the ensured X-axis and the relativeY-axis, placesecures of thethe drives, motor’s transformation position in the Y-axis.mechanisms These components and lines. Since ensured these components the relative were place to beof createdthe drives, using transfor- FDM technology mation mechanismsas part and of the lines. conceptual Since these solution, components their production were to was be accompaniedcreated using by FDM the already technology as partmentioned of the complicationsconceptual soluti and theon, need their for production frequent model was modiﬁcations.accompanied by the already mentioned complications and the need for frequent model modifications. 2.5. Line Design in Z and Z0 Axes Another of the device design’s key components is the mechanism ensuring movement in the Z and Z0 axes. Due to its orientation and the fact that it is to be loaded with two arms Appl. Sci. 2021, 11, x FOR PEER REVIEW 16 of 26

Appl. Sci. 2021, 11, 29282.5. Line Design in Z and Z′ Axes 16 of 25 Another of the device design’s key components is the mechanism ensuring movement in the Z and Z′ axes. Due to its orientation and the fact that it is to be loaded with two arms stagesstages and and a printhead a printhead effector, effector, it is it obvious is obvious that that its cons its constructiontruction was was more more de- demanding manding thanthan with with mechanisms mechanisms in in the the X X and and Y Y axes. axes. The The first first changechange fromfrom thethe original original proposal was proposal wasthe the use use of of two two instruments. instruments. This This step step distributed distributed the the load load between between the the two two mechanisms, mechanisms,which which facilitated facilitated the the drives’ drives’ operation operation and and contributed contributed to to the the stability stability of of the the structure. The structure. Thesecond second step step was was to to use use linear linear guides guides instead instead of of guide guide rods. rods. Both designsBoth in the designs Z and inZ′ theaxes Z are and conceptually Z0 axes areconceptually similar (Figure similar 21). The (Figure movement 21). The movement is ensured byis the ensured Nema by 17 themotor Nema (5), 17fixed motor to the (5), frame fixed through to the frame a plastic through component a plastic (1,2). component (1,2). Subsequent transmissionSubsequent transmission of torque to the of torque guide torod the (7) guide is ensured rod (7) by is a ensured flexible bycoupling a flexible coupling (6). The linear(6). guide The linearis attached guide to is the attached frame towith the three frame brackets with three that brackets provide that its position provide its position and stability.and The stability. trolley (8) The is trolleysupplemented (8) is supplemented with bearings with of type bearings 608 2Z of type(9) and 608 its 2Z (9) and its movement ismovement excited thanks is excited to the thanks guide tonut, the which guide ensures nut, which the ensurestransformation the transformation of the of the rotational movementrotational of movement the guide ofscrew the guideinto a screwsliding into movement a sliding of movement the linear ofguide. the linear The guide. The opposite endopposite of the lead end screw of the is lead housed screw in is a housed bearing in 608 a bearing 2Z located 608 2Z in located the housing in the (11, housing (11, 12). 12). It is attachedIt is attached to the frame to the with frame standard with standard hexagon hexagon socket screws socket and screws M3 andthreads. M3 threads.

Figure 21.Figure Drive, 21. transformationDrive, transformation mechanism mechanism and device and guidance device guidance in Z-axis. in Z-axis.

0 The Z′-axis mechanismThe Z -axis consists mechanism of the consists same of components the same components and principle and of principle operation of operation as as the mechanismthe mechanism for movement for movement in the Z-axis. in the The Z-axis. difference The difference is the change is the in change the dimen- in the dimensions sions of componentsof components 9 and 2). 9 and 2).

2.6. Design of2.6. the DesignX, Y and of Z-Axis the X, YArm and System Z-Axis Arm System Due to the complicated solution associated with the series connection of the individual Due to the complicated solution associated with the series connection of the individual elements of the four arms located on the device. It was necessary to pay increased attention elements of the four arms located on the device. It was necessary to pay increased attention to the so-called “Trolleys” moving along a guide bar and a linear guide. They are based on to the so-called “Trolleys” moving along a guide bar and a linear guide. They are based on a solid trolley in which all the necessary components are stored. In the case of carriages in a solid trolleythe in Xwhich and Yall axes, the necessary these components components include are bearingsstored. In of the type case 608 of 2Zcarriages (1), which in are used to the X and Y axes,support these the components 1st stage arm include (Figure bearin 22).gs They of type also 608 participate 2Z (1), which in its are rotational used to motion. The support the 1stconstruction stage arm has(Figure two 22). components, They also whichparticipate required in its increased rotational attention motion. inThe terms of their construction hasrelative two components, position and which coaxial. required These components,increased attention i.e., the in linear terms ballof their bearing rel- (4) and the ative positionguide and coaxial. nut (2), These are fastened components, to the i.e., carriage the linear body ball through bearing screw (4) and connections the guide(5 and 3). In nut (2), are fastenedthe case to of the a linear carriage bearing, body thethrough screw screw connection connections is realised (5 and on 3). the In housingthe case (8) in which of a linear bearing,the bearing the screw is located. connection Figure is 22realisedb shows on thethe “trolley”housing (8) of thein which Z and the Z’- bearing axes. Its design was is located. Figuremodiﬁed 22b shows due to the the “trolley” need to reduce of the theZ and weight Z’- axes. of the Its whole design mechanism. was modified The difference is Appl. Sci. 2021, 11, x FORdue PEER to theREVIEW needalso to anchoring reduce the on weight the linear of the guide whole realized mechanism. through The M3 screwsdifference (5). Theis also change an- in17 the of type 26

choring on theof linear line was guide necessary realized due through to the M3 increase screws required (5). The in change the system’s in the type stability of line and rigidity in the Z-axis, which supports the effector’s entire weight. was necessary due to the increase required in the system’s stability and rigidity in the Z- axis, which supports the effector’s entire weight.

FigureFigure 22. 22. (a()a Design) Design of of the the truck truck in in the the X Xand and Y Yaxes; axes; (b ()b The) The “trolley” “trolley” of of the the Z Z and and Z´-axes Z´-axes.

The arm of the first stage of the proposed construction consists of a ridge hinge (1), fixed to the carriage through a screw and a nut M8 and six corresponding washers (Figure 23a). The arm further consists of a 20 × 20 mm aluminium profile (6), screws (7), washers (8) and “T” shaped nuts ensuring the position and stability of both end elements. The arm’s opposite side is formed by a hinge (10) with bearings that allow arm 2. The second component of the arm in the X and Y axes is the second stage arm (Figure 23b).

Figure 23. Structural design of the X, Y, Z and Z´ axis arm. (a) The arm of the first stage of the proposed construction; (b) the second stage arm; (c) trolley in Z and Z′ axes.

This arm provides the connection of the first arm to the effector. The method of in- terconnection and transformation of motion is the same as in the previous step. It means that the component has a comb hinge, this time rotated by 90° (2), and an aluminium profile with a 20 × 20 mm diameter, which is connected to the effector holder (7). It is attached to the aluminium frame through screw connections consisting of a screw (7), a washer (8) and a “T” shaped nut. The different shape of the end component is adapted so that it does not collide with the effector through which M8 threaded screws connect it during the movement of the arms in the X and Y- axes. The correct position of the screw connection and the bearings’ trouble-free movement is ensured through washers (9). As for the connecting element, trolley in Z and Z′ axes, its design is smaller and more compact, as shown in Figure 23c. It is a more compact design due to the heavier weight of the linear guide housing, which the drive must handle during the device’s operation. The components of these structural elements are similar. Here is a ball bearing, which was replaced by a linear guide house. The trolley is attached to it through M3 screws (4). Other elements of this construction are bearings type 608 2Z, which are used to fasten the arm’s first stage using a screw and nut with an M8 thread. The last element is the guide nut (3), which ensures, as with other components, the transformation of the rotational movement of the guide screw into a sliding movement of the house along with the linear guide. The lead nut is attached to the component with M4 screws (5). The arm’s second stage in the Z and Z′ axes is substantially identical to the X and Y-axes arm. The only difference is the different orientation of the swivel joint connecting the arm to the effector. This component’s shape is then adapted so that it does not collide anywhere with the effector or other arms during movement.

Appl. Sci. 2021, 11, x FOR PEER REVIEW 17 of 26

Appl. Sci. 2021, 11, 2928 17 of 25

Figure 22. (a) Design of the truck in the X and Y axes; (b) The “trolley” of the Z and Z´-axes

The arm of Thethe first arm stage of the of first the proposed stage of the construction proposed consists construction of a ridge consists hinge of (1), a ridge hinge fixed to the (1),carriage fixed through to the carriage a screw throughand a nut a M8 screw and and six corresponding a nut M8 and sixwashers corresponding (Figure washers 23a). The arm(Figure further 23a consists). The arm of a further 20 × 20 consists mm aluminium of a 20 × profile20 mm (6), aluminium screws (7), profile washers (6), screws (7), (8) and “T”washers shaped (8)nuts and ensuring “T” shaped the nutspositi ensuringon and stability the position of both and end stability elements. of both The end elements. arm’s oppositeThe side arm’s is oppositeformed by side a hinge is formed (10) with by abearings hinge (10) that with allow bearings arm 2. thatThe second allow arm 2. The componentsecond of the arm component in the X ofand the Y armaxes in is thethe Xsecond and Y stage axes isarm the (Figure second 23b). stage arm (Figure 23b).

Figure 23. StructuralFigure design 23. Structural of the X, design Y, Z and of the Z´ axisX, Y, arm. Z and (a )Z´ The axis arm arm. of ( thea) The ﬁrst arm stage of ofthe the first proposed stage of construction; the pro- (b) the second stageposed arm; construction; (c) trolley in Z(b and) the Z 0secondaxes. stage arm; (c) trolley in Z and Z′ axes.

This arm providesThis arm the provides connection the of connection the first arm of theto the first effector. arm to The the method effector. of The in- method of terconnectioninterconnection and transformation and transformation of motion is ofthe motion same as is thein the same previous as in the step. previous It means step. It means ◦ that the componentthat the componenthas a comb hinge, has a combthis time hinge, rotated this by time 90° rotated(2), and byan 90aluminium(2), and pro- an aluminium file with a 20profile × 20 mm with diameter, a 20 × 20 which mm is diameter, connected which to the is effector connected holder to the(7). effectorIt is attached holder (7). It is to the aluminiumattached frame to the through aluminium screw frameconnections through consisting screw connections of a screw (7), consisting a washer of (8) a screw (7), a and a “T” shapedwasher nut. (8) The and different a “T” shaped shape nut. of th Thee end different component shape is ofadapted the end so componentthat it does is adapted not collide sowith that the it doeseffector not through collide with which the M8 effector threaded through screws which connect M8 threaded it during screws the connect it movement duringof the arms the movementin the X and of Y- the axes. arms The in thecorrect X and position Y- axes. of Thethe correctscrew connection position of the screw connection and the bearings’ trouble-free movement is ensured through washers (9). and the bearings’ trouble-free movement is ensured through washers0 (9). As for the connectingAs for the connectingelement, trolley element, in Z trolleyand Z′ inaxes, Z and its design Z axes, is its smaller design and is smaller more and more compact, ascompact, shown in as Figure shown 23c. in It Figure is a more 23c. compact It is a more design compact due to design the heavier due to weight the heavier of weight the linear guideof the housing, linear guide which housing, the drive which must thehandle drive during must the handle device’s during operation. the device’s The operation. componentsThe of componentsthese structural of these elements structural are similar. elements Here are similar.is a ball Here bearing, is a ball which bearing, was which was replaced by a linear guide house. The trolley is attached to it through M3 screws (4). Other replaced by a linear guide house. The trolley is attached to it through M3 screws (4). Other elements of this construction are bearings type 608 2Z, which are used to fasten the arm’s elements of this construction are bearings type 608 2Z, which are used to fasten the arm’s first stage using a screw and nut with an M8 thread. The last element is the guide nut (3), first stage using a screw and nut with an M8 thread. The last element is the guide nut (3), which ensures, as with other components, the transformation of the rotational movement which ensures, as with other components, the transformation of the rotational movement of the guide screw into a sliding movement of the house along with the linear guide. The of the guide screw into a sliding movement of the house along with the linear guide. The lead nut is attached to the component with M4 screws (5). The arm’s second stage in the Z lead nut is attached to the component with M4 screws (5). The arm’s second stage in the and Z0 axes is substantially identical to the X and Y-axes arm. The only difference is the Z and Z′ axes is substantially identical to the X and Y-axes arm. The only difference is the different orientation of the swivel joint connecting the arm to the effector. This component’s different orientation of the swivel joint connecting the arm to the effector. This compo- shape is then adapted so that it does not collide anywhere with the effector or other arms nent’s shape is then adapted so that it does not collide anywhere with the effector or other during movement. arms during movement. 2.7. Design of Other Components of The Structure Based on a theoretical analysis dealing with FDM technology, we know that key components characterize each device’s design. In our case, the following features are the effector with the print head, the Bowden extrusion system and the print pad. The design of the printing pad is based on knowledge from the field of FDM technology. The designed printing pad has a relatively simple manual positioning system (Figure 24). This is based on the principle of tightening the screw (5) and the “T” nut (8) located at the top of the printing pad (1). By turning the screw, we derive the pressing force, which moves one of the corners of the printing pad downwards or upwards when it is released. By positioning each corner of the pad in this way, we then achieve the base’s correct position for the Appl. Sci. 2021, 11, x FOR PEER REVIEW 18 of 26

2.7. Design of Other Components of The Structure Based on a theoretical analysis dealing with FDM technology, we know that key components characterize each device’s design. In our case, the following features are the effector with the print head, the Bowden extrusion system and the print pad. The design of the printing pad is based on knowledge from the field of FDM technology. The designed printing pad has a relatively simple manual positioning system (Figure 24). This is based on the principle of tightening the screw (5) and the “T” nut (8) located at the top of the Appl. Sci. 2021, 11, 2928 18 of 25 printing pad (1). By turning the screw, we derive the pressing force, which moves one of the corners of the printing pad downwards or upwards when it is released. By positioning each corner of the pad in this way, we then achieve the base’s correct position for the printing process.printing Due process. to the series-connected Due to the series-connected design used designand the used fact andthat theour fact proposed that our proposed solution is basedsolution on the is based principle on the of a principle kinematic of amodel kinematic that has model not thatyet been has not tested, yet beenit was tested, it was not our intentionnot our to complicate intention to the complicate solution theusing solution automatic using calibration automatic tools. calibration Their simple tools. Their simple design and thedesign principle and the of principleoperation of were operation based wereon averaging based on the averaging position theof the position limit of the limit switch duringswitch calibration. during In calibration. the case of In larg theer case deviations, of larger it deviations, would average it would a value average higher a value higher than the layer’sthan height the layer’s during height printing. during This printing. fact could This cause fact could insufficient cause insufﬁcient or no adhesion or no adhesion of of the materialthe to material the printing to the substrate printing substratein this design. in this design.

Figure 24. The designFigure proposal 24. The designfor the proposalprinting forpad the solution. printing pad solution.

The conclusionThe of conclusion the design of is the conceptual design is solutions conceptual of solutionsthe effector of theandeffector the system and the system for material forextrusion. material These extrusion. devices These form devices one unit form and one are unitlocated and at are the located end of atthe the X, end Y, of the X, Y, 0 Z and Z′ axes.Zand TheZ effectoraxes. Thehas effectorsix joints has for six the joints joints, for which the joints, were whichcreated were to verify created the to verify the kinematics ofkinematics the six-axis of the device six-axis and device as su andpport as elements support elements that would that be would needed be needed when when using using aluminiumaluminium profiles profiles in the inarms the and arms to and verify to verifythe kinematic the kinematic model model and possible and possible col- collisions. lisions. A BowdenA Bowden material material extrusion extrusion system system was was chosen chosen in inthe the design design to toreduce reduce the the weight of weight of thethe effector. effector. It is It basically is basically a st aandard standard system system with with commonly commonly available available compo- components. It nents. It is basedis based on the on theNema Nema 17 (9) 17 drive, (9) drive, which which ensures ensures the fibre’s the fibre’s extrusion. extrusion. Extruder Extruder design design that providesthat provides the pressure the pressure required required to extrude to extrude the material the material (Figure (Figure 25). The 25 mate-). The material is rial is movedmoved through through a pneumatic a pneumatic coupling coupling (10) in (10)which in a which PTFE atube PTFE (11) tube is fixed (11) isfrom fixed from the the extruder.extruder. Inside, the Inside, material the materialslides toward slides the toward print the head print (12). head There (12). it Thereis heated it is to heated to the the desired desiredtemperature temperature and is andsubsequently is subsequently extruded extruded in the in form the form of a of molten a molten fiber fiber through a through a nozzlenozzle (13). (13). An An atypical atypical nozzle nozzle was was chosen chosen for for the the design, design, which which will will allow allow the the creation of creation of non-planarnon-planar surfaces surfaces on on a larger scale.scale. The effectoreffector (2),(2), i.e.,i.e., a a key key component component of of the proposed the proposeddevice, device, consists consists of of bearings. bearings. A A movable movable joint joint is is formed formed between between thethe effectoreffector and the end element of the arms X and Y of the second stage after the screw connection has been formed. and the end element of the arms X and Y of the second stage after the screw connection The bearings are positioned within the effector so that their axis is always parallel to the has been formed. The bearings are positioned within the effector so that their axis is al- axis of the lead screw of the respective axis. Other elements of this printing set are fans ways parallel to the axis of the lead screw of the respective axis. Other elements of this used as standard. A 20 × 20 × 10 mm centrifugal fan (7) for cooling the passive cooling of printing set are fans used as standard. A 20 × 20 × 10 mm centrifugal fan (7) for cooling the print head and a 40 × 40 × 10 mm axial fan (3) for cooling the layer of material on the the passive cooling of the print head and a 40 × 40 × 10 mm axial fan (3) for cooling the printing pad. Both of these components are fixed to the effector body through standard layer of material on the printing pad. Both of these components are fixed to the effector screws (4, 6). The last component of this assembly is the blower used to direct the airflow body through standard screws (4, 6). The last component of this assembly is the blower under the nozzle. used to direct the airflow under the nozzle. The application of theoretical knowledge to designing a device for printing non-planar surfaces can be seen in Figure 26. The resulting device consists of two pairs of identical arms that connect the individual axes with the end effector. The base frame is made of aluminium profiles measuring 20 × 20 and 20 × 40 mm. Its L-shaped arrangement has enough space for the movement of all four arms. The design consists of two types of guides, and the first is located in the X and Y axes, is based on the principle of a combination of a lead screw, nut and lead bar. The guides in the Z and Z0 axes consist of linear guides and lead screws with nuts. These guides and transformation mechanisms provide the system with sufficient rigidity and fluidity of movement. Appl. Sci. 2021, 11, x FOR PEER REVIEW 19 of 26

Appl. Sci. 2021, 11, x FOR PEER REVIEW 19 of 26 Appl. Sci. 2021, 11, 2928 19 of 25

Figure 25. Display the effector of the proposed device and the Bowden extension system.

The application of theoretical knowledge to designing a device for printing non-planar surfaces can be seen in Figure 26. The resulting device consists of two pairs of identical arms that connect the individual axes with the end effector. The base frame is made of aluminium profiles measuring 20 × 20 and 20 × 40 mm. Its L-shaped arrangement has enough space for the movement of all four arms. The design consists of two types of guides, and the first is located in the X and Y axes, is based on the principle of a combination of a lead screw, nut and lead bar. The guides in the Z and Z′ axes consist of linear guides and lead screws with nuts. These guides and transformation mechanisms provide FigureFigurethe system 25. 25. DisplayDisplay with the sufficient the effector effector rigidityof of the the proposed proposed and fluidity de devicevice of and and movement. the the Bowden Bowden extension extension system. system.

The application of theoretical knowledge to designing a device for printing non-planar surfaces can be seen in Figure 26. The resulting device consists of two pairs of identical arms that connect the individual axes with the end effector. The base frame is made of aluminium profiles measuring 20 × 20 and 20 × 40 mm. Its L-shaped arrangement has enough space for the movement of all four arms. The design consists of two types of guides, and the first is located in the X and Y axes, is based on the principle of a combination of a lead screw, nut and lead bar. The guides in the Z and Z′ axes consist of linear guides and lead screws with nuts. These guides and transformation mechanisms provide the system with sufficient rigidity and fluidity of movement.

FigureFigure 26.26.Design Design ofof atypicalatypical constructionconstruction ofof FDMFDM additiveadditive production production equipment. equipment.

TheThe resultresult ofof thethe useuse ofof FEMFEM cancan bebe seenseen inin FigureFigure 26 26.. AA fullyfully functionalfunctional FDMFDM devicedevice hashas allall thethe relevantrelevant componentscomponents characteristiccharacteristic of of FDMFDM technology.technology. The The end end effector effector allows allows thethe storagestorage of a a tip-shaped tip-shaped print print head head adapted adapted for for the the non-planar non-planar surface surface production production pro- process. Its movement is ensured by the transmission of the carriages’ sliding movement cess. Its movement 0is ensured by the transmission of the carriages’ sliding movement in inthe the X, X,Y, Y,Z and Z and Z′ axes Z axes through through arms. arms. This Thismovement movement is derived is derived from the from rotational the rotational move- movementment of the of theNema Nema 17 17motors motors and and its its transformation transformation into into a a rectilinear slidingsliding motionmotion throughthrough aa leadlead screwscrew andanda a nut. nut. TheThe implementationimplementation ofof thethe proposalproposal itselfitself consisted consisted ofof severalseveral steps.steps. TheThe ﬁrstfirst stepstep waswas toto createcreate aa requestrequest basedbased onon thethe theoretical theoretical knowledge knowledge Figuregained 26. in Design the previous of atypical chapters. construction The of design FDM additive (Figure production27) was created equipment. to apply theoretical knowledge and design requirements for the printing of non-planar surfaces. The result of thisThe creative result activity of the wasuse of a conceptualFEM can be design seen in of Figure a device 26. working A fully functional in three axes. FDM However, device hasthis all original the relevant concept components did not have characteristic good features. of FDM We createdtechnology. the prototype The end effector of the atypical allows theFDM storage device of presenteda tip-shaped in theprint article. head adapted The existing for the type non-planar of Tripteron surface construction production inspires process.the design Its movement of the device. is ensured The main by the purpose transmis andsion reason of the for carriages’ the creation sliding of this movement construction in theare X, the Y, intentionZ and Z′ axes to move through in thearms. ﬁeld This of movement this technology is derived towards from the the rotational development move- of equipment, which allows the production of prints created by a non-planar method. We ment of the Nema 17 motors and its transformation into a rectilinear sliding motion consider this type of construction to be ideal for many reasons. One of them is the possibility through a lead screw and a nut. The implementation of the proposal itself consisted of of expanding the number of axes and drives in these constructions, which subsequently several steps. The first step was to create a request based on the theoretical knowledge allows active tilting of the effector. We consider this fact to be one of the unique advantages Appl. Sci. 2021, 11, x FOR PEER REVIEW 20 of 26

gained in the previous chapters. The design (Figure 27) was created to apply theoretical knowledge and design requirements for the printing of non-planar surfaces. The result of this creative activity was a conceptual design of a device working in three axes. However, this original concept did not have good features. We created the prototype of the atypical FDM device presented in the article. The existing type of Tripteron construction inspires the design of the device. The main purpose and reason for the creation of this construction are the intention to move in the field of this technology towards the development of equipment, which allows the production of prints created by a non-planar method. We consider Appl. Sci. 2021, 11, 2928 this type of construction to be ideal for many reasons. One of them is the possibility20 of 25 expanding the number of axes and drives in these constructions, which subsequently allows active tilting of the effector. We consider this fact to be one of the unique advantages of the chosen structure. For this reason, a new, conceptual version of the device has been of the chosen structure. For this reason, a new, conceptual version of the device has been created. Due to the continuity and ideology of the RepRap project, the structure’s individ- created. Due to the continuity and ideology of the RepRap project, the structure’s individual ual components were designed so that they can be manufactured using FDM technology. components were designed so that they can be manufactured using FDM technology. The The third step was the procurement of elements characteristic of FDM devices, fasteners third step was the procurement of elements characteristic of FDM devices, fasteners and and subsequent structure implementation. subsequent structure implementation.

Figure 27. Implemented design of atypical equipment of additive manufacturing technology FDM. Figure 27. Implemented design of atypical equipment of additive manufacturing technology FDM. The presented construction of a prototype FDM device is characterised by a combi- The presented construction of a prototype FDM device is characterised by a combination of characteristic elements of several devices connected in series. Due to this fact, nation of characteristic elements of several devices connected in series. Due to this fact, we tried to adapt the operating parameters for the test samples as much as possible to we tried to adapt the operating parameters for the test samples as much as possible to commercially available FDM equipment. The print settings for printing test samples can commerciallybe seen in Table available5. FDM equipment. The print settings for printing test samples can be seen in Table 5. Table 5. Print settings used to print test samples. Table 5. Print settings used to print test samples. Print Settings First Layer Print Settings Print Settings First Layer Print Settings Bed temperature [◦C] 50 Bed temperature [◦C] 70 BedExtruder temperature temperature [°C] [◦C] 50 195 Bed temperature Extruder temperature [°C] [◦C] 70 210 ExtruderExtrusion temperature width [mm][°C] 195 0.45 Extruder temperature Extrusion width [°C] [%] 210 115 ExtrusionLayer width height [mm] [mm] 0.45 0.264 Extrusion Layer width height [%] [%] 115 90 LayerDefault height print speed[mm] [mm/s] 0.264 60Layer First height layer print [%] speed [%]90 35 Infill density [%] 100 Default print speed [mm/s] 60 First layer print speed [%] 35 Infill pattern [–] Grid InfillPerimeter density speed[%] [%] 100 40 InfillNozzle pattern diameter [–] [mm] Grid 0.4 PerimeterFilament speed diameter [%] [mm] 40 1.75 NozzleExtrusion diameter multiplier [mm] [–] 0.4 1.05 Extruder type [–] Bowden Filament diameter [mm] 1.75 Extrusion multiplier [–] 1.05 ExtruderIn terms type of accuracy[–] and Bowden speed of production of this device, it was initially our intention to approach commercially available FDM devices. However, because this is a prototype, the construction of a combination of two devices connected in series, we initially expected and observed a significant deterioration of accuracy. Our next intention was the gradual identification and elimination of these shortcomings. The operating parameters of the device with which it can operate in the current state are identical to the device settings when printing test samples. As already mentioned, due to the selected operating parameter and the device’s design character, we observed the common types of defects (Figure 28). Appl. Sci. 2021, 11, x FOR PEER REVIEW 21 of 26

In terms of accuracy and speed of production of this device, it was initially our intention to approach commercially available FDM devices. However, because this is a prototype, the construction of a combination of two devices connected in series, we initially expected and observed a significant deterioration of accuracy. Our next intention was the gradual identification and elimination of these shortcomings. The operating parameters of the device with which it can operate in the current state are identical to the device settings when printing test samples. As already mentioned, due to the selected operating parameter and the device’s design character, we observed the common types of defects (Figure 28). Among the most problematic were: • Incorrect positioning/position of linear technology and transformation mechanisms. • Oscillations of the system during acceleration and de-acceleration. • Deflection occurring at the end of the arms with the effector. In Figure 28 it can see the selection with several shortcomings caused by the negative effects. As shown in the figure, the main negative of the construction is the poor adhesion of the layers. It causes incorrect adhesion of the material to the printing pad (Figure 28a),

Appl. Sci. 2021, 11, 2928defects in the individual layers (Figure 28b), or sealing of the print head to the model (Fiu- 21 of 25 ure 28c). All these shortcomings can be attributed to the arm system’s undesirable vibration, which proved to be the majority problem in the solution.

Figure 28. ImplementedFigure 28. design Implemented of atypical design equipment of atypical of additive equipment manufacturing of additive technology manufacturing FDM. technology (a) incorrect FDM. adhesion of the material to( thea) incorrect printing adhesion pad; (b) defects of the mate in therial individual to the printing layers; pad; (c) sealing (b) defects of the in print the individual head to the layers; model. (c) sealing of the print head to the model. Among the most problematic were: Minor defects and shortcomings are characteristic of all FDM devices. There are a • Incorrect positioning/position of linear technology and transformation mechanisms. relatively large number of technological and other factors that can affect the final quality • Oscillations of the system during acceleration and de-acceleration. of prints, whether with conventional or atypical FDM equipment. In this case, however, • Deflection occurring at the end of the arms with the effector. it is possible to observe a majority of defects caused by poor adhesion in the layers. These errors are found Inthroughout Figure 28 theit can test see sample the selection at specific with locations. several shortcomings These places causedare charac- by the negative effects. As shown in the figure, the main negative of the construction is the poor adhesion terised by the fact that the individual circumferential perimeters begin and end in them. of the layers. It causes incorrect adhesion of the material to the printing pad (Figure 28a), It is well known that these places are critical in conventional planar printing. For example, defects in the individual layers (Figure 28b), or sealing of the print head to the model samples used for mechanical tensile testing, produced on FDM equipment, accumulate (Fiuure 28c). All these shortcomings can be attributed to the arm system’s undesirable defects, especially in this area, which leads to undesired weakening of the samples at spe- vibration, which proved to be the majority problem in the solution. cific locations. We attribute this undesirable accumulation of defects and their majority Minor defects and shortcomings are characteristic of all FDM devices. There are a representation to the unwanted oscillating system of arms, resulting from the will and relatively large number of technological and other factors that can affect the final quality of minor inaccuracies in the design. This undesired oscillation is reduced in the design by prints, whether with conventional or atypical FDM equipment. In this case, however, it is flexible couplings located between the drive motors and the lead screws, changing the possible to observe a majority of defects caused by poor adhesion in the layers. These errors starting speeds for the perimeter perimeters and installing dampers on the NEMA17 step- are found throughout the test sample at specific locations. These places are characterised per motors. Despite this step, however, undesired oscillations occur. For this reason, in by the fact that the individual circumferential perimeters begin and end in them. It is another areawell of research, known that we thesewill focus places on are changing critical the in conventionaldesign of subsystems planar printing. providing For example, transformationsamples and transmission used for mechanical of motion tensile on individual testing, produced axes of the on device. FDM equipment, accumulate Despitedefects, these visible especially shortcomings, in this area, measures which were leads taken to undesired in Simplify3D weakening to allow of thethe samples at creation of aspecific non-planar locations. sample. We Based attribute on thisit, we undesirable were able accumulationto analyse the ofdevice’s defects current and their majority state and therepresentation impact of its shortcomings to the unwanted on the oscillating quality of system prints. of In arms, Figure resulting 28, we can from see the will and the selectionminor with inaccuraciesseveral defects in thecaused design. by negative This undesired effects. The oscillation main negative is reduced of the in the design by flexible couplings located between the drive motors and the lead screws, changing the starting speeds for the perimeter perimeters and installing dampers on the NEMA17 stepper motors. Despite this step, however, undesired oscillations occur. For this reason, in another area of research, we will focus on changing the design of subsystems providing transformation and transmission of motion on individual axes of the device. Despite these visible shortcomings, measures were taken in Simplify3D to allow the creation of a non-planar sample. Based on it, we were able to analyse the device’s current state and the impact of its shortcomings on the quality of prints. In Figure 28, we can see the selection with several defects caused by negative effects. The main negative of the construction, as shown in Figure 28, the adhesion of the layers is poor. It causes incorrect adhesion of the material to the printing pad (Figure 28a), defects in the individual layers (Figure 28b) or sealing of the print head to the model (Figure 28c). All these shortcomings can be attributed to the arm system’s undesirable vibration, which proved to be the majority problem in the solution. Given the purpose for which the device was created, i.e., the production of non-planar samples, we can say that the device fulfilled its purpose. After modifying the settings, it was possible to partially suppress some negative aspects resulting from the series-connected design’s nature. Given that the change and implementation of corrections negatively affect the equipment’s production time, we recommend a few necessary proposals to streamline production. These proposals include: • Use of more precise transformation mechanisms in the X and Y axes. Appl. Sci. 2021, 11, x FOR PEER REVIEW 22 of 26

construction, as shown in Figure 28, the adhesion of the layers is poor. It causes incorrect adhesion of the material to the printing pad (Figure 28a), defects in the individual layers (Figure 28b) or sealing of the print head to the model (Figure 28c). All these shortcomings can be attributed to the arm system’s undesirable vibration, which proved to be the majority problem in the solution. Given the purpose for which the device was created, i.e., the production of non-planar samples, we can say that the device fulfilled its purpose. After modifying the settings, it was possible to partially suppress some negative aspects resulting from the series-connected design’s nature. Given that the change and implementation of corrections negatively affect the equipment’s production time, we recommend a few necessary proposals to streamline production. These proposals include:

Appl. Sci. 2021, 11, 2928 • Use of more precise transformation mechanisms in the X and Y axes. 22 of 25 • Use of more specific connecting components and mating pins. • Streamlining of drives, which is necessary with the increasing weight of the effector. • Ultimately, after the end of the prototype phase, the replacement of plastic compo- • nents.Use of more specific connecting components and mating pins. • Streamlining of drives, which is necessary with the increasing weight of the effector. The main benefit of using non-planar layers is clear time-saving. According to the • Ultimately, after the end of the prototype phase, the replacement of plastic components. data available from the preparation of a planar and non-planar sample by the same device, a non-planarThe main sample benefit saves of up using to 15% non-planar of time compared layers is clearto a planar time-saving. model. According to the data available from the preparation of a planar and non-planar sample by the same device, 2.8.a Conceptual non-planar Design sample of savesan Alternative up to 15% Printhead of time compared to a planar model. 2.8.As Conceptual mentioned, Design the prototype of an Alternative device Printheadhas relatively high ambitions due to its characteristic shapeAs mentioned, of structure. the However, prototype devicethe just hasified relatively benefit of high the ambitionsnon-planar due method to its character-of lay- eringistic materials shape of can structure. still be However,emphasised. the Severa justifiedl steps benefit can of reduce the non-planar the recycling method of the of layeringplas- tic materialswaste produced can still in be FDM emphasised. production Several by integrating steps can reduce the extrusion the recycling mechanism of the plastic into the waste device’sproduced printhead. in FDM Several production researches by integrating are currently the underway extrusion related mechanism to the into interconnec- the device’s tionprinthead. of these two Several mechanisms researches and are the currently effect of direct underway extrusion related of toplastic the interconnectiongranulation on of thethese prints’ two final mechanisms quality. One and of the these effect researches of direct extrusionis the effort of plasticto create granulation an instrument on the with prints’ its extrusionfinal quality. process One ofprinciple these researches applied to is the the industrial effort to create robotic an arm instrument ABB IRB with 140 its[35]. extrusion This conceptprocess is constantly principle appliedunder development, to the industrial flow robotic analysis arm and ABB heat IRB distribution. 140 [35]. This Simultane- concept is ously,constantly the research under is development, devoted to the flow simula analysistionand of movements heat distribution. and possible Simultaneously, collisions the whenresearch hitting is this devoted device to on the a simulationrobotic arm. of Ba movementssed on the and facts possible and data collisions collected when so far, hitting a conceptualthis device design on a of robotic the effector arm. Basedfor the on devi thece facts created and by data us collectedwas created, so far, as ashown conceptual in Figuredesign 29. of the effector for the device created by us was created, as shown in Figure 29.

FigureFigure 29. 29.IntegrationIntegration and and schematic schematic representation representation of a of plastic a plastic granulate granulate extrud extruderer in a in printhead. a printhead.

As can be seen, when designing the effector itself, we assumed a significant increase in weight due to the mechanism of the print head. For this reason, support can be seen in the effector design in the form of the placement of clamps for the six joints. These are primarily intended to ensure the rigidity of the entire system, even with its increased weight. At the same time, their location is positioned to allow active tilting of the effector during subsequent modifications of the structure. It is inevitable when the device is intended to be used in connection with a non-planar printing method. It is necessary to ensure the printing nozzle’s axis to the printout’s surface. In Figure 29, we can see that the extrusion system is integrated directly into the already designed printhead. However, unlike the common components of the “Hotend” and “Bowden” system, it has a reduced version, similar to the large-capacity device used to process the granulate into a filament. The design of the structure consists of an electric motor (3), which transmits the torque to the feeder screw (8) via a flexible coupling (4). It has a check valve (12) at its end. It is designed to close when the nozzle becomes clogged or Appl. Sci. 2021, 11, x FOR PEER REVIEW 23 of 26

As can be seen, when designing the effector itself, we assumed a significant increase in weight due to the mechanism of the print head. For this reason, support can be seen in the effector design in the form of the placement of clamps for the six joints. These are primarily intended to ensure the rigidity of the entire system, even with its increased weight. At the same time, their location is positioned to allow active tilting of the effector during subsequent modifications of the structure. It is inevitable when the device is intended to be used in connection with a non-planar printing method. It is necessary to ensure the printing nozzle’s axis to the printout’s surface. In Figure 29, we can see that the extrusion system is integrated directly into the already designed printhead. However, unlike the common components of the “Hotend” and “Bowden” system, it has a reduced version, similar to the large-capacity device used Appl. Sci. 2021, 11, 2928to process the granulate into a filament. The design of the structure consists of an electric 23 of 25 motor (3), which transmits the torque to the feeder screw (8) via a flexible coupling (4). It has a check valve (12) at its end. It is designed to close when the nozzle becomes clogged or too high in the injection chamber’s overpressure to prevent the melt from running back into the printhead.too high A in hopper the injection forms chamber’s its other parts overpressure for granulate to prevent (5), passive the melt cooling from running (9) back into placed so as tothe ensure printhead. the correct A hopper course forms of temperatures its other parts during for granulate the extrusion (5), passive of granulate cooling (9) placed or melt. The soheating as to ensuresystem the (10) correct is located course at ofthe temperatures end of the printhead during the and, extrusion unlike ofa com- granulate or melt. monly used Theheater, heating is in systemthe form (10) of is a locatedhoop. It at is the used end due of the to printheadthe need to and, achieve unlike higher a commonly used temperaturesheater, in the is processing in the form of of recycled a hoop. Itplastics. is used The due mechanism to the need tois achieveterminated higher by temperaturesan in airbrush nozzlethe (11), processing the shape of recycledof which plastics. is more suitable The mechanism for non-plan is terminatedar layering by of an mate- airbrush nozzle rial. (11), the shape of which is more suitable for non-planar layering of material. The presentedThe conceptual presented design conceptual (Figure design 30) eliminates (Figure 30) this eliminates device’s this use device’s by eliminat- use by eliminating ing the use ofthe this use device of this and device the granulate and the granulate is processed is processed directly in directly the print in the head. print head.

Figure 30. DetailedFigure 30.descriptionDetailed of description the proposed of the extrusion proposed mechanism. extrusion mechanism.

By integratingBy this integrating system thisinto systemthe device, into thewe device,expect weup to expect a 20% up reduction to a 20% reductionin time in time for for low-capacitylow-capacity production production compared compared to the regular to the recycling regular recycling plastic waste plastic method. waste method. 3. Conclusions 3. Conclusions The article informs about the current state of additive FDM technology, its current The article informs about the current state of additive FDM technology, its current direction and trends in this industry. It presents the characteristic types of structures in direction and trends in this industry. It presents the characteristic types of structures in this industry and analyses the individual elements of their construction in detail. After this industry and analyses the individual elements of their construction in detail. After analysing the particular types of construction and an overview of the current state, the analysing the particular types of construction and an overview of the current state, the work deals with a possible design of the structure or an alternative to current trends in the work deals with a possible design of the structure or an alternative to current trends in field of additive technologies. In the individual chapters, the article presents the gradual the field of additive technologies. In the individual chapters, the article presents the grad- design of the FDM device’s key components and the gradual creation of design subsystems. ual design of the FDM device’s key components and the gradual creation of design sub- It informatively describes designing key features using this technology and the method systems. It informatively describes designing key features using this technology and the and use of FDM devices’ characteristics. The result of creative activity is developing a method and use of FDM devices’ characteristics. The result of creative activity is develop- CAD model of an atypical device of additive technology FDM. This device is modified to ing a CAD modelbe as of adapted an atypical as possible device toof developmentsadditive technology in non-planar FDM. This layering device ofis materialsmodi- by FDM fied to be as technology.adapted as possible It thoroughly to developments describes the in issuesnon-planar addressed layering during of materials the implementation by of the structure. This is based on the shortcomings of the production of key components using FDM technology and the impact of these shortcomings on the equipment’s operation. One of the main deficiencies addressed during applying plastic parts was the angular deformations and misalignment of linear components and transformation mechanisms. The work also presents a solution method by using the finite element method and measurement of negative and positive catches in the production of parts as a suitable solution to eliminate these shortcomings. The work’s conclusion consists of evaluating the design and creating a conceptual design of the printhead with an integrated extrusion system. We assume that this concept will enable streamlining and improving the overall situation of the use and processing of plastic granulate with this technology. It also applies to ordinary users located outside the monitored spectrum of plastic waste producers from this production. The use of new types of constructions for additive manufacturing and the competitiveness of the design in case of further development is one of the presented solutions’ strengths, as with the use of atypical equipment in various areas, such as in the educational process, the Appl. Sci. 2021, 11, 2928 24 of 25

automotive industry or FDM technology. It can figure as an economically available device capable of working in multiple axes, whether for the production of models using planar or non-planar layering of material. Such a device can therefore be considered as a more economically affordable variant of the robotic arms, which uses in connection with FDM technology and production accuracy between 0.1–0.4 mm we consider not available to all consumer groups. As part of another solution after the end of the prototype development phase, we plan to deal with the possibilities of recycling ABS waste in this area, e.g., from the automotive industry. This type of plastic waste has a majority in the automotive industry. In the case of its efficient recycling of used plastic in non-planar printing, we expect a significant improvement in prototypes’ quality and efficiency in this area. We consider the demonstrable improvement of a specific type of prints’ surface quality and mechanical properties as another step towards production efficiency. The integration and use of recycled plastic during construction and the creation of the extrusion system concept can significantly impact reducing the environmental burden produced by a relatively large group of unmapped users in this type of production.

Author Contributions: Conceptualization, J.K.; methodology, J.K.; software, J.K., P.B. and J.T.; validation, Š.G., J.P. and J.H.; formal analysis, J.K.; investigation, J.K.; resources, J.H.; data curation, Š.G.; writing—original draft preparation, J.K.; writing—review and editing, L.K.; visualization, J.T.; supervision, L.K.; project administration, J.K. and Š.G.; funding acquisition, Š.G. All authors have read and agreed to the published version of the manuscript. Funding: This paper is a part of the project VEGA n. 1/0116/20—Research of Application of Structural Topology in a Structure of New Generation of Moulds by 3D Printing Technology. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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