Evaluation of Oak-Specific Consumption, Efficiency, And

applied sciences

Article Evaluation of Oak-Speciﬁc Consumption, Efﬁciency, and Losses from an Aesthetic Veneer Factory

Gneorghe Cosmin Spirchez 1, Aurel Lunguleasa 1,* and Valentina Doina Ciobanu 2

1 Department of Wood Processing and Design of Wood Products, Faculty of Wood Engineering, Transilvania University of Brasov, 1 Universitatii Street, 500068 Brasov, Romania; [email protected] 2 Department of Silviculture and Forest Engineering, Transilvania University of Brasov, 1 Sirul Beethoven Street, 500123 Brasov, Romania; [email protected] * Correspondence: [email protected]

Featured Application: The results obtained in this paper can be applied practically in any aesthetic veneer factory, in this sense with the working methodology and also the values of the losses, efﬁciency, and speciﬁc consumption obtained in the case of oak logs being important.

Abstract: The paper aimed to investigate the losses on the manufacturing flow of an aesthetic veneer factory, in order to know their value and to take measures to limit or use them efficiently. For the analysis, the oak species (Quercus robur) was taken into account, through 25 analyzed logs. Statistical investigation has used the Minitab 18 program, for a 95% confidence interval. Minimum values of losses were obtained for the sectioning-grooming operations with 0.6% and debarking with 4.9%, and the highest values were obtained when cutting veneers with 15.9% and formatting veneers with 22.8%. Based on the losses on the manufacturing flow of 67.3%, the specific consumption index of 2.75 m3/m3 or 1.84 m3/1000 m2 of veneer was determined when the average thickness of the veneers was 0.67 mm. The paper highlights the methodology and the values resulting from the investigation of the technological losses and of the specific consumption from an aesthetic veneer factory. Citation: Spirchez, G.C.; Lunguleasa, A.; Ciobanu, V.D. Evaluation of Oak-Specific Consumption, Efficiency, Keywords: aesthetic veneer; loss; efficiency; oak; specific consumption and Losses from an Aesthetic Veneer Factory. Appl. Sci. 2021, 11, 4300. https://doi.org/10.3390/app11094300 1. Introduction Academic Editor: Giuseppe Lazzara In any log processing factory (be it of timber, chipboard, fiberboards, technical or aesthetic veneer, etc.) it is necessary to know the manufacturing losses for each technological Received: 31 March 2021 operation, but also for the total factory, the main goal being to reduce losses and maximize Accepted: 7 May 2021 the amount of primary product. In the alternative, an additional purpose of knowing these Published: 10 May 2021 losses is to use these losses judiciously, finding the simplest and most economical method of use. In direct correlation with these technological losses, two other global characteristics Publisher’s Note: MDPI stays neutral of the factory are defined, such as the yield of the raw material use (efficiency) and the with regard to jurisdictional claims in specific consumption index, defined with the following two calculation relations: published maps and institutional affil- iations. E = 100 − ∑Li [%] (1)

3 3 Isc = 100 ÷ E [m logs/m veneers] (2) where E is efficiency, in %; L is losses for each technological operation, in %; and I is Copyright: © 2021 by the authors. i sc 3 3 Licensee MDPI, Basel, Switzerland. index of specific consumption, in m /m . This article is an open access article In order to obtain superior efficiency in aesthetic veneers, it is necessary to know in distributed under the terms and detail the technological operations in the factory, so to use all methods of reducing losses conditions of the Creative Commons and obtaining maximum quantities of aesthetic veneers. In the scientific literature, the Attribution (CC BY) license (https:// way of expressing the losses in percentages and the efficiency also in percentages is used. creativecommons.org/licenses/by/ For example, if one knows the value of the total losses of 52% at the factory level, one can 3 4.0/). immediately find an efficiency of 48% and can show that from a quantity of 100 m logs

Appl. Sci. 2021, 11, 4300. https://doi.org/10.3390/app11094300 https://www.mdpi.com/journal/applsci Appl. Sci. 2021, 11, 4300 2 of 14

one will obtain the method of percentage losses 0.48 × 100 = 48 m3 veneer and a specific consumption index of 1/0.48 = 2.082 m3 logs/m3 veneer. Specific to this technology of aesthetic veneers, but especially due to the fact that their price is given in per unit area, is that the specific consumption can be expressed in per unit area of veneer, respectively, per 1000 m2 of veneer. For this expression, a block of 1 m3 of veneer sliced into several veneers of a certain thickness is considered. It turns out that the number of veneers can be easily obtained from this 1-m3 block of veneer, dividing the height of 1000 mm of the block by the thickness of the veneer. Based on these considerations, it can be determined that 1 m3 of veneer could have the following surface: • 1000 m2, when veneer thickness is 1 mm, • 1428 m2, when veneer thickness is 0.7 mm, • 2000 m2, when veneer thickness is 0.5 mm, • 3333 m2 when veneer thickness is 0.3 mm. If one considers the above specific consumer index (2.082 m3 logs/m3 veneer), one will obtain an index of the specific consumption per unit area as follows: • 2.083 m3 logs/1000 m2 veneers, when veneer thickness is 1 mm, • 1.458 m3 logs/1000 m2 veneers, when veneer thickness is 0.7 mm, • 1.041 m3 logs/1000 m2 veneers, when veneer thickness is 0.5 mm, • 0.624 m3 logs/1000 m2 veneers, when veneer thickness is 0.3 mm. These values are given for similar moisture content of logs and veneers; otherwise, the shrinkage of the wood must be taken into account. It is observed that the technology of aesthetic veneers has a series of particularities of expressing the specific consumption, first of all, in relation to the ratio to 1000 m2 of veneer, which depends on the thickness of the veneers (and the thickness of the veneers depends on the wood species; porous and soft wood will have the greater of the veneer thickness). It is also noted that the main solution to reduce specific consumption is to reduce the thickness of aesthetic veneers to 0.2–0.3 mm, an action that is not always possible for all wood species. Based on the above considerations, the following relation of the specific consumption index per unit area can be deduced: 3 2 Isc1 = 100 × t ÷ E [m logs/1000 m veneers] (3)

where Isc1 is specific consumption index per unit area; E is efficiency, in %; and t is thickness of veneers, in mm. The specific consumption of the raw material in the manufacture of aesthetic veneers is dependent on the wood species, being 2.2 m3/m3 for beech and oak and 1.5 m3/m3 for exotic species, mainly depending on the diameter of the logs, because with increasing the diameter of the logs the losses will decrease. The general balance of the use of raw material (logs) in an aesthetic veneer factory that delivers oaks is: veneer 36%, sawdust 4%, log bark 4%, sides 2%, veneer residue 23%, knife residue 24%, and various other losses 8% [1]. Dumitrascu et al. [2] analyzed the influence of oak log defects on the efficiency of log transformation into aesthetic veneers, finding that the diameter and dormant buds have the greatest influence on efficiency. Bernaczyket al. [3] used densified veneers at temperatures of 20 ◦C, 120 ◦C, and 180 ◦C, at a pressure of 1 MPa, for 2 min to obtain plywood. The use of polyvinyl adhesive contributed to a relatively high shear strength value of 2.2 N/mm2, and the use of PPE adhesive contributed to an increase in shear strength to 2.5 N/mm2. Pramreiter et al. [4] used birch veneer with L = 1000 mm, l = 100 mm, and t = 0.55 mm. It was established that the dynamic modulus of elasticity was on average 14% lower than the static modulus of elasticity. Bekhta et al. [5] highlighted the aesthetic properties of different species of thermo-mechanical densified veneer. These properties were highlighted by gloss measurements. The characteristics of the veneers had an influence on the roughness and gloss. Ahmed et al. [6] pointed out that, in veneer drying plants, controllers facing shortcomings act in regulating the optimal veneer temperature. Appl. Sci. 2021, 11, 4300 3 of 14

Kawlerczyk et al. [7] highlighted how the impregnation of birch veneer with a mixture of potassium carbonate and urea affected the properties of fire plywood, shear strength, modulus of elasticity, and modulus of rupture. The veneers were impregnated with aqueous, flame-retardant solution in proportions of 20% and 30%. Impregnation did not affect the modulus of elasticity or the modulus of rupture. Impregnation caused a decrease in the adhesion of the veneers to the plywood with UF adhesive. Buchelt et al. [8] pointed out that, for the production of bonded veneer composites, they are coated with cellulose or layers of paper. The authors described the mechanical properties of such a composite consisting of beech veneer with thickness of 0.35 mm and a layer of cellulose with a thickness of 0.12 mm, glued with PVAc adhesive. Other authors [9] created a guide for obtaining three-layer veneer laminates with a stable shape. A curvature test was performed on plywood from pine veneer sheets (Pinus radiata). Plywood formation temperature and pre-formation moisture content have the greatest influences. Dietzel et al. [10] presented a methodology for determining the properties of elastic material on decorative veneers. Tensile tests were performed at different temperature and moisture content values of the veneers. Fekiak et al. [11] showed that 3D modelling of veneers, as opposed to modelling of plastic or other materials, is limited due to the characteristics of wood. Water and ammonia-water solutions were used. The veneers were tested by immersion in cold water (20 ◦C), hot water (95 ◦C), and a 25% ammonia solution for different times. Experimental results showed that 3D modelling of veneers increased by 66–119% after plasticization with a 25% ammonia solution as opposed to veneers with a moisture content of 7.65%. Franke et al. [12] conducted research on the impregnation of beech veneers with low- and medium-molecular-weight phenol-formaldehyde solutions. Low-molecular-weight phenol- formaldehyde-impregnated veneers showed a higher modelling than high-molecular- weight veneers. Herold and Pfriem [13] showed that, in order to increase the casting performance, the veneer samples were impregnated with furfuryl alcohol for improved plasticization. The degree of plasticization of furfuryl alcohol is comparable to the use of water. Pfriem and Buchelt [14,15] studied the comparison of veneer subjected to mechanical tests, respectively, parallel and perpendicular strengths on fibers. The modulus of elasticity perpendicular to the fibers was smaller than that parallel to the fibres. Dupleix et al. [16] presented the importance of optimal heating temperatures by soaking beech, birch, and spruce. It is necessary to heat the green wood before peeling to improve the peeling process, as well as the quality of the veneer. Zerbst et al. [17] highlighted the importance of tensile and shear tests for veneers under normal conditions but also immersed in water. Kallakas et al. [18] investigated the effects of disposing of different black alder and poplar veneers by replacing birch veneer in plywood with cores of alternately growing species. The results showed that alder and birch plywood have the highest bending strength. The birch veneer had an adhesive consumption of 152 g/m2, while the trembling poplar veneer had an adhesive consumption of 179 g/m2. The low-density wood veneer had a higher consumption of adhesive. Reichel et al. [19] presented the importance of used veneers and cutting speed, but also the importance of veneer preconditioning inside of veneer technology. Gerencser and Bejo [20] presented the importance of water jet cutting as a possible alternative to traditional cutting methods. The width of the veneer decreased as the water jet propagated into the material. Fang et al. [21] presented the modification of the flexibility of the decorative veneer with the help of plastic foil. This method is effective because it widens the application area and the strength of the veneer decreased when its moisture content was higher than 20%. Pramreiter et al. [22] presented the importance of the development of veneer-based wood composites due to the high flexibility of design and mechanical strength compared to solid wood. The study showed the influence of veneer thickness on tensile strength compared to solid wood. Ropes with a thickness of 0.5 mm, 1 mm, and 1.5 mm and thin timber with a thickness of 1.5 mm, 3 mm, and 5 mm were used. From the experimental results it was concluded that the tensile strength was 70% higher than veneer lumber. Appl. Sci. 2021, 11, 4300 4 of 14

Salca et al. [23] presented the properties of plywood made of densified and un-densified veneer. The plywood was made of black alder and birch veneer, using urea formaldehyde (UF). MOE increased with increasing plywood density. The increase in veneer density led to a decrease in MOR. The temperature of 150 ◦C for the densification of the veneer was sufficient to obtain improved plywood properties. Svoboda et al. [24] presented the characteristics of beech and poplar wood plywood, with thicknesses of 6 mm, 10 mm, and 18 mm, when vinyl acetate was used for gluing. The study concluded that the use of carbon fibre and fiberglass led to increased plywood performance. Menezzi et al. [25] presented the evaluation of the potential use of the wood species Sci- zolobium parahyba in the production of laminated veneer lumber LVL. The non-destructive wave test method was used to determine the EdV (dynamic veneer modulus). The authors noted that the higher the EdV values, the higher the mechanical strength values of the LVL. Bekhta et al. [26] analyzed the effect of veneer densification on the change of temperature inside the plywood during the hot-pressing stage. Birch veneer and phenol-formaldehyde resin were used to make the plywood samples. Plywood structures from densified and non-densified veneer layers, with and without adhesive, were investigated. Plywood made of 3, 5, 7, 9, and 11 layers was made in laboratory conditions. It was found that plywood made of densified veneer will reduce the plywood pressing time by 2–29%, depending on the number of layers of veneer. The shear strength values of the densified veneer plywood were twice higher than the standard value of 1 MPa (EN 314-1). From the analysis of the bibliographic studies, we deduced a general conclusion, namely, that, although there are consistent laboratory studies in the field of aesthetic veneers, there are very few studies in situ, respectively, inside some aesthetic veneer factories. There is also a total lack of work in the field of specific consumption of raw materials and losses on the manufacturing flow. That is why this work wanted to analyse the manufacturing losses from an aesthetic veneer factory in order to know their values and to calculate the global, specific consumption indicators of the factory. This study helps the factory management to better coordinate its activity of managing the secondary resources in the factory.

2. Materials and Methods Investigations on losses, efficiency, and specific consumption index were performed at the company LOSAN Romania SRL (Brasov, Romania) on batches of 25 pieces of round oak wood (Quercus robur) at which losses were quantified at each point in the technological flow, respectively, for the following technological operations: log debarking, grooming and sectioning, shaping of logs, cutting of veneers by flat cutting, drying of veneers, and formatting of veneers. The logs were purchased from Romania and Croatia, respectively, from areas as close as possible to the location of the veneer factory. The diameter at the thin end was 40–55 cm and the average length was 3.4 m, with a variation of 2.7–3.6 m. Of the three quality classes, only class B of logs was taken, with a taper less than 1 cm/m, a curvature less than 15%, and a maximum ovality of 8%. Logs were sorted and sectioned according to their length into cut-logs corresponding to the opening length of the planer cutting machines. Additionally, the ends of the defective logs were removed and, on the outside, the traces of logs and gallstones were removed. The percentage losses were determined as the ratio between the volume of material that fell during this operation (the volume of losses, in the form of log ends, sawdust, and other pieces) and the volume of logs taken into work, with the following equation:

Pi = (Vi − Vf) ÷ Vf × 100 [%] (4)

where Pi is the value of losses, in %; Vi is initial volume of the log before the technological 3 sectioning operation, in m ; and Vf is the ﬁnal volume of the hubs, after the sectioning operation, in%. The debarking of the logs, with the analysis of each log, was done on the debarking ramp with a milling machine, after the thermal plasticization treatment of the logs, and Appl. Sci. 2021, 11, x FOR PEER REVIEW 5 of 14

Logs were sorted and sectioned according to their length into cut-logs corresponding to the opening length of the planer cutting machines. Additionally, the ends of the defective logs were removed and, on the outside, the traces of logs and gallstones were removed. The percentage losses were determined as the ratio between the volume of material that fell during this operation (the volume of losses, in the form of log ends, sawdust, and other pieces) and the volume of logs taken into work, with the following equation:

Pi = (Vi − Vf) ÷ Vf × 100 [%] (4)

where Pi is the value of losses, in %; Vi is initial volume of the log before the technological sectioning operation, in m3; and Vf is the final volume of the hubs, after the sectioning Appl. Sci. 2021, 11, 4300 5 of 14 operation, in%. The debarking of the logs, with the analysis of each log, was done on the debarking ramp with a milling machine, after the thermal plasticization treatment of the logs, and meantmeant the the quantification quantification of of the the losses losses in in the the form form of of bark bark or or wood wood waste waste that that diminished diminished thethe initial initial volume volume of of the the log. log. For For this, this, 25 25 logs logs were were taken, taken, finding finding the the volume volume of of wood wood that that waswas lost lost from from each each log. log. In In order order to to obtain obtain the the losses, losses, a apercentage percentage ratio ratio was was made made between between thethe volume volume of of losses losses from from the the logs logs and and the the initial initial volume volume of of the the log log considered, considered, with with the the EquationEquation (4). (4). The The logs logs were were shaped shaped on prisms, on prisms, in order in order to obtain to obtain larger larger quantities quantities of tan- of gentialtangential veneer. veneer. This This operation, operation, performed performed with with a horizontal a horizontal band band saw, saw, resulted resulted in in losses losses ofof longitudinal longitudinal edges edges and and sawdust. sawdust. The The amount amount of of percentage percentage loss loss was was determined determined by by the the samesame relation. relation. The The shaped shaped logs logs were were transformed transformed into into veneer, veneer, resulting resulting in in manufacturing manufacturing residuesresidues in in the the form form of of knife knife residue residue and and undersized undersized veneer veneer remains. remains. The The veneers veneers were were cutcut with with a avertical vertical plane plane cutting cutting machine, machine, fixi fixingng the the prism prism by by vacuum vacuum and and multi-nail multi-nail plate plate (Figure(Figure 1).1).

Figure 1. Plan—vertical cutting of aesthetic veneers: 1—prism; 2—knife; 3—veneer; 4—press bar; Figure 1. Plan—vertical cutting of aesthetic veneers: 1—prism; 2—knife; 3—veneer; 4—press bar; 5—prism5—prism mounting mounting plate; plate; 6—vacuum 6—vacuum prism prism fixi ﬁxing;ng; 7—alternative 7—alternative rectilinear rectilinear vertical vertical movement; movement; 8—zone8—zone of of multi-nail multi-nail prism prism fixing. ﬁxing.

TheThe losses losses by by drying drying the the veneers veneers were were due due to to their their shrinkage shrinkage from from moisture moisture content content ofof over over 30% 30% at at the the time time of of introduction intointo thethe dryer,dryer, up up to to a a moisture moisture content content of of 8% 8% at theat exit of the dryer with belt and nozzles. The volume losses of all veneers obtained from logs the exit of the dryer with belt and nozzles. The volume losses of all veneers obtained from were determined, but the reporting was the same as the previous cases to the initial volume logs were determined, but the reporting was the same as the previous cases to the initial of the log from which the veneers were obtained, with the help of a similar relationship volume of the log from which the veneers were obtained, with the help of a similar rela- with Equation (4). tionship with Equation (4). For the veriﬁcation of the data obtained experimentally, the coefﬁcient of volumetric shrinkage for oak was used from Fibre Saturation Point up to 8%, obtained on 10 specimens of 100 × 20 × 20 mm, extracted from the wood of this oak species and using the principle expressed in Figure2 and the following relation:

Sv(USF-8) = ((Vmax − Vmin) × (FSP − MC8)) ÷ (Vmax × FSP) × 100 [%] (5)

3 where Vmax is the maximum volume of the test piece, before drying, in mm ;Vmin is the ◦ minimum volume of the test piece, after drying in the oven at 105 C, for 12 h; FSP-MC8 is the moisture content difference between ﬁbre saturation point and veneer moisture content after drying of 8%; and FSP is the ﬁbre saturation point (usually 30%), in%. Appl. Sci. 2021, 11, x FOR PEER REVIEW 6 of 14

For the verification of the data obtained experimentally, the coefficient of volumetric shrinkage for oak was used from Fibre Saturation Point up to 8%, obtained on 10 specimens of 100 × 20 × 20 mm, extracted from the wood of this oak species and using the principle expressed in Figure 2 and the following relation:

Sv(USF-8) = ((Vmax − Vmin) × (FSP − MC8)) ÷ (Vmax × FSP) × 100 [%] (5)

where Vmax is the maximum volume of the test piece, before drying, in mm3; Vmin is the minimum volume of the test piece, after drying in the oven at 105 °C, for 12 h; FSP-MC8 is Appl. Sci. 2021, 11, 4300 6 of 14 the moisture content difference between fibre saturation point and veneer moisture content after drying of 8%; and FSP is the fibre saturation point (usually 30%), in%.

Figure 2. Diagram of veneer shrinkage.

The veneers obtained were tangential andand had three quality classesclasses dependingdepending onon thethe admissibility of thethe defectsdefects andand thethe dimensionsdimensions ofof thethe packages,packages, respectively,respectively, 175 175× × 1414 cmcm for thethe firstfirst class,class, 120120 ×× 12 cm for the second class,class, andand 6060 ×× 10 cm for the third class.class. TheThe average thickness of the veneersveneers waswas 0.670.67 mmmm withwith aa standardstandard deviationdeviation ofof ±± 0.06 mm. The calculationcalculation of thethe residuesresidues fromfrom thethe veneerveneer formattingformatting waswas donedone onon allall thethe packagespackages obtained from each log. The packages of 12 veneers were formatted in length and width, the remainsremains resultingresulting fromfrom thethe guillotineguillotine scissorsscissors beingbeing inin thethe formform ofof veneerveneer strips.strips. TheThe reporting of the veneerveneer residuesresidues [[27,28]27,28] waswas donedone asas inin thethe previousprevious casescases toto thethe initialinitial volume ofof eacheach loglog considered,considered, withwith aa similarsimilar relationshiprelationship asas EquationEquation (4).(4). The analysis of the losses on the manufacturingmanufacturing flow flow was first first performed tabularly, after whichwhich itit proceededproceeded to to the the statistical statistical processing processing of of the the results. results. The The individual individual values values of theof the losses losses obtained obtained at eachat each technological technological operation operation were were statistically statistically processed, processed, obtaining obtain- theing arithmeticthe arithmetic mean mean of the of the values values and and their their standard standard deviation. deviation. Based Based on on the the individual individ- losses,ual losses, the sumthe sum of the of totalthe total losses, losses, the percentagethe percentage efficiency, efficiency, and theand index the index of use of ofuse the of raw the materialraw material for obtaining for obtaining aesthetic aesthetic veneers veneers were were obtained. obtained. For the statisticalstatistical processingprocessing of thethe experimentalexperimental values,values, thethe MinitabMinitab 1818 programprogram (Coventry,(Coventry, UnitedUnited Kingdom)Kingdom) waswas used,used, togethertogether withwith itsits interpretationinterpretation graphsgraphs suchsuch asas probability plot, empirical CDF, histogram, and I-MR chart. Through these graphs we probability plot, empirical CDF, histogram, and I-MR chart. Through these graphs we ob- obtained as statistical parameters the average survey and standard deviation, but also other tained as statistical parameters the average survey and standard deviation, but also other parameters of influence, for a 95% confidence interval and, respectively, an error α = 0.05. parameters of influence, for a 95% confidence interval and, respectively, an error α = 0.05. 3. Results 3. Results Results were expressed graphically, on the base of the registered tabular values. Results were expressed graphically, on the base of the registered tabular values. 3.1. Losses When Cutting Logs 3.1. LossesThe Empirical when Cutting Cumulative Logs Distribution Function (CDF) from Figure3, performed to determineThe Empirical log section Cumulative losses, Distribution highlights theFunc fittion of each(CDF) experimental from Figure 3, value performed with the to cumulativedetermine log distribution section losses, curve. highlights It is observed the fit of that each “S experimental curve” is asymptotic value with both the cumu- at the horizontallative distribution line of thecurve. value It is0% observed and at that the “S horizontal curve” is line asymptotic of 100%, both and at the the real horizontal values approachline of the the value empirical 0% and curve, at the thus horizontal demonstrating line of 100%, the normal and the distribution real values of approach values. the empiricalBased curve, on the thus average demonstrating value of the the section normal losses distribution of 0.7%, of thevalues. standard deviation of 0.097%, and of taking over two standard deviations for a confidence interval of 95%, the limiting interval of 0.616–0.894% was obtained. Appl. Sci. 2021, 11, x FOR PEER REVIEW 7 of 14

Appl. Sci. 2021, 11, 4300 7 of 14 Appl. Sci. 2021, 11, x FOR PEER REVIEW 7 of 14 Empirical CDF Normal

Mean 0.7008 100 StDev 0.09731 N25 Empirical CDF 80 Normal

Mean 0.7008 100 StDev 0.09731 60 N25

Percent 40

60 20

Percent 40 0

20 0.5 0.6 0.7 0.8 0.9 1.0 Log sectioning loss

Figure 3.0 Empirical CDF for loss of log sectioning. 0.5 0.6 0.7 0.8 0.9 1.0 Based on the average valueLog of sectioningthe section loss losses of 0.7%, of the standard deviation of 0.097%, and of taking over two standard deviations for a confidence interval of 95%, the FigurelimitingFigure 3. 3.Empirical intervalEmpirical of CDF CDF 0.616–0.894% for for loss loss of of log log was sectioning. sectioning. obtained.

3.2.3.2. LossLossBased onon Debarking Debarkingon the average LogsLogs value of the section losses of 0.7%, of the standard deviation of 0.097%,TheThe and resultsresults of taking forfor thisthis over operation operation two standard withwith losses, losses, deviations respectively,respectively, for a confidence the the debarking debarking interval operation operation of 95%, on theon thethelimiting proper proper interval ramp, ramp, focusedof focused 0.616–0.894% on on the the data datawas collected obtained.collected in in the the corresponding corresponding tables, tables, are are visible visible in in FigureFigure4 .4. An An average average loss loss of of 4.9% 4.9% was was observed, observed, with with a a standard standard deviation deviation of of 0.18%, 0.18%, for for thosethose3.2. Loss 25 25 lots onlots Debarking of of logs logs examined. examined. Logs ThisThis valuevalue isis signiﬁcant,significant, eveneven ifif itit seemsseems toto bebe veryvery small.small. TheThe smallsmallThe results valuevalue of offor this this this peeling peeling operation lossloss with is is given given losses, by by the respectively,the relatively relatively the small small debarking thickness thickness operation ofof the the oak oak on barkbarkthe proper ( Quercus(Quercus ramp, robur robur focused)) of of 4–5 4–5 mmon mm the and and data also also collected by by the the diameter diameterin the corresponding of of the the logs logs used, used, tables, with with are a a rangevisible range of ofin 52–8752–87Figure cm cm 4. [ 1[1].An]. average loss of 4.9% was observed, with a standard deviation of 0.18%, for those 25 lots of logs examined. This value is significant, even if it seems to be very small. The small value of this peeling loss is given by the relatively small thickness of the oak bark (Quercus robur) of Probability4–5 mm and Plot also of by log the debarking diameter loss of the logs used, with a range of 52–87 cm [1]. Normal - 95% CI 99 Mean 4.959 StDev 0.1859 95 N25 Probability Plot of log debarking loss AD 0.449 90 Normal - 95% CI P-Value 0.255 99 80 Mean 4.959 70 StDev 0.1859 N25 6095 AD 0.449 50 90 P-Value 0.255 40 Percent 3080 2070 60 10 50 405 Percent 30 20 1 4.50 4.75 5.00 5.25 5.50 10 Log debarking loss % 5

Figure 4.1 Loss when peeling logs. 4.50 4.75 5.00 5.25 5.50 Log debarking loss %

Appl. Sci. 2021, 11, x FOR PEER REVIEW 8 of 14 Appl. Sci. 2021, 11, 4300 8 of 14

Figure 4. Loss when peeling logs. The graph from Figure4 was obtained for a 95% confidence interval (respectively, for an errorTheα graph= 0.05) from and Figure a normal 4 was distribution, obtained for observable a 95% confidence by framing interval all values (respectively, between thefor twoan error extreme α = 0.05) limits. and The a normal two parameters distribution, of observable the graph, by respectively, framing all thevalues Anderson– between Darlingthe two (AD)extreme and limits.p-value, The were two interpretedparameters together,of the graph, because respectively, the used the the Anderson–Dar- experimental dataling to(AD) determine and p-value, if null were hypothesis interpreted was together, rejected or beca alternativeuse the used hypothesis the experimental was accepted data (respectively,to determine ifif itnull falls hypothesis within a normalwas rejected distribution). or alternative It was hypothesis observed was that accepted the p-value (re- ofspectively, 0.225 was if higherit falls within than the a normal error value distribution). of 0.05, whichIt was observed confirmed that the the normality p-value of of 0.225 the distribution.was higher than By knowing the error thevalue value of 0.05, of the whic standardh confirmed deviation the normality of 0.18 and of the distribution. confidence intervalBy knowing of 95% the (corresponding value of the standard to two deviation standard of deviations), 0.18 and the the confidence interval interval of the values’ of 95% variation(corresponding (4.589–5.329)% to two standard was also deviations), determined. the Similar interval values of the werevalues’ obtained variation by (4.589– other authors5.329)% [ 1was,2]. also determined. Similar values were obtained by other authors [1,2].

3.3.3.3. Losses Losses in in the the Grooming-Sectioning Grooming-Sectioning Operation Operation of of the the Logs Logs TheThe probability probability plotplot diagram diagram for for cleaning cleaning and and sectioning sectioning (Figure (Figure5 )5) shows shows that that all all experimentalexperimental valuesvalues fellfell within within the the extreme extreme limits, limits, i.e., i.e., the the normality normality of of the the distribution distribution withoutwithout aberrant aberrant values values was was conﬁrmed. confirmed. Moreover,Moreover, basedbased onon thethe same same graph graph and and for for a a 95%95% conﬁdence confidence interval, interval, the the limits limits of of the the lower lower and and upper upper values values of of variation variation of of losses losses for for grooming-sectioninggrooming-sectioning were were determined, determined, respectively, respectively, 0.860–1.203%. 0.860–1.203%.

Probability Plot Normal - 95% CI

99 Mean 1.033 StDev 0.08596 95 N25 AD 0.753 90 P-Value 0.043

80 70 60 50 40 Percent 30 20

10 5

1 0.7 0.8 0.9 1.0 1.1 1.2 1.3 Log cleaning and sectioning

FigureFigure 5. 5.Probability Probability plot plot for for log log cleaning cleaning and and sectioning. sectioning.

3.4.3.4. Losses Losses from from Log Log Shaping Shaping (Trimming) (Trimming) TheThe EmpiricalEmpirical Cumulative Dist Distributionribution Function Function (CDF) (CDF) for for log log trimming trimming loss loss in Fig- in Figureure 6 6is is a acurve curve in in the the shape shape of the letterletter “S”“S” andand representsrepresents the the cumulative cumulative percentage percentage proportionproportion of of each each value value in in the the total total values, values, given given that that the the actual actual values values of of losses losses were were foundfound on on the the Ox Ox axis. axis. To To obtain obtain this this curve, curve, the the first first percentage percentage ratio ratio between between the the first first value value andand the the total total number number of of values values on on the the vertical vertical axis axis were were ordered, ordered, and and the the second second percentage percent- ratioage ratio was addedwas added to the to first the and first so and on untilso on the unti lastl the ratio, last theratio, percentage the percentage at which at thewhich value the ofvalue 100% of was 100% obtained. was obtained. The proximity The proximity of the real of values the real to thevalues empirical to the curveempirical was curve observed was andobserved the extreme and the values extreme of the values losses of by the shaping losses by were shaping found were for 95% found confidence for 95% intervalconfidence of 7965–10,347%.interval of 7965–10,347%. Appl. Sci. 2021, 11, 4300 9 of 14 Appl.Appl. Sci. Sci. 2021 2021, ,11 11, ,x x FOR FOR PEER PEER REVIEW REVIEW 99 ofof 1414

EmpiricalEmpirical CDFCDF ofof LogLog trimmingtrimming NormalNormal

MeanMean 9.156 9.156 100100 StDevStDev 0.5955 0.5955 N25N25

8080

6060 Percent Percent 4040

2020

8.08.0 8.58.5 9.09.0 9.59.5 10.010.0 10.510.5 LogLog trimmingtrimming

FigureFigureFigure 6. 6.6.Empirical EmpiricalEmpirical CDF CDFCDF for forfor loglog log trimming trimmingtrimming loss. loss.loss.

3.5.3.5.3.5. Losses LossesLosses from fromfrom Veneer VeneerVeneer Cutting CuttingCutting TheTheThe framing framingframing of ofof the thethe values valuesvalues of ofof the thethe losses losseslosses in inin the thethe form formform of ofof a aa knife knifeknife residue residueresidue from fromfrom the thethe flat flatflat cuttingcuttingcutting of ofof the thethe veneersveneers betweenbetween the thethe two two controlcontrol limitslimits limits (Figure(Figure (Figure 7)77)) showedshowed thethe the normalnormal normal distri-distri- dis- tributionbutionbution ofof of thesethese these values.values. values. Also,Also, Also, thethe the valuesvalues values ofof of thethe the Anderson–DarlingAnderson–Darling Anderson–Darling coefficientcoefficient coefficient (AD)(AD) (AD) andand and pp-- pValue-ValueValue confirmedconfirmed confirmed thethe normalnormal distribution distribution ofof va values.values.lues. Based Based onon thisthisthis diagram, diagram,diagram, the thethe values valuesvalues of ofof thethethe loss lossloss values valuesvalues range rangerange of ofof 13.76–18.22% 13.713.76–18.22%6–18.22% for forfor 95% 95%95% confidence confidenceconfidence interval inteintervalrval (plus/minus (plus/minus(plus/minus 2 22 standard standardstandard deviations)deviations)deviations) were werewere found. found.found. This ThisThis loss lossloss was waswas quite quitequite high, high,high, being beingbeing ranked rankedranked second secondsecond after theafterafter losses thethe losses fromlosses veneerfromfrom veneerveneer formatting. formatting.formatting.

ProbabilityProbability PlotPlot ofof KnifeKnife restrest NormalNormal -- 95%95% CICI

9999 MeanMean 15.99 15.99 StDevStDev 1.615 1.615 N25 9595 N25 ADAD 0.667 0.667 9090 P-ValueP-Value 0.072 0.072

8080 7070 6060 5050 4040 Percent Percent 3030 2020

1010

11 1010 1212 1414 1616 1818 2020 2222 KnifeKnife restrest %%

Figure 7. Probability plot of knife rest from flat cutting of aesthetic veneers. FigureFigure 7.7.Probability Probability plotplot ofof knifeknife restrest fromfrom ﬂat flat cutting cutting of of aesthetic aesthetic veneers. veneers.

Appl.Appl. Sci. Sci.2021 2021, 11, 11, 4300, x FOR PEER REVIEW 1010 ofof 14 14

3.6.3.6. Losses Losses from from Veneer Veneer Drying Drying TheThe CumulativeCumulative Distribution Function Function (CDF) (CDF) curve curve of ofthe the drying drying of the of theveneers veneers (Fig- (Figureure 8) 8resulting) resulting from from the the 25 25 logs logs examined, examined, by by approximating thethe realreal pointspoints to to the the em- em- piricalpirical values, values, had had a a normal normal distribution distribution of of values. values. Based Based on on the the two two statistical statistical parameters parameters ofof trend trend (arithmetic (arithmetic mean) mean) and and spread spread (standard (standard deviation), deviation), as as well well as as by by establishing establishing a a conﬁdenceconfidence interval interval of of 95%, 95%, a range a range of variation of variat ofion the of values the values of drying of lossesdrying (6.088–9.288%) losses (6.088– was9.288%) obtained. was obtained.

Empirical CDF of Drying loss Normal

Mean 7.688 100 StDev 0.8001 N25

Percent 40

6 7 8 9 10 Drying loss %

FigureFigure 8. 8.Empirical Empirical CDF CDF of of loss loss on on veneer veneer drying. drying.

BasedBased on on the the value value of of the the volume volume shrinkage shrinkage coefficient coefficient on on the the moisture moisture content content range range 8–30%8–30% that that was was determined determined with with Equation Equation (5), (5), a value a value of 7.61% of 7.61% was was obtained, obtained, very very little lesslittle thanless thethan one the obtained one obtained experimentally, experimentally, but which but fellwhich within fell thewithin limits the imposed limits imposed by ±5%. by ±5%. 3.7. Losses from Veneer Package Formatting 3.7. FigureLosses 9from shows Veneer the Package probability Formatting plot curve for expressing losses from veneer formatting. The averageFigure 9 value shows of the 22.88% probability was the plot largest curve of for the expressing total losses losses from thefrom manufacture veneer format- of aestheticting. The oak average veneers. value The of normal22.88% distributionwas the larg ofest the of the values total of losses these from losses the was manufacture observed byof framingaesthetic theoak values veneers. between The normal the two distribu limitstion on of the the diagram, values of but these especially losses was by the ob- correlationserved by framing between the the values Anderson–Darling between the two coefficient limits on (AD the = diagram, 0.264), p -valuebut especially of 0.667, by and the thecorrelation error α = between 0.05. Based the onAnderson–Darling the mean value and coefficient the standard (AD deviation,= 0.264), p-value the loss of interval 0.667, and of (17.87–27.89%)the error α = 0.05. was Based obtained on forthe amean 95% confidencevalue and the interval. standard deviation, the loss interval of (17.87–27.89%) was obtained for a 95% confidence interval. Appl. Sci. 2021, 11, 4300 11 of 14 Appl. Sci. 2021,, 11,, xx FORFOR PEERPEER REVIEWREVIEW 11 of 14

Probability Plot of Formatting loss Normal - 95% CI

9999 Mean 22.88 StDevStDev 2.509 2.509 N25 9595 N25 AD 0.264 9090 P-Value 0.667

8080 7070 6060 5050 40 Percent Percent 3030 2020

1010 55

11 15.015.0 17.517.5 20.0 22.5 25.0 27.5 30.0 32.5 Formatting loss

Figure 9. Probability plot for veneer formatting loss. FigureFigure 9. 9.Probability Probability plot plot for for veneer veneer formatting formatting loss. loss.

3.8.3.8. Total Total Losses Losses BasedBased on on the the averagesaverages obtainedobtained for each each te technologicalchnological operation, operation, but but also also on on the the in- individualdividual values values of of the the 25 25 logs logs taken taken into into acco accountunt at each at each loss, loss, the total the total technological technological losses losseswere werefound found by summation by summation in the in form the formof 25 ofva 25lueslues values thatthat werewere that were statisticallystatistically statistically interpretedinterpreted interpreted usingusing usingthethe histogramhistogram the histogram inin FigureFigure in Figure 10.10. TheThe 10 normalnormal. The normal distribudistribu distributiontiontion ofof valuesvalues of waswas values observedobserved was observed and,and, basedbased and, onon basedthethe averageaverage on the averageandand thethe andstandardstandard the standard deviationdeviation deviation expresseexpresse expressedd in this histogram, in this histogram, the variation the variation interval intervalof 60.41–66.99% of 60.41–66.99% was found. was found.

Histogram of Total loss Normal

Mean 63.70 6 StDevStDev 1.645 1.645 N25

3 Frequency Frequency

0 60 61 62 63 64 65 66 67 Total loss %

FigureFigure 10. 10.Histogram Histogram of of veneer veneer total total loss. loss.

Individual-MovingIndividual-MovingIndividual-Moving Range RangeRange (I-MR) (I-MR)(I-MR) forforfor total total lossloss (Figure(Figure (Figure 11) 11)11 ) isis is individuatedindividuated individuated byby by twotwo two di-di- diagrams,agrams, the the first ﬁrst for for individual valuesvalues andand thethethe second secondsecondfor forfor moving movingmoving range. range.range. These TheseThese control controlcontrol diagramsdiagrams show show us us that that the the technological technological process process of of making making aesthetic aestheticaesthetic veneers veneersveneers was waswas under underunder Appl. Sci. 2021, 11, 4300 12 of 14 Appl. Sci. 2021, 11, x FOR PEER REVIEW 12 of 14

controlcontrol because because all all the the values values were were arranged arranged between between the the two two control control limits, limits, respectively, respectively, LCLLCL (low (low control control limit) limit) and and UCL UCL (upper (upper control control limit). limit). The The control control limits limits in in this this case case (both (both diagrams)diagrams) were were taken taken for for a a probability probability of of occurrence occurrence of of values values of of approximately approximately 99.97%, 99.97%, respectively,respectively, for for a a range range of of plus/minus plus/minus 3 3 standard standard deviations. deviations. The The second second diagram diagram was was mademade by by movingmoving thethe firstfirst interval so so that that the the lower lower limit limit (LCL) (LCL) was was equal equal to zero. to zero. For Forthis, this,the value the value of each of each loss losswas wassubtracted subtracted from from the average the average of the of values the values (first diagram (first diagram in Fig- inure Figure 9), thus9), thusobtaining obtaining another another 25 values, 25 values, closer closer to zero to if zero the ifdifference the difference was small was smallor further or furtheraway from away zero from if zerothe difference if the difference was larger. was larger.A new A average new average of values of valuesof 1.911% of 1.911% and an andupper an upperlimit of limit 6.243% of 6.243%were also were obtained. also obtained. These values These were values confirmed were confirmed by other byresearch- other researchersers [9,14]. [9,14].

I-MR Chart of Total loss

70.0 UCL=68.78 67.5

65.0 _ X=63.70 62.5 Individual Value Individual 60.0 LCL=58.61 1 3 5 7 9 11 13 15 17 19 21 23 25 Log number

UCL=6.243 6.0

4.5

3.0 __ MR=1.911 Moving Range 1.5

0.0 LCL=0 1 3 5 7 9 11 13 15 17 19 21 23 25 Log number

FigureFigure 11. 11.I-MR I-MR chart chart for for total total loss. loss.

FollowingFollowing the the in in situ situ analysis analysis of of the the manufacturing manufacturing losses losses in in the the aesthetic aesthetic oak oak veneer veneer factory,factory, a a total total loss loss of of 63.7% 63.7% was was obtained. obtained. Based Based on on this, this, a a percentage percentage efficiency efficiency of of 36.3% 36.3% waswas determined determined with with the the help help of of Equation Equation (1) (1) and, and, with with the the help help of of Equation Equation (2), (2), a a specific specific consumptionconsumption index index of of 2.754 2.754 m m3 logs/m3 logs/m33veneers veneers waswas alsoalso obtained.obtained. If If we we take take into into account account thethe average average thickness thickness of of oak oak veneers veneers of of 0.67 0.67 mm mm at at the the delivery delivery moisture moisture content content of of 8%, 8%, a a specificspecific consumption consumption index index per per unit unit area area was was obtained obtained of of 1.845 1.845 m m3 logs/10003 logs/1000 m m2 2veneers. veneers. BasedBased on on the the data data from from this this research, research, respectively, respectively, from from the the losses losses obtained obtained in in the the form form of of veneer,veneer, the the management management staff staff of of the the veneer veneer factory factory designed designed and and dimensioned dimensioned a pelletizing a pelletiz- lineing ofline the of veneer the veneer residues, residues, thus increasingthus increasing the turnover the turnover of the of factory the factory by about by about 15%. 15%.

4.4. Conclusions Conclusions ThroughThrough methodology, methodology, results,results, and statistical statistical interpretation, interpretation, the the paper paper highlights highlights the thedetermination determination of ofthe the values values of ofmanufacturing manufacturing losses losses in inorder order to tofind find ways ways of ofsuperior superior re- recoverycovery and and re-use. re-use. The The efficiency efficiency values for thethe batchbatch ofof 2525 oakoak logslogs studied studied were were between between 1%1% for for the the sectioning sectioning operation operation and and 22.8% 22.8% for for the the veneer veneer formatting formatting operation. operation. A A total total loss loss 3 2 ofof 63.7% 63.7% was was obtained, obtained, as as well well as as a specifica specific consumption consumption index index of of 1.84 1.84 m mlog/10003 log/1000 m m2 3 3 veneerveneer or or 2.754 2.754 mm3 logs/mlogs/m3 veneers.veneers. The The resulting resulting values values of the of thelosses losses obtained obtained on the on man- the manufacturingufacturing flow flow of ofthe the aesthetic aesthetic oak oak veneer veneerss and and based based on MinitabMinitab statisticalstatistical program program helped the factory management to keep them under control and/or to find methods of their helped the factory management to keep them under control and/or to find methods of superior capitalization, and also to be able to correctly organize the activity of supplying their superior capitalization, and also to be able to correctly organize the activity of sup- the factory with logs. plying the factory with logs. Appl. Sci. 2021, 11, 4300 13 of 14

Author Contributions: Conceptualization, A.L. and G.C.S.; methodology, G.C.S.; software, A.L.; formal analysis, V.D.C.; investigation, V.D.C.; writing—original draft preparation, A.L.; writing— review and editing, A.L.; visualization, A.L.; supervision, V.D.C. and G.C.S. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: The data presented in this study are available on request from the corresponding author. Acknowledgments: We would like to thank the Transilvania University of Brasov and the Losan Ro- mania SRL Company, especially Eng. Ciprian Morosanu, for all the support provided in conducting the research and drafting the paper. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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