Multi -Disciplinary Senior Design Conference Kate Gleason College of Engineering Rochester Institute of Technology Rochester, New York 14623 Project Number: 09226 COMPOSITE FILAMENT WINDING MACHINE Christofer Brayton /Electrical Engineer Tiago Santos /Mechanical Engineer Daniel Weimann/Mechanical Engineer Shijo George/Project Lead Alexander Sandy/Chief Engineer I. ABSTRACT revolution (i.e. a cylindrical shape will produce tubing) Composite tubing is known for its high strength and Feed Eye – guides fiber to be laid onto mandrel from lightweight characteristics, but also for its high cost. resin bath and creel The goal of many SAE teams is to implement composite materials into vehicle design without vastly Fiber Orientation Angle – angle at which fibers are increasing cost. RIT does not have the capability to laid onto the mandrel, correlates to physical develop composite tubing on its own, but could benefit characteristics of product (i.e. tensile strength, from the use of such materials. The goal of this project compression strength, etc.) is to develop a low cost, first generation filament winding machine which produces simple composite Fiber Volume Fraction – ratio of volume of fiber to tubing. With this platform as a stepping stone, future volume or resin Senior Design teams can improve upon the design and Programming Table – table generated that maps out increase the scale and scope of tubular composite steps for stepper motors to travel in order to achieve manufacturing. Learning more about composite certain fiber orientation angles at varying speeds materials and design, this project has an end goal of having a machine that can produce plastic reinforced III. BACKGROUND tubing at or near raw material cost. Filament Winding is a process through which fibers II. NOMENCLATURE are wrapped around a spinning body, known as a mandrel . The fibers are held to each other by an Resin – adhesive/polymer matrix that holds fibers adhesive resin or epoxy , known as the matrix together material . The fibers are “impregnated” with this material in a resin bath , guided by a feed eye , before Impregnation – the process of wetting fibers with resin being laid onto the mandrel. The fibers and matrix to a desirable level (volume fraction, V ) which is f material are cured over time or with heat and the related to product quality finished part is removed from the mandrel. The quality Creel – spool-like object that holds fibers and characteristics of the part are determined by many aspects of the process including type of fiber and resin, Resin Bath – container filled with resin, used to tension in the fiber, ratio of fiber to resin volume impregnate fibers (fiber volume fraction ), and the angle at which fiber Mandrel – object over which the fiber is wrapped to is laid ( fiber orientation angle ). form different products depending on surface of Copyright © 2009 Rochester Institute of Technology Donated from Dr. Hany Ghoniem, the team worked located within the bath and their shafts. The issues with a Craftsman Mk. 1 6-inch lathe because its basic with this design were that we had little control over the functions are the foundation for simple 2 axis filament final tension value as well as little to no adjustability winding. The rotating headstock controls the mandrel once the machine was built. while the rack and geared tool carriage guide the fiber Another method we considered was using rubber as it’s laid. The fiber orientation angle that determines bushings to provide a resistance to the pull of fiber the characteristics of the finish part can be determined from the spool. The first iteration of this design was by the following formula: to simply use a cylindrical rubber bushing to take up the clearance between the shaft diameter and the inner diameter of the spool. While this method is certainly capable of providing the required resistance it leaves little room for adjustability. The subsequent second iteration of this design used tapered rubber stoppers. where, θ is the fiber orientation angle; N m is the These rubber stoppers were bored to the shaft diameter rotational speed of the mandrel (lathe headstock); and and fit to the spool. Furthermore with the addition of Vc is the translation speed of the feed eye (lathe a threaded rod as the shaft itself it provided an avenue carriage) for improved adjustability by using a wing nut. By tightening or loosening the wing nut the tension can be Throughout the design process, mini teams were changed. created to separate aspects of the machine in order to The other major design we studied was the use of an better focus concept generation, design, build, and test. electrical motor or brake to effectively take up the The creel/tension team developed methods to hold the slack and provide resistance to the pulling motion and spool of fiber and provide tension to the fiber being therefore impart tension into the fiber. We began with laid. The mandrel team designed both the mandrel looking at an electromagnetic brake or clutch, the itself (in relation to how it would mount onto the prices associated with these devices and their required lathe) and possible ways to remove the finished part controls was too high to be considered a good from the mandrel at the end of the process. The solution. The next iteration was an electric motor on impregnation system team developed methods to best the spool shaft itself. At the time this solution was fill the fiber with resin. The motors/control team also outside the budget. The other issue with using an researched the best motors to drive the system and electrically controlled system as opposed to a purely effective methods in controlling the position and mechanical system is of course the control structure. speeds of both the mandrel and feed eye in order to To have a properly operating system their needs to be accurately wind a part. feedback from some type of tension sensor. This will be discussed further in the future design IV. PROCESS considerations. With these possible designs choices in mind we Creel/Tension selected the tapered rubber bushings/stoppers. We felt that this method provided the least amount of Overview questions from an adjustability and implementation In order to properly wind the fiber onto the mandrel an perspective. Coupled with the relative low cost amount of tension varying from 1-10 lbs is called for. comparatively this method was chosen over the others. This amount of tension ensures that there is no slack in To begin the design of the support structure that with the system and that you have a consistent wind. To the spool and tension comprises the creel we need to ensure this tension we looked at various approaches to look at the requirements of the system. To ensure the the problem. Some of the variety of solutions that we fibers receive no damage in the process while the looked at included a variable spring rate rotary carriage moves it is suggested in the ASM Composites tensioner, using a torturous path, using rubber Handbook that the angle of the fiber from the spool to bushings for resistance, as well as using a motor to the resin bath not exceed 20 degrees [1]. With the take up the slack. relative location of the resin bath and mandrel known it was a relatively simple process of using basic Concepts trigonometry to determine the required location of the Initially we looked at a variable spring rate tensioner spool. from Fenner Drives. While this device was more than For the structure itself the design began with mounting capable of applying tension through a pulley it pieces of 2”x1/8” aluminum with a support piece in provided too much tension, approximately 30 lbs. place to assist in preventing bending towards the Along with too much tension there were also concerns mandrel. While this system worked well in bending with positioning within the system as it would have towards the mandrel, due to a miscalculation the needed to be mounted in line. design showed instability in side to side motion. To The method of torturous path depended on the use of remedy this issue the pieces were remade from 1” L friction between the rolling surface of the rollers P09226 Page 2 of 8 stock of 1/16” thickness. Then installed this system There are multiple options for part removal from the was adequate. mandrel that fall into 2 categories: (1) mandrel deformation or (2) mandrel lubrication (used in conjunction with deformation). (1) Mandrel Deformation relates to the material properties of the mandrel. Foams and other dissolvable materials (such as Aquacore) have the positive attribute of being removable but also carrying negative attributes of being both brittle and carrying poor surface finishes. The combination of the tension of the fiber and rotation of the mandrel can produce unwanted nicks and recesses in the mandrel that will be reflected in the finished part. Wax and other heat released materials are more promising and further testing can be done to see their responses and reactions in the process. Wax mandrels bring the positive effect of melting away during the oven curing process. One Figure 4.1 Table with flat stock creel structure concern would be the application of heated resin to the wax mandrel, which may produce unnecessary deformation and compliance. Metals, such as Aluminum and Steel, provide smooth surface finishes and can be machined for tighter tolerance limits. Another aspect of metal mandrels is metal expansion under heat. Further testing must be completed to see if the change in area is significant enough for finished part removal. (2) Mandrel lubrication pertains more specifically to metal mandrel materials. Heated activated release agents and lubrication can be applied to the mandrel prior to the winding process.