Mechanical Engineering Department
BS in Mechanical Engineering
The aim of this project was to develop a more automated process for drawing and twisting of graphene fibers than was currently in place. This was implemented by having two chemical baths with variable speed rollers at either end, and intermediate roller to spool fiber between stages, and a twisting cylinder with integral spool to twist the fiber as it is collected. The goal was to have this first iteration deliver a working prototype, however due to manufacturing delays and timing constraints, that will be missed. A second follow-on project would be able to continue the work presented here and fulfil the stated aims of the project. The bulk of the structure is fabricated from PVC pieces waterjet cut from a large sheet. This allowed for quick manufacture of most pieces in the design. From there, some secondary machining was done to add mounting and fastening locations. PVC pieces were attached to one another primarily through the use of #8-32 screws with washers and a brass threaded insert. Due to PVC being a soft material, tapping threads into it directly was avoided. The baths were sealed mostly with an automotive gasket compound to permanently seal one half, while one wall was sealed with a silicon gasket laser cut from a sheet. This makes the bath wall removable for maintenance. Two baths were made to allow multiple stages of drawing or one coagulation stage immediately followed by a drawing stage. From the drawing, the fiber advances to the auxiliary roller. The range of speeds required to get desired properties at all stages did not permit the fiber to go from coagulation to drawing to twisting in one process, therefore following the drawing bath, it is wound on to the auxiliary roller. After the drawing process is finished, the fiber can be pulled from the auxiliary roller into the twisting mechanism, running at a lower speed so as to give the requisite number of turns per length of fiber to yield the optimal fiber twist angle. The twisting mechanism is a PVC cylinder supported on horizontal rods and driven by a motor mounted beneath the cylinder and connected via a plastic belt. The cylinder, motor, and support rods are encased in a box with one face open to allow the fiber into the cylinder. Inside the cylinder is a spinning rod mounted across the diameter that collects the fiber as it is twisted. The aim of the project called for a quick-release mechanism so that the rod can be removed quickly for storage of the fiber or other testing steps. All of the motion is powered by small 5V DC motors that go through a 20:1 worm gear reduction. This increases the torque while decreasing the speed from roughly 10,000 RPM to more useful ranges. The motors are powered through a NPN power transistor with the logic being controlled by an Arduino Nano that takes in an analog voltage and converts it to a PWM waveform to control the motor duty cycle. In total, the project came in under budget, using 84.01% of the $1500 allocated for the project. A third of this cost came from the need to expedite the waterjet cutting by going to a third-party outside of the campus community. Had on campus resources been successfully utilized, the total cost would have been closer to the $925.38 estimate first presented.