This week on the SCP Actuator team we focused on creating a more suitable setup for the coil insertion process. Last week’s insertion process resulted in uneven coils; therefore, Wenzhong and I suspected that this was due to the fact that the thread was not held in the same plane as the rotation of the motor. As a result we have 3D printed a press fit attachment for the stepper motor that allows the paper clip to attach directly to the center. In addition, we coded the stepper motor to run at 200 RPM, which was the cited RPM requirement for 1-ply actuator formation in Fabrication Parameters and Performance Relationship of Twisted and Coiled Polymer Muscles. Furthermore, in order to reach the annealing temperature, we ran a simulation using Simulink and found that for standing air if we followed 3s on, 7s off at 0.75V, we would reach 150 degrees C. Due to varying reported relationships between the number of twists inserted and the weight used, we have decided that the best plan of approach will be to run a series of tests holding the length of the thread constant, the RPM constant, and altering the weight used. Several variations of these parameters may be performed in order to fully characterize the twist insertion process. An important relationship that we discovered this week is the relationship between the weight used for coil insertion and the thread length, or rather lack of relationship. It seems as though the 50 gram weight should be suitable, according to Yip. However, for the same material, the Fabrication article states 125 grams as the suitable weight. Therefore, this discrepancy has resulted in problems in recreating the actuators.

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