Development of fully automated manufacturing equipment for conductive Nylon thread actuators and evaluation of their characteristics

Abstract

The nylon thread actuator, a type of super coiled polymer actuator, proposed by Haines et al. in 2014 has many useful advantages, including its relatively high power, lightweight, and low cost. Although the fabrication process seems simple, to fabricate such actuators, we must do so by hand because the finished products are not currently for sale. Thus, we are developing fully automated manufacturing equipment for overtwisted-type actuators using Ag-coated sewing machine nylon threads. In this study, we depict the details of a prototype machine and the basic specifications of conductive nylon thread actuators through experiments. This machine has three stepper motors. We found the maximum recommended drive speed of each spindle: the twist spindle with the drive is approximately 32.8 [rad/s] (313 [rpm]), the feeder speed is 37 [mm/min], and the winding speed is 61 [mm/min]. This condition provides steady overtwisted patterns with simply open-loop control, and the measured tension is approximately 20-30 [cN] during twisting, whereas it is approximately 40-50 [cN] during annealing. These processes run continuously for a single long thread; thus, the overall throughput is equal to the winding speed, which is determined by both the desired annealing tension and time.

Keywords

• super coiled polymer (scp) actuator
• conductive nylon thread
• thread twisting machine
• annealing