This is meant as an educational tool to demonstrate a grasping mechanism for a robotic arm.  

I used a remix of the “Flexible Grippers” by PrintChallenge but implement with a method for faster actuation so the way in which the compliant fingers grip and release objects could be easily demonstrated.

The assembly is shown in the attached photos.  Note that the rubber band must be strung between the threaded rod and housing prior to starting the remainder of the assembly.  Also pay attention to the orientation of the gripper fingers when slipping them into the retaining mechanisms.