Getting from a rough idea to a mechanism that actually works meant a long series of 3D-printed prototypes, not one clean jump from sketch to final part. Each iteration tested something specific: how the gripper should engage the film without tearing the perforations, how much torque the crank needed to transmit before the drive train bound up or slipped, how a detent should feel under a thumb.
Some of those early prints barely resembled what ships today. Others got the geometry right on the first or second try and just needed better tolerances. The full series, and what each version actually got wrong before the next one fixed it, is worth its own walkthrough.