This actuator can be attached to the top of a NEMA17 stepper motor, to create a simple cyclic linear motion. Two versions of the piston wheel are included, with and without spur gear teeth. The gear teeth are module 1, 40 teeth.  Two (2) M4  nuts and bolts are required to attach everything together. I'd suggest using nyloc nuts or use some lock tight for a final build.

The piston will need base supports enabled to print, but should print ok. All other parts can be printed without support.