Replicator 2 Extruder Upgrade

This extruder upgrade for the Replicator 2 replaces the Delrin plunger with a pinch roller. Using the spring specified in the parts list below, this pinch roller provides about 60N of force on the filament, which provides enough driving pressure on the filament, in combination with the stepper drive gear to prevent stripping. Unlike other designs, this one uses a pin style bush on which the pinch arm rotates. This provides a large lower friction surface for the pinch wheel arm to rotate on, and allows the mounting screw to be fully tightened so there is no chance of it working loose. I have extensively tested this design, which has evolved through numerous iterations, and I have also tested several different springs. With the specified spring I can hold the drive gear with my thumb and pull hard on the filament without it stripping, and its done numerous unattended prints with troublesome clear PLA filament - so I can confidently say __it works__. ### UPDATE (Mar 4th 20