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,