Lyman Filament Maker Calculations
- The extruder motor has a 168 fold geardown. It has a 173 kg-cm (1730 N cm) torque! 
- 3000 N cm torque stepper - $60 - . That is about 300 kg cm.
Stepper has over 2x performance to cost ratio
The torque of the Precious Plastic shredder is recommended at 70 rpm with a 1/4 hp or higher motor. Using the Motor Torque Calculator, that comes out to 2800 N cm. The stepper motor above meets this specification.
The Recyclebot motor (the stepper) has 15 geardown. Say steppers go up to 1000 RPM - that is exactly about 70 RPM if there is a 15 fold geardown.
Take a regular Nema 17 with 72 oz in torque. That is about 5 kg cm. To get to 300 kg cm - need about 60 geardown.
As a first try, it is useful to go with the 15 geardown stepper above for an initial version of the shredder.