There are 4 stepper motors on the 3d printer: one for each axis and another for the extruder. I wanted to user a motor that could be powered with a computer power supply, was under 750ma (A3967 compatible), had a small step angle and maximized the torque. I evaluated many (too many) options, but settled on the 162027 from Jameco:
This motor is 600ma, is compatible with the A3967, has a .25″ spindle which fits without modification the sprockets from electric goldmine, and has plenty of torque to handle the
RepRap uses a toothed belt which engages plastic pulleys. The toothed belt and pulleys are fairly expensive and require precision gluing. I was intrigued by the idea of using ‘ball chain’
and am considering milling custom sprockets eventually. In the mean time, Electronics Goldmine has rollerchain and sprockets for very cheap – $1.25 per sprocket, and $2.50 for 23″ of mini-chain. I used 9 Sprockets and 5 sets of roller chain. They are fairly quiet and you can’t really beat the price.
sells a stepper driver based on the Allegro A3967. This chip is a microstepping stepper driver capable of driving a stepper up to 750ma. It requires lots of tuning to drive the stepper correctly (varying parameters such as step frequency, current limiting via a pot, etc). It is also subject to motor noise.
I’ve been working with Zach on from the RepRap research foundation
on a higher power stepper driver based on the A3977 which will drive 2.5a and is dip switch configurable for full step or microstep. You can follow the project on SorceForge
. Until that project is completed and available, this combo seems suitable for light duty FDM extrusion.