Extruder Stepper Heat Issues

Hello everyone! I’m having a strange issue with my smoothieboard.

I am using the smoothieboard to power a 3d printer that extrudes silicone plastic. The extruder is hooked up to a stepper in a DIY syringe pump. During prints, the extruder gets really hot, hot enough to leave a pretty nasty burn on the skin if you touch it. The strange thing is that when the smoothieboard actuates the extruder on its own, even with a high load, the stepper doesn’t get hot at all. I’ve also determined its not something with the heat bed. I think something is up with the smoothieboard itself… it shouldn’t be getting this hot at all but I don’t know what could be causing it.

For power, we are using the attached computer as a 5V power source. For the motors and heat bed, we have connected one 24V, 10A power supply to the VBB pin, and another for the heat bed. Extruder is limited at 0.75A in the config, and the stepper is rated for 1.5A.

The printer design I am using is a rep rap design (now discontinued) similar to an ultimaker with two z steppers that control the height of the build plate.

Thoughts?

EDIT: I forgot to add that there is no temperature control setting in the config for the first extruder because it is not heated. Just for reference.

Imported from wikidot

Hey.

Some stepper motors will just heat up a lot, that’s by design, and unless you are using a very unusual stepper motor, it should be fine for it to get hot ( or even very hot ).

Cheers.