View Full Version : Stepper moters

06-26-2003, 09:06 PM
The other day someone mentioned leaving the computer and shopbot on overnight in a paused state so that the cut could be resumed the next day. Today, after about 12 hours running I noticed the stepper moters were very hot. Not so hot you couldn't touch them but hot enough you didn't want to hang on for over 30 sec. or so. I left the whole thing on, but hit MO and they were still hot an hour later. Is this a normal condition? And is it safe to leave everything on and paused overnight?

06-26-2003, 10:11 PM
Jim, I leave my system on most of the time. My computer goes into sleep mode, but otherwise my system is always on. I regularly leave files paused in "Stop" mode overnight and resume the next morning. I've had no problems in nearly 3 years. Are you saying your motors were "hot" after 12 hours continuous use....or just from sitting in a paused position? I've never noticed my steppers getting very hot.... and never after sitting overnight....D

06-26-2003, 11:45 PM

Just for the record, _MOST_ stepper motors are rated at a maximum temp of 100'C (212'F). So, no, you are not hurting your motors by leaving them on.

The "rule of thumb" for how hot a stepper motor should be is: can you hold for finger on it for 5 to 10 seconds without burning it.

And FYI, stepper motors use the most energy (generate the most heat) when they are just sitting. That is why most stepper drives incorporate a current reduction system in their drives.

If you want more information about steppers and stepper drivers, check out this "white paper" on steppers:

Hope this helps,

06-27-2003, 01:11 PM
Thanks Darell and Bruce, I think the heat buld up is within the tolerance of Burce's numbers. We had a barn fire here about three years ago and I think it left me a little paronoid about the possibility of fire. I appreciate the re-assurance.


06-27-2003, 01:33 PM
Hey Jim...(lunchtime here)...just as an addendum to this thread.... After reading Bruce's post, just to be safe, I came in this morning and checked all my motors after leaving them paused again overnight. Every one of them was cool to the touch. That has pretty much been my experience..... but I certainly recommend you do whatever feels safest in your own situation. I tend to run large 3D files and don't like the little nervous twitch (steppers cycling) the Bot has when you turn it on and off....D