Stepper Motor is Hot

Just finished a three hour project. While I was vacuuming the dust, I touched the stepper motors. Although most of them were very warm, the x axis stepper was on fire. If I held my finger on it I would of gotten burnt.

Is this normal? How hot is too hot? Anyone else having same issues on long projects?

Unfortunately, unlike the Z- and Y-axis motors, the X-axis motor is not bolted to a large metal plate, so doesn’t have an easy way to shed heat. Motors work the hardest when holding position, so it used to be the Z-axis motor which had this difficulty.

The motors have a wide operating temperature range, and shouldn’t be exceeding them during normal operation. Work out some way to measure the motor temp. during / after a job, and if need be make a mount for a fan?

It is possible that the motor is bad — try swapping w/ another one, and if that’s the case, contact for a replacement.

“On fire” and “very hot” are two very different things. As Will says, they’re designed to run pretty hot, at least to 75C (about 165F) which I wouldn’t want to hold my hand on. I wouldn’t be surprised if they were spec’d to 80C, but I can’t find a data sheet that calls it out.

An “uncontrolled exothermic reaction” would certainly be scary, but this isn’t that. Lets not get carried away here.

I’ve measured this on mine (with a higher powered spindle motor):
After extended running (about an hour) the spindle cartridge is running 102F, the body of the motor is 136F, and the top cover (where the hall sensors are) is 99F. The back aluminum panel that serves as the heat sink for the boards is 92F. The stepper bodies I can reach are 104F.