What is a safe temp for the stepper motor?

What is a good safe temp for the stepper motor. My extruder motor is running around 70c to 74c. Is that too hot or normal?

 

I'm not sure about the steppers Robo uses, but I do know that when talking about industrial steppers, anything above 80C will start to degrade the magnetic cores (basically shortening the life of the motor by some difficult-to-gauge amount for every second over that temperature).

That's the internal temp of the motor, not ambient temp. So it's kind of hard to measure properly anyway. Safe to assume that if you're measuring 70-74C on the surface of the motor that the internals are hotter though, so you need to turn down the driver current and slow the speeds you push the machine down until they don't overheat any more if you're going to go the passive cooling route.

Alternatively, get a bunch of fans and heatsinks and mount them on the steppers as well as the stepper drivers, and put them on an independent power supply that you turn on whenever you run the printer.

Here is a decent general article on the subject.

http://www.sd3d.com/stepper-motor-cooling/

 

Thanks guys. The extruder is not the one that came on my Robo. I had to replace it with a spare I had for my Flash Forge Creator Pro. On the FFCP they have a heat sink but I did not use it. I am not sure how I am going to mount the heat sink or a fan yet because it may cut down on my X axis build size.

 

With the gearing on the Greg's Wade you theoretically don't need the large Nema 17 motor that is on the rest of the axis. They use all the same because of bulk purchasing. I think you can get away with a smaller Nema 17 that should give you room for a heat sink or fan. BUT really you shouldn't need either if you calibrate your stepper driver on the RAMPS board like @daniel871 originally suggested.