I just finished the build of my MPCNC, and I’ve played a bit (10-15 minutes) with Estlcam and repetier host drawing circles in the air.
After that short time, I touched my drivers heat sinks and quickly removed my finder : it was hot.
I’ve set Vref to 1.06 - 1.07V, my drivers are A4988 and my motors are these. I don’t have any fan on them for the moment.
I know I’m at the higher limit for my drivers, but I don’t know if I can continue like this, or if I just need some air flow, or if I need to low that Vref…
I guess mine are very similar. Please reduce the current to about 1.2-1.3 A. In my case changing the drivers to DRV8825 helped as well -> temp. went down, however I also reduced the Vref to ~ 0.6-0.65V. Have to add, that after couple of hours of uninterrupted running, motors are warm. And yes, stepper motors can be hot (Siemens professional may be about 80 C deg, as example), however I would question the thermal isolation in those cheap what we are usually using.
And yes, drivers heat sink are hot. Use fans. Cheap 40x40 (50x50) will suffice.
I’ve ordered some DRV8825, but I have those A4988 so wanted to be able to use them. I know motors can be hot and that it’s usual, but didn’t know for drivers.
Initially, I set them to 0.7V, so 1.25A, but with just a little force I was able to stop an axis.
I’ll plug this fan, low just a bit amps for these drivers and see how it goes. If they don’t fit the job, I’ll go for some DRV8825.
Usually drivers are getting hotter than the motors.
You can either put bigger heatsinks on them, or use a fan to blow cool air, or even both.
As long as they stay cool enough there should be no problem. You don’t need to worry too much, they should not fry, they have a built in system to prevent them from burning. If they get too hot, then they will just pause for a few milliseconds, then restart, then pause again, and so on. Sure it will ruin any job you are doing at that time, but the electronics should remain just fine.
