It seems like the High Powered stepper drivers (installed on both the x and z) are causing my steppers to heat up more when Idle more than what they should from my experience. I will say I haven’t used steppers quite this big much, but they both are very hot to the touch from even just sitting idle holding position.
Has anyone else experienced this?
HAHA I posted this on another forum yesterday. I have not swapped drivers yet but I noticed my X axis is hot. I probed it and found it to be 114° just sitting. The other motors are just warm. Not sure if this is normal.
I was going to take a temp but my thermal gun won’t turn on!!!
Normal operating temp for nema 23 motors is between 50 and 90°c (122° ~ 194° F). Depending on the humidity which dictates how fast they can cool off. Turn them off when not using them.
I wouldn’t worry about it. I’ve left my machine on overnight a couple times for one reason or another and they’re not too hot to me. Plus they’re cheap, if you burn them up you can also use it as an excuse to get servos. 
I figured out what the issue was. I didn’t realize the E-stop doesn’t cut cabinet power. So the drivers were powered on for a few days. At least it was something stupid!
I have a relay box that controls all the power 240 / 120 with E stop switch.
Push the button and its all off with the exception of the computer. Amazon Photos
Nice! We are planning on building something similar with PLC and power on and off switches. Partly to switch power between our laser cutter and the MR1, but we haven’t quite got to that project yet.
The holding current is controlled by dip switches on the stepper driver. A higher holding current is one of the reasons to upgrade the drivers. More current equals more heat. This is a feature and not a bug.
That machine looks awfully clean:) Those lights are a nice touch.
Boy I am glad you posted that. I wondered how that was determined.
So if you could go to a lower hold current on this machine what would the drawbacks be??
Don’t forget that stepper motors a “running” when they are “idle”. They are holding their current step location and thus using electricity.
Ummm you answered you own question, less holding power.
If the holding current is decreased than the holding torque of the motor will decrease.
Assuming these steppers have permanent magnets on the rotor, the main concern with heat is probably weakening the field strength of the magnets while operating. The field stength starts top drop off the closer the magnet is to its curie tempature. Even low cost rare earth magnets usually have a working temp around 150c and going hotter will not permanently damage them as the curie temp is probably more than twice that.
I live on Arrakis and have had no known issues with heat. The motors do steam when splashed with coolant. I have been considering increasing the current as I still occasionally have issues with missed steps roughing and the limit switches have such poor repeatability that I don’t want to rehome between operations.
So when the holding power only in play? What activates the hold or how does it know its at idle? Something gives that output to hold the motor correct and that would not be during an operation?
I ask because I have seen several times I have commanded Y to move and I have seen the DRO on X creep as well. So even though I commanded Y to move is X still in the hold state?
The stepper motors don’t have any encoders or other feedback mechanism. If you see the DRO for X creep then something in the software told X to move.
Nicer stepper drives have the option to switch to lower power when the steppers are seen to be at idle.
Thats scary. Jake at Langmuir has suggested I have a bad controller. You cant move both axis at the same time so it has to be a controller issue.
So if you command y to move will X release its hold state?
There is no “hold state”. If the steppers aren’t told to move then they are holding. The input to the steppers from the controller is very simple, there are two signals STEP and DIR. DIR is a binary signal that chooses to turn CW or CCW. Every time STEP goes from 0 to 1 the motor moves a tiny measurable amount (1600 steps per revolution on the MR-1). “Hold” just means that STEP is staying at 0 for a long time.
That is all of the signals from the controller board to the steppers.
That makes sense. Thanks for the clarification!
