Z axis motor gets very very hot

My Z axis stepper motor the Nema 17 gets very very hot, I have a new linear z drive where the motor sits on top and is direct drive, the router is dewalt 611, is the motor powerful enough or do I need to get a Nema 23

I am away from the workshop at the moment and I am guessing that the motors I got with the Xcarve are Nema 17, I will double check Tomorrow, are they stamped 17 or 23

Mind you, steppers do take heat quite well and if temps are below 170degF you really haven’t passed the temp limit yet. Close to, but not passed it.

But given the cost of a Nema23 of suitable size an upgrade is a no-brainer :slight_smile:

BTW - Nema17 = 1,7" wide casing, Nema23 = 2,3" wide. Length vary.

Well it seems that the motors are Nema 23, the are not stamped 23, I am just going by the width of the casing which is 2.3 inches, so will I just carry on and not worry about the heat

Nema23 then - probably the 140oz/in^2 (56mm long case)

With a smooth linear drive 60% of the weight will be transferred to the motor. Ball screw can be even higher.
The Z do work bit despite being stationary for most of the time. (3D carve with continuous X/Y/Z even more)

If you can touch the casing for like 3s without feeling burnt you are in the 55-60degC range (<140degF) which the motor will take fine. You could derate the current limiter for Z in case it is a little high, this can also cause case heat.

How do I check the driver current, I have the X controller, is there something I can read up on, and I can hold my hand on it but a few degrees more and I could not.

Then I wouldn’t worry about it.

I once had a Nema17 on Z and I could boil water on it, any water would fizz away instantly :exploding_head:
It didn’t fail on me though… Since replaced with a 270oz/in^2 Nema23 which barely feel warm to the touch.

In the upper right hand corner you can see part of the silkscreen for the current limit setting for the X-controller. The numbers around the dial are approximations of the current limit if the dial is pointed to one of the numbers in the outer ring.

The potentiometers beside the DIP switches are the controls to set the current limit for each axis.

You can also use the test points (TP) to set the current limit using a voltmeter if you need to be more precise.

Thank you all for your help, I will check the current limit on Monday and get back to you, I don’t know if I have a 270oz/in^2 Nema23 or not .

Tell me the length of the motor casing.

I have never replaced the motors so they must be 140 oz, I will measure the length of the casing and check the current limit when I get to the workshop, I am looking around at the moment and found these stepper motors, which are very reasonably priced, I was looking at the 265 oz http://ooznest.co.uk/NEMA-23-Stepper-Motor

You have a linear slider right, then a larger Nema23 will fit. 265oz is plenty strong and mine dont even get luke warm.
Choose a motor with a low mH-number if you can choose, not a critical factor by itself but they are better suited for low voltage supply voltage like 24V.

Thank’s Haldor

Larry, I have opened the X controller to have a look, I don’t see a dial pointing to the outside numbers and I don’t really know what I am doing in there, so I won’t alter anything in there for now ,I have ordered a 265oz motor and will try that first, the motor I have is hot all the time the machine is switched on even when not in use

Then the current limit of that driver is set high, dialing it down a little would reduce that. But as stated earlier, if you are below 140degF there is no danger.

Idle steppers get full current to hold them in place. That’s why they are always hot.


That’s where the Xcontroller’s auto-torque reduction kicks in which limits the current going to an idle stepper to help with heat on the steppers. Unfortunately, it also causes a reduction in holding torque.

You can take a picture of the same area in Larry’s photo and we can look and tell you and show you what to look for.

Thank you Justin, very good information, I will take a photo and post it in the morning when I am back at the workshop

I have never altered anything in here, the only thing I done was add the linear rail

Potmeter to adjust motor current is here, encircled in red. Dial in down (counter clockwise) 1/8 of a turn and see if the motor temp change. You can also set dip #4 on the pale blue box next to it to “ON”. This will reduce current to motor when it doesnt move.

You can also calculate the current limit by measuring the DC voltage over TP4 (GND) and TP3 (Positive) - circled in yellow.
Use the formula (I = Vref * 2.13) to determine the current.
For example, if you measure 1V you have the limit set to 2.13A.

Thank’s again Haldor, you have been a great help, I will install the new motor when it arrives today and see how hot that is and if it is the same i will adjust it