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Temps for stepper motors and stepper drivers?

Posted by SvdSinner 
Temps for stepper motors and stepper drivers?
March 12, 2016 11:12AM
What temperatures are "normal" for basic NEMA-42 stepper motors? What about for the driver chips on RAMPS boards?

As I'm setting up my first RAMPs machine from scratch, I'm noticing the temperatures of the stepper driver heat sinks (I'm using Chinese-clone DRV8825 drivers @ 1/32 microstepping) are often very different amongst the channels ranging from about 30C to 85C in my observations. The stepper motors themselves can run from about 30C to 55C. (All temps measured while things are energized, but not moving.)

At what temps should I be thinking about a blower fan on the RAMPs board? What temps are dangerous to the drivers? What motor temps are dangerous for the steppers?

A big factor I've noticed in them is that my steppers audibly squeal at times when not moving, but energized. My guess is it is micro-stepping related, since jogging the axis that is squealing by .1mm, will change the squeal noticeably. Depending on which .1mm the axis stops at, the motor may be quiet, or squealing at different volumes and frequencies, however, each .1mm has a repeatable squeal sound. (IOW, if 10.1mm produces a certain squeal, and I move the axis all around but back to 10.1, it will squeal at the same volume/frequency as when it was first at 10.1mm ) The louder the squeal, the hotter the drivers and the motor gets. Is this squealing a concern?

Are there any other things that can cause the temps to be higher than they should? (Beyond motor load.)

NOTE: This is my first RAMPS from-scratch build, so I may have something configured wrong. I'm not very confident if my current limiter pot is set correctly on the drivers. I simply started low, and increased until they worked. I then increased until I heard some audio anomalies in the motor operation, and then back down to midway between "just working" and "too much" points. However, when a motor squeals, adjusting the pot doesn't seem to have an impact on the squeal.
Re: Temps for stepper motors and stepper drivers?
March 12, 2016 01:48PM
Are you actually attempting to run NEMA-42 size steppers using a 8225 driver on a RAMPS board? How big is the printer? I would not think that an 8225 driver could provide enough current to heat up a NEMA-42 motor, but the driver may get pretty hot. I'd say if it feels uncomfortably warm to the touch, put a fan on it.

The squeal is caused by the 8225 drivers. There have been many threads about it - do a search in these forums.

If you really are using NEMA-42 motors, I would think you'd want to use an external, higher current, DSP based driver and a high voltage power supply. A little 8225 and 12V supply aren't going to be able to control such a big motor very well. You may get it to turn but it will vibrate a lot and torque will be very low.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Temps for stepper motors and stepper drivers?
March 12, 2016 03:29PM
NEMA 42, like to see them in action!!. but I suspect these are an aliexpress hybrid stepper which the Chinese describes as nema 42, which is reference to the dimensions 42 mm sq which can be either a nema 14 or a more common reference to nema 17.

In my experience there's no need for steppers or drivers to get overly hot.
sinner have you read stepper calibration caution and a steady hand is required its all to easy to short a driver.

Quote
sinner
"just working" and "too much" points. However, when a motor squeals, adjusting the pot doesn't seem to have an impact on the squeal.
just to be sure you turning the power off and pulling out the USB cable before adjusting the pots.

Edited 4 time(s). Last edit at 03/12/2016 03:52PM by jinx.
Re: Temps for stepper motors and stepper drivers?
March 12, 2016 08:59PM
Quote

NEMA 42, like to see them in action!!

Hmm, that would be a thing of beauty. Had to work a bit to find a real '42 on Aliexpress, but here's one: [www.aliexpress.com]

2832 Oz-in and a cool $400 CAD. That would power quite the printer, and it seems it's actually one of the smaller nema 42s. Perhaps we should use it for an extruder. grinning smiley

Motors should be fine up to about 50C, typical max rating is around 80C. High temperatures may shorten the lifespan of the motor, so you don't want to run them hotter than necessary.

The drivers will hit thermal shutdown at about 160C on the die, that's likely to register a lot lower externally. I'd be looking to add cooling if you are seeing more than 50C on the heatsink, but they should be perfectly ok running up to about 80 or so. It's worth getting a multimeter and measuring the vref on the pot. Then at least you can make meaningful adjustments and get back to a previous setting if you need to.
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