HOT!! Stepper motor!!

[Paul714]

Hi guys i previously posted on the forums about my issues setting up and getting to work my Taig Microproto 2000 micromill. I finally got it up and working, i am
Using the 2000 Driver Box with the Nema open loop steppers and Maxh 3. Everything seems to be finally working now but now my Y Axis stepper is getting very very HOT! It literally takes 5minutes to get up to 208f degrees. The wierd part it is working fine. My other steppers X and Z are a normal 84f degrees. I asume the Y axis is drawing alot of current correct? What could cause this problem? I checked the steppers and they are all working fine no shorts. I am asuming i have a bad Y axis port or shorted port? What do u guys come conclude?

[john-100]

depending on the manufacturer , stepper motor data sheets I have read usually give the maximum temperature of 70 to 80C (158F to 176F)
so 98C / 208F is too hot and I expect the Y axis driver is set to too high a motor current

have you ever had the system working correctly ?
are the stepper drivers set to the correct motor current ?

if the three stepper motors are the same
check the Y axis driver is set to the same current as the other axis

do you have a manual giving the details of how the drivers should be setup ?

photos of the stepper drivers inside of the control box , the motor connectors and part numbers of the stepper motors will be useful

John

[Paul714]

Hi john-100 thank you for your reply and feedback. I bought this machine from some fellow who could not get it to work because he did not have the software to get it to work. He said the person he bought it from had it working. So now i am here tring to get it up and working correctly. Now my question to you is how do i check the current in the drivers? The gentlemen gave me some basic manuals on setting the machine up but does not talk about the current output and drivers. I will look into finding the part number of steppers and photos, and post them as soon as i can. Thank you again kindly

[john-100]

depending on how old the stepper drivers are

you could find they use some thing like the Sanken SLA7078 that is used on the old Hobby cnc boards that drive unipolar stepper motors

the IC data sheet will give instructions on how to adjust a potentiometer to set the IC reference


if its a later design you could find a bipolar stepper driver from Sanken / Allegro electronics

more resent stepper driver designs stepper have jumpers or DP switches to set the motor current to one of several fixed setting instead of the continuous adjustment a potentiometer gives you

once you find the stepper motor data sheet you will know what the motor current should be


john

[Paul714]

How or where do i look to determine what driver board i have john, upon opening the microproto 2000 box?

[john-100]

it all depends on what information is printed on the boards

some times you have the stepper driver part number printed on the board
and the part numbers of the components
with the instructions to set the motor current

other times there is little or no information printed on the board and with no manual
you have to look for the part number printed on the stepper driver IC

the number of wires between the board and the motor connector an the back of the control box
will give you a clue as to which type of motor you have (6 wire unipolar V 4 wire bipolar)

john

[Paul714]

Here is a pic.

[Paul714]

Another pic. They are driver boards by Kurt

[Paul714]

In the back of the driver box someone swapped X and Y axis erasing the original X and Y port letters and using a black marker to label X and Y ports around, hmmm why would someone swapp the ports around?


Also on stepper motor is label “S step Motor”

[Paul714]

Last pic, the circuit boards look clean and not abused.

[lsces]

Paul714 ... there are no current settings on the Taig/Microproto drivers, they are built for the motors as supplied. And for some reason I'm not seeing any pictures just to confirm if they are unmodified. You don't say if you are using Mach3 or the original DOS based software, but if the motors have already been swapped then I would suspect Mach3? I'd swap X and Y back and check if it is the motor or the 'current' X channel that is faulty. Do you have the fourth axis fitted in the driver? In which case if it is a driver fault you can use A instead, or if the Y motor stays the one getting hot, then it probably need replacing. These drivers are unipolar, so one need a 6 wire or 8 wire motor to replace it.

Mach3 settings for motor pins are in the 'pins' setting window, motor tab, and you just swap the X and Y pin numbers over.

[john-100]

Hi Isces

thanks for the information
do you know what is the specification of the original motors ?

I guess the drivers are old enough to be using using a driver IC like the Sanken SLA7078
with a couple of resistors providing a fixed reference voltage to set the motor current

swapping the A axis motor with another would be my next move

to see if the A axis motor runs hot when connected to another driver
the motor could be faulty or has been changed at some time

John

[lsces]

Kurt designed the driver using 'real' components, so it's easy to replace a FET if one blows and the current limit is just a resistor as far as I've established. We never did see the actual circuit, but a run around a dead driver with the multimeter quickly identifies a shorted drive FET. The motors are 6 wire and I think only a bit over an amp per phase. I've been fitting a 180Ncm motor which has been working fine as a replacement when the old ones get 'soft'. Does the hot motor look different to the others. The older motors just had loose wires and a metal strap to help protect the connection.

[wizard]

Often stepper motors are specified with either an absolute max temperature or an acceptable temperature rise. This does vary with stepper motor brands. Your motor does seem to be operating hot but we really can't say that it is too hot without a data sheet for that specific stepper.

Now an important aspect with respect to Stepper running on modern drives, they DO NOT operate like brushed DC motors. The drives are set up to run the windings as very specific currents. This current level is variable based on the step mode selected. A micro stepped motor can have the coils running at several different levels of current depending upon where the motor is in the step cycle. Note the current is controlled by the drive based upon the step cycle, and not the load as would happen in a brushed motor.

So what I'm saying is that if the drive is matched correctly to the stepper, the motor should be running at the right current level. How hot it gets isn't a problem as long as the it is operating with in specs. So one of two things either the drive is set wrong (or not working correctly) or the stepper isn't matched to the drive correctly.

[Paul714]

Hi guys i finally debugged the problem, i found 2 bad MOSFET transistors that were shorted. They were located on X and Y axis power outputs to stepper motors. It was a quick easy fix and cost under $10 well worth it. Thank you guys for all your help! And Have a happy new year and be safe!