Failing Stepper Drivers


#1

I am having an issue with the stepper drivers failing. When I first assembled the printer, all of the stepper drivers would overheat and result in layer shift and under extrusion. I replaced all of the driver boards and everything started working fine and I got good quality prints. Now I’m starting to have trouble with the extruder driver overheating and the motor clickin; it’s intermittent right now but as past experience has shown it will get worse and stop extruding all together. The machine maybe has 50-75 hrs on it and I didn’t expect to have driver problems already. Would anyone have an idea what could be causing the drivers to go bad? Could it be a bad pica board?


#2

Did you calibrate the vref on the stepper drivers?


#3

Vref

This the best video on how but long.

This is short and to the point.

Basically get earth from the board and even the power in earth is good. Positive side of the voltmeter to the center of the trimpot on the stepper and see what you have.

99% of the steppers I buy have the trip set very high. There is maths to work out the numbers but I would start about 0.4 - 0.6v run a test print and feel the motors. They should be a little warm but not hot, feel the steppers they should be warm but not to hot to touch.

If you have cooling on your motherboard that will help a lot.

Thing to know if you have miss matched steppers and motors. Motors can run hot and most are rated as high as 80degC and still run fine but steppers don’t like too much heat. So if you can run the numbers on the stepper that seems good you can run the motors hotter and get away with it.


#4

Thanks for the info. I’ll look into doing the vref calibration. I think I misspoke though. The drivers and motors don’t get that hot, they are warm to the touch but not hot. But they are exhibiting similar symptoms of overheating. When I go to print something, everything seems to be working fine until a around an hour or so into the print. Then the extruder motor starts missing steps and clicking. The drivers and motors aren’t hot just warm to the touch. There is also a cooling fan for the board and drivers. The last time this happened I replaced the driver boards and that appeared to have fixed it, but now the same thing is happening again.


#5

Another thought. When I first had this problem when the machine was new it was suggested that the dip switches on the driver sockets could be bad. Would that cause the drivers to wear out this quickly?


#6

One more thing to check is cabling, I thought I had a similar issue but it turns out a cable would snag just about the same spot… Just a thought.


#7

I did the vref calibration on the drivers. They were all around 250mV and I adjusted them to around 420 as per the video. Hopefully that will solve the problem. Thanks for the help.


#8

So after calibrating the drivers I was able to get one good print, then things are starting to act weird. The next time I went to print, the print head drove down into the bed and broke the glass during homing. So I replaced the glass, now it’s able to get through homing and bed leveling but when it starts printing, the nozzle doesn’t get close enough to the glass and the layers don’t extrude properly. It also moves outside of the perimeter skirt while printing, see picture below. Could all this be related to the drivers?


#9

You most likely want to adjust your z offset, using m851. Unfortunately I can recommend a good guide for this one, only something I worked out through trial and error.


#10

Not sure what gear you have, but if you adjusted vref and everything else seems right. Please check your power supply. It should be checked when you have your bed and extruder heating up. The voltage should be at it’s lowest from your power supply, about 12v-13v when you reach your temp make sure the voltage does not change much.

Check this at the power supply input to the Pica board. If you have an oscilloscope check for high frequency noise when the unit is heating. You’ll likely see some noise when the steppers are going but while the machine is still you should see less than 0.5v of noise on the power.

you may also want to check how solid your 5v is on the pica board. It should be very clean and hold at 5v while the machine is running. the vRef is generated off the 5v supply and if the regulator is putting noise on the line etc you’ll get erratic behavior.

Best luck to you.