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Printrboard Z axis not holding

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Hey everyone, I recently salvaged a printrboard Rev D from another printer...

And I'm running into issues with the Z motor not holding after a move command is given.

I have no firmware access, as I am unable to successfully compile on Arduino from numerous verify errors. So all changes need to be done by Gcode and saved using the M500 command.

Basically, X and Y after a move, holds its position, but the Z motor free rotates. This is immediately after a movement command.

Does anyone know whats wrong? Ive also swapped stepper motors and the result is the same for the Z axis.

I can't tell you about the Z issue but firmware wise I can help.

https://github.com/scwimbush/Printrboard-HID-Arduino-IDE-Support

This allows you to compile for the Printrboard with a modern Arduino. I have successfully put on Repetier Firmware, and it should work for Marlin. I'm about to try Klipper soon.

This is usually a sign that power to the steppers is turning off completely after a move or there is simply not enough standby voltage to hold it.

When I go and spin the motor it is completely off. Does anyone know how I can change this?

I’ve looked at the gcode M84 for the timeout power off, and it appears to be off, the other steppers still have power and continues to hold after a move command.

Or if it’s he standby voltage issue, where do I make the changes to make this work? Is it the little trimmer resistor on the board?

Can you manually drive the Z motor with whatever software you have? If not, then I'd suspect wiring or a blown servo driver (assuming X and Y are OK). If you can, then it is something else. Have you dumped your EEPROM? What's the Z steps per mm? If it were zero.... maybe?

Yes, I am able to manually use software to control the stepper motor. I have not dumped eeeprom yet... I’ll look into that procedure now.

Z steps set to 400. I am using a 2mm pitch Leadscrew.

Then it seems like the electronics are probably OK. And 400 steps per mm ought to give you some motion, I think. However, typically, a Printrboard is 1/16 step, I think. So assuming 1.8 degree steps that's more like 1600 steps/mm. However, that wouldn't put it off.

Is Z homing working? Assuming you are homed if you put in the terminal something like:

G1 X10

Does it cause the Z axis to go up?

Homing does not work yet because I’m waiting for the micro switches to come in, as soon as I hit home it moves a bit and stop because there’s nothing plugged in and the firmware is reading high across all limitswitch pins.

But putting G1 Z10 does move it 10mm up. Approximately anyways, still need fine tuning etc.

So it’s odd that it would do these commands, and then release the motor right after move is complete. Could this be the little pot thing on the Printrboard? That’s the voltage reference for getting the right amount of current to the motors, does it affect the holding at all?

The pot controls the drive strength to the steppers. Too much overheats, too little doesn't deliver enough torque. It should not just kill the motor.

But the fact that you can manually control it tells me that it is something to do with your printing -- slicing, G-code setup, homing, etc.

I’m not too sure exactly because I used the Printrbot bolts hex file from the original simple printer. I could try other hex files and then make adjustments via gcode.

I have the DFU Bootloader and using the FLIP software to write precompiled hex files to the board.

I’ve looked at the process for getting other boot loafers, I can do that, but the rest of the process to compile, USB drivers, the avrdude fuse settings etc is really confusing. I’m trying to avoid that.

I give up, thanks for the help anyways. the board does not connect to PC anymore so its done....

Sorry man, best of luck!