Motor thumping

Do I need another board? Just going thru lots of ABS and just about to use a hammer on it.

I'm using a printrboard/Marlin/Slic3r/Pronterface setup with Kysan steppers and 2mm pitch linear belts with 36 teeth pulley ( smallest # of teeth I could find), Head at 230 bed at 110... and it would be printing fine then the whole system would then start "thumping" in mid print and the motors would miss/skip/ratchet on the x or y axis. I had swapped the x and y motor to see if it was one or the other, I have adjusted the pots. Everything test fine but when I start printing , after a bit, it starts thumping and everything skip/misalign then thumping stops and everything continues but skewed. Then it would start up again I even pulled motor connections in midstream to see which motor if any was causing it. I tried cooling the board, tried slowing the print speed too. The thumping would occasional start before a print but not strong thumps and when I tell Pronterface to turn off motors, the thumps go away. I started with a Gen6 and it failed maintain communication and error out with all the computers I tried it with. It had high pitch noise.

Do you have heat sinks on the printrboard stepper driver chips? What your motors are doing sounds like the drivers overheating, and then turning on and off to prevent damage from getting too hot.

---

Help improve the RepRap wiki! Just click "Edit" in the top-right corner of the page and start typing. Anyone can edit the wiki!

Sounds like you need to turn down the gain on the stepper drivers very slightly.

I am using a Printrboard and it NEVER overheats. The only time it "skips" is when there is a power issue, the printrboard is EXTREMELY sensitive to power failure. The only way I could get my printrboard to stop acting funny was to feed it pure power from a UPS battery backup. Also, what is the holding torque on your motors.

I have no heatsink on the controller chips but I have done the "turn down the pots until it does not move to 1/8 when it does" several time. The only motor that is hot is the extruder motor. I tried putting a 60mm fan directly on it but no change. I thought about a possible power issue as well and the setup has been on a 1500VA APC UPS since yesterday. It could be that my PSU is not that clean. It's a Coolmax 600W. The thumps happens whether if I'm on a laptop or desktop. I may try separate UPS for the laptop and the Prusa as well as digging up another PSU. I think the holding torque on the Kysons are 52 Ncm. I got all of them from Ultimachine. I updated Slic3r to the newer ver this AM. Is there a tweak for the Martin firmware load?

Comment from Polygonhel "Sounds like you need to turn down the gain on the stepper drivers very slightly."

I have had a similar problem that suggested I turn dow the gain on steppers. I have no idea as how to do this. I know there is an adjuster on the pololu board, but don't recognize it?

Any suggestions or direction to point me to?

Thanks,

Bob

There are these trim pots next to the chip/heatsink of the pololu boards. The pots look like a 5mm square with a circle in the middle with a line indent going across the circle that you can carefully insert a small flat heat screwdriver onto.
Each Pololu has a trimpot located next to the heatsink. The trimpot controls the current that is sent to each motor. Turning the trimpot counter-clockwise reduces the current to the motor, turning it clockwise increases the current to the motor.
Start by adjusting the trimpot down until your motor vibrates on the spot rather than turning cleanly. Now turn the trimpot in a clockwise direction in small increments (1 eighth of a turn) until the motors just start running. Then give the trim port a final turn of about 1 eighth of a turn and your should be good to go and easy on the turning of these pots and if possible use a plastic screwdriver.

On the Pololu's there is a very small pot on one side of the board (can't remember if it's left or right, it looks like a silver square with a silver circle on top that might take a phillips head screwdriver.
One of my machines is very picky about exactly where this is set, it's largely todo with the steppers.
If it's set too low, you'll lose steps intermittently, if it's set to high the driver chip will over heat and go into protection mode and it will look like missed steps, you'll also often hear and sometimes see the motor stutter, if the motor starts to do that I find it easiest to adjust the pot as the motor is stuttering until it stops, usually we are talking about turning it down 1/16th or less of a turn.

Fans can work wonders.

I should go larger fan than the 60mm? I though the 60 was a bit overkill. I had tried it both on the board and the extruder but no charge.The only thing that was hot was the extruder motor and I have no problem with the extrusion sofar...

Oh you did try a fan. Yeah. 60mm should be plenty and more.

"pulled motor connections in midstream"

You had the power disconnected when you did this?

Quote

I even pulled motor connections in midstream

Very bad idea. 50% chance you break the steppper drivers this way. If they still work, you had luck.

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY

had luck but still make the thumping/misstep after abit then it goes away and then comes back. Now in process of gutting another ATX power supply just to see. Everything starts fine but that random thumping/ratheting/misstep thing is just fustrating and depressing me and I have to walk way from the project for a few days.

Zimtower Wrote:
-------------------------------------------------------
> I am using a Printrboard and it NEVER overheats.
> The only time it "skips" is when there is a power
> issue, the printrboard is EXTREMELY sensitive to
> power failure. The only way I could get my
> printrboard to stop acting funny was to feed it
> pure power from a UPS battery backup. Also, what
> is the holding torque on your motors.


It's the power. Zimtower was spot on!! Feed thru an UPS did not help but the new PS worked perfect. No skipping or "ratcheting".The old PS was at 11.9V smooth and the new unit is at 12.15V smooth. Would not have guessed the slight voltage difference made that much of a difference..