Y skips with marlin not sprinter

Hi Everyone,
I have started using slic3r + pronterface + sprinter + ramps 1.3 and have gotten many nice prints. (Except for the fact that some of my prints don't center and thus run off the edge, but that's another issue.) When I switched over to marlin, I seem to get Y motor skipping like I have in the picture. I started at the lowermost square and every time that it tries to do a bigger move (in this case going to fill in the right part of the base) you hear it grind a bit and it doesn't move. This is strange because it doesn't seem to happen as often with sprinter (although I do exhibit the same thing on certain models). I feel the Y motor and the stepper driver and they don't seem hot and when I move the Y normally it seems to travel fine. When the power isn't applied the Y travels very smoothly (I have linear bearings).

Does anyone know why this would be happening?

Thanks!

Edited 1 time(s). Last edit at 12/22/2011 07:33PM by ambiguousphoton.

Maybe your maximum feedrate is set too high, so the axis can't follow what's commanded. You should hear this, trying to run a motor faster than possible gives some "eeek" sound without the motor axis turning. A too steep acceleration can be an issue, too.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

I have had the same issue...

My rooting around the interwebs has revealed that the max acceleration rate on marlin is set to 3000 by default. Try setting it to 1000-1500. I have not tried this myself yet, but I intend to on Saturday.

That's a great suggestion! I noticed that the Y motor would just buzz when it got to the point where it was supposed to move. I thought that the gear wasn't secured at first but it didn't appear that shaft was turning without the gear when I looked at it closely. When I loaded up the default values for X and Y, they were 9000 for the max acceleration! (The default acceleration was 3000, maybe I should turn that down.) The feedrates are 500mm/s by default so I am not sure if that is too fast too.

EDIT: It totally worked, but I had to drop the acceleration down to 500. I wonder if part of the issue is that my Y motor is a single stack nema 17 while the other motors are the double stacked kind and can deliver a lot more torque. Thanks again for the help!

Edited 1 time(s). Last edit at 12/23/2011 11:24AM by ambiguousphoton.

Quote

The feedrates are 500mm/s

It looks like some firmwares set this value to something unreasonable high and trust the host / G-code compiler to never send a G0.

This has something to do with the typical users unwillingness to configure the firmware at all. For example, I often heard Teacup would be slow. It's just the default maximum speed which is set slow and people simply don't recognize this. Configure it properly and everything is fine.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY