Help. Y shift halfway through a print. [SOLVED]

I'm curious if i'm missing something here. I'm in the process of printing new parts for my Sturdy90. It's 2 and a half years old and some of the X brackets are showing some fatigue.

Anyway, i'm trying to print the X Motor Bracket and half way through the job the print shifts 1mm on the Y axis of the printbed around the same Z height. I thought it was just a bug or my belt was old. So I replaced it. Attached pic shows the two prints after switching the belt. I'm at a loss. A loose wire on the motherboard (nope, I checked)? An issue with the Gcode or STL (nope both seem to be fine)? Only thing else I can think of is if the motherboard is overheating or maybe the firmware needs to be reinstalled. What else am I forgetting to check?

Edited 1 time(s). Last edit at 05/29/2015 08:35AM by lions3.

Is it 1mm or 0.8mm?

The former is hard to explain but the latter is a skipped motor step. A skipped motor step means not enough torque for the acceleration. I.e. increase the motor current or reduce the acceleration. Or it can be caused by too much friction if the bearings have seized.

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[www.hydraraptor.blogspot.com]

Quote
nophead
Is it 1mm or 0.8mm?

The former is hard to explain but the latter is a skipped motor step. A skipped motor step means not enough torque for the acceleration. I.e. increase the motor current or reduce the acceleration. Or it can be caused by too much friction if the bearings have seized.

You nailed it. it must be a skipped motor step. I'm getting ~0.7mm on the calipers but it's hard to get a good measurement with the angle. So yeah, it's either motor current or bad bearings. So i'll probably slow down my print job and finish the part. Then I can get on with the rest of my Printer update. (new bearings, rods, printed parts, a PEI covered printbed, and finish adding a custom acrylic enclosure).

Edited 1 time(s). Last edit at 05/29/2015 08:35AM by lions3.

I have experienced the same, although slightly worse effect and traced it down to the pololu driver getting too hot on one axis, this caused it to lose steps randomly. Improving the heat dissipation fixed this problem for me.

When the drivers get too hot you normally get much bigger errors as it shuts down for much longer than one step.

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[www.hydraraptor.blogspot.com]

Slowed the printer down to 40 mm/sec and part came out perfect. thanks again for the help!