X axis shifting

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b8smat
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X axis shifting

Post by b8smat » Fri Jun 13, 2014 3:27 am

Recently my M2 seems to have started developing an x-axis problem. It only happens on certain prints and looks like it is related to what model and what part of the model it is printing. Nothing seems to be loose. Could it be belt skip? Or the x-axis steeper motor missing steps?

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jimc
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Re: X axis shifting

Post by jimc » Fri Jun 13, 2014 3:47 am

if you print the same gcode twice, does it skip in the same spot on the model each time? i know you said everything is tight but check anyway.....if its on the x axis be sure the setscrew in the pulley is tight and make sure the belt is not loose. as the printer is printing wiggile the wires going to the stepper motor and see if it causes a jump.

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Tim
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Re: X axis shifting

Post by Tim » Fri Jun 13, 2014 3:59 am

And. . . I've said this elsewhere, but I'm going to keep repeating it. . . One cause of x-axis shift is the motor rotating in the mount, which can happen if the mount develops a crack. Which seems to happen pretty often. It's also much more subtle than you might expect. I had one print shift over by half a centimeter, and the rotation wasn't that obvious, mainly because the fans block the view of the extruder and mount. It also tends to happen on certain prints in certain places, especially if the part gets warped, starts peeling off the bed, and so pushes hard against the nozzle. Overhangs often curl up a bit and harden, and then the nozzle plows into them on the next layer, which can also knock the extruder askew if it's not firmly in the mount.

Or, . . . it could be something else. Just keep all the alternatives in mind.

b8smat
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Re: X axis shifting

Post by b8smat » Fri Jun 13, 2014 4:08 am

Every print is different, even though it's the exact same model.

My suspicion is something is slipping in the x-axis drive train during high speed head moves. I'm going to try slowing down the head speed for the next print.

b8smat
Posts: 37
Joined: Sun May 11, 2014 12:16 am

Re: X axis shifting

Post by b8smat » Sat Jun 14, 2014 3:33 pm

After seeing you guys' replies I went back and double checked the extruder motor mount and it was a little bit loose. However after tightening it up I did another print (nothing else changed) and it STILL went wrong after about 30 layers.

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jimc
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Re: X axis shifting

Post by jimc » Sat Jun 14, 2014 4:13 pm

The shifting thing really stumps me. I have had it happen here and there and so have many others. Its not limited to makergear either. Every brand of printer has the problem. What is strange is that some people never get it, some occasionally and some all the tine. What the actual cause is other than mechanical stuff i have no idea. Every thread you read on the net all end with no resolution other than changing the occasional bad motor cable.

b8smat
Posts: 37
Joined: Sun May 11, 2014 12:16 am

Re: X axis shifting

Post by b8smat » Mon Jun 16, 2014 4:49 pm

I think the only thing in common with the failed prints is either overhangs that curled up or edges that curled up due to insufficient bonding to the glass. Which would suggest that the slippage is due to the head catching on the print and the X-axis motor unable to overcome the resistance.

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