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jeffn

Shifting/Slipping Axis

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Hello,

Having increased frequency of intermittent shifting in x-axis.

What hasn't helped so far:

Tightened all the set screws to the pulleys including the ones attaching gear to stepper motors

Checked tensions on all belts including short belts.

Marked the pulleys and rod locations with ink, have not identified any slippage at marks after multiple shifts.

Removed a piece of the LED lighting with adhesive failure causing it to drop into the pulleys.

Slowed down the prints, reduced acceleration to 1500.

Here is a video of such a slip occurring- http://vimeo.com/114431802 at the 10 second mark, a sound is heard but I can't locate where the issue is.

Head does not seem to be snagging on anything raised in the piece.

Occurs with a variety of print settings- this particular occurrence one was PLA 200C, 0.1 mm layers, 35mm/sec with 70mm/sec infill.

IMG_6468.JPGIMG_6469.JPG

Any ideas?

Jeff

 

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I'm not entirely sure what the behaviour would be if a limit switch was incorrectly triggered during a travel move (would the print head continue after it triggers?) but could that be something?

Weird cross talk between wires and the board under the printer?

Just guessing wildly here.

 

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You're skipping steps during fast travel moves it seems; I don't really see anything in the video, but then again at the key moment the head pretty much obscures the whole of the back of the printer and the belts and motors which might have something interesting going on. If you could get some video of that right back corner when it's happening, that might be helpful for diagnosis.

One thing I noticed is that the sound seems to happen right as the head passes in line with the camera. There's no chance that any about the camera or its mounting hardware is catching on the sliding block, is there?

What travel speed do you have configured in Cura's advanced tab?

If you power off the machine and move the head by hand, do you notice any tight spots? You can add some light machine oil such as sewing machine oil to the cross rods and axes to help lubricate things.

 

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The camera setup is completely outside the printer- just looks close because of the fisheye, but I did reposition to get a closer look from above at the right back corner.

Travel speed is set to 150 in cura- I haven't messed with it, should I try lowering it?

When turned off I could move the head around with my hand in all directions. But since I have not oiled it in its first 500 hours of use (the rods always felt like they had a little lubricant on them still) I tried cleaning the rods and a very light coating of fresh oil and noticed the the effort to move the head in both directions was significantly lessened.

So far I have printed a couple smaller prints without the shift and the printing overall is much quieter. Am going to retry so larger prints that were inducing this shift later this week.

 

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noticed the the effort to move the head in both directions was significantly lessened.

 

That's a good sign!

Try putting the acceleration back to 5000mm/sec/sec or whatever it had been. You will get better quality with higher acceleration (because you don't want the extruder to ever slow down and if it does you want it to be brief).

Um - yeah - a limit switch could also cause this problem. If the LEDs are somehow hitting it or it's getting shorted out - follow the wiring with your eyes and maybe it gets pinched under one of the metal covers (the limit switch for the "bad" axis).

 

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Hi Jeff,

Problem still solved?

Since yesterday I see exactly the same problem on my UMO, with exactly the same sound.

The displacement is random from 5 to 30 mm. It starts to occur within a certain z range and happens at relatively slow speed.

Disassembled and cleaned all rods, the printhead moves easily, tightened all screws. :?:

 

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