Print shifting back and forth during print

Hey Guys,

Attached a picture of my last part that I printed. After a while of printing the printer slightly moves off course, and then moves back to his original location after a few layers. You can see that during the print it went back and forth four time. I have a prusa mendel, sangulou electronics, wades extruder. My belts are tight, and I can't think of anything else what would cause this. I am printing at perimeters = 30 infill =40. Anybody have any ideas as to what else could be causing this?/

Thanks for the help!

Loose pulley?

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[www.hydraraptor.blogspot.com]

If you only have this shift in one axis then it's most likely to be the pulley (or set screw loose) as nophead states. or a lack of motor current.

Can you see if the head is catching on the infill and causing the head to jump - (motor missing some steps)? if the part is symmetrical it may well be catching occasionally in both directions on one of your axis - Try to increase your motor current a little on the offending axis.

Are you using Stepstick's or Pololu's?

You'll find other ideas to fix this issue on the Art of 3D print failure group here

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[richrap.blogspot.com]

What firmware are you using?

I was having a similar issue with my Prusa Mendel printer (although it was only tending to lean in one direction, not rocking back and forth). The problem turned out to be that I did not have enough compression in my levelling screw springs, so the whole build platform could rock to one side. Winding down all the levelling screws to put some real compression in the springs (and re-setting the Z end-stop!) fixed it.

Hope this helps!

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Follow my Mendel Prusa build here: [julianh72.blogspot.com]

I did away with springs and went with linear bearings, an MDF square ring and the aluminium heat bed fixed to that all stays perfectly level

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Experimenting in 3D in New Zealand

This happened to me, but also, only in one direction. My parts were shifting in Y axis (randomly). It was as simple as replacing the spring clamps that fasten my glass to my print bed. They would allow the plate to shift during rapid directional cycling in Y. Stiffer clamps fixed that. I'm sure I could also correct this in skeinforge by slowing down directional changes, right? I'm still new.

One other thing that I caught was the y axis motor mount was flexing enough that the misalignment of the pulley would cause a skip now and then. The belt would actually try to climb up the fender washer (pulley wall). A zip-tie took care of that.

Edited 1 time(s). Last edit at 01/26/2012 02:00AM by Skypuppet.