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Ultimaker Original Plus randomly moves print

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As you can see from the image above, my 3d printer changes the position of the object it is printing, once above about 7 hours. The circles were a part of a large print that I did, which was 23hr 27min long, however within 8 hours, the 3d printer started printing off the original object.


As you can see above, I did a large object which kept turning out of angle, I am not sure exactly how to describe it, but I have checked the screws on the sides, as the image shows below.


I am not sure what the problem is, could it be to do with power, or the printer reseting itself during a long print?

Any suggestions would be much appreciated.





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See this guide:


So is it both axes or just one axis? If just one axis then which?

This is almost always caused by a loose pulley that screw you pointed to needs to be incredibly tight. The tool you use - it should be scary tight. if you have an L wrench it should really hurt your fingers. If you have the screw-driver like tool it should almost twist the steel.

Make sure you get ALL the pulleys on the given axis. One axis has 5 pulleys, the other has 6.

Having said all that there is a tiny possibility your stepper drivers overheat and shut off for part of a second occasionally. This is more common with Z axis. Not common with X or Y. But theoretically possible. Consider lower the current.

More likely there is also a possibility that your friction is too high or acceleration or jerk parameters. Are you using cura?

I think default jerk and accel for XY is 20mm/sec and 5000mm/sec/sec which should be quite safe values to use. Did you mess with these?

Check friction - push the head around with your hands. Add one drop of oil to the 4 larger rods and the 2 smaller rods. The 2 smaller rods shouldn't really need oil in theory but I found in practice it seems to help. Check that the smaller rods that go through the head are perpendicular by pushing the rod to each of the 4 sides to see if the end blocks on the rods seem to reach their end point at the same time. Sometimes this is crooked and adds lots of friction.

You should be able to move the head with only one finger on each hand pressing on the side blocks.

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I have the same problem with an interesting twist. I do gang printing of a small object. When I print 18 up "One at a Time" it prints perfectly. When I print 66 up "All at Once" It prints the second layer a negative value (the same every time) on the Y axis.

This seems like a slicing (software) issue and not a hardware issue. Any suggestions?

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The motion planner code in Marlin is quite complex and still has some bugs in it. When you do basic motions where only x,y,e axes are moving, most of the time, the actual accelerations are reasonable. But sometimes you get very high accelerations and you lose steps on a motor or a pulley slips.

I strongly suspect it is not the slicer's fault - it's just that you have higher acceleration somewhere.

To prove if the problem is with the pulleys, use a sharpie pen. A permanent marker pen. And mark all SIX pulleys (for the slipping axis or all 12 pulleys) and rods with the marker to see if the pulley slipped during the print where you get this axis shift.

If the problem is NOT an axis slip then you should be able to narrow it down to just a hand full of gcodes where the problem occurs. It sounds like very close to a Z move and there are bugs in marlin when the Z axis *and* X or Y are also moving. You could just separate the move into two separate moves (move Z first) and possibly also lower the feedrate. This fix is more work and only fixes one gcode file and will definitely solve your problem temporarily regardles if it is a loose pulley or just too much acceleration for the stepeprs to perform.. But fixing the pulley is the better solution and more permanent.

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I had lots of x/y slips on my umo+ until I changed the pulleys to gt2.

For the first 5months of use on my first umo+ I had (2+ years ago) it had troubles and the reseller imakr did sent me pulleys and short belts to replace, but the issue never disappeared completely. With the gt2 it never happened again.

About the planner, no idea. Could be nice to know Ultimaker opinion about the planner and if that bugs @gr5 says are documented or fixed on any Marlin release or if just noone plan to update old machine firmwares.

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