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Allignment problem


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Posted · Allignment problem

Hey guys

I have a problem that I cannot solve. I will show the problem using a basic shape.

I have a cylinder with a wall thickness of 1,6 mm. In Cura I set the shell thickness to 0,8 mm. This will create 2 inner and 2 outer shells which together should form the 1,6 mm solid walls.

The problem now is that there is a gap between the inner walls (green). And it is a very particular reoccurring gap only at the left bottom and the right top. Therefore I suspect a hardware related problem.


In the picture you see a top view drawing of the layers. At the location of the gap, the wall thickness is 1,9 mm and at the location without the gap the wall has the right thickness off 1,6 mm.

I also show the path of the nozzle. The shells on the outside go counter clockwise and the shells on the inside go clockwise.

My suspicion was that the problem is caused by belt tension differences or miss alignment of the axis. I tested both parameters by continuously making small changes, making a new print and see if there was an effect but I could not see significant differences in the gap size when doing so.

Under extrusion also doesn't seem to be the problem because my extrusion works fine.

Does this look familiar to anybody? It would be great if anyone could help me because I am running out of ideas.


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    Posted · Allignment problem

    Yes, very familiar. It's backlash. Make sure the short belts are TIGHT. The long belts shouldn't be too tight but reasonably tightened. If you really want to get rid of the backlash on your UMO, I recommend switching to direct drive and replacing pulleys and belts with GT2 belts. With those two changes I got the backlash on my UMO down to about 0.05mm.


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