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Left Fan scratches side wall!

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Hi everyone,


we got our UM2 roughly 6 weeks ago and since then it has been our most busy employee, but sometime through last week, print quality started to drop significantly and i cannot figure out why..


Some of it can be seen on the images below:

First of all, I had two serious cases with grinding, which were so bad that I had to dismantle the feeder to clean up.


Next is a totally uneven extrusion for infills [notice the blue object; it's supposed to be 50% (or 60, don't recall...) infill but some lines look like 100%] and shells [black object, some shells have tiny holes or too much material]. Other than that, the black object's top layer is clearly not finished, which became worse over the week.


Last but not least, when I lubricated and oiled the rods this morning because I thought this might help a bit, I noticed that the left fan (or as it looks, the screw that holds it) is scratching the side wall! This happened all the way to the front of the machine, but i centered the image on where it is most visible.


uneven and unfinished extrusion

uneven extrusion

Fan scratches

Does someone happen to have some quick ideas what might be wrong there? Especially the scratching fan... That really looks like it has the potential to mess prints



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What didier said. Look at the other side - they should be symmetrical.

Your blue part is suffering from "play" aka "backlash". You can look up that term in wikipedia. Look at the blue part carefully - notice that the infill is not touching the shell and that every other pass touches and then there is a gap - this is exactly expected of play. More details here (posts #7 and #8):


To fix the play on the UM2 first check the long belts - they are probably fine. More likely the short belts - one of them needs to be tightened. To do this is very easy - loosen the 4 screws that hold the motor then push down hard on the X or Y stepper until the short belts are tight again and tighten the 4 screws.

The problems with the black part on the sides can be also explained by "play" if it was doing some passes clockwise, and other passes counter clockwise.

The top layer of the black part looks like you printed with layers too think. I don't recommend going any thinner than .1mm as quality can get worse - same thing with the sides of the black part - instead of play that might be "too thin layers" or a third possibility: printing too fast.

The slower you print usually you get better quality.


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