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Outline wall problem with Benchy on UM2+

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Hi All,

maybe one of you could give me some advise on how to fix this problem on my print?

Here's a picture:


Its the standard Benchy, sliced at 0.1 Layer height, this particular one in Simplify3d, using default setttings provided with Simplify3d for the UM2.

Filament used is the Silver PLA that came with the printer (tried it with a roll of Innofill, the problem stays the same, its just less visible as it is not as shiney). It is absolutely consistent on subsequent prints. I tried slicing with Cura, again with the standard settings at 0.1 and the "spot" started at lower layers and was shaped a bit different, but was still there as well.

I tried with 0.2 layers and the problem is gone. I have no clue what to do.

Any help highly appreciated,

Thank you

Edited by Guest

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Hi and welcome,

This looks to me like curling due to the overhang. There's no real solution for this at the moment, it's due to the retraction of the material basically. And indeed it doesn't surprise me that you don't have that issue with 0.2mm layers because this effect reduced with bigger layers.

You can check this topic which explains it more in details

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Yes cooling helps. The more cool the better. You want fans at 200% if there was such a thing. Add a desk fan? There's a huge discussion about this. *while* it's printing if you look at ti carefully you will see the edge of the front of the boat is raised and the head hits this edge. More talk about it here:


Skip right to "page 2" and look at foehnstrum's video and read all the posts after that possibly. It's not until around post #39 and later that we really begin to understand what causes the issue.

The problem has to do with the fact that liquid PLA is stretchy like melted mozzarella cheese or like mucus. The liquid plastic is pulling like a rubber band as it goes down and creates a lip or raised edge where there is an overhang. The effect gets stronger on each succeeding layer. It is what causes the lower quality "look" of overhangs. Sometimes the part will actually rip free from the bed because of this (which is easily fixed by making parts stick like hell - another topic).

Also printing super slow (5mm/sec) can help as it remelts the layer below. Any faster than that speed and it doesn't seem to make any difference. This is talked about in the topic above.

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Interesting thread. Anyway, I managed to decrease the size of the blemish by increasing temperatures to 220 and disabling Coasting. Not sure why this helped, but I am content for now.

Also, printing in Colorfabb NGen, the problem ist pretty much gone - however: NGen and I are not quite seeing eye to eye yet, it gets extremely brittle. But that's a different thread.


.. and i seem to lack picture taking skills as well ;-)

Thanks again for your help!

Edited by Guest
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