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Ugly surface using support structure

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I don't have an UM3, so this is only a guess: from the photo there appears to be a way too big gap between support structure and bottom of the model. So the first layers of the model do sag. Also it looks like the support structure is not dense enough: not enough contact points between support and model for good support. I can't comment on the cause: a problem in the design? Or a problem with underextrusion of the support material? Or wrong settings?

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First turn on the hidden setting of support Z distance.


The minimum support Z gap is 1 time layer height if you don't want them totally fused together. What you can do is to change the support Z distance to 0.1 for 0.1mm layer height, 0.15 for 0.15 layer, etc. And also turn on the complete support interface. That's going to give you better bottom.


The default should be 0.4 for 0.2 layer, and 0.2 for 0.1 layer, which I totally disagree.

The double layer height Z gap is guaranteed to produce horrible bottom like what you have. I don't know why Cura has default like these.

Imagine there is a 0.4mm gap, plus the 0.2 for the print layer itself, the nozzle would be 0.6mm away from the support surface, even larger than the 0.4mm nozzle diameter itself. How is that ever gonna work? Cura probably don't do over-extrusion to compensate for the gap either.

Same thing for the default gap for raft settings. 0.3 gap for 0.1mm layer. I honestly don't know how that could work.

Edited by Guest

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I have had good results using the optional support roof, the particulars I can't remember, but it basically makes much more dense (by user definition) top on the support. It's perfect for horizontal overhangs.

I can't see the other side of your part, or know its desigb intent, but it looks like it may be better suited to printing inverted.

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Try turning on "Enable support interface" and reducing "Support Z distance". I had the same issue as you and this seems to help a lot

Not a good idea if using the same material for support as the model. If using PVA it works wonders, but if using same material as the model, it will bond to it like a wall.

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With a single nozzle machine like my UMO, the options are more limited. I sometimes split my model in 2 horizontally, and place the 2 halves split side down on the glass. The resulted glued part has a very consistent flat glue joint, and 2 printed top surfaces, and no supported surface on the finished part. Otherwise, have used the support roof option both with and w/o the support interface. I think the support interface can be set to undrrextrude which allows for better separation. I would like to explore a using very dense support roof (think top surface) with a dense, but thin and underextruded interface and zero distance to the supported surface.

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Well you have a UM3 so the obvious answer is to use PVA support.

There are other great answers above but... can't you rotate the model such that the edge that is pointing downwards in the photo is the bottom? Cura has the ability to rotate your part in any axes. Click on the part and on the left side choose the icon for rotating then click on a circle and drag.

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