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tried searching but couldn't find anything. I do not have a 3d printer so can't really experiment on my own, which means that when I am going to order a 3d print I want to get it as good as possible. So, my question:

Do quality of geometry matters when 3d printing? Will 3d printer only print quads, or ngons are fine? Are there shapes to avoid?

Cheers :) M.

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  • $\begingroup$ There are design issues based on the printing method. Do you know what kind of printer they're using at the print shop you're considering? $\endgroup$
    – Jay
    Dec 24, 2016 at 20:34
  • $\begingroup$ As commented on my answer, you should specify the technology which you are asking about. SLA or FDM are quite different in terms of the quality which you can achieve for example. $\endgroup$
    – Sean Houlihane
    Dec 24, 2016 at 20:35
  • $\begingroup$ It is going to be Ultimaker 2 most probably. $\endgroup$
    – Mariusz Kubiński
    Dec 24, 2016 at 22:23

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Welcome to the site!

In regards to quads, vs polygon. People will often reduce the overall detail to make it easier to print. But so long as after you export it to a STL and verify that your Manifold edges were done correctly and what you though was solid is solid, you should be good to go. As near as I can tell so long as you can export it to STL then it doesn't matter what meshing you use. That said I see Polygons more than anything.

Worst case you can run it through a STL repair program and it will make the required changes for you. Usually I used these tools to fix poorly rendered files. My favorite is Nettfab. which is now part of microsoft.

You can verify if it will print by downloading slic3r, then "slicing" the file. After that you should be able to view a layer by later output.

Article talking about quads vs triangles from design

Shapeways article on preparing blender files for 3d printing

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  • $\begingroup$ Thanks for the comprehensive guide, this is true what you posted - I will going to fight with a lot of those issues but still your answer is not what I need, I will try to detail my question more: I wonder if 3d printer (PLA one) will have issues with triangles and ngons - like pentagon and higher (one face made from more than 4 verticles). Will it be able to print such polygons, or I have to make sure my geometry is clear, made from quads only? $\endgroup$
    – Mariusz Kubiński
    Dec 23, 2016 at 20:15
  • $\begingroup$ Updated. In short if you can export it you should be good. I cannot find anything saying you have to use a poly mesh vs something else. However you will likely want to reduce the quality to something more simple to printing. $\endgroup$
    – StarWind0 ♦
    Dec 23, 2016 at 20:30
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If you're talking about the shape of the end result, rather than the constituent elements of the model - the answer is no, there is no simple geometric restriction. Have a look at 3D benchy for an example of how print quality can be affected by different aspects.

One obvious issue is overhangs, so the orientation of the part is important for printing. A flat circle will (on a cartesian printer) come out smooth as X any Y move in sync, and have good support. A vertical circle will have steps introduced by the slicing which quantises X and Y from layer to latyer.

Sharp, un-supported corners may be the weakest aspect to resolve in the print - extruded filament tends to shrink as it cools, but as far as I know the errors like this can be reduced by printing more slowly (and reducing the dynamic flexing of the frame too).

Talking about a top surface of an extruded n-gon, if you look at the slicing output, you'll see infill in the bulk, with a layer filling only the top 3 or 4 layers. There are several infill patern options, but yes, there is scope for a scenario where the top layer needs to bridge a long way. However, since the alternate layers fill in orthogonal directions this should be a minimal effect. Tweaking the infill percentage, or chamfering the corners can fix these small defects.

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  • $\begingroup$ The overhangs are only a problem with FDM printers. The poster didn't mention which type of printer he is considering $\endgroup$
    – Jay
    Dec 24, 2016 at 20:33

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