Mesh Geometry for 3D Printing

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bavariaSHAPE
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Mesh Geometry for 3D Printing

Post by bavariaSHAPE »

Dear Everyone,

my question relates to the mesh geometry. The first mesh (Image 1) I created from FreeCAD with the default setting (0.5). On the second try (Image 2) I have the model exported as STEP, and produced the mesh with the software Gmesh.

Now my question: which mesh geometry is better for 3d printing? Or it makes no difference?

I hope my question is understandable, since my native language is not English.
Attachments
Mesh geometry with FreeCAD default settings (0.5)
Mesh geometry with FreeCAD default settings (0.5)
Mesh_Standard.png (56.7 KiB) Viewed 2948 times
Mesh geometry with Gmsh
Mesh geometry with Gmsh
Mesh_Gmsh.png (109.22 KiB) Viewed 2948 times
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quick61
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Re: Mesh Geometry for 3D Printing

Post by quick61 »

Hello bavariaSHAPE, Welcome to FreeCAD and the forum.

It can make a difference, but the major one is the fineness of the mesh, regardless of which method you use. changing FreeCAD's tessellation to something like 0.05 will produce a much finer standard mesh than what you have there. The real difference you will see between the two is in ultra high resolution 3D printing and CNC machining. If your using a desktop 3D printer, just changing FreeCAD's tessellation will be more than you need to have good prints. When the tessellation is too coarse, you can end up with what is suppose to look like a circle, looking like a polygon.

Personally, I have used both types of meshes and for 3D printing, the biggest detectable difference between the two is the size of the STL file. ;) For 99% of all cases, a fine standard mesh will do just fine.

Mark
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ickby
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Re: Mesh Geometry for 3D Printing

Post by ickby »

gmsh is intended to be a fem preprocessor and this you can see in the mesh: It creates meshes with a rather uniform triangulation with a higher density at critical (round) parts. This is realy good for fem as you want a uniform mesh to ease the solution and get a good quality approximation over the whole part. However, this is unneeded for 3d printing. There it is enough to triangulate a plane with two triangles, it gives you no loss in precission. all you care about in 3d printing is how non-flat surfaces and curfes are aproximated. and for this gmsh and freecad provide an identical measure: the maximal allowed deviation.

So in theory it should be without difference for you which mesh you use if the deviation parameter is set to the same value. In general freecad sometimes produce rather curious meshes, so if you choose a high allowed deviation the triangles which can be seen may look strange.

Also note that you can use different mesh creation methods from freecads mesh workbench, see menu->create mesh from shape. You have additional options there which can produce equivalent meshes as gmsh ( as both can use netgen :) )
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bavariaSHAPE
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Re: Mesh Geometry for 3D Printing

Post by bavariaSHAPE »

Hello Mark, hello ickby,

many thanks for the detailed description. I have tested the variant Mefisto and Netgen in FreeCAD also. Sometimes I had no clean rounding. With the default setting I had often holes especially when rounding. After a long construction time I start FreeCAD new, and the problem is mostly resolved. For this reason I made the detour with Gmesh. But the easier way I think is using the standard settings.

By the way Mark. For starting into FreeCAD your YouTube movies have helped me really. Of course not only your movies. Also the many useful posts in this forum.

And when I'm fit with FreeCAD, I hope to also make my contribution. The result of my FreeCAD constructions is always the 3D printed. I do not have a 3D printer. For this I go to a 3D Printing Service, because the quality is better.


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