Author Topic: Separating a model into different parts for multi material 3d printing  (Read 257 times)

searcher

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Hi,

I have the following model of a foot insole that I would like to separate into multiple models for multi material (or more specifically multi density) 3d printing.



I would like to separate the model into 3 parts:
1. The outer 1mm perimeter of the insole (see image below).
2. The top 2mm of the insole (accross the whole top surface which isn't flat).
3. The rest.

The first part would look a bit like this (except it wouldn't be a foot shape)...



I'm new to Meshmixer. Is this possible? What features of Meshmixer do I need to use?

Thanks for your help!

MagWeb

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Re: Separating a model into different parts for multi material 3d printing
« Reply #1 on: September 07, 2017, 04:18:04 PM »
Could be done in MM but might be easier if you do it in your CAD app where you built that insole.

In MM you need to define Face Groups of the surfaces for part 1 and 2. You might do this (what's best depends on your mesh's triangle structure) via EDIT/GenerateFaceGroups (see:http://www.mmmanual.com/generate-face-groups/) or manually via a selection in SELECT/Modify/CreateFaceGroup.

Now, if there's a consistent FaceGroup for the footprint (part 2) you can use EDIT/GenerateComplex. DoubleClicking this part2-surface will create an complex inlay of this surface. You can define its depth clicking on the inlay's seam and setting the desired depth (2mm) in the tool's flyout "OffsetDistance"... (see: http://www.mmmanual.com/complex-tools/)

Don't think the Complex tool will work for your part 1. So you'll have to go the Boolean way. To get the right result needs extractions/extrusions of the outer almost "vertical" surfaces to construct a subtrahend object.......
(could you post the file or send me a link?... might be much easier to explain....)
I'm just a user as you are. Being no Autodesk employee: I do not know where this road will lead to, nor do I claim to've all stuff got right.

searcher

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Re: Separating a model into different parts for multi material 3d printing
« Reply #2 on: September 07, 2017, 04:40:15 PM »
Hi MagWeb,

Thanks for your response! I appreciate your help. I have attached the model...

Unfortunately I can't do this work in the CAD software because the STL file is either coming from a scan or its coming from the output of a proprietary CAD system that I can't modify.

I tried your steps for part 2 and that seems to work well. I'm keen to hear your thoughts on part 1.






searcher

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Re: Separating a model into different parts for multi material 3d printing
« Reply #3 on: September 19, 2017, 07:11:50 AM »
Hi MagWeb, thanks for your help before. I am still keen to hear more about how you would do part 1.

Thanks again!

MagWeb

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Re: Separating a model into different parts for multi material 3d printing
« Reply #4 on: September 19, 2017, 11:53:15 AM »
Sorry, forgot this....but you'll get nice images now ;)

Your STL comes with a slight error which makes it hard to get nice results. At its edges top/side and top/bottom are tiny faces with normals disturbing a smooth surface(image 1.1). For they are small you can get rid of them selecting all and running Edit/Reduce. A slight reduction is enough (image 1.2).
EDIT/GenerateFaceGroups will now create a single group on the side and the bottom. To join the groups at the top select the side plus the bottom group and in vert this selection. Run Modify/CreateFaceGroup to join this selection to a single group.
Select the side group (> 1.3) and run Edit/Extract with an Offset of 2mm (> 1.4). Separate this offset shell via Edit/Separate (> 2.1: red).
Select the top group  and run Edit/Extract with an Offset of 2mm too. Separate this offset shell via Edit/Separate (> 2.1: yellow).

Now SelectAll of the yellow top object and run Edit/Extrude at minus 3 mm (it's offset is 2mm > gives 1 mm intersection) in Direction "Normal (>2.2).
Run EDIT/GenerateFaceGroups to get a group at the extrusion's side. Select this group and using Edit/Transform scale it up along X and Y dragging the square handles (> 2.3)

Duplicate the yellow and blue objects. Run BooleanIntersection on one pair and with the blue being activated at first BooleanDifference on the second pair.

Now SelectAll of the red side shell and run EditExtrude at minus 4 (its offset is 2mm > gives 2mm intersection) in Direction "Normal" (> 2.4).
Run EDIT/GenerateFaceGroups to get a group at the extrusion's sides again. Select the lower side's group and transform or extrude (> 3.1).

Duplicate the rest of the blue and the red object. Run BooleanIntersection on one pair and with the blue being activated at first BooleanDifference on the second pair.
I'm just a user as you are. Being no Autodesk employee: I do not know where this road will lead to, nor do I claim to've all stuff got right.

searcher

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Re: Separating a model into different parts for multi material 3d printing
« Reply #5 on: September 21, 2017, 02:31:44 AM »
Hi MagWeb,

Thanks so much for your help. Unfortunately I spent a few hours on it today and got a bit stuck (doing the duplicate and BooleanIntersection). I also have other models that I am trying to do the same procedure on and am struggling a bit with them too. I might revisit this in a few weeks time.

Thanks again!

MagWeb

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Re: Separating a model into different parts for multi material 3d printing
« Reply #6 on: September 21, 2017, 03:27:43 AM »
If there are issues doing the Booleans:

Sorry I did not mention that you need to rise Density in Remesh on the different parts to get a denser meshes.
I'm just a user as you are. Being no Autodesk employee: I do not know where this road will lead to, nor do I claim to've all stuff got right.