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Let's say I've made a 3D scan of my face and managed to get that into FreeCAD. How might I then create an object (it's a mask, okay?) that conforms to the shape of my face, with a given thickness, such that I can export and 3D-print that part only?

So if I printed it, it would fit over my face, but still look like my face from the outside, too. It would be, say, 3mm thickness througout.

To be clear, I'm not looking to make a 3D model of my head (the world does not need such a thing), or 3D model of a mold that I can use to replicate my head. I just want to make parts that conform to the shape of other, complex, parts.

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Instead of using FreeCAD, I would import the mesh data into a vertex-based 3D modeling software, such as blender.

After stitching the model in any areas where you still have gaps, you remove any vertex belonging to areas you do not want to use for the mask. This leaves you with pretty much a skin-tight base for your mask. Select all the remaining surfaces and scale S them in all directions in regards to the origin so you create a little airgap 5% extra (1.05) should create enough space to sit somewhat comfortably, but you might prefer a little more. As a stand-in for the face, I use this approximation of a forehead...

enter image description here

Next, we thicken that surface using the modifier menu: Select the Solidify modifier and set a thickness that looks good to you and that might be printable. Then make sure it pushes away from where your face is. Also make sure the Offset is at 1 or -1 to ensure that it does not stick out from the face-scan surface to the back! enter image description here

Now you got a perfect base to model on the outside of using the sculpt features while retaining the inner surface! Do yourself a favor though: print at least part of this model as a test fit and adjust the mask as needed.

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  • $\begingroup$ Excellent point. Maybe I'm using the wrong tool for this particular job. I'll try Blender as you suggested and see where I get to. :) $\endgroup$ – Neil Barnwell Apr 19 at 13:21
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    $\begingroup$ note that cast would be the wrong term: you mold an item over a base/buck $\endgroup$ – Trish Apr 19 at 13:24
  • $\begingroup$ Great stuff. Always happy to learn and use the correct terminology. I'll correct the original post as necessary. $\endgroup$ – Neil Barnwell Apr 19 at 13:29
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It depends on the software you're using, but here is an example with TinkerCad.

Step 1: Import your 3D model (imagine that the ball is a head):
enter image description here

Step 2: Change its type from "Solid" to "Hole" enter image description here

Step 3: Create a "Solid" box around your imported model.

Here is the inverted Solid/Hole version: enter image description here

Here is the Solid version with the Hole model inside your Solid box: enter image description here

Step 4: Select both models and group them: enter image description here

Step 5: Add a box covering half of your mold (ideally splitting it in half):
enter image description here

Step 6: Duplicate the mold and the box enter image description here

Step 7: Group the left mold with its surrounding box: enter image description here

Step 8: Invert the box of the left mold by taking its left corner and dragging it over to the right side of the mold: enter image description here enter image description here

Step 9: Group the right box and the mold.

Step 10: You now have two molds for each half of your model: enter image description here

Based on your comment, I'm adding a couple more steps:

Step 11: Take your cast, duplicate it, enlarge the duplicate, make it a hole and fit it over your cast (like so):
enter image description here

Step 12: Group the left cast with the larger "Hole" copy: enter image description here

And if you're going to 3D print it and fit it over the old model, then you might want to enlarge the cast by a few mm.

It's now up to you to figure out how to clamp the molds, inject them, and then separate them.

A few things to keep in mind:

  1. You might want to play with the placement of the model inside the mold a little better so it's not at the bottom of the mold but more towards the middle.
  2. You could also get a bit more creative with the joining of the two molds by adding channels or some kind of way that they can fit into each other with greater precision. Here is an example: mold.
  3. If the parts are more complex, then the cast will be more challenging and might require to be split into more parts.

Good luck! :)

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  • $\begingroup$ That is excellent, thanks! I should perhaps have been more clear, though. What I want to do is use a casting-type method in software, such that the final object can be 3D-printed and will fit over the base object but also look like it from the outside. $\endgroup$ – Neil Barnwell Apr 19 at 13:05
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    $\begingroup$ Aaah, got it... well, that's a bit more tricky and doesn't work too well with complex models, but I'll add a couple of steps at the end to show you how. $\endgroup$ – Kiril Apr 19 at 13:17
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    $\begingroup$ Different Software can do this much easier: Vertex based ones. $\endgroup$ – Trish Apr 19 at 13:21
  • $\begingroup$ @Trish that's an excellent point and very useful for 3D prints that require more precision. $\endgroup$ – Kiril Apr 19 at 13:25

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