Make object 4mm wider in all dimensions

Support Modeling
1

Hi. So I have an STL object with curves and bumps and straight sections, etc. I’m trying to make a negative mold model of it and that I can do (block, boolean subtract, etc). But I want to create a “glove mold”, which requires the object to be made 4mm wider in all dimensions - and it’s a super complex mesh.

I’ve explored solidify, extrude on face normals, and a few other options and I can’t seem to find what I’m after.

I’d like something like: Take block, remove object. Solidify object with -4 thickness, then remove that part as well. The problem is that doesn’t work.

Or instead, Solidify with -4, but the inside of the object stays solid / faces stay paper thin - e.g. remove the inner structures. It’s a very complex mesh and I don’t think doing that by hand is a good use of time.

Anyone know areas I can explore to help do this?

Thanks!

2

Can you scale up the model by 8mm (4mm in each direction)? That’d keep the figure looking the same. I know extruding along normals can alter the proportions of your model, but scaling keeps proportions intact. Try adding 8mm to any axis in the dimensions panel of the transform menu,
Screen Shot 2020-06-28 at 5.43.05 PM

then copy-paste the scale of the altered axis to the other axes and apply scale.
Screen Shot 2020-06-28 at 5.43.11 PM
Screen Shot 2020-06-28 at 5.43.37 PM

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3

Why does it have to be exactly 4 mm?

Simply scaling it slightly would solve a lot of unnecessary problems.

4

Thanks guys. I will definitely experiment with scaling. I don’t think it’s quite as simple as adding the 0.004, but I have math skills and can figure that out. It is super promising. It’ll likely be this weekend before I can get back to this but I wanted to say thanks for the new area to explore.

5

I think displace modifier will work the best for your case.

EDIT: you can also scale along normals in the edit mode with alt+S

6

Hi Anthony. It doesn’t have to be 4mm exactly. I’m trying to make a urethane rubber mold around the object of about 4mm so it can hold the needed shape but still be peeled away. But 3mm or 5 also works. Just the thicker it gets the harder it is to work with. 4 was picked because I am printing 3D mold negatives to go around the positive model and getting all the alignment parts right is tricky. So 4 gives a mm or so of wiggle room.

Thanks fo the input. I’ll be experimenting with scaling and seeing how that looks. I appreciate the inputs.

7

Hi Jerzy. Thanks. I’ve never heard of that one - but that’s why I came here :). I appreciate it and will look into it.

8

If you set Displace modifier with midlevel:0 and strenght: 0.004 I belive it should make you mesh thicker by exaclty 4mm.

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9

You could also try MeshMixer for thicken/offset, it seems to work pretty well in situations where the thicken/offset would fail in Blender or other poly modeling apps.

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Hi BlenderSpendor. Tried that and its a complex twisted bumpy thing and the scaling doesn’t grow out from normals. It adds up errors along the way and the end of the object is way out of line.

Thanks for the attempt. I’ll be trying the other ways suggested next (been a bit since I could work on it)

11

jerzygorskiart - Boom for the win. Thank you so much. That was awesome and will be so useful for many things I do going forward. You rock. I appreciate it.

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