Having a hard time subtracting volume in a mold

victor_elmander

Hello, pretty new to the surfacing side of onshape. After a lot of struggle, and a lot of circulat patterns of surfaces, I created a specific ornament design I've been thinking about for a while, but I can't seem to get the bolean to subtract the negative space in the mold (to be...). Am i doing anything wrong? Any other way around it?

https://cad.onshape.com/documents/2688279a528bbd2af1b71ea3/w/4f3d12af8efbb18006ef06c8/e/aab31efccd18f415bc91a1a2?renderMode=0&uiState=66fdc4b39d32d03c7606a128Error

jelte_steur814

@victor_elmander :

here's an example of how you could approach it:

https://cad.onshape.com/documents/65f7c6c9f2b966ffd379b657/w/87dcdd466097de5cb104cbad/e/a81b6daafedb7fcf75b6bb97

I couldn't help myself and try this approach

glen_dewsbury

This Boolean add of the 2 parts. See mass properties in lower right corner.

https://cad.onshape.com/documents/e4f73206564fcbec2c5f5ae4/w/302c910b85f39225c5c3a6c8/e/b9e7f994f861cf2201480586

wayne_sauder

@victor_elmander

Even though you have a composite part, it is made up of nothing but a bunch of surfaces. I don't think Onshape will let you use surfaces in a boolean. Also, if you can convert this to a proper part as is, I expect you will see the classic non-manifold geometry error come up.

jelte_steur814

I'd figure out the smallest section of the ornament that you can find that doesn't repeat itself. try and design that and create it into a solid slice.

(perhaps you can even do that by deriving some of these surfaces into a new part studio and trimming it smartly.)

then create one circular slice for the mold

then create a circular part pattern and mirror for both the mould and the part.

that'll save a whole lot of work and compute….

victor_elmander

Thank you for the ideas, haven't got the time to test it further, as far as I understand it on your answers theres no easy way out. I might try to create it as a solid model from scratch, probably gonna need a lot of workarounds. Would be easy if the walls in a solid "followed" other surfaces when the transform command is used.

Might also try other CAD-softwares or 3D-modeling softwares. Thanks for the answers!

MDesign

https://forum.onshape.com/discussion/comment/108025#Comment_108025

While you can use composite parts to subtract volume... They have to be a solid body. I've subtracted clean watertight STL files from native geometry successfully. The part in you example and the screenshot below will need some TLC to be able to use it in this case as onshape doesn't see it as a watertight object..

jelte_steur814

@victor_elmander :

here's an example of how you could approach it:

https://cad.onshape.com/documents/65f7c6c9f2b966ffd379b657/w/87dcdd466097de5cb104cbad/e/a81b6daafedb7fcf75b6bb97

I couldn't help myself and try this approach

victor_elmander

@jelte_steur814 Thank you for the solution, will go through it and try it by myselft!