Cannot modify a part that has mesh as one surface

matti_suuronen

I have a 3d scanned mesh surface, that I imported as .obj, and I have created a solid that fits that surface, or rather that one part of the solid is that surface. It seems I cannot freely remove/add to that solid by extruding. I might understand this if the resulting geometry would somehow touch the mesh surface, but I cannot even create a small pocket on one of the flat non-mesh surfaces, no matter how shallow the pocket is, or how far from the mesh surface. And with some other similar one-side-is-a-mesh solids this works just fine. What might be causing this? Can I work around it somehow?

jnewth_onshape

Something about the preceding Split and/or Lip operations leaves you with a bad edge on that top face. The parasolid kernel is not able to make further operations to a face bordered by a bad edge, so your hole operation fails. I would recommend not doing the Lip and Split operations and instead do one extrude to remove the top body:


This results in the same geometry but without the bad edge. I was then able to make the failed extruded hole operation succeed without modification. 

wayne_sauder

@matti_suuronen
It's a bit hard to say without a link to your document to see a few more details. 
Are you sure that you're not working with all surfaces? 

matti_suuronen

I'd think these are not surfaces, as the part results from a split of a body that originates from an "enclose". Here is the link https://cad.onshape.com/documents/542c31bb37c34cd27d8bfae0/v/9b6a17dd435e3f31e8e0bf73/e/7c2c8434f546ad1e760de18c

wayne_sauder

@matti_suuronen
 You have something weird going on right under the surface that is causing non-manifold geometry when you try to extrude. 

jnewth_onshape

Something about the preceding Split and/or Lip operations leaves you with a bad edge on that top face. The parasolid kernel is not able to make further operations to a face bordered by a bad edge, so your hole operation fails. I would recommend not doing the Lip and Split operations and instead do one extrude to remove the top body:


This results in the same geometry but without the bad edge. I was then able to make the failed extruded hole operation succeed without modification. 

wayne_sauder

@matti_suuronen
Sorry it looks like I was only partially right, @jnewth_onshape posted a much more complete and helpful answer. 

matti_suuronen

I need both the top and the bottom parts, so I needed to copy the body in place, but now it works, thanks!

 I've used splits quite a lot with meshes, as it seems like extrudes do not always work with them, but it is good to know that it sometimes matters how you arrive to a certain geometry, and extrudes have their place. Of course it would be nice to know _why_ the spilt (or something) corrupted the edge..

jnewth_onshape

matti_suuronen said:

I need both the top and the bottom parts, so I needed to copy the body in place, but now it works, thanks!

 I've used splits quite a lot with meshes, as it seems like extrudes do not always work with them, but it is good to know that it sometimes matters how you arrive to a certain geometry, and extrudes have their place. Of course it would be nice to know _why_ the spilt (or something) corrupted the edge..

Mesh support is a fairly new feature in Onshape, and a fairly new one for the Parasolid kernel (as I understand it). I would also like to figure out why that edge is corrupted. Please file a bug using our built-in reporting tool:



 It's enormously helpful to the dev team because then we can share the issue with Parasolid and investigate the root cause ourselves.

matti_suuronen

Great, I will do that, thanks for pointing out the bug reporting possibility👍