Extrusion problem I don't understand

daniel_kukieła

Hi,

I'm creating 3D-printable Power supply hole cover for PC cases that use the so-called Pico PSU (a hole for it will be added later). For now, I created the base shape and I am configuring options. I added mesh and I'm trying to add back material where the screws are coming in. The problem is extrusion works fine for 1 out of 4 spots only. The spot that it works:

But as soon as I'm trying to add another spot to Extrude 4 (from Shetch 3):


Honestly, I have no idea what it is complaining about. I tried so many things but I decided to ask.
The document URL: https://cad.onshape.com/documents/02e11ac6c38230e5a1618296/w/7d6a0710d7bed4906d5b365c/e/cdcb218ee44614c759821038?configuration=List_XmLQE1L57Tz3hC=Full&renderMode=0&uiState=63d742925336de296233612f

I'll be glad if anyone can explain what's wrong here.
Thank you in advance.


- Daniel

NeilCooke

It's because you are making a very small tangent sliver which is creating "non-manifold geometry" which the kernel doesn't like. Edit your sketch and add that small red area to it and you should be fine.

daniel_kukieła

My goal is to make it somewhat configurable, so I cannot add a single small piece there since if you modify the hexagonal mesh settings, it won't look the same. Is there anything else that can be done to fix it that does not require manual fixing?


- Daniel

nick_papageorge073

Off topic, I made some similar hex shaped openings for fan cooling on a design for my dayjob. I ended up with a few thousand holes. It slowed down the model substantially, and even reached the 10 min timeout limit so I was stuck. What I found helped a lot, was to union all the hex parts to a dummy plate part. So the result is one part made of "dummy plate plus all the hexes". Then, union subtract that from your main part to make the hex holes. This improved the regeneration times quite a bit.

nick_papageorge073

For your question, in the real world these hexes would be  punched with a hex shaped tool in a sheetmetal part. Wherever you would need a screw, the entire hex would be removed, as it would not be punched at all. There is not a "half hex" tool. Its all or nothing. You are 3d printing it, so of course these rules don't apply. But, maybe they can help your design intent. Maybe you can draw a radius of your screw diameter, and any hexes that fall within that radius are deleted. I don't know how to automate this in OS, but if you or someone does know how to automate this, it would solve your thin geometry issues causing the failures, and make your part more "proper".

dirk_van_der_vaart

If you are lasercutting the hexes in all different sizes you can add an extrusion to close a few of the hexes first and then extrude the hole.
That's not difficult to do in a configuration.

S1mon

Why not use a fill pattern?

https://www.onshape.com/en/resource-center/tech-tips/how-to-use-the-fill-pattern-custom-feature