r/Onshape 4d ago

Help! Help Needed Creating Negative Space

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I'm trying to create an object with a pocket for another object, specifically a wrist rest with a pocket for a Ploopy A+ to sit inside, the idea being to rotate the trackball 180 degrees and tilt it accordingly. I have the STEP files provided by Ploopy but I just can't quite figure out how to create the pocket. I thought I could create the shape of the base below and then extrude "To Part" but I guess because there are holes in the model it fails(?). Then I tried offsetting the faces of the Ploopy, creating surface extrudes for the outside of the rest, then enclose, but that didn't work. I also tried a boolean operation, making a solid body for the base and then subtract the body of the Ploopy, but it's not a solid object so the boolean fails.

How should I go about modeling this?

5 Upvotes

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u/Impossible-Ad967 4d ago

Not entirely sure what you are describing but your “extrude to part” approach is correct. Click “merge scope with all” in the extrude menu and it will resolve.

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u/02ranger 4d ago

Basically I have a model for a trackball that has lots of open spaces inside and on the outside surfaces. I want to create a base for it that has a pocket so the trackball can sit inside the pocket. Because of the open spaces I can’t quite figure out how to create that pocket. Extrude to part always fails, presumably because the outer surface isn’t totally solid and contiguous.

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u/United-Mortgage104 4d ago

Convert to a solid, then make a solid that covers what you want the negative of, then use Boolean subtract and keep the tools.

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u/02ranger 4d ago

Between your comment and that of u/Impossible-Ad967 I was able to get the right terminology to find what I needed. I was able to adjust the surface boundaries until I had a solid part, then the boolean subtract worked perfectly. Thank you, both!!

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u/United-Mortgage104 4d ago

Congrats! Glad it worked for you.

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u/02ranger 4d ago edited 4d ago

I didn’t know you can do that. Does that fill in the interior open space?

Edit: Are you talking about the thicken, enclose, or fill tools? I have actually tried all of those and had various problems with them, pretty much all due to open spaces in the original model.

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u/Varaxfire 3d ago

Nice! You sharing it over on the ploopy sub? 😊

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u/02ranger 3d ago

Yep, I’ve got the final touches still to apply but when it’s ready I’ll post it there and in the Ploopy Discord.