Custom Feature: Black Market Boolean

Derek_Van_Allen_BD

-Link to feature up front-
One of my favorite things about switching to Onshape from other CAD software has been how seamless the sheet metal engine makes projects. Seeing your parts represented in 3d and 2d state simultaneously and letting the software just handle the bookkeeping of ensuring your parts are always manufacturable in a flattened state on something like a laser cutter was a game changer for our production practices when I pushed my company to make the switch a year ago. Solidworks and Fusion certainly have the tools for you to make manufacturable parts, but they place the burden of manufacturability on the shoulders of the user to remember to use those tools rather than automatically always sticking to manufacturing rules. Huge respect to the devs for the engine that they've built.

But what if you want to break those rules?

As a lifelong rule breaker there are certainly times I've been using a sheet metal tool and run into a case where I need to apply a feature to a sheet metal body that isn't allowed by the engine and certainly wouldn't be allowed by any of my metal vendors - but a feature that nonetheless would be useful for drawing views, or some kind of part marking, or some weird workflow that I'm doing with my laser cutter at home where I can accept the terms and conditions of my own illegal linework because I know I'm the problem. Yes, you can always Finish Sheet Metal, but that isn't helpful when you need to apply the feature to a part with bends and have the geometry show up in the flat view as well. Sheet Metal Form offers a partial solution in the form of sketch placement, but I work in 3d formats wherever possible and I need depth to my flat pattern features.

If you, too, wish to add illegal geometry to your sheet metal parts, I offer the Black Market Boolean.

Useful for manufacturing contexts where you have bendy parts made from sheet goods that are not intended to be produced on a purely 2 axis machine. Maybe you're cutting your sheet goods on a mill or router and your file export format of choice is .STEP because you've been burned by 2d formats too many times. Maybe you use shallow cuts in 3d parts to denote an engraving operation with your vendor because .STEP AP 242 somehow has metadata for every manufacturing industry in the world except for the one that feeds parts to all of those other industries and your emails to a global conglomerate to get that added to the menu for the next version have gone nowhere. Maybe you just want to put 5mm Countertweeped holes into your next drawing to see how much the mill guy sweats when he sees them. Whatever your reasons are for breaking the rules, I sympathize and offer a solution.

And bear no responsibility for what you do with this tool

Enjoy.

S1mon

Very cool. I haven't tried your tool yet, but I hope it might solve this:

https://forum.onshape.com/discussion/13974/sheet-metal-extrusion-for-flexible-printed-circuit-boards-etc

[Edit: Tested it. Only subtraction is enabled. 😥Any chance of adding to a sheetmetal part?]

Derek_Van_Allen_BD

https://forum.onshape.com/discussion/comment/125360#Comment_125360

Partially, currently the sheet metal boolean tool registration operation only works on flat faces and only subtractive context so those are limitations to work around still. If either of those two limitations are lifted though this tool will see an update. From @lana's comments in the other thread it seems like an improvement that needs made on the core side to handle curved surfaces which makes sense because if you had a tool on a curved surface it would need to stretch and warp to fit the 2d domain correctly, or vice versa, and some of those cases can get real weird. Truth be told, this is part of why I have been exploring generalized FFD algorithms for solid bodies so I could start laying bricks for even more foldy unfoldy stuff.

S1mon

In theory Form can add to a flat face and leave it thicker, but the nice thing about your tool is it cuts out the steps needed to create a form library, and could be used directly on imported STEP files from ECAD tools to make an unfolding FPC.

{Edit]
I just finally tested this out, and the steps to create a form library are much more complicated than I'd like. It is indeed possible to just add material to a sheet metal part with a Form tool, but as you already pointed out, all you get in the flat view is a sketch.

I'm also less concerned about stuff across bends. I've lived with that limitation for years in Solidworks, so it's less painful. Just being able to add extrusions or imported bodies to a sheet metal model on the flats would be amazing.

Derek_Van_Allen_BD

Sad there's no additive support in the function this runs on though. I can't peek behind the engine curtain to see if there would be some reason why an additive Boolean operation isn't possible from a technical perspective, it probably is. But they likely developed the functions with the assumption that they wouldn't have a weirdo trying to use their sheet metal kernel to make folding live hinge 3d prints or kerf cut walnut shelves that would want additive operations. If you think of your sheet metal tools like sheet metal tools it makes perfect sense but my brain isn't wired that way.

Derek_Van_Allen_BD

https://forum.onshape.com/discussion/comment/125362#Comment_125362

There was an alternate build I attempted with Form that skipped the need to build a library, just select your parts and do the thing. It doesn't do anything useful to the flat pattern though, that function expects to dump a sketch into the flat view. I did manage to spawn randomly oriented invisible tool bodies into the sheet metal context that would be an extremely interesting support ticket for me to start though. I should probably do that.