Boolean Blues – When Same-Size Cylinders Just Don’t Subtract

[Leonard_Elias_Böker]

Hey everyone,
I’m working on a medium-sized body that I modeled using surfaces, curves, and lofts. Now I’m trying to subtract a top and bottom cylinder using Boolean Difference, essentially like adding “lids” that cut into the body. The weird thing is: it only works when the cylinders are slightly smaller in diameter than the body. If they’re exactly the same diameter, Rhino just refuses to perform the Boolean operation.

I’ve had similar issues before — I know Rhino sometimes struggles when geometries are exactly aligned or have matching dimensions. Is there a clean workaround for this? Or is there a best practice for avoiding these kinds of Boolean hiccups when dealing with flush geometry?

Appreciate any tips!

Boolsch difference dosent work.3dm (2.7 MB)

[martinsiegrist]

Create a copy of your object with a larger diameter.

I deleted the cilyndrical surface of your object and used the gumball plane handle to 2D scale the outer edge of the up down surfaces. Splitting or boolean difference works best when there are no coincident surfaces. Hence I moved the bottom surface of the top cap down 5 units.

Same for the bottom piece. I split it with a line so it has the right height.

Boolsch difference works.3dm (3.1 MB)

PS: your object is circular so it should be centered on the origin. It wasn’t so I moved it.