Okay, so the goal here is to take that MDF piece, and make a 3mm offset of it right? So, to start with, Boolean is not the right way to do this. The way you are approaching the modeling is what is causing your problems. This is not what Boolean is used for. And, as stratosfear has pointed out, you’ve got all sorts of weird overlapping issues that will just make a mess of your surface. Also, your surface is made up of far more surfaces than is needed. By my math you only need 10 surfaces to describe this object. You’ve got 29. This is how quick and easy it is to make a “clean” version of your surface:
I used the DupEdge command to grab all the relevant surface edges.
I used Rebuild on all of them at once, and set it to degree 5 points =7. The max deviation was something like .002 mm.
I then used Loft with it set to Straight Sections to create all the surfaces except the end caps.
I joined the surfaces with Join.
I ran Cap to create a closed solid. Cap is a nice check too - it won’t work unless the openings are planar.
Lest you think doing it right takes longer, I timed myself. 2 minutes 29 seconds.
Now, to create your 3mm offset, I copied the object, and exploded it. I then joined the surfaces that were to be offset, using Join.
I ran OffsetSrf with it set to 3mm, accuracy to 0.01, and corners set to Sharp, no Solid.
I used MatchSrf to make the outside sides of the object match up to the top surfaces.
I joined the surfaces, and then ran Cap.
Cap did not work, since the opening was no longer planar, due to the offset.
There are two ways you can solve this. One is to extend the surfaces and then trim. The other is to simply edit the points along the opening so that they are planar. Since they were very very close to planar, I opted for the latter. I exploded the surfaces, turned the points on and used SetPt to make the opening planar. Turned points off, joined the surfaces with Join.
Ran Cap and it closed perfectly.
2 minutes, 49 seconds.
I’m writing this out to show you that there are totally different ways of working in Rhino from what you’re doing. This is the easy way to do stuff.
The way the meshes are interacting on this tells me from experience these surfaces are for all intents and purposes identical.
Boolean fail on intersecting solids_SkyG_Version.3dm (599.8 KB)