Why does this oh so basic L section beam fail Boolean Difference?


It gets no more basic than this, L profile med blue sweep1 to med blue rail, then light blue L sweep1 to light blue rail, need cut out from light blue the med blue L sctn angle iron, Boolean Difference the med blue from the light blue, it fails.

all rail curves were setpt X, planar, L profiles intersext checked as ok…

A simple L sctn angle build and 40 mins trying to get the joint made.:confounded:

I even tried roadlike right,

…by the way why is the result in 5 parts ? ???

try trim, select med blue then hit enter and click the light blue get a mess.

Why should such a simple shape fail, this could be chapter 1 verse 1 of lets make a shape in Rhino., only to fail the beginner. Should Rhino handle such a task ?
Boolean Difference Fail simple L angle iron.3dm (820.4 KB)

Hi Steve - please check the curves used to make the objects - the one for the vertical is an open curve with overlapping ends.

Course, it still does not work when that is fixed - too many coincident faces and edges, I guess… use wirecut, maybe, or just good old trimming at the surface level…

V6 gets it right… with clean extrusions.

In general, booleans are not an elegant way to build things. First of all, it’s almost impossible to change them because the original geometry is gone or merged. Secondly, you get problems with co-planar faces just like you’re seeing.

Instead, use curves (and keep them!) That way, you get cleaner stuff and changes are just a few steps away.

Here’s an idea:

  • Draw a “L” shape curve, use it for a profile
  • Draw a square curve, use it as a path
  • Surface → Sweep one rail

I think there is an option for mitered corners.