Living in FilletEdge Hell

I’m trying to fillet all of the edges of this part to 1/8".

part.3dm (1.4 MB)

I’ve watched multiple videos and understand there is an order about these things, but I can’t seem to crack the logic of this part. Generally speaking its generating a lot of “shards” and not trimming and joining. Any thoughts?

To start with, you’re modeling in Feet with a tolerance of 0.01 feet.
You have surfaces you’re trying to fillet that read 0.02 wide.

Do you really mean to fillet to 1/8 inch?

A couple of general “rules”:
1 - Your tolerance should be one order of magnitude tighter than your smallest modeled feature.
2 - You radius has to be less than 1/2 the width of the surface if you’re going to fillet both sides. the “rolling ball” can not run out of surface to follow.

John –

Thanks for responding quickly. Sorry. I pulled this out of a bigger file and didn’t reset the tolerances. I am modeling with appropriate tolerances in the mother file.

Yes I did mean 1/8". This is going to be rotationally molded and that’s the minimum radius to break it out of the mold. I guess my radius is exactly 1/2 of the width of the surface. I can change that, but I’m having errors even in places where I have a much more generous surface.

I was told this by a wise McNeel staffer: Watch out when you change tolerances. It only affects new stuff made, not the other stuff already there. Now you’ve made the problem worse by having geometry in your scene with TWO different tolerances.

I always set it pretty high (0.001 with mm) before I make anything.

I definitely don’t mess with tolerances once they’re set. I pulled this piece of a file out so I wasn’t uploading a fat file with superfluous models. I will implement advice from the thread in the properly toleranced file.

If you do mess with tolerances, the very next thing you should do is Explode your polysurfaces and polylines, then Join them again and make sure everything is closed as you expect it to be. You may need to rebuild edges before you Join them again.

You have some complicated corners where multiple surface meet at different angles along a straight surface. FilletEdge in V5 or V6 can not automatically handle them.

You will need to Explode and use FilletSrf to manually model the complicated intersection.
These techniques are covered here:

I reviewed that link already. It helps resolve some of the issues in isolation, but not all of them concert.

Thanks anyway.

When I switched to inches, tightened the tolerance, Exploded/RebuiltEdges/Joined, then tried FilletEdge at 0.08, I had far fewer corners to clean up.

Awesome! I’ll try that.

Oh god. That is Fillet Hell. I spent 30 minutes tackling it from many logical orders.

The worst of it is that you probably will need to manually trim the surfaces based on the rolled fillet “chutes” and then blend them with spheres as shown in:

That however, is such a tedious process as to become it’s own kind of hell.

I would look into softening and sub-dividing the resultant .stl mesh in another software.
Also, you might try AppleMeshSoftening in the Windows version.

Automatic and accurate filleting (trimming) has always been a big weak point for Rhino, Windows included. Automation for something this complex may be better served by nPower, Power Solids…
But that’s $400 bucks and only Windows (noticing a pattern?)

Welcome to hell. : ) It’s nice a warm in all other respects here.

Also, you should consider using the TOOLING of the die maker to effect your fillets with Radiused mill bits and ballnose cutters. This can be programmed at CNC time, and exterior corners of a female mold can be softened by hand.

1/8th of an inch is so little, this can be done by hand, even could be vibrated (knocked down) with physical media. Just some thoughts.