Increase internal fillet resulting from a shell operation?

[Anonymous]

Hi.  I have created a hollow casting pattern by modeling a solid and shelling the back to leave 1/4" of material.  Several of the outside surface corners are filleted, causing the inside surfaces created by the shell operation to be filleted as well with a radius 1/4" less than the outer surface.

The model looks fine mechanically; however, some of the resulting back side radii are 1/8" and require a 1/4" ball end mill to cut down to those surfaces.  At its deepest point, the hollowed out back is 2.25" below the back plane.  In other words, to reach the deepest surfaces with the 1/4" ball end mill, the tool must have at last 2.25" of stickout below the toolholder.  This is fairly skinny for a 1/4" cutter at 9X the tool diameter.

My model includes 2° of draft angle on all the "vertical" surfaces (i.e., normal to the back face).  I have found 3° patternmaker's tapered ball end cutters, but I'm not seeing 2° tools.

Is there a straightforward method to increase the inner radius of fillet surfaces created as the result of a shell without modifying the shell thickness or otherwise changing the outside surface radius prior to shelling?

[HughesTooling]

A couple of ideas. First select all the filets selected in your last image and delete, Fusion should heal everything on the inside back to sharp corners then try applying a new fillet at 1/4". If that fails try increasing the external fillet to 1/2" before your shell feature, after the shell select all the external fillets, delete then refillet at 1/4.

Mark

[jeff_strater · Accepted solution]

Deleting the internal fillets and re-creating them...  Good idea, @HughesTooling.  I was approaching it much differently, using Press/Pull.  You can do it, but it is a bit convoluted, due primarily to a workflow glitch in the Press/Pull command, requiring you to select the faces to offset while the command is running.  So, to make this easier, I chose to create a selection set.

But, the basic idea is to use "create new offset" mode in Press/Pull to offset the internal fillets.

Here's a screencast:

Jeff

[HughesTooling]

@jeff_strater Nice try but did you notice the wall section changed?

Mark

[jeff_strater]

Crap, you are right.  I thought I had this figured....  I guess deleting and re-creating the fillets are the best way.  Sorry...

[Anonymous]

Great input from both of you -- I had no idea I could modify a filleted surface, but there's so much still to learn about this software!

I was forced to go back and think through exactly what exterior surfaces were creating the small internal surfaces and where/what I could modify to produce more machinable geometry.  I found a solution for this particular part, but the input you both provided will still be used elsewhere, so thanks for sharing, especially the Screencast that opened my eyes up to Selection Sets.

Thanks again!

Tom