What's a good way to add a Tolerance to a Cut/Intersect?

[DrCyanide]

I've got several parts that intersect, kind of like a stacking 3D jigsaw puzzle. Like a jigsaw puzzle, I need to keep both the tool and the body I'm cutting a connection out of, but I also need to add a tolerance so that when I make the physical part they connect nicely. Each piece has edges that are based off of forms, so I can't just offset part of the sketch and extrude/cut. 

The only way I can think of is to create a copy of each piece, make a shell that's my tolerance size larger, then cut that shell copy away from the connecting piece, repeating that over and over again for every piece (minimum of 12 connections so far).

While I don't doubt that would work, it just sounds like the wrong way to go about this. Any tips on a better technique would be greatly appreciated.

[wmhazzard]

I use offset face but I don't know if that will work for you. It would help if you attach an f3d file so people can see what you are talking about. 

[DrCyanide]

OK, back at my computer so I can upload what I'm working on.

[jeff_strater · Accepted solution]

here is how I've done it in the past - it is a bit tedious to select all the faces (and you can make that a bit less error-prone using Selection Sets).  The basic idea is to just create an Offset Faces feature to add the tolerances.  I see you already have a Tolerance user parameter, so I used that:

[DrCyanide]

That offset face is exactly the kind of thing I was hoping for. Thank you!

[bryn.parrott]

Really ? Can't imagine this without a picture ?Oh my god !.

Its exactly the problem I also have. Imagine a part (A) that has another part (B) designed to fit. (A) needs to acquire a hole big enough to fit (B). When 3D printed, small variances in size come about through various sources: The slicer, the printer, the filament.
The hole in (a) ends up needing to be slightly larger to take the variances into account. When (B) is combined as a cutting tool into object (A) there needs to be an invisible margin around all intersects of (B) to make the hole slightly larger. This is such a common engineering issue, but Autodesk seem not to understand it, instead bend their efforts to make the cuts "exact", which is unlike real life.

[g-andresen]

Hi,

What is the problem?
I have been doing this with offset face for a long time.

günther

[bryn.parrott]

Its a workflow thing

Imagine you are using a model someone else created in blender. Designed to print as a whole object, but not fitting your printer. So it has to be cut up into pieces using existing parts in the model, and intersecting parts must be made non intersecting, so they fit together and screws and pegs are applied for reassembly..

So, there are many instances where combine is used to cut out a hole in piece A to allow piece B to fit  into it. There needs to be a tolerance gap around the whole of the outside of piece B to ensure  the vagaries of 3 D printing dont make that hole too small.  so for a square piece thats 4 faces that need to be offset. multiply by however many such instances exist in the design.

Whilst offset face might work once or twice its pretty tedious to go thru the whole model doing this on all the intersecting faces. Dont get me started on having to select all the tiny triangular faces the F360 did not  automatically combine together as one planar face.

There needs to be an efficient workflow added to F360 that deals properly with the issue of the very common issue of part fitting tolerance. It would be a small amendment to the combine function.  

[TheCADWhisperer]

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@bryn.parrott wrote:
…but Autodesk seem not to understand it, 

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@bryn.parrott 
Use the Autodesk Mold Design tools. 
Attach your file here if you can’t figure it out.