Interlocking joints in Sheet metal?

[bhahn1]

I have been trying to work out how to make interlocking joints in sheet metal parts. The attached screen shot is the only way I have found to do it in Inventor, but it is a cheat. One of the flanges is a 85˚ bend because if it were 90˚ it would give an error "Flange Body intersects with existing body or self intersects." Can anyone think of another way of doing this that wouldn't have the error and wouldn't have to cheat the final shape?

Thanks

[mrattray]

You need to model the "teeth" a bit smaller to provide proper clearance. You'll need it in order for the part to be manufactured anyways, which brings me to another point. How do you plan to make that?

[JDMather]

Attach the file here if you can't figure it out.
In fact "cheating" is not the way to model the part.

There is a correct way.

[bhahn1]

Thanks Mike, your suggestion sparked me to try someting different that worked. Instead of making the flange the correct size and trimming away the "teeth" I have made the flange short and added the "teeth" to it with an extrude. As long as there is an "air gap" between the teeth (thanks Mike), it folds and unfolds correctly.

As for how to manufacure? I have already made a few with a metal cutting laser and hand bent the peices just fine. These will be small run items. - Once I work out the bugs.

[mrattray]

I would avoid using tools from the 3D modeling tab (extrude). Stick with the sheet metal tools. Extruding things can lead to problems with unfolding a flat pattern if you're not careful.

[petedude]

I mastered this technique in 2010. You can see the results at

http://www.outfab.com/gallery.php 

I used integer math within an excel spreadsheet to calculate the interlocking fingers count and pitch. The math is strong enough that the number of fingers is independent from sheet thickness, and can also follow spline curves! I used the sheetmetal module to ensure perfect finger fit; I had to determine the neutral axis of my custom plywood as 0.75. 

I got this process really rockin and was ready to go to market when the machinery was relocated and everyone shifted interest. It's a shame since I led the world with the most complex and elegant fingerjoining designs.