Bendbox experiment
Posted by
timjedwards
 
Joined Jul 9, '16 

I’ve grumbled several times about the steep learning curve of Fusion 360, but it keeps drawing me back, like Don Quixote to a windmill. So I present to you the Bendbox (aka the “Box-on-a-Diet”), which represents my stab at learning the sheet metal tools and the colorific plugin for the Glowforge:

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I started with a “simple” sketch of the profile of one side. (It was simple in appearance, but fiddling with properly constraining the relationship between curves was fiddly.) Next I swept a surface and used rotated copies as snipping tools to carve the side into its hourglass shape:

The top and bottom tabs were easy enough, but the curved tabs are tricky. Not only do the sides meet there at a non-square angle, but one side curves over the edge of the other:

This is where Fusion 360 really shines… I could make modifications to the sketch and instantly see them reflected in the rendering of the 3D corner as they were propagated forward through the entire construction history. So cool! A quick interference check let me know exactly when I had things adjusted properly. (My Inkscape workflow would have required lots of tricky math or, more likely, a series of prototypes as I honed in on the right values.)

Finally I converted the thickened side into a sheet metal part and generated an unfolded view:


I used the colorific plugin to export an svg and experimented with living hinges in Inkscape. (This is where Fusion 360 comes up short… I was not going to fiddle with cutting profiles with that many cuts, as that part of the system is still very manual.

My first attempt was a hexagonal living hinge (from the Obrary swatches), but it was far too fragile even for my gentler bend radius:

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So instead I made a fine mesh of offset dashes for maximum bend-ability. (My prototyping material of choice is Home Depot 1/8" chipboard, not a high-flex material.) Here’s the mesh mid-burn (gotta love that burn ordering algorithm):
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Next some alcohol on the tight bends:

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And then into the jig (a Fusion 360 quickie that snaps together at top and bottom):

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And then assembly:

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And that’s about it! No adjustments were necessary, everything fit perfectly just as Fusion 360 showed:
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It’s definitely a nice tool to have in the arsenal!


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