Two birds, one stone...maybe...

Like many of the guns I've built so far,  CETMEs use a receiver flat that gets folded into a receiver shell.  I'm going to make my own bending jig because I can.  A problem with these flats is getting them folded straight and to the right size.  Instead of making a bending jig and a separate straightening mandrel, I'm going to try to do it all at once.  I'm going to use a 3D printed jig mostly to see how it works.  Instead of just a round rod in the center, I drew up a mandrel to match the contours of the inside of the receiver.  Hopefully it will keep things straight and symmetrical.  Since I have a large piece of G3 receiver left over, I decided to flatten it out and test my jig idea with it.  I printed out a 3" piece of jig for the test.  Here's how it looks before bending:

And after bending.  The jig pieces aren't even printed solid, it's only 8 walls and 25% infill, and it bent this chunk of receiver without breaking a sweat.  Just out of curiosity I kept pressing until I crushed the upper mandrel, and it took a lot more force to crush the jig than it did to bend the receiver chunk.  I have to do a little bit of tweaking on the mandrel shape, but so far it really shows promise.

When I tried my "crush to destruction" test, the lower jig didn't even flex.  There's a lot of contact surface area where the receiver is pushing down on it and the base is wider than the top to help keep the sides from flexing out.  The upper mandrel stayed pretty intact too, it crushed directly under where the pressure  from the press was applied.  Keep in mind that this wasn't printed solid either, just 8 walls and 25% infill too.  Here's the upper mandrel post-destructive test.  It didn't even really crack and there is no layer separation, it just kind of smooshed until the plastic tore.