Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4286527.
UPDATE (Apr 18, 2020) : I redesigned the "U-Bar" piece to be maybe a bit less like the original cast iron piece that I remember, but more attractive and just as functional.
UPDATE (May 5, 2020) : Fixed a slight misalignment with the captured bar in the "U-Bar" piece. I'm sure nobody even noticed it.
When I was a wee lad, my grandfather had a cast iron version of this puzzle in his livingroom. It became kind of a rite of passage that us kids would have to each complete the puzzle on our own without any help. I have now recreated it for the masses.
I looked online, and apparently this puzzle is called "Heart Breaker" or "Iron Heart". I found several variations of it. The idea is simply to separate the heart from the other piece (although since they print as separate pieces, I guess the goal for you will be to put them together.. unless you can find someone who knows how to put it together for you before you start)
This should obviously not involve any breaking or flexing of the material.. remember, this was cast iron.
I printed this with 50% gyroid infill at a 0.2 layer height with supports. I actually scaled mine down to 66% so that I could print both pieces together on the print bed... just remember that the smaller you make it, the more flex it will have which isn't great.
Post processing: Probably nothing on the heart piece. On the other piece, remove all the supports, and sand out the rough spots. The top bar should be loose and able to move around, but captured within the rings on the "U" part of it.
If you don't find this puzzle challenging enough, maybe hand it to an 8 year old :)
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