I also made the file available in AutoCAD if someone wants to modify this thing.
File Number 0 - head to connect in the left and right.
File Numbe...r 1 - head to connect in the top and bottom.
No Number - Letter.
It is necessary to adjusts this thing after printed to put them together.
It not easy to insert letters inside the puzzle.
I use sandpaper to give the pieces a better finish.
First layer and layer height: 0.3mm
Infil: 5% ( if you don't finalize good the pieces with sandpaper, last layer maybe break when you will mount)
No Support is required
About 30 minuts to print one piece. I usually print 3 or 4 together (about 1" and 40 min)
I printed it in ABS and PLA. I think rubber is perfect.