Croc-savers (pins)

Crocs are cheap footwear from supermarkets - very handy in the garden and for various lazy moments. What to do if the plastic rivet holding the strap in place breaks? Rip the strap off? Buy new crocs?

At first I made the replacement rivet with an M4 thread holding the parts together. Printing such a small thread is fiddly and most importantly - the pin breaks quite easily in the  4mm screw part. This press-fit-with-barbs design is much sturdier, sturdier than the original rivet. Easy on hands: many small barbs hold stronger and are easier to press to gether than construction with one circular holder. The push-pin part barbs are designed with more slanting leading edge angle steeper angle on the trailing edge. The socket part has internal circular grooves. As you press the pin in, it stays in. It is one-time use - which is along the original design idea. 

Print in PETG with 100% infill for max mechanical strength. No supports necessary. It feels impossible to break (please write here if it breaks, but I think I would need a hammer to break it) 

Assembly: Since the barbs and the grooves are small, it is not easy to see them without a magnifying glass, but they do the job well. First manipulate the socket in place; when both the croc and the strap are threaded on the socket cylinder, you press the pin in. It feels tight, gives ratchety click-click as you push. It does not require much force. If on your printer it gets too tight (printers have different tolerances), just print the push part smaller by 1%.

If you feel that the outside diameter of the socket is a little too wide, adjust the FreeCAD file. However, I think this “max diameter” approach is the best for strength.