Some weeks ago I showed how I had heat formed some lightweight ABS gears and Evan tried the same with Acetal. If I recall correctly, Evan tried heating the blank but the forming failed.
Now that I have some black plastic which is probably not Acetal but I tried it anyway. It is much harder than the ABS was and there was no sign of it forming without added head.
This time I put the blank on an arbor in the chuck and mounted the steel gear on the tool post, I pressed the gear against the rotating blank which started the familiar rumbling sound then I put my heat gun to the edge of the gear and when the rumbling eased I advanced the feed and repeated until the teeth were formed at full depth. Success!
Well formed teeth that appear to be full strength but I can not get rid of the hairy edges!