Kinda similar to making plastic. Except the mill roll, rotor screw, mixing barrel, etc are on a much larger scale. I wish i had made some videos years ago to share. Made my fair share of barrels, gearboxes, and repaired broken screws. The whole process is kind of like making bread when you step back and look at it.
HUGE fan of Bob and Ray!!!! Some record company had them do a weekly program of push artists and songs interspersed with many of their classic bits, and sent that for airing to college radio stations on custom LPs. I fell for Bob and Ray then. I have a goodly collection of B&R material, including those LPs. On a trip to NY once, I went up to the station they were working at, WOR I think, and got invited into the studio while they were doing their show! RIP, Bob and Ray!