On Tue, 14 Dec, 2021 at 1:53 PM, John Dammeyer <jo...@autoartisans.com> wrote:
To: 'enhanced machine controller (emc)' Gene Reading through my copy of "Gears and Gear Cutting" by Ivan Law (#19 in the workshop practice series) and some more research suggests that since both the cup and the ring gear should have over 135 Teeth that the tooth shape approaches the diameter of a rack and therefore they really aren't involute anymore as much as just triangular. That probably explains why the drawings I've seen suggest an ever so slight sine curve to the tooth. In either case though, the paper talks about how as the gear bends it bends along the same neutral point that say a toothed drive belt bends. That appears to cause less stress than bending them in the opposite direction. But I'm an amateur and a pretty poor mechanical designer since it's not my field or talent. I bought some PETG yesterday. I have some parts to make out of metal and still need those bearings so until all that arrives this project is on hold. John John: If your printer is bowden tube fed, and the bowden tube goes clear into the hotblock to seal against the back face of the nozzle, you WILL have trouble with PETG, as its 240C territory heat requirement will make the teflon bowden tube go away slowly, so the hot plastic will leak at the back of the nozzle, slowly running out until it drips on the work, and the next time the head comes by it will knock your work loose on the bed. Or it will run back up the tube and freeze in the cooler area up in the heat sink. Either one is a PITA. I even had one freezeup in the Prusa MK3S I have but that stopped when I replaced the heat brake tube with a titanium version, much less of a heat conductor. The E3D hot end the Prusa kit uses, uses a heat brake that stops the bowden tube up in the cold end of the heat brake, and other than occasionally warming it up to about 260C and retightening the nozzle again, it Just Works with PETG. Take care and stay well John. Cheers, Gene. -- _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
