On Wednesday 27 January 2021 16:04:45 Chris Albertson wrote: > This is a machine-tool related list. Many of us have 3D printers > too. So if you have both additive and subtractive tools available and > want to make a harmonic drive may be the best option is to make a > hybrid design with some parts of the drive made with different > techniques. > > Metal really is the best material for anything that needs to flex > because metal can be made so thin and is still strong when thin. 3D > printed plastic must be about the worst material for this. > > So I ask, Would it be possible to design an easy to make flex gear? > I think so. Most of the flex cup is made on a lathe then you mill > the teeth on the outside. I think it could be machined from a short > section of large-diameter steel tube. Then a bottom plate is press > fit. > > Maybe I could cut the teeth first, like making a gear, then place the > part in plastic holder and chuck the holder in a lathe and bore the > center out until the ring is very thin. The trick is to support the > ring with a 3D printed rigid backing fixture while boring it. > > The rest of the harmonic drive could be plastic. > > The big question for the group here is if the flex ring is something a > normal person could make one at a time. What kind of metal is best? > Is this kind of metal available in tiny quanity > > On Wed, Jan 27, 2021 at 12:36 PM Gregg Eshelman via Emc-users < > > emc-users@lists.sourceforge.net> wrote: > > Instead of a one piece flex cup, how about making a flex ring that > > connects to a rigid base with teeth or pins - something that > > interlocks but allows radial movement of the flex ring with respect > > to the base? No constant bending back and forth to break the print > > layers apart.
I like this idea too. Cut or 3d print, the equ of a small pitch box joint on the bottom of the flex gear, matched to engage the "fingers" on the output disk, it could slid in and out radially on these "box": pins, and do it without the flex that normally breaks the cup off the disk at that joint. That would replace the spot that is the major breaking point, with a hinge like joint, which might prolong its life by many times what it is now. The splined part would then need to be restrained axially to keep it from wearing the ends of the cylinder it becomes, from rubbing on the housing. Perhaps a very mild dovetail? But that would lead to backlash and problems assembling it. Enough extra length on the cups pins to project a thou or so past the disk and drive a flat head 0-80 screw in the the end of the pin, pin sized so the angled underside of the head would prevent it from pulling apart. Wouldn't take a screw per pin, one in every 4th or 5th pins should do it. 3d print a bit of the 0-80's underside head angle on the disks fingers and screw head could actually sit below the disk face. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
