Have you considered having the flex gear part printed by one of the 3d printing services in nylon? You could then print all the other parts yourself to fit. Most of the services can give you a quote if you send a file.
On Fri, Aug 28, 2020, 4:55 PM Gene Heskett <ghesk...@shentel.net> wrote: > On Friday 28 August 2020 16:04:11 Chris Albertson wrote: > > > Gene, > > > > I thought you had the STEP file for this. If you did not download > > it, I did and you can have my copy of it here > > https://a360.co/2EHlpMr > > > I do have it, but opening it with the latest freecad, does not get me > down into it to modify it. > > > I've been reading about printable harmonic drives and the best idea I > > found is to use a stainless steel drinking cup as the flex cup (after > > cutting off the rim) and gluing a timing belt to the cup to make the > > teeth. The steel/rubber composite seems to last a long time. > > Sounds good, and may work for gear reduction ok, but there would be a > huge, high frequency cyclic speed variation due the the shape of the > teeth in a timing belt. And that isn't exactly friendly to guiding a > star gazers telescope. These won't be that great either, but why design > in a known flaw? > > > On Fri, Aug 28, 2020 at 11:37 AM Gene Heskett <ghesk...@shentel.net> > wrote: > > > On Friday 28 August 2020 12:36:07 Todd Zuercher wrote: > > > > If you think about it the metal toothed cups used in harmonic > > > > drives, have to flex in a rather nasty way (it is a little more > > > > than just squeezing the mouth into an oval). I'm surprised they > > > > last as long as they do. I'm not surprised you are having cracking > > > > problems with the pla. What is the distance from where the cup is > > > > pinched by the bearing to the face of the cup? Increasing that > > > > distance should improve the durability. Also I think I would > > > > slightly increase the thickness and add a slight fillet to the > > > > inside transitioning from the wall to the cup face. Then taper > > > > the cup wall down and have it be it's thinnest (probably thinner > > > > than you have it now) for the majority of the height of the cup > > > > then thicken it again to accommodate the toothed surface at the > > > > bottom. > > > > > > I don't have the original src, just the stl's that the slicer can > > > make g-code out of. So the limits of my ability to adjust such is > > > limited to the xyz scale settings of the printer. > > > > > > > I do have the remains of a busted commercially made harmonic drive > > > > in a box on a shelf. It was in the tool changer of a used machine > > > > we bought. I don't know how it was originally broken, but it to > > > > failed at the transition of wall to face, the previous owner had > > > > tried to fix it by welding the cup back together. It worked for > > > > about 6 months after we bought the machine, until the welds > > > > fatigued and failed. In the mean time the part was redesigned by > > > > the harmonic drive manufacturer with a much taller cup for the > > > > replacement part (also requiring us to replace of a number of > > > > other parts in our tool changer to accommodate the redesigned > > > > part.) > > > > > > I fail to grok the reason they used a expensive part like a harmonic > > > drive for speed reduction in a tool changer. Boggles what little > > > mind I have left at my years. An eletric wiper motor can be made to > > > do that job with adequate accuracy. Really precise location can be > > > had by backing up aganst a pawl. Abuse the motor to get the power to > > > move a long chain if needed, its not something that has to run 500+ > > > miles non-stop in a blizzard. It doesn't run long enough to get hot > > > at any one time unless the designer is an idiot. Oh, wait, I've met > > > some of them. Some are. > > > > > > Stay safe and well Todd. > > > > > > > Todd Zuercher > > > > P. Graham Dunn Inc. > > > > 630 Henry Street > > > > Dalton, Ohio 44618 > > > > Phone: (330)828-2105ext. 2031 > > > > > > > > -----Original Message----- > > > > From: Gene Heskett <ghesk...@shentel.net> > > > > Sent: Friday, August 28, 2020 11:10 AM > > > > To: emc-users@lists.sourceforge.net > > > > Subject: SPAM: Re: [Emc-users] precisiomn indexer > > > > > > > > [EXTERNAL EMAIL] Be sure links are safe. > > > > > > > > On Friday 28 August 2020 06:18:32 Thomas J Powderly wrote: > > > > > Gene an old client called about using a Newbould indexer on his > > > > > machine. > > > > > > > > > > I remember it was a hirth 'gear' or coupler > > > > > > > > > > Very accurate stacking 'gears' , a way to set a part at precise > > > > > angles > > > > > > > > > > I thought... "Hey Gene could _print_ one" > > > > > > > > > > as if you dont have enough to do :-) > > > > > > > > > > just FYI > > > > > > > > > > TomP > > > > > > > > > > https://en.wikipedia.org/wiki/Hirth_joint > > > > > > > > > > https://www.youtube.com/watch?v=3EGGuR5YziE > > > > > > > > The odd tooth version could probably be done in sub-degree jumps > > > > but not with a 3d printers tolerances. > > > > > > > > I'm learning how to make flexgears for a harmonic drive out of > > > > TPU. PLA hasn't enough flex and breaks in less than 5 minutes > > > > running time. > > > > > > > > And I've two that have now run at an output speed of about 1 rev > > > > in 4 seconds for over 24 hours. Unlike the really preciely made > > > > metal one's, it has to have a touch of backlash, but with a decent > > > > driver, and none of the TB series fit that description, because > > > > they don't auto-throttle the currants, it looks like I'll have > > > > enough torque from a nema 17 motor to drive the worm of a clone > > > > BS-1, under cutting load no less. > > > > > > > > TPU can be a cast iron bitch, its 100x more finicky about temps > > > > and speeds than PLA. Currently seems to be working, but at a > > > > nozzle temp 15C above whats noted on the no-name box I bought 2 of > > > > for a $70 bill. Virtually zero extruder drive grip allowed in a > > > > Micro-Swiss hot end that moves the extruder motor to the X > > > > carriage. > > > > > > > > Thanks TomP, stay safe and well, both of you. > > > > > > > > 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 > > > > > > > > > > > > _______________________________________________ > > > > Emc-users mailing list > > > > Emc-users@lists.sourceforge.net > > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > 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 > > > 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 > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
