On Friday 28 August 2020 21:53:50 Greg Bernard wrote: > 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.
I'm about 1mm from having te 3rd one I need completed. Then I might need to epoxy or superglue the bearing carrier to the motor shaft. That was also a weak spot in the design. > > On Fri, Aug 28, 2020, 4:55 PM Gene Heskett <[email protected]> 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 > > > <[email protected]> > > > > 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 <[email protected]> > > > > > Sent: Friday, August 28, 2020 11:10 AM > > > > > To: [email protected] > > > > > 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 > > > > > [email protected] > > > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > > > > > > > _______________________________________________ > > > > > Emc-users mailing list > > > > > [email protected] > > > > > 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 > > > > [email protected] > > > > 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 > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > [email protected] > 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
