Perhaps save it as a step file or iges. I can't read that scad file. > -----Original Message----- > From: gene heskett [mailto:ghesk...@shentel.net] > Sent: December-20-21 3:10 PM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] Harmonic Drive > > On Monday, December 20, 2021 1:49:18 PM EST Chris Albertson wrote: > > Yes, he used maybe 30 pounds of metal parts. And I only saw a few degrees > > of rotation in the video, run it for 100 hours and see what happens. Flex > > is what kills the plastic so after 100 hours it will have had a few million > > cycles. But still it is 99% made of metal. > > > > I want to see a 100% plastic unit stand up to 100 hours of use. It can be > > done but not if the plastic parts flex. > > > Yes it can be done, the drive I posted the openscad file for last week, made > out of petg, has been sitting on my kitchen counter, running at 400 to 600 > rpms input, since the middle of September. How many hours is that assuming a > 24 hr day? > > On Mon, Dec 20, 2021 at 10:39 AM Sam Sokolik <samco...@gmail.com> wrote: > > > Did you watch this video til the end? I time stamped it. > > > > > > https://youtu.be/eW1GGI55Epc?t=878 > > > > > > sam > > > > > > > > > > > > On Mon, Dec 20, 2021 at 12:26 PM Chris Albertson < > > > albertson.ch...@gmail.com> > > > > > > wrote: > > > > On Fri, Dec 17, 2021 at 6:05 PM Sam Sokolik <samco...@gmail.com> wrote: > > > > > Hmm - seems we are making things a bit more complicated than they need > > > > > > to > > > > > > > > be.. Why didn't the simple flex gear work ok? You need to make the > > > > > system with fine enough splines that the flexure is at a minimum... > > > > > > > > You > > > > > > > > > can lower the backlash to a minimum by applying a small amount of > > > > > pressure to the system. > > > > > > > > The problem with small splines is that he is making this with printed > > > > plastic. There is a minimum feature size that works. Seriously you > > > > > > want > > > > > > > to stay above module 0.5 and bigger if you can. Mod 1.0 is more > > > > realistic There are two reasons. (1) plastic is not very strong unless > > > > you make the parts big and (2) the printer makes parts with dimensional > > > > tolerances of about 0.4 mm so if your parts have 1mm features you can > > > > expect 50% dimensional errors. That said, modulo 1.0 gears work really > > > > well. Smaler ones have a short life. > > > > > > > > Finally ANY flexing at all is the death of printed parts. They fail by > > > > > > the > > > > > > > failure of interlayer adhesion. Think of printed plastic like it is > > > > soft > > > > pine wood. When making gears from yellow pine, the direction of the > > > > > > grain > > > > > > > matters a lot and no one would think of making module 0.5 gears with > > > > > > pine. > > > > > > > I've been able to build an entire CNC conversion kit for a mini-mill > > > > from > > > > printed plastic. The stuff is VERY rigid and strong if you make the > > > > > > parts > > > > > > > large enough > > > > > > > > > sam > > > > > > > > > > On Fri, Dec 17, 2021 at 7:46 PM John Dammeyer <jo...@autoartisans.com> > > > > > > > > > > wrote: > > > > > > Alright. So it spins really freely but keeping the planetary > > > > > > cluster > > > > > > centred is a bit of an issue. So the attached photo shows roughly > > > > > > > > (very > > > > > > > > > > roughly) what I had in mind. > > > > > > > > > > > > With the right coupler between the motor and the gear cluster the > > > > > > planetary assembly should stay in the same place. There really > > > > > > isn't > > > > > > > > any > > > > > > > > > > axial load. There is a place for a 40mmx19mm bearing that I happen > > > > > > to > > > > > > > > have > > > > > > > > > > > on hand. > > > > > > > > > > > > But what about the driven ring gear? In one of the model shops > > > > > > today I > > > > > > > > > saw a package of 100 5.5mm stainless steel balls they sell for > > > > > > putting > > > > > > > > into > > > > > > > > > > > paint bottles to help mix them up. > > > > > > > > > > > > Seemed and ideal size for a bearing race between the two ring gears. > > > > > > > > > > Kind > > > > > > > > > > > of like what Gene H. stated he did on his setup. (Pictures?) So > > > > > > the > > > > > > > > > > Blue > > > > > > > > > > > Gear is fixed. The Green Rotates. The lazy susan like bearing > > > > > > between > > > > > > > > > handles axial pressure in the direction of the blue gear. But > > > > > > really > > > > > > > > the > > > > > > > > > > only thing holding up the green ring gear is the planetary assembly. > > > > > > > > > > > > Say we wanted to mount a face plate or chuck onto the green gear. > > > > > > I'm > > > > > > > > > open to ideas on how to stabilize that. Sketches would be great. > > > > > > > > > > > > Methinks a part that surrounds the blue gear and extends over the > > > > > > green > > > > > > > > > and they also have a bearing race between. Or we make a similar > > > > > > > > bearing > > > > > > > > > > mount to the rear one for the front with the gear cluster holding > > > > > > this > > > > > > > in > > > > > > > > > > place extended out to the bearing. Now the faceplate is attached to > > > > > > > > > > this. > > > > > > > > > > > But a lot more axial twist on the small bearing in the middle. > > > > > > > > > > > > Thanks > > > > > > John > > > > > > > > > > > > _______________________________________________ > > > > > > 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 > > > > > > > > -- > > > > > > > > Chris Albertson > > > > Redondo Beach, California > > > > > > > > _______________________________________________ > > > > 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, 1940) > 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
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