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
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