Here's a link to the photos. Two views of all the parts not including the bearing arm. www.autoartisans.com/harmonicdrive/HarmonicDrive-1.jpg www.autoartisans.com/harmonicdrive/HarmonicDrive-2.jpg
I didn't have the larger ID bearings so I used one with OD 47 but ID 20mm and recreated the appropriate hubs for the smaller diameter. www.autoartisans.com/harmonicdrive/HarmonicDrive-3.jpg As I only found two of the correct size bearings in my parts bin I down sized the bearing wheel to have less wheels and speed up the print process. www.autoartisans.com/harmonicdrive/HarmonicDrive-4.jpg This photo shows that the printed teeth appear to match the drawing in -7 www.autoartisans.com/harmonicdrive/HarmonicDrive-5.jpg And because the bearing actuator is 1mm too short the cup is just barely stretched enough and does clear but only just. www.autoartisans.com/harmonicdrive/HarmonicDrive-6.jpg This one shows the drawing of spline gear and cup (cup not flexed) and either because the STL files were not converted properly to STEP or the drawings just weren't correct to start with. The prints of the cup and spline gear were done directly from the STL. www.autoartisans.com/harmonicdrive/HarmonicDrive-7.jpg I still think it will be better to use LCNC and make the gear parts out of metal. John > -----Original Message----- > From: John Dammeyer [mailto:jo...@autoartisans.com] > Sent: November-30-21 1:07 PM > To: 'Enhanced Machine Controller (EMC)' > Subject: Re: [Emc-users] Harmonic Drive > > So nothing as complicated as: > https://journals.sagepub.com/doi/pdf/10.1177/1687814019850656 > > I did detailed measurements on the cup version I printed and there are two > issues. The worst is the shrinkage of the plastic results in > the bearing holder being 1mm too small in diameter compared to the drawing. > Outside of Bearing to Bearing should be 84mm and is > 83mm. That leads to the teeth not entering the spline gear as deep as they > should. > > There's also shrinkage across each tooth from the 3D print process so that > even as they mate they bottom out before the sides > contact. And based on other reports of 3D printed harmonic gears the > thickness behind the teeth should be 1mm rather than > 1.5mm which ends up being too stiff. > > Then end result is this version has backlash but it turns quite nicely. > The max I can get with this small Size 23 old surplus stepper is 8 > seconds in one revolution with the 35:1 reduction at 1600 micro-steps/rev. I > also can't grab the hub and stop it. > > Finally, the spline gear and support body must be a lot thicker as it moves > under load which shows up in the original authors video > too. > > I'll put together a folder with the photos. > > John > > > > -----Original Message----- > > From: Sam Sokolik [mailto:samco...@gmail.com] > > Sent: November-30-21 12:46 PM > > To: Enhanced Machine Controller (EMC) > > Subject: Re: [Emc-users] Harmonic Drive > > > > I will post them later tonight.. To be honest - I took a video of the one > > of the drive mfg and kinda measured the tooth angle. (mine are just > > triangles..) > > > > sam > > > > On Tue, Nov 30, 2021 at 2:30 PM John Dammeyer <jo...@autoartisans.com> > > wrote: > > > > > Hi Sam, > > > Could you share the STEP file for the flex gear? I want to look at the > > > tooth shape. > > > Thanks > > > John > > > > > > > > > > -----Original Message----- > > > > From: Sam Sokolik [mailto:samco...@gmail.com] > > > > Sent: November-27-21 8:18 PM > > > > To: Enhanced Machine Controller (EMC) > > > > Subject: Re: [Emc-users] Harmonic Drive > > > > > > > > I found that a while ago - That was what I initially started to build. > > > > But the cup seems to not handle flexing. Atleast pla (I never tried it > > > > with petg). When Andy mentioned the style with no cup - I went that > > > > direction. I first made the flex gear out of pla - but it fatigued > > > > after > > > > about 6 hours of running full speed (of the stepper). Which might be > > > just > > > > fine for a hobby 4th axis. Your not running the rotary axis at 100% > > > > feed > > > > all the time. I bought a role of petg and printed a flex gear with > > > it. > > > > As much as I have run this setup (petg flex gear and pla splines) - I > > > have > > > > not had the petg flex gear fail - even after torque testing it. > > > (although > > > > I have not taken it apart) but it still runs and doesn't randomly stall. > > > > > > > > sam > > > > > > > > On Sat, Nov 27, 2021 at 10:05 PM John Dammeyer <jo...@autoartisans.com> > > > > wrote: > > > > > > > > > For those who have 3D printed the gear portions of the harmonic drive > > > what > > > > > plastic did you find worked the best? > > > > > > > > > > Thanks > > > > > John > > > > > > > > > > > -----Original Message----- > > > > > > From: John Dammeyer [mailto:jo...@autoartisans.com] > > > > > > Sent: November-26-21 11:18 PM > > > > > > To: Enhanced Machine Controller (EMC) > > > > > > Subject: [Emc-users] Harmonic Drive > > > > > > > > > > > > List has been quiet lately on the harmonic drive subject. I > > > stumbled on > > > > > this site. > > > > > > > > > > > > > > > > > > > > https://howtomechatronics.com/how-it-works/what-is-strain-wave-gear-harmonic-drive-a-perfect-gear-set-for-robotics- > > > > > > applications > > > > > > > > > > > > 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 > > > > > > > > > > > > > _______________________________________________ > > > > 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 > > > > > > > _______________________________________________ > > 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 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
