I've added a photo. www.autoartisans.com/harmonicdrive/HarmonicDrive-8.jpg The new wave generator pieces puts the bearings 1mm further out. Was also able to bring it a bit closer to the motor so the bearings now sit in the middle of the fixed spline gear.
I've run it with 18,000 steps per second through a driver that does 1600 steps per rev. It still has that rough plastic against plastic sound. I need to add a few more nyloc nuts and Loctite to prevent things from coming loose from vibration but with that small motor I can't grab onto the 40mm output drive and stop it from turning. If anything a bit of load on it makes it quieter. I'll also add some white lithium grease and then run it for a number of hours. I suspect , like Sam's it will break. Oh and those speeds: 11.25 revs per sec for the motor (675 RPM). With the 35:1 that's 19.2 RPM for the output shaft or 3.11 seconds for one rev. I think that would work fine as one arm on a robot style automatic tool changer. John > -----Original Message----- > From: John Dammeyer [mailto:jo...@autoartisans.com] > Sent: November-30-21 1:41 PM > To: 'Enhanced Machine Controller (EMC)' > Subject: Re: [Emc-users] Harmonic Drive > > 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 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
