I popped it apart so I could measure the bearings (couldn't remember the size). It looks quite good still considering the torque testing and stuff...
https://photos.app.goo.gl/6DcMdFQp98aTvbQi8 https://photos.app.goo.gl/cDcRrPErWqH4c8gV7 sam On Wed, Dec 1, 2021 at 1:22 AM John Dammeyer <jo...@autoartisans.com> wrote: > 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 > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
