Gene, I haven't tried PETG yet. I have a 'real' harmonic drive like Andy's so this is all just for a brief detour while I wait for parts for my draw bar.
An Mechanical Engineer once told me that if I want to write for Mech. Eng. people to keep the sentances really short with lots of white space. He feels that they otherwise have trouble comprehending. Of course I tend to run on with long sentences but I try to make up by posting lots of pictures which they say are like 1000 words each. I still write long sentences. Can't help myself. >From the sound of your description it's a lot like the one Sam built. His >videos have been invaluable. The web page, description and photos of the one >I built is good except his design is poor. I've posted a comment but a week >later it hasn't shown up yet. Still under review I guess. So if you have a chance to post some photos I'd love to see them. John > -----Original Message----- > From: Gene Heskett [mailto:ghesk...@shentel.net] > Sent: November-30-21 1:31 PM > To: Emc-users@lists.sourceforge.net > Subject: Re: [Emc-users] [emc-users] Harmonic Drive > > Hi John; > > > I designed and built, from petg, the loose belt version based on Sam idea but > quite a bit smaller. I can drive it with a 1NM 3 phase > motor which has an 8mm d-flatted shaft after grinding the dflat quite a bit > wider. No metal in the hub, its just a press fit on the > motor shaft. > Consisting of a hub that about 1mm eccentric plus and minus. Two 3d printed > ball bearings pressed onto the hub, useing crosman > bb's for balls. They drive the inside of a toothed belt, printed in petg. The > 60 teeth on the belt are triangular, facing outward. The > belt is 19mm wide and is moderately thin to encourage its flexibility. Two > rings with the same triangular teeth surround the belt, > sized so the armatures eccentricity pushes to full engagement at the maximum > measurement of the armature, but the triangular > splines are disengaged at the amatures minimum measurement, 1 9.4mm wide ring > has 60 teeth, the other has 62. > > > One ring is pinned into the ID of the housing, the other is pinned into the > face of the output shaft/disk, whose OD carries the groove > of another similar bearing, with the OD of the bearing glued into the housing > cup. > > > I left it running on the kitchen counter for a month at about 500 rpm for the > input armature, no breakage. Output is taken from a 23 > tooth sprocket fitted into, and pinned and superglued into the output disk. > Designed to fit on the A drive furnished with a 6040 > Gantry mill when bought as a 4 axis. The existing motor and gear ratio has > very low holding power, this does. Backlash is in the > driving belt as its not quite tight enough and it will need an idler fitted > to snug up the belt. On that drive, the spacing is not > adjustable. > > > > Once you have a printer that can use petg AND survive, I've a room full of > failed printers, it took an $800 prusa kit before it Just > Worked, you can make this for around $15. Theory is if it breaks, print > another from the leftovers. > > > Announced much earlier this summer on the list, I have had zero enquiry's. > > > You can have the OpenSCAD file when I get a working machine up again, or I > can mail you one drive and the motor+driver for $200. > Right now I'm in the recovery process of bringing this machine back to life > after a 6 month old 2T drive failed totally in the night last > Thursday. And debian bullseye plus a raid10, all from SSD's is being a PITA > to get setup and running like the stretch install that > puked. So I'm using webmail cuz its all thats working. > > > Take care John, Gene > _______________________________________________ > 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
