On Thursday, January 27, 2022 12:45:22 AM EST dave engvall wrote: > I assume everyone knows about these. > https://www.fennerdrives.com/trantorque/ > Not cheap but tend to work. > > Dave > > On 1/26/22 8:30 PM, Ralph Stirling wrote: > > I had some problems today with a small XL timing > > pulley slipping on a NEMA17 stepper shaft due to > > the set screw loosening after running for long > > periods (multiple days). I drilled and tapped a > > second set screw hole, and I can probably apply > > some thread locker, but I got to wondering if it > > would be possible to make a miniature taper lock > > type bushing and pulley to clamp onto a stepper > > shaft. Anybody ever seen anything like that? > > > > The original taper lock system has a split bushing > > with an 8 degree taper against the pulley. They > > also have a clever set screw arrangement to tighten > > the pieces together and to jack them apart when > > removing. If you haven't used them before, a video > > is the best way to understand them: > > https://www.youtube.com/watch?v=-3K_vf_7fhM > > > > I like to 3d print my timing pulley perimeters, but > > a metal hub is nice (as has been discussed on here > > in the past). I'm pondering how I could make hybrid > > pulleys with a taper locking hub. Threading the holes > > in the plastic pulley wouldn't work so well. Perhaps > > some threaded metal insert can be incorporated from > > the back side. > > > > Enough of my musings. Looking forward to hearing > > other ideas and suggestions. > > > > -- Ralph
I'm printing an 8mm hole with an expanded dflat in the center of the elliptical armature for my version of the harmonic drive. The hole is spec'd at around 8.35 mm in diameter and a square about 8mm wide is positioned inside the hole and makes the dflat. Its is a tight friction fit, after the dflat has been ground about 1mm deeper, so a caliper ob the flat, measuring about 6.5mm to the back of the rounded shaft. Fits repeatedly with a friction fit, no backlash but with a teeny amount of eccentricity that shows up as a slight error in the output angle when running, which translates to a speed warble is it turns an A axis from my 6040 mills 4th axis on my kitchen counter, So the overall accuracy is probably 30 arc-minutes. The motor is a 1NM 3 phase stepper, with a big printed 60 tooth gt2-3 pulley replacing the sloppy key fit OEM pulley on the chuck shaft, and the output pulley of a 50/1 loose belt harmonic drive is 53 teeth resulting in a belt that tensions about right without a tensioner. It been running, both directions, for about a month now, no failures. I can't stop it by hand so I think I can carve tracks in a piece of steel in that 3" chuck, with an 1/8" mist cooled SC mill turning 20k revs.. carving square threads for instance, I have visions of making the 1"x 18" bolts for a woodworking vise with it. Or maybe even in a hard maple wooden dowel of even larger diameter. I'm cheap, the drive is 100% printed in PETG, and the only metal in it is the 5 printed bearings, 4 on the armatures ellipse, to drive the loose belt and the huge, single row, output disk bearing nearly 90mm in diameter, the balls are crosman bb's inserted into the printed races. I don't think I have more than 10 dollars in it not including my time baby sitting the printer. If it breaks, print another one, No metal in that hub. I have an idea that might smooth up the motion, based on the dflat pushing the armature a thou or so off center, interchange the signs that make the ellipse to put that potential wobble not in line with the engaged splines, but inline with the slack disengaged splines, effectively turning the dflat 90 degrees. But that has not been tried yet, I'm life testing what I have. The previous, smaller, 30/1 version ran 4 months, no failures. The Fenner method looks interesting but $50 for an 8 or 10mm bore? So I made taperlock hubs smaller than anything Browning sells for all that stuff when I put those mini ball screws into The Little Monster. When I found the lower dual pulley in the Sheldon all wallered out cuz somebody back in the fog of time had installed it bass ackwards and left out the key so it slipped and tore up the shaft trying to tighten the grub screw enough to stop the slippage, I took it to TLM and rebored it for a homemade taperlock. flex slots for all that cut with EDM. zero burrs to clean up. Hell to do the jack screws inside that yoke, very little room for the allen wrenches cut way down short arm, but it works, probably better than the OEM setup. Take care & stay well everybody. Cheers, Gene Heskett. -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
