On Saturday 16 May 2020 16:01:08 Ken Strauss wrote: > 3 Nm is about 2.21 ft-lb so at 12:1 reduction I think it would provide > about 26.5 ft-lb. For comparison, the Tormach microArc4 (harmonic > drive with NEMA 34 stepper) claims to provide a maximum holding torque > of 28 ft-lbs but they suggest using only half of that to avoid > excessive wear. I don't know the reduction ratio for their unit. > See https://tormach.com/microarc-4-4th-axis-38412.html > I don't know as I ever seen a nema 34 that short, and neither of those lb/ft rating are very impressive. I'd be a heck of a lot more comfortable with 100 lb/ft. With the BS-1 being a 40/1 worm, I'd expect well north of that when stationary. Asking the worm to move it at 50lbs might tax things though. I wonder if the cycloidal drive could be shrunk to serve as the worm drive on a BS-1? Say 3" OD?
Interesting train of thought. And small enough I might be able to make it on the G0704. I'll go back and look at the wiki drawings. > > -----Original Message----- > > From: Gene Heskett [mailto:ghesk...@shentel.net] > > Sent: Saturday, May 16, 2020 3:22 PM > > To: emc-users@lists.sourceforge.net > > Subject: Re: [Emc-users] Cheaper than normal FHA-25B > > > > On Saturday 16 May 2020 15:09:08 Chris Albertson wrote: > > > One interesting and fun option is to make your own cycloidical > > > reduction. These are completely buildable on a CNC mill that can > > > do 2 1/2 D machining on mild steel. Unlike most other gears, > > > these can be cut from plate stock with just an end mill. THey > > > can be 3D printed too. > > > > > > See the wiki link below. In a real system, the purple and grey > > > parts are made from sealed bearing units and you'd have two moving > > > plates stacked 180 degrees out of phase so as to counterbalance > > > each other. But the good points are (1) high torque, (2) very low > > > backlash, (3) compact size, (4) very simple 2D geometry > > > https://en.wikipedia.org/wiki/Cycloidal_drive > > > There are 100 Youtube videos about people making these with 3D > > > printers but they work better with metal. These have become > > > popular with people building robot arms and robot legs but could > > > also be driven with a servo motor and used as a rotational axis > > > for a machine tool. > > > > > > In a machine tool application, you would place a rotational sensor > > > on the axis and close the servo loop inside the controller. A > > > cycloidal system can be back-driven (just like spur gears or > > > timing belts) so they MUST be used in a closed-loop > > > > Which then brings up the need for some math. So how would one go > > about getting from a 3 phase stepper motors holding power, say 3 NM > > to lbs/ft at the output of a 12/1 cycloidal gear? > > > > Assuming zero losses in the bearings, which I'd guess at 5% if > > decent bearings. > > > > Could that 3NM motor hold it, or even move it under cutting loads? > > > > > > 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) > > 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 > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users 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) 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
