I had never found an analysis of repeatability or transmission accuracy in the advertising or Wikipedia for Cycloidal gear boxes.
Given the non engineering drawings at https://www.darali.com/page17.html, I was thinking they would allow greater holding power on a stepper motor in a fourth or fifth axis. Thank you. James Isaac. ________________________________ From: David Berndt <ber...@uberwin.com> Sent: May 16, 2020 2:18 AM To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net>; Roland Jollivet <roland.jolli...@gmail.com> Subject: Re: [Emc-users] Cheaper than normal FHA-25B Why are you particularly worried about that? Cyclodial gear boxes and harmonic drives are both basically 0 backlash, with potentially some lost motion. Most are repeatable well under 1 arc minute, which compared to a lot of rotary tables already out there. And that's something like a .0017" displacement on a 12" radius. Angular transmission accuracy would seem to be almost as big an issue that you'd have to start to think about if you're concerned about those levels of backlash. Also overall mechanical stiffness. -Dave On Sat, 16 May 2020 01:49:58 -0400, Roland Jollivet <roland.jolli...@gmail.com> wrote: > I've been thinking about 4th axes; > While motorised reduction drives are readily available, the issue is > obviously backlash. > > One way to make a zero backlash drive is to use two identical > gearbox/drives. Place them at opposite ends of the axis, and pit them > against each other by a few encoder counts. > So they will track and retain the zero-backlash. > > Of course, the total power available is now less than one drive motor, > but > it is an option to use almost any pair of reduction drives that can be > got. > But there is also the cost of the second servo amp. > > > On Fri, 15 May 2020 at 14:11, andy pugh <bodge...@gmail.com> wrote: > >> The normally appear on eBay at up to 6x this price. >> https://www.ebay.co.uk/itm/233587431605 >> >> The B versions have conventional incremental encoders and hall >> sensors, so are easy to integrate. Lots of torque, zero backlash and a >> very strong and fancy big crossed-roller bearing make them an >> almost-complete 4th or 5th axis just needing a bracket and a drive. >> >> I have no connection with the vendor, if you order one and receive >> dolls-house furniture instead don't blame me. >> >> -- >> atp >> "A motorcycle is a bicycle with a pandemonium attachment and is >> designed for the especial use of mechanical geniuses, daredevils and >> lunatics." >> — George Fitch, Atlanta Constitution Newspaper, 1912 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
