On Saturday 20 April 2019 16:44:29 andy pugh wrote: > On Sat, 20 Apr 2019 at 21:27, Leonardo Marsaglia <[email protected]> wrote: > > I plan to use some chinese rack and pinions (MOD 2 with 30 teeth > > pinions rotating at a max speed of 200 RPM) for the obvious reason > > of the budget. But I can get hardened and ground rack and pinions so > > I think that sounds pretty good. Anyway, I think I should stick with > > the straight rack and pinion since it's the simpler solution and > > being hardened and ground I think they will behave pretty well but I > > would like to hear your opinions. > > Helical might be slightly smoother, but won't have less backlash, so > any advantage is quite subtle. > > > 2- For the servo-to-pinion reduction: Planetary servo reducer or > > worm and gear reducer with timing belt? > > How much reduction do you need? You need to be careful to eliminate as > much backlash as possible, so if you could get all the reduction in a > single stage with a belt drive, that might be best.
Those designs that use a full length belt, anchored solidly and under tension at the ends, running the timing belt face down, but hit an idler pair at the gantry riser to turn the belt upwards towards the motors pulley where it loops over to hit the next idler on the bottom, seem to be at least as rigid as a ball screw, and possibly, given well adjusted tensioning, even less backlash. Watching some of the home-brews on you-tube I get the impression they can handily outrun the ball screw using versions. Ball screws have a tendency to whip in the longer versions at higher speeds. 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) Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
