If you use bushings over round rails how will you support the rails? A two meter round rail will sag. Bushings work well on short rails that don't need support. I have some on 10mm dia by 250mm long rails.
On Sat, Apr 27, 2019 at 1:57 PM Leonardo Marsaglia <ldmarsag...@gmail.com> wrote: > > > > Any rack you make, even if machined perfectly will have some backlash. > It > > is unavoidable. Belts have zero backlash if you use the belt the way > it > > was designed -- the belt moves > > > I said rack because I didn't know how to call it but the idea is to make > the rack in wich the belt can travel. In a certain way it's a rack, but not > engaged against a pinion, instead I'm thinking about the ServoBelt system. > But not gluing a belt to use it as the rack, I think it's a lot better (at > least for me) to machine the teeths in aluminum and mount them in tandem as > normal racks. > > If I were building this I'd use either V-track or round rails. Chips can > > not build up on a V or a round. Then pull the carage with a long belt. > IF > > you do you calculatins right (or ask for help) belt streach is a > > none-issue. > > > I'm thinking about using round rails as you suggest. I'm almost conviced to > use linear ball bearings but I'm also wondering how these could work: > http://www.nationalbronze.com/News/self-lube-bushings-what-are-the-options/ > > I suspect the torque needed to move the gantry with those bronze bushings > would be a lot more but I don't know if the benefits justify them. I like > them because of the increase in rigidity and also because I guess they are > less prone to damage because of dust and grit. But I've never used them so > I can't tell how they behave. Anyway, since I'm decided to use round rails > I can try them anytime I want. > > El sáb., 27 abr. 2019 a las 14:37, Chris Albertson (< > albertson.ch...@gmail.com>) escribió: > > > Any rack you make, even if machined perfectly will have some backlash. > It > > is unavoidable. Belts have zero backlash if you use the belt the way > it > > was designed -- the belt moves > > > > If you want to use a belt, contact the sale engineers at > > https://www.sdp-si.com/ or at least read the technical article on their > > web > > site. They have a lot of good engineering advice and real data SDP/SI > is > > *the* place to buy this kind of stuff. > > > > If I were building this I'd use either V-track or round rails. Chips > can > > not build up on a V or a round. Then pull the carage with a long belt. > IF > > you do you calculatins right (or ask for help) belt streach is a > > none-issue. > > > > But does it matter? Maybe for wood cutting a 1mm tolerance is OK? > > > > > > > > On Sat, Apr 27, 2019 at 8:08 AM Leonardo Marsaglia < > ldmarsag...@gmail.com> > > wrote: > > > > > > > > > > Cutting your own racks, while doable is a heck of lot of work for the > > > > lengths you are talking about, even if you make it in short sections. > > If > > > > your time is worth even a fraction of minimum wage you would be > better > > > > off using off the shelf rack and pinions. > > > > > > > > > I know it sounds like a pain in the ass but I can get some really nice > > and > > > squared 6061 aluminum profiles to make the racks. And I'm planning to > > mount > > > them on the turret of the Mazak and use a fly cutter on a shaft between > > > centers to machine the racks in a serial way. That way I can make them > > in a > > > easy way. I already have the jig to mount them so it's only a matter of > > > program the job and start to cut. I need to make some holes and > registers > > > to mount the racks but still I think it's not that big deal. > > > > > > It's just that gluing the belt sounds cheap and/or not at all a secure > > > option for me. But it's just the way I see it. > > > > > > El sáb., 27 abr. 2019 a las 12:01, Leonardo Marsaglia (< > > > ldmarsag...@gmail.com>) escribió: > > > > > > > With any rack or rack-like drive a gantry can have zero racking > > problems > > > >> by connecting the drive on both sides with a shaft. > > > > > > > > > > > > Gregg, sounds you don't trust too much on having two motors driving > the > > > > gantry. I've seen too many machines working this way but I would like > > to > > > > hear your opinion about that matter. I have zero experience with > > gantries > > > > so I like to hear all the opinions. I have to say I do like more the > > two > > > > motors approach but I would like to know what do you think about it. > > > > > > > > El mié., 24 abr. 2019 a las 11:16, Les Newell (< > > > les.new...@fastmail.co.uk>) > > > > escribió: > > > > > > > >> > > > >> > 10m, 35mm width T5 for $60 > > > >> > > > > >> > > > > > > https://www.aliexpress.com/item/10Meters-T5-open-ended-timing-belt-T5-30-W-30mm-T5-timing-belt-polyurethane-with-steel/2051875939.html > > > >> > > > >> > > > >> That's a good price. Two of those would do both sides of a 4M > machine. > > > >> That is steel cored which is stiffer than Kevlar. Pity one reel > isn't > > > >> quite enough to do a 2.4m machine. Of course it would be enough for > a > > > >> 'tank track' style mechanism. Must...resist...temptation... > > > >> > > > >> Les > > > >> > > > >> > > > >> > > > >> _______________________________________________ > > > >> 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 > > > > > > > > > -- > > > > Chris Albertson > > Redondo Beach, California > > > > _______________________________________________ > > 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 > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
