> > 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
