On Thursday 25 March 2010, Mark Wendt (Contractor) wrote: >At 12:38 PM 3/25/2010, you wrote: >>On Thursday 25 March 2010, Mark Wendt (Contractor) wrote: >> >At 11:56 AM 3/25/2010, you wrote: >> >>At 165 pounds, it may be that the gantry is actually taking up some >> >> backlash as its stopping from the longer moves which would be faster. >> >> Can you, as its hooked up & the motors enabled, induce a motion >> >> visible on the indicator by manually pushing or pulling it? And, >> >> equally important, does this 'slack' remain constant as you move it >> >> with the motors? If constant, then perhaps adding some backlash comp >> >> might help (but that's only effective for motion reversals of course), >> >> or if its position related, it might be possible to map the screws >> >> error. Wear patterns can be elusive, and mapping a cyclic error can >> >> be 'fun' for some definitions of fun. If you have many hours on the >> >> machine doing the same cuts over and over it might even be advisable >> >> to replace the screws. Or if the cutting dust can get to them, a >> >> really good cleaning might help. >> > >> >I'll give it a try manually moving the machine while the motion >> >control system is up and running. Haven't tried that as of >> >yet. It's a brand, spankin' new machine that has not cut anything >> >yet, so if there's wear patterns anywhere, it'll be on my forehead >> >where I've been rubbing in consternation... ;-) >> >>ROTFLMAO! > >Heh, I've been designing and building this monstrosity for a little >over 5 years now. Been much hair pulling and forehead rubbing during >that time, and now that it's almost all together, I just want the >damn thing to work right... ;-) > >> >> > I disconnected the pinion gears from the racks, moved the >> >> > gantry back and forth the length of the X axis a few times by hand, >> >> > and didn't really notice any binding. It seemed pretty smooth, and >> >> > relatively easy to move a 165 lb gantry on the rails. >> >> >> >>Pinion gears, same thoughts about cleaning apply. I assume they are >> >>preloaded? >> > >> >Pinions are preloaded. Here's the R&P >> >setup: >> ><http://www.cncrouterparts.com/product_info.php?cPath=21&products_id=50> >> >>Cool. I'd have reservations about sub thou accuracy with it. Straight >> cut rack & pinions will have some cyclic errors, repeatable on a tooth >> per basis, but that has already been said. > >Yeh, sub-thou ain't necessary, but a wee bit less than .005" - .010" >is definitely what I'm shooting for. > I would think that if the belt is tight, and the pinion mesh is solid, then the rest of it would be the cyclic error of the gears and that can be profiled out. I might be tempted to raise the ratio between the motor and the pinion by 2 or 3x to relieve that effect. I assume you are micro- stepping at about 8, so the increased ratio would make any cyclic error there smaller by the same amount. If small enough, then the rack & pinion cyclic error will be the dominant one. Compensation for that of course means the use of highly repeatable home switches to establish your zero point, else the compensation would be applied in a random manner per powerup. That could be a real forehead damager when it occurs to one that the mapping must have a starting at zero reference point. ;-)
Question? Are you going to be sawing or cutting with a knife? I'd think that cutting might be subject to the knife wanting to follow the grain of the bamboo. A bigger error the machine cannot hope to compensate for. But the rod will be stronger if its allowed due to less cross grain cutting. Slight crookedness is then pulled back out in the glueup. I once had a cheap bamboo rod with a pronounced 1/4" wobble that would not 'hang out' in the last foot of it, and it was still the sweetest rod I ever owned. I could set a 5 gallon bucket someplace where I had clear working room and put a #14 fly in it 90% of the time at 50 feet, half the time at 80 feet. The late thing with the carbon fiber is still 10x too darned stiff for me. I have one and it is in the boat, but rarely used. The feel of the line back into your hand just isn't there. Have you considered what the finished price range will be? I might be a potential customer if I don't fall over first. >>-- >>Cheers, Gene >>"There are four boxes to be used in defense of liberty: >> soap, ballot, jury, and ammo. Please use in that order." >>-Ed Howdershelt (Author) >> >>Once harm has been done, even a fool understands it. >> -- Homer > >Mark > > >--------------------------------------------------------------------------- >--- Download Intel® Parallel Studio Eval >Try the new software tools for yourself. Speed compiling, find bugs >proactively, and fine-tune applications for parallel performance. >See why Intel Parallel Studio got high marks during beta. >http://p.sf.net/sfu/intel-sw-dev >_______________________________________________ >Emc-users mailing list >[email protected] >https://lists.sourceforge.net/lists/listinfo/emc-users > -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) When the going gets tough, everyone leaves. -- Lynch ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
