On Sunday, April 29, 2012 08:51:00 AM Steve Blackmore did opine: > On Sat, 28 Apr 2012 15:34:46 -0400, you wrote: > >So, does anyone have any pix or drawings of one that you know to work > >well on Nema 23 motors? > > Hi Gene - have a read of the following. > > http://www.google.com/patents?id=pWQeAAAAEBAJ&printsec=abstract&zoom=4&d > q=5295411#PPP1,M1 > > The math for the "rattler" design criteria is on there too. > > I made one for the Z axis on my router, which suffered from resonance > problems. It cured it completely, but it is noisy - only until the HS > spindle starts cutting though :) > > There was little thought to the design other than what fitted in the > diameter available with what material I had lying around, nevertheless > it works. > > Mine is 62mm dia, 20mm thick in Al. It has four 17mm "rattler" holes > bored on a 36mm PCD with 15mm ground steel slugs for rattles. It's bored > 10mm to fit stepper shaft and held in place on shaft with two 4mm > setscrews at 90 degrees to each other. Top and bottom covers are 2mm > thick Al held in place with 8 - 3mm CS screws. > > Steve Blackmore
Thanks Steve. While the patent refers to a 4 or 5 pulse/rev design, I get the impression that for a 1.8 degree stepper, 200 pulses/rev in the full step mode, it would seem to want the holes to rollers fit to be quite a bit 'tighter', and if done right, shouldn't be that noisy, because the rollers would be rolling as opposed to actually impacting the sides of the holes. So a lot of the effect at working speeds would be from the translation of the angular speed of the roller, to one of a radial movement because a speed variation would make them roll up (toward the center axis of the container). This is assuming a sufficient speed that the rollers would naturally be riding in the outer diameter of the clearance they have. Based on that line of thought, hole to roller clearances of perhaps 5 to 10 thou should work well for steppers. Microstepping the motor reduces the amplitude is the excitation signal, but to get the full advantage the current mapping needs to be determined almost on a per motor basis because the iron isn't quite linear, so a well calibrated 2.5 amp motor won't need the same current map at 2.2 amps where the iron is much more linear. With the microstepping at /16, using the 2m542 drivers, I note that resonance problems and noise are considerably attenuated compared to the /8 setting, but the D525MW board can't issue steps fast enough so following errors are the order of the day at only 18-20 ipm. This is with a 20 u-sec base-thread. This also makes the speed changes scale up in amplitude, encouraging the skip and lock, so /8 is probably the best compromise for me. I haven't even tried a /4, and perhaps that would enhance the speed attainable if the dampers were doing a good job. It would also, in my experience with a xylotex driver, make stuff laying on the table holding the mill or lathe, walk right off the table with something falling off about every 5 seconds! It was _that_ much noisier. I bought a 3" castor, 175lb rated, that felt like it had a good flywheel effect yesterday, but they don't sell them loose, but as an assembly, so that's $5 a wheel. I am thinking of boring it about halfway thru for room for elastomer between the sleeve that fits and setscrew locks to the motor shaft, say about 1/4" of clearance, and filling the gap with Goop. 2 degrees of give or a bit less should be pretty close to ideal. I also have some 1x3x6 blocks of alu the mill could convert to flywheels for this 'rattler' design. I might make one of each just for S&G. The new controller board walked up and set itself on the front porch yesterday, (my mailbox wasn't quite big enough) but it was cold & raining intermittently, so I didn't try to install it. I need to develop a scheme to mark wires as the newer boards use that green setscrew type of Euro connector I am learning to hate, in this case because there are as many as 3 wires to insert & get a grip on. Very crowded compared to spade lugs stacked 3 high on a cinch terminal strip. Cutting the lugs off also cuts the number markers off. A right PIMA. And Lowes no longer sells wire numbering tape. 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) My web page: <http://coyoteden.dyndns-free.com:85/gene> Schlattwhapper, n.: The window shade that allows itself to be pulled down, hesitates for a second, then snaps up in your face. -- Rich Hall, "Sniglets" ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
