On Thursday 12 December 2013 08:42:15 Mark Wendt did opine: > On Wed, Dec 11, 2013 at 2:12 PM, Gene Heskett <ghesk...@wdtv.com> wrote: > > On Wednesday 11 December 2013 13:50:30 Leonardo Marsaglia did opine: > > > > > > It sounds like an interesting project Leonardo, so please post a link. > > > > Question: Is this enough of a velocity variation to effect the > > performance of the hardening process? Or cause premature wear > > anyplace from the vibration, like in the cable trough feeding this > > carriage? > > > > Maybe this is a case where the vibration dampers on the rear end of > > our steppers that are often used, might be expanded into a damper big > > enough to absorb the majority of this "vibration'? > > > > This damper gismo isn't an area well characterized, or at least I've > > not found someone proposing formulas for their making on the net, so > > most of use make our own according to our own thinking. If the rear > > shaft isn't available, then a thin flywheel on the drive end, with a > > tubular rim filled with large ball bearing balls for rolling weight, > > running in heavy grease to dampen the motion of the balls relative to > > the rim could make a noticeable difference, but with the reduced rate > > of available acceleration that swinging weight would cost. Not > > talking my nema 23's here, where such a constuct might be the size of > > a roller skate weheel but something perhaps 8 to 10" in overall > > diameter, keeping in mind it needs to strong enough to take the rpms > > involved. It goes without saying that its demise at speed would of > > course become quite a hazard. :( Containment cages could be > > indicated/demanded by the safety people. > > > > Just an old fart, thinking out loud, I'll go away now. ;-) > > Gene, > > A bunch of the stepper guys over on the CNCZone forum have used hockey > pucks as dampeners, with reportedly good results. > > Mark
I'd expect they would, but if rigidly mounted, they would just lower the resonant frequency. If lowered to the point where the stepper had some real oomph, I'd expect it to make a quite noticeable improvement at the higher speeds where the flywheel effect would help it tolerate a step thats late because of latency, where w/o the flywheel it would slow and then be to slow to accel & catch up in one step=stall. I followed a somewhat different school of thought more in line of a shock absorber. I found a sheet of what looked like innertube rubber at a yard sale, about .1" thick, Then made a long steel spool for the back shaft on the motor, with a separate flange on one end, then stacked rough cut disks of the rubber with smaller than the shaft holes, stretched over the shaft of the spool which made the rubber a little thicker at the hole, alternated with the biggest heaviest fender washers I could get at TSC, 10 or so of those. Set the other end flange on and pushed it up pretty snug. Put it on the motor, marked the edges of the washers with a magic marker and ran the motors. The idea was that the washer would be a flywheel that could slip, and in slipping would absorb the resonances. To get an idea of its effectiveness, if I take the one on the mills Z motor off, I will get stalls very easily in the 9-11 ipm range, put it back on and I have made it move at 34 ipm, but thats pushing the heck out of a triple stack 425oz nema 23 motor with only a 28 volt supply so my maxvels are set about half that. Since the X motor on the lathe is on the rear of the carriage, thats too much weight back there, making it very easy for the front of the carriage to lift off the V-way, so I don't have one on that double stack 262 oz nema 23. With direct drive on an 8mmx2.5mm ball screw, maxvel is about 20 and working is even less. On the lathes Z, a 16mmx5mm screw, with a 2/1 drive gear, the flywheel weight of the 2/1 gears, and the damper I borrowed off my A tables motor, I can run that Z at 60 ipm with around 37 to 38 volts on the motors. I can run a G76 cycle cutting threads at 700+ revs but normally run it at around 350, 700 rpms and the whole machine is doing the sailors hornpipe sitting on top of a mid-sized TSC toolbox on wheels while cutting a .350" long 1/4-28 thread on a #209 nipple for one of my BP rifles. Needless to say, carriage gib adjustments are very critical with that much weight on the rear of the carriage. The front apron, carrying the Z nut, is quite substantial but alu and if I ever come across a block of steel or cast big enough to make another apron that would set heavier on the ways to prevent its twisting and lifting up the ramps of the V-way till caught by the gibs, I will do that. The OEM cast apron weighs 2x what the beefier alu nut carrier weighs. I can measure it with a dial indicator on the apron, and another on the rear of the motor, the apron will move about 2 thou before the motor moves, and it may move a thou the wrong way before it finally moves the right way. Shloppy, 1995 made Chinese stuff, newer ones I am told are much more precisely machined. _Anything_ I open up on this thing needs serious fitting before I put it back together. Looking at the OEM half nut, I am amazed it ever worked! LCNC's electronic half nut is at least 100x more precise than the OEM ever was. I can finally say I can do decent, repeatable work on this thing as opposed to guess cut, measure, guess cut, measure, spending a day making scrap before getting the 3rd or 4th attempt in tolerance. It was frustrating to make an understatement. You folks might not be impressed, but its with your help and advice that this POS works as well as it does, thank you all. 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) Genes Web page <http://geneslinuxbox.net:6309/gene> Dismissed. That's a Star Fleet expression for, "Get out." -- Capt. Kathryn Janeway, Star Trek: Voyager, "The Cloud" A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ Rapidly troubleshoot problems before they affect your business. Most IT organizations don't have a clear picture of how application performance affects their revenue. With AppDynamics, you get 100% visibility into your Java,.NET, & PHP application. Start your 15-day FREE TRIAL of AppDynamics Pro! http://pubads.g.doubleclick.net/gampad/clk?id=84349831&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
