On Tuesday 30 April 2013 12:06:13 Cecil Thomas did opine: > Gene, > You need to remember that the seemingly high hp ratings of these > relatively small motors is due to the very high rpms at which the > ratings are valid. > These 1 1/2 to 2 hp motors develop that hp at 5000 to 6000 rpm. You > will have to rethink your drive coupling system to reduce that speed > down to something usable especially for threading.
I am aware of that, the toothed belt pulleys stock on the 7x means its turning about 8000 revs to get the 2500 rated in high back gear. I very rarely use it as there isn't enough torque to even cut alu 1/2" in diameter. > I am using a 2 1/2 hp treadmill motor with its original speed control > on my converted jet 9 x 20. I had to use a 4.5 to 1 pulley reduction > to get reasonable torque in the 200 rpm spindle range but still have > about 1400 rpm available at top speed, which is good enough for > me. That would also suit me just fine, low range is about 1200revs right now, and this motors is in trouble at work diameters above one inch in steel. > I have plans for a shiftable double reduction setup which will > be closer to 3:1 in hi and 12:1 in low. At that ratio the motor will > cut anything that the toolpost will hold up to even at 150 rpm > cutting a very coarse thread. That is part of my problems, the tool tip is often hanging out in front of the way pads, and it has been known to tip and dig in, bringing everything to a halt in 3 degrees of rotation. > I feed the speed controller through an optical isolator with PWM at > 200 hz out of the parport with LCNC. Be sure to use an optical > isolator. And DON'T try to compare the PWM into the isolator with > the output with a dual trace scope.... Ask me how I know. Chuckle, I know too, blew a C41 and a JT250 all to hell. And it does interesting things to scope probe ground leads too. And is the main reason I bought me one of those pocket scopes. But ISTR I settled on a PWM at about 1000/sec. Basically I went up till it started hunting because of poor resolution, then backed off to well below the hunt point. Subject of course to changes with gedit to the .hal file. :) But you say you are strobing the pot arm with an opto? That should give faster response I would think, one of the major problems with the C41 approach, that thing is ssssslllllllooooooooowwwwwwwwwwwwww as shipped. > I made my encoder wheel out of a CD which I painted black. It has 20 > equally spaced notches with one twice as deep for the index. I used > two optical interupters for the A and B quadrature and a third one > set deeper into the index notch. I mounted all the interrupters on > aluminum L brackets with supermagnets holding the brackets to the > metal of the enclosure. I watched the Halscope while shifting the > interupters around till I got the quadrature right and the index not > coinciding with the A or B transitions. When all the signals looked > right on the halscope I put a drop of superglue at the edge of the > bracket...waited til it set then drilled the mounting screw holes > through the bracket and into the sheet metal. Much more easily done > than described. Yup, but my disc is brass, 50 slots + long index. All 3 opto's mounted on a home made pcb, so the center one is the index. > > The 80 transitions per rev is plenty of resolution for anything I'll > ever do and the pulse rate doesn't challenge the system. Not at 20 slots. I did some math and came to the conclusion that LCNC was capable of tracking its 50 slots at nearly 6k revs. Absolutely NP at 1200. :) > > Cecil > ------------------------------------------------------------------------ > ------ Introducing AppDynamics Lite, a free troubleshooting tool for > Java/.NET Get 100% visibility into your production application - at no > cost. Code-level diagnostics for performance bottlenecks with <2% > overhead Download for free and get started troubleshooting in minutes. > http://p.sf.net/sfu/appdyn_d2d_ap1 > _______________________________________________ > 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) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! My views <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> You can't take damsel here now. A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET Get 100% visibility into your production application - at no cost. Code-level diagnostics for performance bottlenecks with <2% overhead Download for free and get started troubleshooting in minutes. http://p.sf.net/sfu/appdyn_d2d_ap1 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
