On Monday 29 April 2013 15:50:03 Jon Elson did opine: > Gene Heskett wrote: > > It sounds as if its a 3 phase AC motor turning a DC generator which in > > turn powers a DC motor that actually drives the spindle? > > Essentially right. > > > For those DC controls, I'd think it would be a lot more power > > efficient to toss the rheostats in favor of pwm controlled hexfet > > power devices that linuxcnc can control directly by using > > opto-isolation techniques which would give 10 to 1000 times faster > > control, with perhaps 1/100th (or less) of the power losses the > > rheostats will have, directly from a quadrature sensing disk and > > opto-interrupter detection of not just spindle speed, but spindle > > position in real time as it rotates. > > Lathes don't really need to change speed on a dime.
True Jon. But when running a G76 cycle, you do need a stiff speed control because of the phase lag between the spindle and Z is time of rotation sensitive, as I found when I cranked up the spindle revs in the middle of cutting a thread. The thread moved lengthwise on the part and wrecked it. Minor detail, an inch of 1/2" cold roll wasted, so NBD. But it did surprise me until the lockup method was explained by one of you kind folks. That effect is exacerbated by my own tendency to use lower accels in favor of achieving higher rapids speeds. > The spindle is not usually used as a positioning axis. The rheostats > control generator field and > motor field, and are not that large. For low-speed range they control > the generator field, > then for the high speed range they weaken the motor field. > > Jon Thanks for that explanation Jon. Now if I can get my wet ram to remember it. :( 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> I'm so miserable without you, it's almost like you're here. A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ Try New Relic Now & We'll Send You this Cool Shirt New Relic is the only SaaS-based application performance monitoring service that delivers powerful full stack analytics. Optimize and monitor your browser, app, & servers with just a few lines of code. Try New Relic and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_apr _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
