On Thursday, February 3, 2022 10:08:54 PM EST Robin Szemeti via Emc-users wrote: > If using microstepping drives, you will struggle to get fast enough > pulses out without external pulsgen ... you need around 20kHz to get > the motors up to corner speed .. below that, you are not getting max > power from the motors, so I think you will struggle. > > On Fri, 4 Feb 2022 at 02:49, Kenneth Lerman <ler...@se-ltd.com> wrote: > > I'm considering converting a surface grinder to CNC. To start, I'll > > probably just convert the longitudinal and transverse axes. > > > > I'll go with steppers for this -- I'm thinking NEMA-42 motors. > > nema 42's available are too high inductance, an old 1600 inch nema 34 was only able to get to 29 ipm microstepped at /8 on my g0704's 50+ lb z axis, but a 940 now drives it at 120 ipm with a dedicated AC powered stepper driver making around 130 volts.
It takes voltage to drive a big stepper fast. And that is limited by the cost of that higher voltage driver. Using an rpi implies using a mesa card, which removes the step rate limit, but bigger motors with their higher inductance implies $200+ per axis self powered drivers. > > My current Bridgeport clone uses servos and Jon Elson's hardware on a > > little Intel Atom Box. I'm thinking of using a Rpi for this. It will > > need a minimal display/control panel when completed, but initially > > will need a display with touchscreen or mouse and possibly a > > keyboard. In the long run, some buttons. and perhaps an mpg might be > > useful. > > > > I'd like to use a raw Rpi without adding special hardware directly. > > That probably means using a USB or ethernet interface to control the > > steppers. I'm thinking of using Mesa hardware. > > > > Can someone suggest the most cost effective way to do this? (Although > > I have to admit, that after buying the timing belts and pulleys, the > > steppers, power supply, stepper drivers, ..., it's too late to be > > really cost effective.). And the surface grinder only cost me $300. Is its bed still flat and true? If, it was a steal at $300. > > Thanks, > > Ken > > > > > > > > Kenneth Lerman > > 55 Main Street > > Newtown, CT 06470 > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > . Cheers, Gene Heskett. -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
