On Thu, 11 Apr 2013, Jon Elson wrote: > Date: Thu, 11 Apr 2013 11:32:55 -0500 > From: Jon Elson <el...@pico-systems.com> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] Closed loop stepping system > > Gene Heskett wrote: >> >> Somebody thinking "outside the box", and making perfect sense. The only >> fly in the soup is the 10,000 step encoder, and servicing it at 200 rpS to >> get that 12,000 rpms > If you run a stepper motor at 12,000 RPM, it will burn up in minutes. You > can spin a typical stepper with the spindle motor, and above 1000 RPM it > will > get very hot with no current at all in the windings. That is all iron loss. > 12,000 RPM will require insane voltages be applied to the drive, several > hundred Volts. A typical stepper may generate 50 V at 1000 RPM, so > that would require a 600 V supply just to equal the back EMF at 12K. > > Oh, but then cogoman said : > > "the stepper motor could be designed with less steps per rev. " > > Yes, then why make it a stepper at all? How about an 8-pole > brushless servo motor? These work GREAT, used by Fanuc > since the late 1980's, and now available from many sources. > I make affordable servo amps for brushless motors, and > have one on my minimill. You do need to get rotor position > info from the motor, most small ones have Hall sensors that > you connect to the servo amp. I use 500 cycle/rev encoders > on mine, that is quite satisfactory. > > Jon
The Leadshine closed loop step motors actually do have some advantages. because of the high number of poles (50 typically), when run in step motor mode the torque vs displacement curve is much steeper than a normal brushless motor which allows a clever hack when stationary. When staionary the motor can be run in step motor mode (radial pull vs tangential pull) with reduced current. This eliminates the +- a count or so jitter that full servo systems have when stationary (especially with static load) You still have the torque vs speed limits because of the number of poles and stepmotors even run as servos are not as efficent or as high performance as normal brushless motors but in the size ranges that make sense, closed loop stepper systems are very nice. > > > ------------------------------------------------------------------------------ > Precog is a next-generation analytics platform capable of advanced > analytics on semi-structured data. The platform includes APIs for building > apps and a phenomenal toolset for data science. Developers can use > our toolset for easy data analysis & visualization. Get a free account! > http://www2.precog.com/precogplatform/slashdotnewsletter > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ Precog is a next-generation analytics platform capable of advanced analytics on semi-structured data. The platform includes APIs for building apps and a phenomenal toolset for data science. Developers can use our toolset for easy data analysis & visualization. Get a free account! http://www2.precog.com/precogplatform/slashdotnewsletter _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
