Sherline lathe motors are not known for torque at very low speeds, which is probably why Sherline sells this piece of kit for cnc threading:
http://sherline.com/product/6500-stepper-motor-mounting-kit/ This will work (very slowly!) for cnc threading if a modest size Nema 23 stepper motor is used. Some folks get a little tired of waiting and swapping back and forth between stepper and regular motor for turning and threading. A couple of people came up with this setup: Stepper KL34H2160-62-8A; 1810 oz-in NEMA 34 Stepper driver - MA860H Power supply - 500W Rockstone step up/step down transformer. Spindle is geared 1:1 with stepper The stepper driver can accept a maximum of 80V AC or 110V DC. The power supply (Amazon sells it) can accept several voltage inputs stepping down to 110V AC, one of which is 200V. 200V:110V is .55% reduction, so input 110V into the 200V and out comes ~60.5V which is fed to the stepper driver. Apparently this cost effective solution results in the ability to turn and thread with only a tool change in between and reasonable DOC on the threading so that it doesn't take forever. The whole shebang is controlled by a PIC microchip, which also measures the output of a spindle encoder on the lathe (10 pulses per revolution IIRC) and then "sends" one ppr to Mach 3 to coordinate the the Z axis. This looks a promising solution, and I think with Linuxcnc, the microchip could come out of the equation. I came across Clearpath servos and wondered if this might be a more elegant system? https://www.teknic.com/products/clearpath-brushless-dc-servo-motors/ The trouble is I know nothing about servo driven spindles, would they have the same problem with poor torque at low revs that the Sherline DC motor does? Since the integrated drive and controller must be measuring servo spindle speed/direction, couldn't I use that (if I can actually access it!) for lathe spindle speed? Martin ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
