As Ed just mentioned in another thread.. Why oh why use steppers ;) (although we have a few stepper machines and haven't had any real issues with them)
anyhoo... we have a couple compact 5 cnc (integrated cnc control) that are dead. The original steppers are non-hybrid 72 steps per rev. They worked ok but quite under powered, Hot and slow - 30ipm max. We purchased some small pittman servos a few years ago cheap. iirc they where like $9.99 with a heds 500 line encoder on the end. We also have some amc pwm/dir input drives. Peter was nice enough to make me a bit file for a 5i25 that had pwm gens on the external plug and encoder counters on the internal plug. The emcos have 2.5mm (approx 10tpi) pitch ball screws with a 2.5 belt reduction. we made the pullys fit the servos and new mounting plates http://electronicsam.com/images/emco/EmcoServo.JPG http://electronicsam.com/images/emco/EmcoCompare.JPG and after a bit of tuning we got the following error down to .0002 with a top speed of 150ipm 30in/s^2. (testing with a lowly 1a 25v archer power supply) https://www.youtube.com/watch?v=lTNzBLNBNiE I think we could tune them a bit better. Peter suggested adding more I until it is unstable - then backing it off. I am really surprised how well it works. We thought the servos might be a bit undersized - but now playing with it - it seems to be a good match. I don't think the servo will turn the ball screws inside out. This is basically the setup Linuxcnc -> mesa 5i25 pwm -> Cheap Bob -> AMC drive -> Servo -> Encoder -> mesa 5i25 encoder counter -> Linuxcnc Not that I am trying to cheap out by not buying a mesa analog daughter board.. We just didn't need that much i/o for this lathe. So - 2 printer ports worth of i/o is more than enough for this machine. (good match for the 5i25 or 7i92...) sam ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
