Terry Neilson wrote: > Gentlemen, > So would it be safe to assume that the best place for an encoder to be > mounted would be on the screw and not mounted to the motor shaft? > Also once tuned using linear compensation, with other factors being even, > rotary encoders will be at least as accurate as linear scales. True? > > If you are using a belt reduction, then putting the encoder on the end of the leadscrew eliminates any error introduced by the belts and pulleys. There is always some cyclical error in these parts. There should be no backlash between motor and encoder in this setup, so it should not complicate servo tuning. If you have a belt drive, the end of the leadscrew should be available for mounting a shaft encoder. You want the drive pulley to be between two bearings, and then the encoder can be driven using a helical-slit coupler.
If your leadscrew is a ground screw in good condition, then this should cause no significant loos of accuracy. Thermal expansion of the screw will still affect accuracy, but most home shops don't run into that problem. If your leadscrew is a crummy rolled screw with some backlash, then the shaft encoder will not directly correct for this. The machine error compensation table can help with this. Jon ------------------------------------------------------------------------------ This SF.net email is sponsored by Sprint What will you do first with EVO, the first 4G phone? Visit sprint.com/first -- http://p.sf.net/sfu/sprint-com-first _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
