On 06/02/2015 03:22 PM, dave wrote: ... snip
> To summarize: Glass scales gave me excellent position but were very > difficult > to tune. Encoders on the ballscrews were easy to tune but were worse in > positional accuracy (because of backlash). Since you already have the > expensive part (linear) adding encoders on the ballscrew for P and D and > using the scale for I would give you the best of both worlds. ... snip In my opinion... Backlash has some purely mechanical effects. On climb cutting after a direction change, the tool can pull the workpiece into the cut and overload the tool or cause a bad surface finish. The backlash compensation in LinuxCNC does nothing to address this problem. Manual mills usually need to have the operator learn how to deal with backlash by; locking axes not involved with the cut, using a "conventional" cut rather than climbing, and always starting a cut from the same direction. One can't rely on manual machining technique with a CNC, so it is imperative to get rid of backlash in every part of the system. Everything else comes _after_ that. Without backlash, an encoder on the motor or ballscew has proven to work well. Adding a linear scale for better position control may help, but without backlash, is generally redundant. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
