Bruce, I"m not second guessing your suggestion, just trying to educate myself. What advantage does having an encoder mounted on the lead screw on the end opposite of the motor have compared to mounting it anywhere else on that screw? It being a solid screw, why would it matter?
On Fri, Apr 24, 2015 at 9:32 AM, Bruce Layne <[email protected]> wrote: > LinuxCNC does a good job of compensating for backlash when it can, but > software can only do so much. Backlash is still a limiting factor that > degrades CNC performance. Position feedback isn't really needed for > backlash compensation as backlash can be measured and is repeatable and > predictable. However, position feedback is very useful in detecting > other positional errors and shutting down the machine, possibly before > ruining a part and probably before crashing the machine. These would be > the errors that occur because a stepper motor loses steps or a shaft > coupling is slipping. Most stepper motor based machines use large > enough stepper motors that they aren't on the edge of losing steps, to > provide confidence that the stepper motors are moving as commanded. > Servo motor based systems can run closer to the edge, because the > position feedback is constantly monitoring the position. Closed loop > control is needed for servo systems, but it provides good peace of mind > in stepper systems as well. > > A relatively easy way to add position feedback is to put a rotary > encoder on the lead screw or ball screw, on the end opposite the motor. > Adding an encoder on the other shaft of a dual shaft motor would detect > lost steps, but would be unable to detect a slipping shaft coupling. > Your linear scales should detect all positional errors. > > > > > > On 04/24/2015 07:57 AM, Matthew Clemence wrote: > > Dear list, > > > > I have working stepper system on a small mill which is quite an old > machine > > (a BCA jib borer). One > > of the features is that it does have quite a lot of backlash on the lead > > screws. I have the opportunity > > to fit some linear scales (ortec) and wondered if there would be any > > advantage in changing the > > system to closed loop control with the steppers and the scales rather > than > > the current open > > loop stepper system. > > > > If so - are there are examples of the required closed loop > configurations ? > > > > Regards > > > > Matthew > > > ------------------------------------------------------------------------------ > > One dashboard for servers and applications across Physical-Virtual-Cloud > > Widest out-of-the-box monitoring support with 50+ applications > > Performance metrics, stats and reports that give you Actionable Insights > > Deep dive visibility with transaction tracing using APM Insight. > > http://ad.doubleclick.net/ddm/clk/290420510;117567292;y > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > ------------------------------------------------------------------------------ > One dashboard for servers and applications across Physical-Virtual-Cloud > Widest out-of-the-box monitoring support with 50+ applications > Performance metrics, stats and reports that give you Actionable Insights > Deep dive visibility with transaction tracing using APM Insight. > http://ad.doubleclick.net/ddm/clk/290420510;117567292;y > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
