I put encoders directly on the screws of my knee mill. It was tricky to mount on the y axis. I used one with a through hole and put it where the micro dial was. I'll see how it works out if I ever get it going.
On Fri, Apr 24, 2015 at 11:16 PM, Bruce Layne <[email protected]> wrote: > An encoder anywhere on the ball screw would work. It's usually easier > to mount an encoder on the end of a ball screw or motor shaft rather > than between the motor and the ball screw. There are motors with a > shaft protruding on each end and it's common practice to mount the > encoder on the back shaft of the motor, with the shaft coupling to the > ball screw on the other side of the motor. That's what I was > discussing. There's nothing wrong with mounting the encoder on the back > of the motor if you want to catch the common problem of missing pulses > on a stepper motor, but an encoder on the back shaft of the motor would > have no way to detect positional errors caused by a slipping shaft > coupler. It would see the motor turning as commanded, and would have no > way to see that the screw isn't turning with the motor because the > coupler is slipping. > > BTW - For very precise machines, even a large diameter ball screw is not > "a solid screw". There is measurable torsional twist when accelerating > and decelerating that can cause minor positional error that is > significant in some precise applications. One trick that's used is to > place an encoder on each end of the ball screw and detect the slight > difference in rotation from one end of the screw to the other due to > twisting. Some math is done to compensate for the positional error that > would be caused by the twisting ball screw between the motor and the load. > > > > On 04/24/2015 08:28 PM, Joe H wrote: > > 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? > > > > ------------------------------------------------------------------------------ > 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
