On Mon, 2012-10-22 at 16:18 -0400, John Kasunich wrote: > Oops, replied to Dave instead of the list. > > ----- Original message ----- > From: John Kasunich <jmkasun...@fastmail.fm> > To: dave <dengv...@charter.net> > Subject: Re: [Emc-users] LinuxCNC Week in Wichita > Date: Mon, 22 Oct 2012 16:17:16 -0400 > > > > On Mon, Oct 22, 2012, at 03:44 PM, dave wrote: > > On Mon, 2012-10-22 at 07:09 -0500, Stuart Stevenson wrote: > > > Do you mean the G&L that had the Allen Bradley control on it? > > > We found the X, Y and W (table) axes have a lot of backlash. We are > > > replacing the balls in the ball nuts. This has tightened them very nicely. > > > The X axis ball nut does not mount solidly to the table. We are working on > > > that right now. > > > The Y axis scale is broken beyond repair. I believe we can run just as > > > accurate using the motor and compensation. > > > > > > On Sat, Oct 20, 2012 at 3:53 PM, Jon Elson <el...@pico-systems.com> wrote: > > > > > > > > > > > > Stuart Stevenson wrote: > > > > > > > > > Oh, yeah, I've been meaning to ask what ever happened to the > > > > K&T horizontal? Did you ever get the encoder fixed or replace > > > > it with something more robust? > > > > > > > > Jon > > > > Hi Stuart, > > Indeed I think you can especially with tight ball screws. In fact, if > > you really want to be anal put a high count encoder eg. >= 10 K > > counts/rev on the ballscrew for position and an encoder on the motor for > > control; or emulate your 5 axis with I on the ballscrew and the rest on > > the motor. > > My ease of tuning increased considerably when I went from glass scales > > to encoders on the ballscrew. > > Several years ago we did the experiment on the X axis. We used two PID > loops, one with feedback from the motor encoder, the other with feedback > from the glass scale. We set P, D, FF, etc on the one that used the > motor > encoder, and I on the one that used the glass scale. The outputs are > summed before they go to the drive. It worked - the motor encoder loop > keeps things stable, and the I gain from the glass-scale loop takes > care of things like screw errors and screw growth from temperature > changes. > > I haven't been active at all in EMC/LinuxCNC for the last few years, > but if my work schedule permits, I think I will try to make it to > Wichita next summer. Sounds like fun! > > John Kasunich
Thanks John for the memory bump. I'd forgotten the summer in the loop. I'd like to use age as an excuse but I'm only 74. Dave ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_sfd2d_oct _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
