On Sun, 2008-01-27 at 12:59 -0800, richard harris wrote: > Hello, > > I started cutting today on a machine that was recently converted. > During the course of two hours the y axis drifted about 15 thousandths > and the x axis 5. I have this machines sibling running 20 hours a > week and it shows no signs of drift. The sibling is running emc 1.xx > and a different servo amp. > My understanding of tuning is that if I have a bad tune the machine > might not get where I tell it to go, but it will still know where it > is. Similarly with backlash if it has 3 thousandths in backlash if it > moves to the right then the left and returns to a mid point the > backlash should cancel out and I return to where I should. > The machine is running a pico-system servo setup with emc 2.1.7(I > think). Encoders are on the motors and the motors are belted to the > ballscrews. I have new belts and similar tension to the other > machine. > Is this drifting a function of the iron or the controller? > > As always thanks. > Richard
Just shooting from the hip, it sounds to me like you are dropping encoder counts. During my HNC conversion, I had threading problems. One of the problems was that the spindle encoder was losing counts due to VFD noise (the other was, my axis acceleration settings where too low). I put a filter on the VFD mains input and the problem went away. I could see the problem with Halsope showing irregular encoder pulses, and with Halmeter giving me varying numbers of encoder counts between index pulses. -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending) ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
