Re: How do glass scales work on other machines?

Thanks for informative response. I'll look into this.

Roland

"RogerN" <regor@xxxxxxxxxxxxxxxxx> wrote in message
news:OV48g.549$y4.190@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Does the .001 float on all axis or just one of them? My controller did
something similar and I had to zero the controller and servo drive to
correct the problem. Many motion controls use + and - 10 volts to the
servo
amplifier to control the speed and direction of a servo. Zero volts is
for
zero speed, -10V for full speed reverse, +10V for full speed forward.
With
a zero speed command, such as when you are "in position", the controller
should be giving a 0V command to the servo amp. With a 0V command, the
servo amp should not be trying to move the servo motor. If the controller
is out of adjustment, or the amp is out of adjustment, it can command a
move
when it's not supposed to. This could cause all your moves to either
overshoot or undershoot the commanded position. The integrator in the
control system will slowly build up over time and correct for this offset,
giving you a couple of seconds delay and then moving the axis to the
correct
position.

If all your commanded moves overshoot in the same direction (i.e.. 0.001,
10.001) or undershoot (i.e.. -0.001, 9.999) you can probably correct it by
adjusting an offset or zero pot on the amplifier (and/or controller). If
all of your motions are coming up too short or too long, you may need to
adjust your PID gains. I'm not sure if this is what it going on with your
system, but it sounds like it could be. Hope this helps



So where is the .001 float coming from? The difference between the motor
encoder, with Electronic Thermal Comp, lead screw comp, and any other
comps
applied to the motor encoder and the positioning of the glass scale. So
in
order to eliminate the float the motor encoded with comps applied to
match
the location of the glass scales and any temperature.




.

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