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Configuring the PrecisionFlo Module
You will be entering Kp and Kd values more than once
while you are starting up the PrecisionFlo module.
The first time you enter values is to simply load materi-
al into the dispense system. (See page 21 for more
information). After you have successfully loaded
material into the dispense system you will enter Kp
and Kd values to ensure PrecisionFlo module accuracy
and repeatability.
Adjusting Kp and Kd to Ensure Accuracy
and Repeatability of Metering Valve
Operation
The accuracy and repeatability of the PrecisonFlo
module depend on precise adjustment of the operating
parameters Kp and Kd. The module uses these
parameters to control metering valve operation and
must be adjusted to compensate for such module
characteristics as hose lengths and diameters, dis-
pense device tip sizes, supply pressures and flow
rates, and material viscosity.
Kp, the proportional term, dictates how close the
pressure control loop will get to the set point.
Kd, the derivative term, sets the amount of damp-
ing used to prevent oscillation and instability in
module output.
For example, if the module receives a command to
output a pressure of 1000 psi, higher values of Kp will
result in output pressures closer to 1000 psi. Low
values of Kd will “soften” or slow module responses to
changes in the command input voltage, while higher
values of Kd will “tighten” or speed up module re-
sponses. If either Kp or Kd is set too high, the module
may become unstable and oscillate, which will show up
as a ripple or wave pattern in the material bead.
Preparing to Adjust Kp and Kd
To adjust the Kp and Kd parameters, you need:
robot program you created, see page 23
dual channel storage oscilloscope (optional)
If you do not have an oscilloscope, adjust Kp and
Kd by dispensing material onto a surface.
Fig. 17 shows the major steps to follow to adjust Kp
and Kd values.
Make sure that:
1.
Material has been loaded into the dispense sys-
tem.
2.
You have disconnected the electrical cable to the
flow meter, if the PrecisionFlo module is using a
flow meter.
Dispense test
material
Fig. 17
Adjust Kp and Kd
Confirm material
has been loaded
Disconnect
electrical cable
from flow meter
End Adjust Kp
Using
Connect
oscilloscope
Reconnect
electrical cable
to flow meter
Yes
No
and Kd
Set Kp
value
Set Kd
value
oscilloscope?
