Rockwell Automation 1771-QDC, D17716.5.93(Passport) PLASTIC MOLDING MODULE - Manual (Page 231)

Tune Your Machine
Chapter 10
10-3
Important: In most cases, adding a derivative term to pressure control
algorithms makes it too sensitive and does not enhance loop stability.
Use only proportional and integral control.
Use the highest possible P and I gain constants for inject-mode profiles
for precise performance without hammering your hydraulics, but use the
lowest possible P and I gain constants for clamp and eject profiles for
repeatable performance.
First tune your proportional gain. Then add integral gain.
Typically, the integral term will be larger than the proportional term.
The QDC module’s pressure algorithm differs from classic PID
algorithms.
Use an oscilloscope, if available. You can tune loops faster and easier
with it connected to QDC module’s output driving the selected valve.
Important: If you have an oscilloscope, skip to the section Tune Pressure
Loops with an Oscilloscope.
Tune Pressure Loops Without An Oscilloscope
Repeat this procedure for each applicable pressure profile.
Before you begin tuning PID pressure loops, confirm that you:
selected the pressure vs. position algorithm
selected closed-loop control
disabled
ERC
reset ERC values
disabled
ramping
ATTENTION: Verify that you have correctly set the following
words and bits in CPC and OPC that control zone overrun to
guard against damaging the clamp or mold.
CPC03-B11 = 0: execute low pressure close if zone overrun occurs
set CPC61 to a value larger than normal for a larger mold-protect zone
OPC03-B11 = 0: execute open slow if zone overrun occurs
set OPC61 to a value smaller than normal for a larger open-slow zone
1. Enter an operational profile representative of the characteristics you
desire for your production cycle.
2. Check that you zeroed the profile’s integral and derivative terms.
Leave the proportional term at the value you entered in chapter 7.