Tune Your Machine for Producing Parts
Chapter 10
10-2
So far, you ran open-loop profiles with the QDC module’s PID and VelFF
control algorithms disabled. We suggest that you use open-loop control for:
spanning
valves
troubleshooting machine performance
when the machine has no pressure sensors for feedback
Important: You can achieve considerably better consistency of finished
parts when the QDC module operates in closed-loop control. With few
exceptions, you should run machine production with closed-loop profiles.
Correctly tuned closed-loop injection profiles are essential for precise,
repeatable operation. In chapter 7 you entered our recommended values.
They may give you desired machine performance. If you need to improve
performance, continue with this section.
General Guidelines for Pressure Tuning
In this section we present two procedures:
Tune Pressure Loops without an Oscilloscope
Tune Pressure Loops with an Oscilloscope
Repeat either one of these procedures as needed for tuning the pressure-
control loop of these profiles:
Injection – Pressure vs. Position (or Time)
Pack and Hold – Pressure vs. Time
Plastication – Backpressure vs. Position (or Time)
Follow these general guidelines when tuning closed-loop pressure profiles:
Disable
ramping
Disable Expert Response Compensation (ERC)
Set IPC04-B11 = B10 = B09 = B08 = 1
Set HPC04-B11 = B10 = B09 = B08 = 1
Set PPC04-B09 = B08 = 1
Set PPC04-B11 = B10 = B09 = B08 = 1
Reset ERC values to zero. Set DYC05-B15 (B34/463) = 1.
The QDC module resets this bit to zero after resetting ERC values.
Important: Tuning constants differ between pressure profiles. The
dynamics of loads being moved and different hydraulic characteristics
warrant separate PID tuning considerations for each profile.
Use only proportional and integral control.
Important: In most cases, adding a derivative term to pressure control
algorithms makes it too sensitive and does not enhance loop stability.
Closedloop Control
Tune Closedloop
Pressure Control