Rockwell Automation 1771-QDC, D17716.5.86(Passport) PLASTIC MOLDING MODULE - Manual (Page 242)

Tune Your Machine
Chapter 10
10-34
ERC is not required for:
repeatable clamp positioning. Without ERC, the QDC module may
force the clamp to overshoot by a constant repeatable amount (relative
to cylinder speed and QDC module 2 ms scan time). Landing the clamp
precisely on the position you programmed is unimportant.
Do NOT use ERC when:
spanning your valves
using velocity feedforward gain
using slow (low value) profile ramp rates to smooth clamp operation.
Ramp rates and ERC do not always function properly together. Be
careful whenever using both in the same profile.
you have NOT tuned the machine in closed-loop control
ATTENTION: Jerky, abrupt clamp motion may result if you
apply ERC to a control loop that has not been properly tuned.
ERC Minimum Percentage Values
If using ERC, use minimum percentage values recommended in chapter 7,
except for the following:
If ERC is enabled (on) and: Then:
The actual velocity or pressure swings wildly
around the setpoint from cycle to cycle
Decrease the ERC minimum %
The actual velocity or pressure takes several
cycles to achieve the desired setpoint
Increase the ERC minimum %