Chapter 3. Machine Adjustment Procedure | VFD-VJ
3-17
Start the plastic injection operation. The “Target value” is low pressure (＜50 bar) and low flow
rate (＜30%)。
Press the “injection" button on the operation panel for the injection operation or the machine
will enter the pressure holding operation (depending on the position of the cylinder)
In the pressure holding state without causing the vibration of the motor, increase the speed
bandwidth to the maximum value 40Hz (Pr. 00-10).
In the pressure holding condition, if the pointer of the pressure gauge or the monitored
pressure waveform has no fluctuation, it means that the pressure is stably fed back. It is
allowed to increase the three Kp values.
When the pressure feedback becomes unstable, reduce the three Kp values by 20% (example:
the three Kp values are reduced from 100.0 to 80.0). Adjust the three Ki values to eliminate the
steady-state error so to speed up system response.
When the above steps are completed, increase the "target value" for the pressure command.
Observe if the pressure feedback is stable. If there is an abnormal condition, please solve it as
follows:
Solve the pressure instability problem
Instability at high pressure
If the hybrid servo drive has an overload condition, please increase the power rating of the
hybrid servo drive
Instability over the entire pressure range
1. Set Pr.00-09 = 0 to switch to the speed control
2. If the hydraulic circuit is in the closed state, send a low speed command so as to allow a
pressure feedback value of 40-50% of the value for pressure command (Pr.00-07)
3. By using the monitoring software, observe if the pressure waveform has irregular
fluctuations.
Pressure waveform fluctuates
It may be a ground interference problem. If the motor or the three-phase power
supply is grounded, disconnect the ground wire. If the motor or three-phase power
supply has no ground wire, you can install a ground wire for anti-interference
protection.
It may be a grounding problem of the shield mesh (as the red thick line shown below).
If the shield mesh is properly grounded, the ground wire can be removed; if the shield
mesh has no grounding wire, install a ground wire for anti-interference protection.
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