80043_VDA-M_12-2020_ENG 7
3. OPERATION
3. OPERATION
3.1. Power-on
Power is supplied by the PLC to which the amplifier is
connected; therefore, the amplifier is powered on and off
simultaneously with the PLC.
The amplifier is completely operative 0.5 seconds after
power-on.
3.2. Calibration
3.3. Control During Molding Operations
The data stored during calibration are used as a reference to
detect any problems during molding operations.
With regard to the amplifier, a molding cycle starts at mold
opening and ends at re-opening of the mold after another
molding.
The PLC has to perform the following operations:
• Activation of the reset signal for clamping force (Reset
CF) from mold opening to the start mold clamping
(closing of the two mold halves).
• Comparison of the strain curve generated during closing
with the reference curve stored during calibration.
If measured values exceed the set tolerance band, you
must stop the machine immediately to protect the mold.
During the transition from “closed mold” to “clamped
mold” the reset signal is activated to protect the mold
(Reset MP).
• Measurement of injection cycle signal, from
which the “mechanical relaxation” signal stored
during calibration is subtracted. The resulting
signal is the cavity pressure signal generated
by the mold opening force caused by injection.
This lets you check correct mold filling (attention: this
does not measure absolute cavity pressure value, but
compares the measured profile to the ideal injection
profile).
Before working, you have to calibrate the following signals:
• clamping force;
• mold protection;
• cavity pressure profile.
Run about a dozen of dry molding cycles (without injection),
measure the data, and calculate the average to obtain
reference values for calibration.
3.2.1. Calibration of clamping force
Clamp the mold by applying the clamping force and measure
the strain either on the tie bars (with the GE1029 sensor) or
on the platen on toggle (with the SB46 sensor).
The measured value, which typically differs from the sensor’s
full-scale value, will be set on the PLC as a value equal to
100% of the mold clamping force.
You can convert from μεto tons / kN with the Gefran QE1008
measurement system.
3.2.2. Calibration of mold protection
Run a dry molding cycle (without injection) and store the
values during mold closing.
Using this strain curve as average value, set a tolerance
band on the PLC (depending on the mechanical noise of the
molding machine), which will be the allowed tolerance during
molding operations.
3.2.3. Calibration of cavity pressure profile
We measure actually the mold-breathing or mold opening
caused by the cavity pressure (F = area multiplied by the
pressure in the cavity). This leads to a – very small – stretching
of the tie bars. This stretching is proportional to the cavity
pressure, thus we can gain the cavity pressure profile.
But this signal is superimposed to the relaxation signal of the
machine after the machines is locked.
Clamp the mold and store the decreasing signal deriving
from the reduction of clamping force.
The relaxation takes always place and is 0.5 to 1.5% of full
locking force and is different with softer or stiffer molds.
In order to separate these 2 signals:
1) Lock the machine and reset the CPP signal.
2) Wait 10 seconds (this is NOT used during manufacturing,
just set-up).
3) Reset again (signal is now zero and stable).
4) Now start Injecting: the cavity pressure profile is
displayed.
