© MOOG 2019
This document is subject to MOOG INTELLECTUAL AND PROPRIETARY INFORMATION LEGEND . The details are on page II.
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MRJ06301
2-2-6. WITH ACCUMULATOR BLOW MOLDING MACHINES
When used with accumulator machines, the DigiPack
Ⅲ
controls the parison wall thickness relative to the
accumulator position as the plastic is being extruded. In this case the displays (LCD) vertical axis is accu-
mulator position and the horizontal axis is die gap opening.
The total quantity or volume of plastic extruded is proportional to the accumulator position, then the result-
ing parison wall thickness at any given point on the length f the container is related to the accumulator
position when that point on the parison was extruded through the die gap.
A potentiometer measures the accumulator position and controls the vertical axis of the program display.
The desired shape of the parison wall profile is commanded digitally by the operator using the display. The
size of the tooling opening or die gap, as measured by a die gap position transducer, is compared with the
operators commanded die gap opening as set on the DigiPack
Ⅲ
display.
The error between the operators commanded die gap opening and the actual position causes the servo-
valve to control the oil flow to the actuator and reduce the difference between the commanded and the
actual die gap opening (position error) to a very small value. This feedback process ensures that the actual
die gap opening follows the commanded die gap opening very accurately.
The operator can also set the accumulator working stroke, Shot Size, and the desired position at the end
of the accumulator push out, Cushion, the DigiPack
Ⅲ
also provides interfacing signals for these functions
with the machines PLC, which then controls the motions of the accumulator.
2-2-7. WITH CONTINUOUS BLOW MOLDING MACHINES
When used in a continuous blow molding machine, DigiPack
Ⅲ
controls parison wall thickness by relative
value to the time required for one machine cycle. The vertical axis of the LCD display is time and the
horizontal axis is the die gap opening amount. The cycle begins, for example, when the parison cutting
knife cuts the parison (actually when the start signal is input). The end of the cycle can be determined by
one of the following:
a) Fixed cycle time set by operator
b) Automatic cycle time (cycle time is controlled by the blow molding machine) set by repeatedly meas-
uring the time between cuts by the parison cutting knife (the time until the next start is input)
c) Detect a fixed time cycle and activate machine functions such as closing the core (cycle time is con-
trolled by DigiPack
Ⅲ
)
The desired shape of the parison wall profile is commanded digitally by the operator using the display. The
size of the tooling opening or die gap, as measured by a die gap position transducer, is compared with the
operators commanded position as set on the DigiPack
Ⅲ
display.
The error between the operator commanded position and the actual position caused the servovalve to
control the oil flow to the actuator and reduce the difference between the commanded and actual die gap
opening (position error) to a very small value. This feedback process ensures that the actual die gap
opening follows the commanded die gap opening very accurately.
