Inject_1_2012_en.pdfDownload - Sumitomo (SHI) Demag

MACHINE TECHNOLOGY
The simulation model of the injection unit in Matlab/Simulink with the central blocks target value specification, regulation, injection
unit and injection mould (left). The injection procedure commences with the high dynamics required: a comparison of the measurement
on the machine with the simulation results confirms the fineness of the simulation model (right).
D68x Series Servo Valves
The Moog D68x Series Servo Valves
are known mainly by their high
valve dynamics, due to its fast,
direct-operated pilot valve with
spool in bushing design. An advantage
of the pilot valve is low
oil leakage when the valve spool
is in the center position. Energy
savings on the machine are gained
or realized during those phases of
the cycle in which the valve does
not operate. This advantage especially
pays off on machines that are
constantly in use, and has a positive
impact in the energy balance. The
high quality standards of Moog
ensures that both valve dynamics and spool geometry maintain within
narrowly-specified limits. Thus, Moog contributes to meet Sumitomo (SHI)
Demag‘s high demands permanently.
copies of complex systems and controls.
The elasticities and dampings, among
other features, were obtained from the
simulation of the control paths on the
computer. Once the path has been defined,
the valve is integrated and the
control is simulated. Following the simulation,
Moog showed the simulation
results in valve technology and individually
matched the control piston geometry
to the El-Exis SP. The control piston
geometry influences the current resistances
of the hydraulic axis both during injecting
and also during deceleration.
The respective control piston was modified
for the corresponding axis in such
a way that it fulfilled all demands of the
user requirement specification. Subsequent
tests in the Schwaig test area have
shown that the simulation on the computer
and the test on the actual machine
agree to a very precise degree:
the regulators work in a highly dynamic
and precise manner in all areas of pressure.
By combining hydraulics and the
opportunities of the latest generation
NC5 plus controls, the optimum regulation
design was derived for both axes
respectively: in this way, the software regulator
came about which can represent
all the curves specified for the valve.
Greater precision during injecting,
switching and re-pressing
The more dynamically and precisely an
injection moulding machine works, the
more exact the part can be formed. High
dynamics expand the possibilities of
guiding pressure throughout the cycle:
the pressure stages are covered more
quickly and more precisely – both during
injecting and also during active braking,
that is to say during switching to hold
pressure. The expanded possibilities
provided by the new valve reduce the
fluctuations from cycle to cycle and increase
the repetitive precision of the
process.
Injection, which is regulated, depending
on the path, with the assistance of
the position of the screw, is followed
from the switching point onwards by
the pressure-dependent guidance of the
hold pressure, which is decisive for determining
many quality criteria. The high
precision and high level of dynamism
of the new valve enable lightning fast
switching and a reduction in pressure to
10 % of the injection level within 35 milliseconds,
instead of the 120 which has
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