division of BIOLAB
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Honeywell Linear Transducers
Applications
Injection moulding machine clamping, injection, and ejection control
PROBLEM:
The goal of an injection moulding machine is to make as many quality parts
as possible each day. The basic operations of closing the mould, injecting
the plastic, opening the mould and ejecting the finished product all take
time. The faster each operation can be performed the more parts can be
made. The objective is to move all the components as fast as possible
during each step of the process while maintaining precise control.
In a single moulding cycle the large moving portion of the mould must be
rapidly accelerated from a dead stop to a high velocity, sometimes up to
90 inches per second, and then slowed to close gently as it meets the
stationary half. If these heads were to collide it could ruin the mould
and damage other components. The injection of the plastic into the mould
also goes through a series of varying speeds as the plastic first flows
into the empty mould and then is forced under pressure to fill all the
voids and create the proper density material. If precise control is not
maintained not only will the efficiency be reduced but also the quality of
the parts. It is important to monitor the eject cycle to insure that the
machine has removed the part to make way for the next unit.
SOLUTION:
Today this process is set up in a closed loop feedback, monitored
continuously from beginning to end. The location of the moving mould head,
the auger feeding the plastic, and the ejector position are all monitored
by continuous output potentiometer position sensors.
The rugged LONGFELLOW and SHORT LONGFELLOW position sensors are used
extensively on machines world wide. Their ability to provide reliable
position information around the clock in tough factory environments has
made them the selection of some of the largest manufacturers. In many
cases, the position signal is converted into a velocity for use by the
control system software.
ENVIRONMENT:
The atmosphere in an injection moulding plant can vary from benign to
hostile. In many instances, the units are subjected to hydraulic leaks,
high humidity, and high vibration and shock levels.