Meaning
The high-precision tracking of linear or rotational movement in injection moulding machinery using light-based sensors provides real-time feedback on screw position and injection speed. This optical encoder scanning allows the machine controller to monitor the movement of the injection screw with sub-millimeter accuracy. Having this level of detail is necessary for controlling the transition from injection to holding pressure and for ensuring consistent part weight.
Moulders use this information to maintain process stability and detect any drift in the machine’s performance.
Measurement Method
The system works by shining a light through a glass or metal disk that has been marked with a series of fine lines. During optical encoder scanning the sensor detects the pulses of light as the disk rotates or moves and converts them into digital signals. These signals are sent to the machine’s computer which calculates the speed and position of the screw.
Because the system relies on light it is not affected by electrical noise or magnetic fields which makes it highly reliable in a busy factory. It provides the high-speed data transfer needed for modern closed-loop control.
Moulding Application
Controlling the velocity of the screw during the filling phase is critical for achieving high part quality. By using optical encoder scanning the moulding machine can adjust the hydraulic pressure to maintain a constant injection speed even as the viscosity of the melt changes. This control helps to prevent defects like flashing or short shots by ensuring that the mould is filled at a consistent rate.
It also allows the machine to switch from velocity control to pressure control at the exact same point in every cycle. This repeatability is essential for holding tight tolerances.
Process Optimization
Analyzing the data from these sensors can help moulders identify problems with the moulding process or the machine itself. If the screw speed or position starts to drift it can indicate that the non-return valve is worn or that the heater bands are failing. By monitoring the signals from the optical encoder scanning system technicians can detect these issues before they lead to defective parts.
This preventative maintenance can save a lot of money by reducing downtime and scrap. It also helps to ensure that the machine can handle the high-speed movements needed for thin-walled parts. For these reasons almost all modern high-performance injection moulding machines are equipped with these sensors.
In addition the high-resolution position data can be used to generate process capability studies that prove the stability of the moulding cycle to the customer. This level of quality assurance is often required for high-precision automotive and medical mouldings.
