Closed-Loop Valve Gate Control Mechanics in High-Cavitation Tools
Closed-loop servo valve gate control uses cavity pressure and needle position feedback to eliminate weight variance and cut cycle times in multi-cavity tools.
Linear Encoder
Meaning
Electronic feedback instruments measure the physical position of a moving machine component along a straight path. A linear encoder tracks the location of the injection carriage and the clamping platen in real time. The device registers travel distance directly, bypassing the errors introduced by ballscrews or hydraulic cylinder linkages.
Positional Accuracy
Precise positioning of the screw ensures that the transition from speed control to pressure control happens at the exact same point in every cycle. By using a linear encoder, a machine adjusts the switchover point within fractions of a millimetre, ensuring repeatable shot volumes. This precision minimizes flash and short shots by keeping cushion size consistent.
Signal Feedback
Optical or magnetic sensors read a graduated scale mounted along the machine frame to generate position signals. Optical linear encoder designs use etched glass scales to provide high resolution but require protection from oil droplets and dust. Magnetic variants offer slightly less resolution but survive the harsh, warm environments typical of polymer processing plants.
Quality Assurance
Machine controllers compare the actual travel profile of the injection ram against the programmed setpoints during each cycle. Scrap output drops when the linear encoder detects a deviation in screw stroke, triggering an automatic gate to divert the suspect part. This immediate detection is far more reliable than manual part weighing and provides a complete electronic history for medical moulding batches.