Direct Pin Sensor Placement and Dynamic Viscosity Control in Micro-Moulds
Direct pin pressure sensing in micro-moulds compensates for melt viscosity drift by dynamically adjusting injection speed to hold precise shear rates.
Butterworth Filter
Meaning
An electronic or digital signal processing algorithm provides a flat frequency response in the passband to remove high-frequency noise from melt pressure transducers without introducing excessive phase shift. In polymer extrusion and injection molding systems, the butterworth filter cleans raw voltage data from sensor outputs. This mathematical treatment separates true pressure changes from machine vibration or electrical interference up to a specified cutoff frequency.
Signal Smoothing
Acquiring clear sensor readings requires the attenuation of high-frequency fluctuations caused by hydraulic pump ripple and heater band switching. Digital implementations of the butterworth filter apply mathematical coefficients to sequential pressure readings. This operation yields a smooth curve that matches the actual force profile inside the mold.
The resulting dataset enables precise determination of the transition from fill to pack.
Response Delay
The calculation of smoothed points introduces a minute time lag into the control loop. In high-speed injection molding runs where the filling stage lasts under half a second, the phase delay of the butterworth filter can cause the controller to miss the peak pressure threshold. The filter configuration balances the mathematical order against this lag to prevent mold flashing or short shots.
A lower order minimizes the delay but leaves some noise in the channel, while a higher order cleans the signal but shifts the control action too late. This trade-off determines the accuracy of the transition.
Data Integrity
Clean pressure curves are necessary for automatic gate-closing systems and quality sorting routines. Statistical process control software analyzes the filtered signal to detect short shots or blockages. Raw unrefined readings trigger false alarms and cause the sorting gate to reject acceptable parts.
Stable data ensures that the machine behaves consistently over millions of cycles.