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.
Micro Cavity Flash
Meaning
An injection molding defect occurs when pressurized polymer melt escapes the parting line of a microscopic part or a small mold feature, creating thin, unwanted webs of plastic. Microelectronic and medical parts are highly susceptible to micro cavity flash because the volumes are small and the viscosity of the material must be kept low. This defect ruins the function of high-precision parts and requires costly secondary trimming operations.
Defect Root
High injection pressures and elevated melt temperatures lower the flow resistance of the resin, causing it to run into extremely small vent lines or worn mold faces. The liquid polymer fills gaps as narrow as a few micrometers before the plastic can freeze. This capillary action creates the flash during the packing phase.
Tooling Precision
Preventing this defect demands exceptionally tight tolerances on the mold mating surfaces. Toolmakers must hand-lap the parting lines of micro-injection molds to ensure that the clearance between plate halves remains below the critical threshold for the specified resin. This tolerance is often less than five micrometers for low-viscosity materials such as liquid crystal polymer.
Process Correction
Adjusting machine parameters can stop the leak. Reducing the melt temperature or switching to a material with a higher viscosity reduces the flow of polymer into microscopic gaps.