Validation of moulding productivity with two self-regulating melt pressure valves

Abstract

A self-regulating melt pressure valve has been developed to proportion melt pressure relative to a control force without the need for a pressure transducer or a closed-loop controller. The lean and agile plastics injection moulding, realized through the use of multiple self-regulating melt pressure valves that provide independent zone-based control of the polymer melt pressure and flow rate, is characterized. The process productivity of a hot-runner injection moulding process with two self-regulating melt pressure valves is validated with respect to flexibility and clamp tonnage requirements. With respect to flexibility, the use of the two self-regulating valves provided the individual tuning of two cavities of varying geometry. The resulting mouldings could not be produced to specification without the self-regulating valves or changes in the mould design. Furthermore, the consistency (as measured by the standard deviation of part weights) of the moulded parts with the self-regulating melt pressure valves was at least twice the consistency of the moulded parts produced with conventional moulding. With respect to productivity, the independent profiling and time shifting of the melt pressure for each moulding zone with the self-regulating valves enabled a 20% reduction in clamp tonnage with no increase in cycle time and a 50% reduction in clamp tonnage requirement with an 8% increase in cycle time compared with conventional injection moulding.