pps proceeding - Abstract Preview
pps proceeding
Symposium: S13 - Injection Molding and Mold
Poster Presentation
 
 

Development of a highly segmented temperature control in injection moulding for reduced warpage and increased process stability

Hopmann Christian (1), Theunissen Matthias (1)*, Schmitz Mauritius (1), Nikoleizig Philipp (1)

(1) IKV - Institute of Plastics Processing at RWTH Aachen University - Aachen - Germany

In the plastics processing industry a growing demand for precision moulded parts can be identified, especially regarding avoidance of warpage as well as achieving high process stability. To meet these requirements, an approach based on local material properties within the injection mould during the moulding process is pursued, utilising the so-called pvT-optimisation. The goal of the pvT-optimised process is the optimisation of the shrinkage by establishing a constant specific volume (v) of the melt and part during the injection moulding process. This is pursued by controlling the holding pressure according to the in-mould pressure (p) and part temperature (T). Due to the nature of flow dynamics and material characteristics the pressure within the mould is inhomogeneous. Especially in injection and compression phase, pressure varies from ambient pressure at the flow front to a high injection pressure caused by the pressure loss. In packing phase the local specific volume varies due to pressure and temperature differences. To establish a local control of the specific volume, in addition to the injection pressure the temperature is added as a controlled variable for this new concept. To achieve an accurate and dynamic temperature control, tempering concepts including fluid-based tempering, CO2-tempering, resistance heating as well as heating by laser radiation and electromagnetic induction are evaluated regarding usability, reaction time and performance. In addition, local temperature and pressure measurements are needed to accurately adapt the temperature in the mould. Therefore, available measurement techniques for injection moulding are evaluated regarding reaction time and efficiency. A mould concept is developed to meet the requirements needed for an inline, online as well as a self-optimising temperature control, based on a model-based measurement correction, predictive temperature control and a system-wide optimisation function.