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TY - THES AU - Schacht, Andreas TI - Thermisch gespritzte Heizschichten für das Kunststoffspritzgießen VL - 77 PB - RWTH Aachen University VL - Dissertation CY - Düren M1 - RWTH-2024-01772 SN - 978-3-8440-9361-2 T2 - Schriftenreihe Oberflächentechnik SP - 1 Online-Ressource : Illustrationen PY - 2024 N1 - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2024 N1 - Dissertation, RWTH Aachen University, 2023 AB - Plastic injection molding is the most important process in plastics processing and is characterized by short cycle times and high cost-effectiveness. The productivity of the process is achieved in particular by cold-temperature molds for rapid solidification of the injected polymer melt. However, an excessively high temperature gradient can lead to premature solidification of the polymer melt and thus to reduced part quality. This effect is counteracted by variothermal temperature control of the mold. While internal systems can be controlled at any time, they are slow due to the thermal mass of the mold. External systems can achieve a higher level of dynamics by heating only the mold surface, but this requires the mold to be open. By applying a heating element of a few micrometers thickness directly to the mold surface, the heat can be generated precisely where and when it is necessary. Such a heating element was developed using atmospheric plasma spraying (APS), a process variation of thermal spraying. The coating system consists of a TiOx/Cr2O3 heating coating embedded in two Al2O3 insulation coatings. The development was carried out in three different technology readiness levels. In the first stage, the relationship between the APS process parameters and the dielectric strength of the insulation coatings as well as the resistivity of the heating coating was identified and quantified using a design of experiments. Thereby, the dielectric strength showed certain independence from the process parameters, whereas the resistivity is significantly determined by the electric current, the H2 secondary gas flow as well as the spray distance. For the second stage, a test rig was developed to emulate the thermal stress of plastic injection molding. Thermal cycles were applied to the heating coating systems. The heating coating system was capable of highly dynamic temperature changes on the surface and was subjected to over 20,000 thermal cycles without damage. In order to be able to control the heating coating within a closed mold, a contacting solution was designed which allows a power supply from the back. In the third stage, heating coating systems were applied on mold inserts and tested in plastic injection molding. Final investigations of the molded parts showed the positive influence on warpage and shrinkage. LB - PUB:(DE-HGF)11 ; PUB:(DE-HGF)3 DO - DOI:10.18154/RWTH-2024-01772 UR - https://publications.rwth-aachen.de/record/979701 ER -