Entformungskräfte beim Spritzgießen in Abhängigkeit von Oberflächenrauigkeit, Stahlwerkstoff, Vorzugsrichtung der Oberflächenstruktur, Beschichtung und Kunststofftyp

Translated title of the contribution: Ejection forces at injection molding depending on surface roughness, mold steel grades, surface structure orientation, coating and plastic type

Martin Burgsteiner

Research output: ThesisMaster's Thesis


A correctly dimensioned ejection system reduces the complexity of an injection mould and raises its effectiveness and reliability, moreover, it protects the molded part from being damaged. To enable an accurate design, it is necessary to know the occurring ejection forces caused by several friction mechanisms between the part and the mold. The aim of this master thesis was to examine the influences of the surface roughness, the surface structure and the contact pressure as well as the influence of different mold steel grades and of a CrN coating, deposited by physical vapour deposition (PVD), on the ejection forces. An injection test mould was used for the experimental investigations, where the moulded part was pressed onto a steel specimen by a hydraulic cylinder. The occurring ejection forces during part demolding were measured and the static and the dynamic coefficients of friction were calculated. For the experiments several steel specimens with a surface roughness from Ra = 0.016 micrometer to Ra = 7.139 micrometer, surface structures from mirror-finished to spark eroded, surface structures with different orientation, surface treatments like blasting and CrN coating, as well as Bohler steel grades M238, M333, M340, M390 and W300 were examined. As polymers an amorphous Polycarbonate, grade Makrolon 2407, and a high crystalline Polypropylene, grade Hostacom PPU X9067HS, were used. A very low surface roughness (mirror-finished) leads to high coefficients of friction. With increasing roughness the coefficients of friction deteriorate to a minimum, before they increase again. An appropriate mould steel as well as a CrN coating reduces the coefficients of friction considerably, depending on the used polymer-steel-combination. A surface structure orientation in demolding direction reduces the friction, however, blasting increases the friction. In comparison to Polycarbonate the use of Polypropylene leads to the same or slightly lower static coefficients of friction but to a clear reduction of the dynamic coefficients of friction.
Translated title of the contributionEjection forces at injection molding depending on surface roughness, mold steel grades, surface structure orientation, coating and plastic type
Original languageGerman
  • Berger, Gerald Roman, Supervisor (external), External person
  • Friesenbichler, Walter, Co-Supervisor (internal)
  • Holzer, Clemens, Supervisor (internal)
Award date18 Dec 2009
Publication statusPublished - 2009

Bibliographical note

embargoed until null


  • ejection forces coating surface structure roughness steel structure orientation plastic PP polypropylene PC polycarbonate injection molding

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