Variotherme Prozessführung im Kautschukspritzguss
Research output: Thesis › Master's Thesis
This thesis covers the subject of variothermal process control in rubber injection molding. The variothermal process control should allow for the production of high quality components within a shorter amount of time than conventional injection-molding processes do and increase the efficiency while consistent or even higher quality of the components and a stable process should be achieved. The injection of material into the cavity at low mold temperatures and its complete crosslinking at higher temperatures can result in a shorter process time. The whole process has been simulated with the aid of Cadmould Pre&Post and Cadmould 3D-F (simcon kunststofftechnische Software GmbH, Würselen, Deutschland). A thermal analysis of the process has been conducted via Cadmould Pre&Post. The derived data has been used for the simulation of the injection molding process in Cadmould 3D-F. A mold to generate plate-shaped and a cylindrical component has been applied for the experimental part. A statistical experimental plan has been developed in order to determine possible influences on the process. Two different materials have been used both for the experiments and for the simulation, one of which being sulfur-crosslinked nitrile rubber (NBR), the other being hydrated nitrile rubber (HNBR) which is cross-linked with the aid of peroxides. Both materials have been chosen because of their distinct crosslinking behavior and mechanism. The simulation of the process demonstrates that homogenous temperature distribution on the molded plate is impossible due to the position of the heating elements. The result in temperature distribution reflects the dispersion of the crosslinking degree. Nevertheless, a high degree of crosslinking has been achieved for all settings in the experimental plan in terms of NBR due to post-crosslinking. However, HNBR shows that a high crosslinking degree is only achievable in crosslinking settings of high vulcanization temperature. The most substantial impact on NBR and HNBR is the vulcanization temperature. The assessment of the plate shaped parts of the experiments was carried out by testing the compression set and the shore A hardness as well as by the tensile test. The Vulcanization temperature has the most substantial influence on the result of the compression set test. The results of the shore A hardness demonstrated a stable hardness with 67 hardness points for NBR and 77 points for HNBR. The results of the tensile tests results do not show any significant distinction in respect to the experimental settings. The compression set allows for a comparison of the simulation results with reality. As a result, only settings with a high difference between mold and vulcanization temperature enable a plausible depiction of reality in terms of both materials. A reason for this could be the deficient depiction of thermal conductivity in the simulation. The simulation maps reality very well in terms of substantial differences in temperature and the highest temperature settings. A stable process control was during the experiments achievable.
|Translated title of the contribution||Rapid heat cycle temperature control for elastomer injection molding|
|Award date||20 Oct 2017|
|Publication status||Published - 2017|