Papers by Keyword: Low-Pressure Injection Molding

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Authors: Yin Wu, Wen Jie Si, He Zhuo Miao
Abstract: A new dewaxing method for low-pressure injection molded ceramics is presented. Supercritical extraction with carbon dioxide was used to remove paraffin wax from the ceramic green parts. The composition of organic additives for low-pressure injection molding feedstock and the extraction condition for the green parts were investigated. Moreover, the properties of sintered ceramic samples dewaxed by supercritical carbon dioxide were compared with those by thermal dewaxing. The results show that the new binder system containing 50wt% paraffin wax, 35% bee wax and 15% stearic acid fulfills the requirements of both low-pressure injection molding feedstocks and supercritical dewaxing, where the feedstock has high fluidity, low viscosity and quick solidification. The efficient extraction condition for supercritical dewaxing from the green parts is at 30MPa pressure and 45°C. Under this condition, defect free ceramic green parts can be obtained. Dewaxing methods have significant influence on the properties of sintered parts. The mechanical properties of the sintered sample can be improved by supercritical dewaxing. With this method, the bending strength of sintered samples (σ = 331.6 MPa) is higher than that obtained by thermal treatment (σ = 312.3MPa). The sintered samples dewaxed by supercritical CO2 have shown the property of higher density and less distortion compared to the thermal dewaxing method. Moreover, with supercritical extraction the dewaxing time can be reduced to about one tenth of the time required by thermal dewaxing.
Authors: Peter Risthaus, D. Göhring, R. Knitter
Authors: Rolf Waesche, Carl Paulick, Gabriele Steinborn, V. Richter, M. Werner
Abstract: It has been successfully demonstrated that ceramic materials can be joined in the green state without a second phase by using low pressure injection molded parts. The investigation of the joining interface revealed that a high quality interface can be achieved by carefully adjusting the different manufacturing steps. The use of monomodal particle size distribution in the used powder CT3000SG is inferior to a broader particle size distribution obtained by replacing 33% of the finer alumina powder by coarser CT1200SG. In this way the dewaxing process is significantly improved when the wall thickness of the part exceeds 3 mm. The investigation of the mechanical properties of the joined and sintered parts revealed, that the bending strength of the joined specimens achieved about 80 % of the unjoined, monolithic specimens.
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