Influences of the aluminium-silicone ratio on the mechanical properties of the wax pattern mould for investment casting

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The fabrication of wax patterns in investment casting remains challenging in the early stages of product development due to long production times and high costs. This study develops an aluminium-filled silicone composite utilised for creating composite moulds for wax injection. Various weight ratios of the mixture, including 0/100, 55/45, 60/40, and 65/35, are prepared, and their mechanical properties, such as hardness and tensile properties, are evaluated. The results reveal that the hardness of the composite significantly increases with increasing aluminium powder content; especially the 65/35 composition exhibits a hardness of 32.5 Shore A, which is over 100 times that of the 0/100 mixture (0.3 Shore A). Furthermore, the increase in aluminium powder content also strongly enhances the Young's modulus of the composites, whereas their tensile strength moderately decreases. The microstructure of the composition is analysed using scanning electron microscopy (SEM). Shrinkage analysis further demonstrated that increasing aluminium powder content improves dimensional accuracy after curing. The actual mould for the wax injection process is successfully fabricated using the 60/40 composite. It is found that wax patterns exhibit satisfactory overall geometry and high dimensional accuracy. The developed compound can be applied for real-world investment casting in the industry.