In addition to two-part resin molding, silicone cavities also are suitable for low-pressure injection molding of waxes for investment casting.
Using a low pressure, injection system, semi-molten wax is forced into the silicone cavity until full. The cavity is then chilled until the wax has fully solidified. The wax is then removed from the cavity and the process repeated. However, due to the fragility of the investment casting wax material, extreme care must be exercised when removing wax parts from the silicone tool.
The advantages of RTV silicone rubber tooling is that it is quick to produce, reproduces detail impressively well and it’s fast for producing a limited number of plastic parts. Disadvantages are poor tool life, cost of silicone rubber and lengthy cycle time. Also, it does not use the final production material (except for wax) or final manufacturing process.
Wax injection is an efficient process. One study found that design, assembly, and injection took 10 days, saving a great deal of time over other processes, which can take two months or more.1 This makes the process highly suited for mass production.
Reduction of the time and cost during the research and development stage of a new product is an important issue. Rapid tooling techniques can reduce the time to market compared to conventional machining approaches. In general, reduction in cooling time plays an important role on cycle time in manufacturing time. Wax injection mold fabricated from aluminum-filled epoxy resin can be employed for small-batch productions of wax patterns. However, the cooling time is much longer compared to metallic wax injection molds due to poorer thermal conductivity. In this study, three kinds of cooling-channel layouts were employed to fabricate wax injection molds for low-pressure wax injection molding using rapid prototyping and rapid tooling techniques. The effects of three kinds of wax injection molds on the cooling time during the low-pressure wax injection molding were investigated. It was found that the reduction in cooling time about 87% can be obtained when a wax injection mold with conformal cooling channels is compared to a conventional wax injection mold fabricated by Al-filled epoxy resin. The manufacturing cost reduction for a wax injection mold with high cooling efficiency about 63% can be obtained using the method proposed in this work.
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