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July 22, 2008
Investment casting at Thompson is basically a twelve-step process.

Investment casting has gained rapid acceptance because of the substantial savings it can provide over alternative manufacturing methods. Near-net-shape investment castings save material, eliminate secondary machining operations and have better surface finishes compared with sand castings. According to Thompson Investment Casting (, investment castings also make part configurations possible that are often impossible to produce with other processes, giving engineers the freedom to design truly intricate parts as one-piece castings.

The company uses the latest technology, along with years of investment casting experience, to pour steel alloys, copper and copper-based alloys into extremely complex shapes with fine details, smooth surfaces and cross sections as thin as 0.020 in.

1. A wax injection mold is designed and built to produce castings to customer specifications.
2. A pattern of recyclable material is produced from the wax injection mold.

3. Multi-cavity tools are used to expedite wax production.

4. Thompson uses its special method of gating and treeing systems to ensure castings are sound.

5. The pattern assembly is dipped into a ceramic slurry, coated with a refractory material and dried. This process is repeated until the desired thickness and strength are achieved.
6. Between coatings, the ceramic shells are dried in an atmospherically controlled environment.

7. With regulated steam pressure, an autoclave melts and reclaims the wax from the ceramic shells.

8. High-temperature ovens cure and preheat the ceramic shells prior to pouring the molten metal.

9. Preheated molds are poured using Thompson’s special process.

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