Ceramic molding process

Ceramic molding process

1. Ceramic molding process VINAYAK KUMAR 212314011

2. INTRODUCTION Ceramic molding has been around for centuries. Ceramic molding is an offshoot of the investment-molding process but can cast materials at much higher temperatures. Ceramic casting uses refractory ceramics for mold material.

3. THE PROCESS Silica grains plus ethyl silicate, water, alcohol and a gelling agent such as HCL are used. Slurry is poured around the pattern. Allowed to gel in about 4 to 7 minutes. Pattern is then removed. Mold is fired by igniting the alcohol. Firing will burn off any unwanted material and make the mold hardened and rigid.

4. Firing of the mold produces a network of microscopic cracks( microcrazing ) in the mold material. These cracks give the ceramic mold both good permeability and collapsibility for the metal casting process.

5. Once prepared, the two halves of the mold are assembled for the pouring of the metal casting. Often, the ceramic mold will be preheated prior to pouring the molten metal. The metal casting is poured, and let solidify. Like in other expendable mold processes, the ceramic mold is destroyed in the removal of the metal casting.

6. PROPERTIES AND CONSIDERATIONS It can produce parts with thin sections. Excellent surface finish, and high dimensional accuracy. Eliminates the need for machining. Can be used to manufacture ferrous and other high melting point metal casting materials because can withstand extremely elevated temperatures. Relatively expensive. Long preparation time of the mold.

7. Features Tolerances: 0.4 %. Surface finish: 2 - 4 µm. Wall thickness: may be as small as 1.25 mm. Weights: Range from 60 gm to 1000kg. Draft allowance: 1° recommended. Patterns: Reusable and cheap. Casting size: generally not restricted.

8. Ceramic Mold Process  Compared with Investment Casting Casting requirements Investment casting Ceramic mold casting Surface smoothness 80-125 µinch 100-125 µinch Intricacy Excellent Excellent but not as investment casting Thinness of metal sections Excellent Excellent Tolerance Excellent Good to Excellent Machining cost Minimum machining required Machining greatly reduced Lead time Longest lead time Very short lead time Adaptability to various sizes Ounce to 300 lb No limitation Adaptability to various metals No limitation No limitation

9. Applications Impellers, complex cutting tools, plastic mold tooling etc. 

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