Question

An expandable pattern is used in

• A. Shell moulding
• B. Squeeze casting
• C. Centrifugal casting
• D. Investment casting

Hint:

Associate "expendable pattern" with processes where the pattern is "lost" during mold making. The two main examples are Investment Casting (lost-wax) and Lost-Foam Casting.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Casting patterns are replicas of the object to be cast. They can be classified as reusable (permanent) or expendable (single-use). An expendable pattern is one that is destroyed during the casting process. The question asks to identify the process that uses such a pattern.

Step 2: Detailed Explanation:
Let's analyze the processes listed:

• (A) Shell moulding: Uses a reusable metal pattern to form a thin-walled sand shell mold. The pattern is not destroyed.

• (B) Squeeze casting and

(C) Centrifugal casting: Typically use permanent, reusable metal molds (dies). No pattern is used in the traditional sense.

• (D) Investment casting: This process, also known as the "lost-wax process," is a classic example of using an expendable pattern. The process involves:


Since the pattern is destroyed in each cycle, investment casting uses an expandable pattern. Lost-foam casting is another process that uses an expendable pattern (made of polystyrene foam).

Step 3: Final Answer:
Investment casting is the process that utilizes an expandable pattern, typically made of wax, which is melted or burned out to create the mold cavity.