Manufacturing Practices (BT-106) - Important Questions

Explain the steps involved in green sand moulding. Discuss the functions of each step and list typical applications where green sand moulding is preferred.

Discuss the types of patterns used in foundry practice and the common materials employed for pattern making. Explain the various pattern allowances and state reasons for providing each allowance.

Describe the elements of a gating system and explain the design considerations for sprue, runner and gates. What is the function of a riser? Describe types of risers and their location principles.

State Chvorinov's rule for solidification time and derive the relation for solidification time of a casting. Using Chvorinov's rule, calculate the solidification time if necessary. The rule may be written as $$t = C \\left(\\frac{V}{A}\\right)^2$$ where $t$ is solidification time, $V$ is volume, $A$ is surface area and $C$ is a constant.

Differentiate between expendable mould casting processes and non-expendable mould casting processes. Give two examples of each and discuss their advantages and limitations.

List common casting defects. For each defect describe appearance, likely causes and remedies to avoid the defect in subsequent castings.

Explain core making process in foundry practice. Describe core prints and their function. Discuss common materials used for cores and the required properties of core sand.

Describe the investment (lost wax) casting process with a neat sequence of steps. State typical applications and advantages of investment casting over conventional sand casting.

Discuss the properties required for foundry sand. Describe standard tests performed on sand such as moisture content, permeability, green strength and clay content. Explain how the test results influence moulding performance.

Explain the modulus concept for riser design and show how the minimum riser size is selected to ensure directional solidification. If required, use the modulus $M = \\frac{V}{A}$ in your explanation.

Explain directional solidification in castings. How does the concept of directional solidification influence the placement of risers and the design of the gating system?

Describe the shell moulding process. Compare shell moulding with conventional green sand moulding in terms of process steps, accuracy, surface finish and typical applications.