Manufacturing Practices (BT-106) - Important Questions

Explain the sand casting process with a neat sketch. Describe each step in sequence and mention the important materials and tools used in sand casting.

Describe the different types of patterns used in sand casting. Explain the various pattern allowances (such as shrinkage allowance, machining allowance, draft, and distortion allowance) and give numerical examples showing how allowances are applied to pattern dimensions.

State Chvorinov's rule for solidification time of castings. Derive the rule briefly and calculate the solidification time using Chvorinov's rule for a casting having volume $V$ and surface area $A$ given the mould constant $C$. Use the relation $$t = C \left( \frac{V}{A} \right)^{2}.$$

Explain the functions of a gating system in casting. Describe different types of gating systems and design considerations. For a simple single ingate system, discuss how gate dimensions and runner design affect metal flow and defects during pouring.

List common casting defects such as blowholes, porosity, cold shuts, misruns, inclusions and hot tears. For each defect explain the likely causes and suggest remedies to avoid them in production.

Compare and contrast the following casting processes: die casting, investment casting, centrifugal casting and shell moulding. For each process mention principle, typical materials, advantages, limitations and typical applications.

Describe the investment (lost-wax) casting process. Explain the steps involved in preparation of the wax pattern, assembly, ceramic coating, dewaxing and final casting. Mention typical applications where investment casting is preferred.

Explain the difference between hot-chamber and cold-chamber die casting machines. Discuss their working principles, suitable alloy systems for each type and list advantages and disadvantages.

Explain the importance of directional solidification in casting. Describe the design and placement of risers (feeders). Using Chvorinov's rule explain how the size of a riser is chosen to feed a casting and avoid shrinkage defects.

Describe the working principles, advantages and limitations of the following melting furnaces used in foundries: crucible furnace, cupola furnace and induction furnace. State typical alloys processed in each type.

Describe non-destructive testing (NDT) methods commonly used for inspection of castings. Explain the principles, indications and limitations of radiographic testing and dye-penetrant testing for casting defect detection.

Explain how rapid prototyping (RP) techniques are used for producing patterns and cores for casting. Discuss benefits and limitations of using RP patterns in small batch production and complex geometries.