Manufacturing Practices (BT-106) - Important Questions

Define foundry. Explain the casting process with a neat labelled diagram showing pattern, mould, pouring basin, runner, gating, riser and mould cavity. Describe the main steps involved from pattern preparation to fettling.

Classify patterns used in foundry practice. Explain the construction, advantages and typical applications of the following pattern types: solid pattern, split pattern, match-plate pattern and cope-and-drag pattern. List commonly used pattern materials and their merits.

What are pattern allowances? Explain shrinkage allowance, machining allowance and draft allowance with examples. Using the relation $P = C\left(1 + s\right)$, where $P$ is the pattern dimension, $C$ is the casting dimension and $s$ is the fractional shrinkage allowance, calculate the pattern size required for a casting of $200\,\text{mm}$ when shrinkage allowance is $1.2\%$.

Discuss the constituents of moulding sand. Explain the important properties of moulding sand (grain size, clay content, moisture, permeability, refractoriness, plasticity, strength) and describe standard tests performed on moulding sand (sieve analysis, permeability test, green strength test, moisture content test).

What is a core? Explain the methods of core making and types of cores. Describe core prints, core boxes and provide typical applications where cores are necessary.

Explain the functions of a gating system in sand casting. Draw and label a typical gating system indicating pouring basin, sprue, runner and riser. Discuss design considerations for gating and the purpose and types of risers.

Describe the construction and working principle of a cupola furnace and an induction furnace used for melting metals. Compare their applications, advantages and limitations in foundry practice.

List the common defects encountered in metal casting (for example: blowholes, gas porosity, cold shuts, misruns, shrinkage cavities, inclusions, hot tears). For each defect state the probable causes and suggest remedies.

Explain the following casting processes: sand casting, die casting, investment (lost-wax) casting and centrifugal casting. Compare these processes with respect to dimensional accuracy, surface finish, production rate, tooling cost and typical applications. Present the comparison in tabular form.

State Chvorinov's rule for solidification time and explain its significance in riser design. Write the rule in the form $$t = C\left(\frac{V}{A}\right)^2$$ and explain each term. Describe how Chvorinov's rule is used to ensure that a riser solidifies after the casting.

Explain the purpose of fluxing and degassing during metal melting. Describe common fluxes used for ferrous and non-ferrous melts and the methods used to remove dissolved gases and non-metallic inclusions.

Discuss the major health, safety and environmental hazards associated with foundry operations. Suggest control measures and good practices for workplace safety, emission control and waste management in a foundry.