Manufacturing Practices (BT-106) - Important Questions

What are pattern allowances? Explain the different types of pattern allowances with neat sketches.

Describe the properties of a good moulding sand. Explain the standard laboratory tests for moulding sand (such as Permeability, Green Strength, Clay Content and Compactibility) and the acceptance criteria for each test.

Explain the different moulding processes used in foundries (green sand moulding, dry sand moulding, CO2 process, shell moulding and no-bake process). For each process give the principle, steps, advantages, limitations and typical applications.

What is a core in casting? Describe materials used for cores, core prints and methods to ensure accurate core location in a mould.

Describe the working principle, constructional features, operational parameters, advantages and limitations of (a) Cupola furnace and (b) Induction furnace used in foundries. Compare both furnaces on the basis of efficiency, control of melting, fuel consumption and suitability for different metals.

Explain the components and functions of a gating system in casting. Describe types of gating systems and the design considerations for sprue, runner and gate to ensure proper metal flow and minimize defects.

What is a riser (feeder) and what are its functions in casting? Using Chvorinov's rule derive the relation required between the volumes and surface areas of a casting and its riser so that the riser solidifies after the casting. Use Chvorinov's rule in the form $$t = C \left(\frac{V}{A}\right)^2$$ and clearly state all assumptions made.

List common casting defects (such as blow holes, pin holes, sand inclusion, cold shut, shrinkage, misrun and porosity). For each defect explain the cause and give appropriate remedies or preventive measures.

What are the materials commonly used for making patterns? Discuss the properties of pattern materials and criteria for selection of a pattern material for production of a given casting.

Explain various core making methods with emphasis on hand core making, machine core making and core shooters (hot-box and cold-box processes). State advantages and typical applications of each method.

Explain the solidification process of metals in casting. Define directional solidification and describe methods used in foundries to ensure directional solidification and produce sound castings.

Describe the typical layout of a foundry shop and explain the purpose and working of common foundry equipment such as sand muller, power rammer, sieves, core oven and moulding tables.