Manufacturing Practices (BT-106) - Important Questions

Define "manufacturing" and explain the main classification of manufacturing processes with suitable examples (e.g., forming, casting, joining, subtractive and additive processes).

Explain the different methods of production: job production, batch production, mass production and continuous production. Discuss advantages and typical applications of each method.

What are pattern materials used in foundries? Describe the various types of patterns (solid pattern, split pattern, gated pattern, match plate pattern, loose piece pattern) and state typical applications of each. Sketch any two patterns.

Define pattern allowances: shrinkage allowance, draft allowance and machining allowance. If a casting is required to be $100\,\text{mm}$ after machining and the shrinkage allowance is $1.2\%$, calculate the corresponding pattern size assuming machining allowance is applied separately.

State Chvorinov's rule for solidification time of a casting and explain the meaning of each term. Use the rule $t = C_m \left( \frac{V}{A} \right)^2$ to calculate the relative solidification time for two castings where casting A has volume-to-surface ratio $\left(\frac{V}{A}\right)_A = 2\,\text{mm}$ and casting B has $\left(\frac{V}{A}\right)_B = 3\,\text{mm}$, assuming the mould constant $C_m$ is the same for both.

What is a gating system in casting? Describe the functions and components of a gating system (cup, sprue, runner, ingate) and explain the principles for designing a gating system to reduce turbulence and entrainment.

Explain the purpose of a riser (feeder) in casting. Describe types of risers and state the principles of riser design including the concept of modulus $M = \frac{V}{A}$. How is the riser size chosen with respect to the casting's modulus according to practical design rules?

Discuss the important properties of moulding sand (grain size and distribution, clay content, moisture content, refractoriness) and describe the standard tests used to evaluate sand such as permeability test, green strength test and compression strength test.

List and explain common casting defects such as porosity, shrinkage cavities, cold shuts, misruns, blow holes and inclusions. For each defect state the probable cause and practical remedies to avoid it.

What is a core in casting? Describe core making process including core box, core prints and core handling. What are the desired properties of core sand and why are they important?

Compare melting furnaces commonly used in foundries: cupola furnace, induction furnace and electric arc furnace. Discuss working principle, suitable charge materials, advantages and limitations of each.

Explain solidification shrinkage and the concept of riser efficiency. How does riser location and shape influence its efficiency? Outline a method to improve riser efficiency for a heavy section casting.