Manufacturing Practices (BT-106) - Important Questions

Define machining. Classify machining processes with suitable examples and briefly state the distinguishing features of conventional and non-conventional machining methods.

Explain orthogonal cutting. Derive the relation for the shear plane angle $\phi$ using geometric analysis and frictional considerations, and state Merchant's relation for $\phi$ in terms of rake angle $\alpha$ and friction angle $\beta$ (show the final expression).

Describe the cutting forces in single point turning. Define cutting force components and explain how they are measured using a tool dynamometer. Discuss typical effects of cutting parameters on these forces.

List and explain the properties required for cutting tool materials. Compare HSS, cemented carbide, ceramics, CBN and PCD in terms of hardness, toughness, hot hardness and typical applications.

Define tool wear and tool life. Explain different types of tool wear mechanisms. State Taylor's tool life equation and express tool life $T$ in terms of cutting speed $V$ and the constants involved. Show how $T$ varies with $V$ using the equation $V T^{n} = C\,$.

Describe the functions of cutting fluids. Classify cutting fluids and discuss the criteria for selection and the environmental/health issues associated with their use.

Define surface roughness parameters $R_a$ and $R_t$. Derive the theoretical expression for arithmetic mean roughness $R_a$ for a single-point turning operation in terms of feed per revolution $f$ and nose radius $r_e$, using the relation $R_a = \frac{f^{2}}{32\,r_{e}}$ (state assumptions).

Define material removal rate (MRR). Derive the expression for MRR in turning in terms of workpiece diameter $D$, spindle speed $N$, depth of cut $a$ and feed per revolution $f$, showing the relation $MRR = \pi\,D\,N\,a\,f\,$ (state units and assumptions).

Explain the grinding process. Describe types of grinding operations, abrasives used, wheel specification, causes of grinding burns, and methods of wheel dressing and truing.

For a drilling operation, write the expression relating spindle speed $N$ (in rev/min), cutting speed $V$ (in m/min) and drill diameter $D$ (in mm). Use the appropriate formula and show the derivation for $N = \frac{V}{\pi\,D}$ (state unit conversions if required).

Discuss the economics of machining with respect to tool life. Using Taylor's tool life equation $V\,T^{n} = C$, outline the procedure to derive an expression for optimum cutting speed that minimizes cost per part (qualitative derivation and assumptions expected).

State the basic components of a CNC machine and list advantages of CNC over conventional machines. Describe the role of part programming (G-code) and explain with one simple example of a G-code command and its function.