Manufacturing Practices (BT-106) - Important Questions

Explain the principle of metal cutting. Describe the chip formation process and the shear plane mechanism with a neat diagram. Discuss types of chips produced and factors affecting chip formation.

Derive Taylor's tool life equation and explain the significance of each parameter. If $V T^{n} = C$, calculate the cutting speed $V$ that gives a tool life $T$ of 30 minutes when $n=0.2$ and $C=900$.

Explain the various types of cutting tool wear (flank wear, crater wear, built-up edge, notch wear). Discuss the mechanisms leading to each type of wear and list methods to reduce tool wear.

Using Merchant's circle and orthogonal cutting assumptions, derive the relation between cutting force, thrust force and shear plane angle. Explain how shear angle affects the cutting forces and specific cutting energy.

Define the principal machining parameters: cutting speed, feed and depth of cut. Explain qualitatively how each parameter affects cutting temperature, tool life, material removal rate and surface finish.

Describe the properties, advantages and typical applications of common cutting tool materials: high speed steel (HSS), cemented carbide, ceramic tools, cubic boron nitride (CBN) and synthetic diamond. Compare them with respect to hot hardness, toughness and wear resistance.

A turning operation is to machine a cylindrical job of length 200 mm from diameter 50 mm to 40 mm using a cutting speed of 150 m/min, feed of 0.25 mm/rev and depth of cut 0.5 mm. Calculate:

1. Machining time for one pass.

2. Material removal rate (MRR) in mm^3/s.

3. If the measured cutting force $F_{c}$ is 1200 N, calculate the cutting power required in kW using $P = \frac{F_{c} V}{60000}$.

Explain the principles of the grinding process. Describe the specification of a grinding wheel (Abrasive, Grit size, Grade, Structure, Bond). Explain the operations of dressing and truing and their effect on grinding performance.

Define the principal cutting tool geometry angles: rake angle, clearance (relief) angle, and cutting edge angle. Explain the effect of positive and negative rake on cutting forces, chip formation and tool strength. How would you choose tool geometry for roughing versus finishing cuts?

Describe the basic components of a CNC turning center. Explain the coordinate system and the general structure of a simple G-code part program. Write a short part program sequence to face off 10 mm from the front of a 60 mm long job and then turn down the diameter from 50 mm to 40 mm.