Week 8

Question 1

What are the categories of material removal processes in machining?

Answer 1

1. Conventional machining (e.g., turning, milling, drilling)
2. Abrasive processes (e.g., grinding)
3. Non-traditional processes (using various energy forms)

Question 2

Why is conventional machining important?

Answer 2

It allows for machining a variety of materials and creating complex shapes with good dimensional accuracy and surface finish. However, it’s time-consuming and wasteful of material.

Example sentence: Conventional machining is commonly used in manufacturing industries for producing precision components.

Question 3

What is the difference between roughing and finishing operations?

Answer 3

Roughing removes large amounts of material quickly, using higher feeds and depths. Finishing achieves final dimensions and surface finish with lower feeds and depths.

Question 4

What are the three cutting conditions in machining?

Answer 4

Cutting speed (v), feed rate (f), and depth of cut (d).

Question 5

What is the formula for Material Removal Rate (MRR)?

Answer 5

MRR = v * f * d, where v = cutting speed, f = feed rate, d = depth of cut.

Question 6

What are the basic types of chip formation?

Answer 6

1. Discontinuous chip
2. Continuous chip
3. Continuous chip with built-up edge (BUE)
4. Serrated chip

Question 7

What is the Merchant Equation for shear plane angle?

Answer 7

ϕ = 45° + (α/2) - (β/2), where α = rake angle, β = friction angle.

Question 8

What is the formula for specific energy in machining?

Answer 8

U = Pc / RMR, where U = specific energy, Pc = cutting power, RMR = material removal rate.

Question 9

What percentage of energy is converted to heat during machining?

Answer 9

98% of the energy is converted into heat, primarily at the tool-chip interface.

Question 10

What are the common forces in metal cutting?

Answer 10

1. Friction force (F)
2. Normal force to friction (N)
3. Shear force (Fs)
4. Normal force to shear (Fn)

Question 11

What is the chip thickness ratio and its formula?

Answer 11

The chip thickness ratio is the ratio of the chip thickness before the cut (t0) to the chip thickness after the cut (tc). r = t0 / tc.

Question 12

What are the components of a cutting tool?

Answer 12

1. Rake face – directs chip flow.
2. Flank (relief face) – provides clearance between the tool and the workpiece.
3. Tool point – where the cutting occurs, with a nose radius.

Question 13

What are single-point and multiple-cutting-edge tools?

Answer 13

Single-point tools (e.g., turning) have one cutting edge. Multiple-cutting-edge tools (e.g., milling and drilling) have more than one cutting edge.

Question 14

What are the primary and secondary motions in machining?

Answer 14

Primary motion: Cutting speed (v)—the speed at which the tool moves relative to the workpiece. Secondary motion: Feed rate (f)—the slow movement of the tool into the material.

Question 15

What is shear strain in metal cutting?

Answer 15

Shear strain can be estimated by γ = tan(ϕ - α) + cot(ϕ), where ϕ is the shear plane angle and α is the rake angle.

Question 16

What are the two types of shearing zones in chip formation?

Answer 16

1. Primary shear zone – where the bulk of shear deformation occurs.
2. Secondary shear zone – due to friction between the chip and the rake face of the tool.

Question 17

What factors affect the shear plane angle in the Merchant equation?

Answer 17

The shear plane angle increases when: 1. The rake angle (α) is increased. 2. The friction angle (β) is decreased by using lubricants.

Question 18

What are the consequences of high cutting temperatures?

Answer 18

1. Reduced tool life.
2. Potential safety hazards from hot chips.
3. Dimensional inaccuracies due to thermal expansion.

Question 19

What is the equation for power consumption in machining?

Answer 19

Pc = Fc * v, where Pc = cutting power, Fc = cutting force, v = cutting speed.

Question 20

What is specific energy, and how is it calculated?

Answer 20

Specific energy (U) is the energy required to remove a unit volume of material: U = Fc / (t0 * w), where Fc = cutting force, t0 = chip thickness before the cut, w = width of the cut.