Advanced Machining

Question 1

What is milling?

Answer 1

Milling is a versatile machining process used to manufacture complex 3D parts by removing material with a rotating tool.

Question 2

What are the two main categories of parts based on geometry?

Answer 2

Rotational parts and nonrotational (prismatic) parts.

Question 3

Which process is suitable for rotational parts?

Answer 3

Lathe turning.

Question 4

What is the difference between face milling and tangential milling?

Answer 4

Face milling: tool axis is orthogonal to the surface; tangential milling: tool axis is parallel.

Question 5

What is feed rate in milling?

Answer 5

Feed rate is the translational velocity of the workpiece relative to the tool (mm/min).

Question 6

What are the axial and radial depths of cut in milling?

Answer 6

Axial depth (ap): engagement along the tool axis; radial depth (ae): engagement perpendicular to the tool axis.

Question 7

Name three common milling operations.

Answer 7

Shoulder milling, gear machining, profile milling.

Question 8

What is shoulder milling?

Answer 8

Shoulder milling creates a step or shoulder on the workpiece.

Question 9

What industries commonly use milling for part manufacturing?

Answer 9

Aerospace, automotive, oil and gas, die and mold making.

Question 10

Name three aerospace components made by milling.

Answer 10

Blisk, turbine disc, wing rib.

Question 11

What materials are typically used in die and mold making?

Answer 11

Cast iron, tool steel, aluminum, tungsten carbide.

Question 12

What is orthogonal cutting?

Answer 12

A simplified 2D model of cutting where the tool edge is perpendicular to the cutting direction.

Question 13

What is the uncut chip thickness in milling?

Answer 13

The thickness of the material layer removed by each tooth (hD or tc).

Question 14

What is the formula for cutting speed (Vc) in milling?

Answer 14

Vc = (π × Dc × n) / 1000 (m/min), where Dc is tool diameter and n is spindle speed (rpm).

Question 15

What is feed per tooth (fz) in milling?

Answer 15

Feed per tooth (fz) is the distance the tool advances per tooth per revolution (mm/tooth).

Question 16

How is the feed rate (Vf) calculated in milling?

Answer 16

Vf = fz × Z × n, where Z is the number of teeth.

Question 17

What is the role of the rake angle in milling?

Answer 17

The rake angle (γ) influences cutting force and chip flow direction.

Question 18

What is the helix angle in milling tools?

Answer 18

The helix angle (λs) reduces vibrations and improves chip evacuation.

Question 19

What is the thrust force (Fd) in milling?

Answer 19

The force perpendicular to the cutting edge, affecting tool/workpiece deflection.

Question 20

How does tool overhang affect stability in milling?

Answer 20

Longer overhangs reduce tool stability, increasing deflection and errors.

Question 21

What is the difference between up milling and down milling?

Answer 21

Up milling: tool rotates against feed; down milling: tool rotates with feed.

Question 22

Why is down milling preferred for roughing?

Answer 22

Down milling pushes the tool away from the workpiece, reducing roughing errors.

Question 23

What is the cutting pressure method used for?

Answer 23

To calculate cutting forces using material-specific coefficients (kc1, x).

Question 24

What is the formula for maximum chip thickness (hex) in milling?

Answer 24

hex = fz × sin(ϕ), where ϕ is the engagement angle.

Question 25

How does tool deflection impact workpiece accuracy?

Answer 25

Deflection causes dimensional inaccuracies in the workpiece.

Question 26

What is the size effect in micromachining?

Answer 26

Material grains and defects become significant relative to tool size, affecting forces and finish.

Question 27

What is the minimum chip thickness effect?

Answer 27

Below a critical thickness (tc,min ≈ 0.3–0.4 × re), chips are not formed efficiently.

Question 28

What happens if the chip thickness is below the minimum chip thickness?

Answer 28

Elastic/plastic deformation occurs without material removal, increasing forces and wear.

Question 29

How does the cutting edge radius (re) affect micromilling?

Answer 29

A large re increases ploughing forces, raising specific energy (kc).

Question 30

What is intermittent chip formation in micromilling?

Answer 30

Chips form intermittently when tc < tc,min, causing force fluctuations.

Question 31

What is the dead metal cap (stable BUE) in micromachining?

Answer 31

A stable accumulation of workpiece material on the tool edge, reducing effective rake angle.

Question 32

How does cutting speed (Vc) affect built-up edge (BUE) formation?

Answer 32

Higher Vc reduces BUE by increasing temperature, but it may persist in micromachining.

Question 33

What are the sources of inaccuracy in micromachining?

Answer 33

Tool deflection, thermal deformation, runout, and material heterogeneity.

Question 34

Why is thermal deformation a concern in micromachining?

Answer 34

Small parts expand/contract significantly with temperature changes, altering dimensions.

Question 35

How does workpiece reference differ in macro vs. micro machining?

Answer 35

Macro: mechanical fixtures; micro: minimized handling (e.g., 5-axis machines).

Question 36

What is runout in micromachining?

Answer 36

Misalignment between tool axis and spindle axis, causing uneven cutting.

Question 37

What is the role of the Quick Stop Device (QSD) in machining studies?

Answer 37

To freeze chip formation for micrographic analysis of cutting mechanics.

Question 38

How does material grain size affect micromilling?

Answer 38

Grain size comparable to tool dimensions causes force variations and uneven cuts.

Question 39

What is the relationship between chip thickness and cutting force in micromilling?

Answer 39

Cutting force increases nonlinearly as chip thickness approaches tc,min.

Question 40

Why is surface roughness a challenge in micromachining?

Answer 40

Tool edge radius limits achievable smoothness, requiring specialized tools/strategies.