Common Machining Operations

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Kalpakjian

Parts of an “Engine” Lathe

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Watchmaker’s lathe Typical “Engine” Lathe

Turret Lathe Big “Engine” Lathe

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60 feet c-c

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Really Big “Engine” Lathes

CNC Lathe: aka “Turning Center”

(carriage is mounted toward back, “upside down”)

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MachiningParameters

DeGarmo

Kalpakjian

Machining: Turning

Depth of Cut = DOC = (Dbefore – Dafter) / 2

Cutting Speed = Speed of metal moving towards cutting tip • Usually called “Surface Feet per Minute”, SFPM, SFM• Each cutting tool & workpiece material combo has a max SFM for decent tool wear. HSS & alum: 800 SFM HSS & 1020 steel: 110 SFM HSS & 1090 steel: 80 SFM HSS & hard 4140: 30 SFM TC & 1020 steel: 1000 SFM• SFM = r*w = D * RPM * (π/12) ≈ D * RPM / 4• RPMmax = 4 * SFM / D (most useful machining formula) E.g., find RPM for turning 2” dia. 1020 steel: RPM ≈ 4*110/2 = 220• RPM may need to be less due to chatter!• Most relations are similar for milling, but D=cutter dia.

CuttingForces

DeGarmo

OrthoganalModel(2-force)

DeGarmo

OrthoganalModel(2-force)

DeGarmo

Chip formation: chip types

Kalpakjian

DeGarmo

Merchant’s Model(Simplified 2-force)

DeGarmo

Kalpakjian

Chatter

Vibrational resonance of entire machining system, especially workpiece-cutter.Causes poor surface finish, fast tool wear, noiseFactors: stiffnesses of workpiece, cutter, machine cutting params: speed, feed, DOC cutter geometry: rake, clearancesSolutions: Change the cutting params esp. speed Increase stiffnesses

Heat rise in Cutting

Kalpakjian

Kalpakjian/Vieregge

Temperature of Cutting Tip

Kalpakjian / Chao & Trigger

Temperature of Cutting Tip

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Max Temperatures of Cutting Materials

Kalpakjian/Sandvik

Machining Time of Cutting Materials

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Layers are 2-10 microns thick:TiN: titanium nitride (low friction, gold appearance)TiCN: titanium carbonitride (wear resistance)Al2O3: Alumina (chemical stability, wear resistance)

Tungsten Carbide substrate (~shock and wear resistance)

Coated Carbide Cutting Inserts:The norm for production machining

Kalpakjian/Kennametal

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Cutter Shape and Geometry

Machining Costs

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References

DeGarmo: E.P. DeGarmo et al, Materials and Processes in Manufacturing, Wiley, 2003.

Kalpakjian: http://www.nd.edu/~manufact/index3.htm