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Common Machining Operations Kalpakjian. Parts of an “Engine” Lathe.

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Presentation on theme: "Common Machining Operations Kalpakjian. Parts of an “Engine” Lathe."— Presentation transcript:

1 Common Machining Operations Kalpakjian

2 Parts of an “Engine” Lathe

3 Watchmaker’s lathe Typical “Engine” Lathe Turret LatheBig “Engine” Lathe

4 60 feet c-c Really Big “Engine” Lathes

5 CNC Lathe: aka “Turning Center” (carriage is mounted toward back, “upside down”)

6 Machining Parameters DeGarmo

7 Kalpakjian Machining: Turning Depth of Cut = DOC = (D before – D after ) / 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 RPM max = 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.

8 Cutting Forces DeGarmo

9 Orthoganal Model (2-force) DeGarmo

10 Orthoganal Model (2-force) DeGarmo

11 Chip formation: chip types Kalpakjian DeGarmo

12 Merchant’s Model (Simplified 2-force) DeGarmo

13 Kalpakjian Chatter Vibrational resonance of entire machining system, especially workpiece-cutter. Causes poor surface finish, fast tool wear, noise Factors: stiffnesses of workpiece, cutter, machine cutting params: speed, feed, DOC cutter geometry: rake, clearances Solutions: Change the cutting params esp. speed Increase stiffnesses

14 Heat rise in Cutting Kalpakjian

15 Kalpakjian/Vieregge Temperature of Cutting Tip

16 Kalpakjian / Chao & Trigger Temperature of Cutting Tip

17 Kalpakjian Max Temperatures of Cutting Materials

18 Kalpakjian/Sandvik Machining Time of Cutting Materials

19 Layers are 2-10 microns thick: TiN: titanium nitride (low friction, gold appearance) TiCN: titanium carbonitride (wear resistance) Al 2 O 3 : Alumina (chemical stability, wear resistance) Tungsten Carbide substrate (~shock and wear resistance) Coated Carbide Cutting Inserts: The norm for production machining Kalpakjian/Kennametal

20 Kalpakjian Cutter Shape and Geometry

21 Machining Costs Kalpakjian

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

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