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Common Machining Operations
Kalpakjian
Kalpakjian
Parts of an “Engine” Lathe
www.blazingtech.net
www.bakerprovan.com.auwww.liberatorcrew.com
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Watchmaker’s lathe Typical “Engine” Lathe
Turret Lathe Big “Engine” Lathe
www.harrismachinetools.com
60 feet c-c
www.practicalmachinist.com
Really Big “Engine” Lathes
CNC Lathe: aka “Turning Center”
(carriage is mounted toward back, “upside down”)
www.machineryvalues.com
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
Kalpakjian
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
www.greenleafcorporation.com
Kalpakjian
Cutter Shape and Geometry
Machining Costs
Kalpakjian
References
DeGarmo: E.P. DeGarmo et al, Materials and Processes in Manufacturing, Wiley, 2003.
Kalpakjian: http://www.nd.edu/~manufact/index3.htm