Post on 22-Dec-2015
transcript
Manufacturing Processes
Fundamentals of Cutting
• South Bend lathe
• Chip Formation
• Chip Breakers
• Feeds and Speeds
• Tool Materials
• Tool Properties
• Tool Wear
• Surface Finishes
• Cutting Fluids
• CNC Lathes
Manufacturing Processes
Speeds, Depth of Cut
• Depth of Cut
• Speed
DOCD D
d
1 2
2
VD N s
1
12N
rev
min
Manufacturing Processes
Cutting Time Considerations• Material removal rate
• Time to Cut CTL
f ipm
MRR D df Nave ipr
Manufacturing Processes
Tool Materials• High
SpeedSteel (HSS)
• CoatedCarbideInserts 0 20 40 60 80
100
250
500
1000S
fpm
Time (minutes)
AL2O3/TiNAl2O3TiC TiNCeramicsTi/Ta/WWC/CoCastHSS
Manufacturing Processes
Tool Properties• High Hardness
• Resist Abrasion
• Resist Chipping
• Hot Hardness
• Resist BulkDeformation (E)
• Chemical Stability
• Adequate Thermalproperties
• Consistent ToolLife
• Geometry
Manufacturing Processes
Tool Wear• slow death mechanisms: gradual wear
on flanks, or rake face of tool (crater)– abrasion, adhesion, diffusion, chemical
• sudden death mechanisms: unpredictable, catastrophic failure– brittle fracture, chipping, plastic
deformation
Manufacturing Processes
Tool Life• Taylor's Equation: Surface Speed
• Variation in material hardness– within piece and piece to piece
• Variation in tool material and geometry
• Vibrations
• Changing surface characteristics of workpiece
Manufacturing Processes
Tool GeometryBackRake
SideRake
EndRelief
SideRelief
Side EndEdges
fig (8) (14) (6) (6) (15-20)
Fe 10 12 5 5 15
Al 20 15 12 10 5
Manufacturing Processes
Cutting Fluids
• Reduces Cutting Temperature– dimensional stability
– reduces thermal tool wear
• Acts as Lubricant– reduces forces and energy consumption
Manufacturing Processes
Cutting Fluids
• Flood Cooling– lowers temperature
– reduces oxidation
• Mist Cooling– Better Visibility
– gets to inaccessible areas