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

South BendEngine Lathe

Manufacturing Processes

Chip FormationDiscontinuous Continuous Built up edge

Manufacturing Processes

Chip Breakers• On the Cutting Tool• In the Material

– Inclusions– Sulfur

Manufacturing Processes

Speed, Feed, Depth of Cut

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

Feed Rates

finches

minipm

orfinches

revipr ff

Nipr

ipm

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

Surface Finishes• Tool Geometry and Feed rate

Manufacturing Processes

Surface Finishes

• Surface Speed and Depth of Cut

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

Manufacturing Processes

Effects of Coolants

• On workpiece– cracking, staining, chemical attack

• On machines– bearings and slideways

• On environment– breathing apparatus, and disposal