4. Heat Generation Zones (Dependent on sharpness of tool) (Dependent on ) (Dependent on 10% 30% 60%
5. Tool Terminology Side relief angle Side cutting edge angle (SCEA) Clearance or end relief angle Back Rake (BR),+ Side Rake (SR), + End Cutting edge angle (ECEA) Nose Radius Turning Cutting edge Facing Cutting edge
12. ‘ Turning’ Forces For Orthogonal Model End view section 'A'-'A' Note: For the 2D Orthogonal Mechanistic Model we will ignore the radial component F t 'A' 'A' c F
13. ‘ Facing’ Forces For Orthogonal Model End view Note: For the 2D Orthogonal Mechanistic Model we will ignore the Longitudinal component
14.
15. Orthogonal Cutting Model (Simple 2D mechanistic model) Mechanism: Chips produced by the shearing process along the shear plane t 0 + Rake Angle Chip Workpiece Clearance Angle Shear Angle depth of cut Chip thickness Tool Velocity V tool t c
16. tool Cutting Ratio (or chip thicknes ratio) t c t o A B Chip Workpiece
17. Experimental Determination of Cutting Ratio Shear angle may be obtained either from photo-micrographs or assume volume continuity (no chip density change): i.e. Measure length of chips (easier than thickness) w t L 0 0 0 w c L c c t
18. Shear Plane Length and Angle or make an assumption, such as adjusts to minimize cutting force: (Merchant) t c t o A B Chip tool Workpiece
19. Velocities (2D Orthogonal Model) Velocity Diagram (Chip relative to workpiece) V = Chip Velocity (Chip relative to tool) Tool Workpiece Chip V = Cutting Velocity (Tool relative to workpiece) Shear Velocity c V s V V s V c
20. Cutting Forces ( 2D Orthogonal Cutting) Free Body Diagram Generally we know: Tool geometry & type Workpiece material and we wish to know: F = Cutting Force F = Thrust Force F = Friction Force N = Normal Force F = Shear Force F = Force Normal to Shear c t s n Tool Workpiece Chip Dynamometer R R R R F c F t s F F n N F
21. Force Circle Diagram (Merchants Circle) R F t F c Tool F N F s F n
27. Specific Cutting Energy (or Unit Power) Energy required to remove a unit volume of material (often quoted as a function of workpiece material, tool and process:
28. Specific Cutting Energy Decomposition 1. Shear Energy/unit volume (Us) (required for deformation in shear zone) 2. Friction Energy/unit volume (Uf) (expended as chip slides along rake face) 3. Chip curl energy/unit volume (Uc) (expended in curling the chip) 4. Kinetic Energy/unit volume (Um) (required to accelerate chip)
29. Specific Cutting Energy Relationship to Shear strength of Material SHEAR ENERGY / UNIT VOLUME FRICTION ENERGY / UNIT VOLUME APPROXIMATE TOTAL SPECIFIC CUTTING ENERGY
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