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Part Fabrication

This article explores the various machining processes such as turning, milling, grinding, and drilling, and discusses strategies to maximize metal removal rate, minimize surface roughness, extend tool life, and reduce power consumption. It also covers factors impacting machinability, including chip formation, tool wear, and vibration, offering practical solutions to improve process stability and productivity.

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Part Fabrication

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  1. Part Fabrication • Additive Processes • molding, casting, sintering • Subtractive Processes • turning, milling, grinding, EDM • Forming Processes • sheet metal • bending, shearing, punching • Joining Processes • fasteners, adhesives, welding

  2. Material Removal Processes • Turning • work rotates, tool translates • Milling • tool rotates, work and tool translate • Drilling • tool rotates, tool translates • Grinding • tool rotates, work may rotate, work or tool may translate

  3. Chip Formation

  4. Turning

  5. Milling Operations

  6. Geometry of Milling Process

  7. Face Milling

  8. Milling Forces

  9. Machinability • Maximize metal removal rate (MRR) • Minimize surface roughness • Maximize tool life • Minimize power required • Available parameters: • tool type (geometry, material, and tool holder) • rotation rate (speed) • translation rate (feed) • cutting path • cutting lubricant

  10. Feed & Speed Charts

  11. Tool Wear • Abrasion • Adhesion (built-up edge) • Diffusion (migration of atoms between work and tool) • Fatigue • Chemical (oxidation)

  12. Tool Wear

  13. Machinability • The enemies: • heat • vibration

  14. Process • Rigidity: • use shortest tool and tool holder • keep workpiece firmly clamped • avoid speed/feed/depth combos that chatter • Heat: • use coated tools when heat is a problem • keep chips cleared (liquid or air coolant) • hard chips get harder • soft chips stick to tool • don’t go too fast OR too slow • Chip load: • keep volume removed constant! • especially watch tool entry, exit, corners

  15. Form Errors • Deflection of cutter (in end milling) or work (in turning) causes form error

  16. Vibration (chatter)

  17. Vibration

  18. Vibration • Choose highest spindle RPM • Tune tool length to stay in a stable lobe at top spindle RPM

  19. Vibration

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