1. Machining: Family of Material Removal Processes
Material is removed from a starting work part to create a desired geometry

2. Principle of the process
Structure/Configuration
Process modeling
Defects
Design For Manufacturing (DFM)
Process variation
Module 6

3. Machining Process - Concept
Material In
Removal of chips
Material Out
- Not any type of materials could be cut: ceramic not
- There is a family of machining processes: abrasive, etc
handout 9 machining process

4. handout 9 machining process
Various types of machining processes
Drilling
Turning
Peripheral milling
Face milling
handout 9 machining process

5. handout 9 machining process
What function and quality level can machining processes achieve?
- Dimension accuracy: mm
- Surface quality: 0.4 µm
- Any shape
handout 9 machining process

6. handout 9 machining process
What are generic features with any machining operations to make cutting processes work?
- Two motions: tool motion and work motion
- Primary speed and secondary speed (or feed (rate)
- Relative motion between the two motions generates mechanics to form chips and remove them
handout 9 machining process

7. handout 9 machining process
Cutting Tools
Cutting Mechanisms
handout 9 machining process

8. handout 9 machining process
Cutting Tools
Major cutting parameters
Material Removal Rate
MRR = (v)(f)(d)
handout 9 machining process

9. Principle of the process
Structure/Configuration
Process modeling
Defects
Design For Manufacturing (DFM)
Process variation
Module 6

10. handout 9 machining process
Engineering Analysis
Machine equipment to do material removal process:
Chip formation, energy, and power
- Tool life: tool failure causes quality problem
- Productivity
- Quality assurance
handout 9 machining process

11. handout 9 machining process
Theory of chip formation
Orthogonal Cutting Model –converts 3d to 2d Ls tc to
Chip thickness ratio, r = to/tc (tc > to)
MRR = (v)(to)(w)
handout 9 machining process

12. handout 9 machining process
Theory of chip formation
E- Efficiency that accounts for loss of the machine tool
handout 9 machining process

13. handout 9 machining process
Tool life
Fracture failure: force becomes excessive, causing sudden brittle fracture
- Temperature failure: temperature is too high, causing the material at the tool point to soften
- Gradual wear: (1) crater wear (2) flank wear
handout 9 machining process

14. handout 9 machining process
- The objective of selecting tools should ensure that only the gradual wear mode will occur
- Tool design: materials and geometry
- Except for tool design parameters (system parameters), tool life is a function of operating parameters
(d) (f) (v)
Cooling methods ( fluids)
handout 9 machining process

15. handout 9 machining process
Productivity
Productivity is also called removal rate which is computed by the following equation:
(d) (f) (v)
Quality
System parameters
Operating parameters
Example:
- Rough cutting (f: mm/rev; d=2.5-20mm)
- Finish cutting (f: mm/rev; d= mm)
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16. handout 9 machining process
Summary
System and product parameters
Operating parameters
Tool
(d) (f) (v) -> Power
Material
Cooling methods
Goal: Select operating parameters to ensure no failure with the whole system and satisfactory quality
handout 9 machining process

17. Principle of the process
Structure/Configuration
Process modeling
Defects
Design For Manufacturing (DFM)
Process variation
Module 6

18. Design Considerations in Machining
Design parts that require little, and if possible, no machining
Use net shape or near net shape processes
Specify tolerances
Use tighter tolerances only where required
Specify surface finish
Use better surface finishes where required
Avoid machining sharp features (i.e. internal corners) where possible
Require sharp cutting tools that can break more easily
Avoid deep holes that must be bored
Difficult to maintain tool stiffness
Provide seats for drilling
Design part so standard cutting tools can access easily

19. Design Considerations in Machining
Design with materials that have good machinability
Design part features that used standard cutting tools
Avoid unusual hole sizes, threads, angles, and shapes requiring special form tools or special contouring
Design part with simpler geometries
Minimize or avoid angles and contours where possible
Design parts to have as few setups, one if possible
I.E. changing position of part and changing cutting tool

20. Design Considerations in Machining
Design machined part sizes that are close to standard available stock sizes
Less material to cut
Design machined parts to be rigid enough to withstand cutting forces and clamping
Avoid thin and narrow parts
Avoid undercuts as they require additional setups and special tooling

21. Summary:
Machining is a material removal process by cutting tools on work material (stock).
For machining, one need to select tools and operation parameters (v, f, d).
The selection criteria: tool life, quality.
The productivity is the multiplication of v, f, d.
Operating principle: chip formation with two important angles (rake angle, and frank angle).
DFM rules