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

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

4. 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

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

6. 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

7. 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 along with force to form chips and remove them
handout 9 machining process

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

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

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

11. handout 9 machining process
Engineering Analysis
Material removal process:
Chip formation, energy, and power
- Tool life: tool failure causes quality problem
- Productivity
- Quality assurance
handout 9 machining process

12. 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

13. handout 9 machining process
Theory of chip formation
Cutting power
Cross cutting power
Specific cutting power
E- Efficiency that accounts for loss of the machine tool
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14. 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

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

16. 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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17. handout 9 machining process
Summary
System and product parameters
Operating parameters
(d) (f) (v)  Power
Tool
Material
Cooling methods
Goal: Select operating parameters to ensure no failure with the whole system and satisfactory quality
handout 9 machining process

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

19. Design Considerations in Machining
1. Design parts that require little, and if possible, no machining
Use net shape or near net shape processes
2. Specify tolerances
Use tighter tolerances only where required
3. Specify surface finish
Use better surface finishes where required
4. 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

20. Design Considerations in Machining
Design with materials that have good machinability
Design part features that use 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 if possible
Changing position of part and changing cutting tool

21. Design Considerations in Machining
Design the sizes of machined parts, which are close to the 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

22. 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

23. Drilling machining
Milling machining