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1. 1
Principles of Machining
Advanced Machining
Processes

2. 2
Types of Advanced Machining
Processes
 Chemical Machining
 Electrochemical Machining
 Electrical Discharge Machining
 Wire EDM
 Laser Beam Machining
 Electron Beam Machining
 Plasma Arc Cutting
 Ultrasonic Machining
 Water Jet Machining
 Abrasive Jet Machining

3. 3
The Need for Advanced
Machining Processes
 Traditional machining processes
• Material removal by mechanical means, such as chip
forming, abrasion, or micro-chipping
 Advanced machining processes
• Utilize chemical, electrical, and high-energy beams
 The following cannot be done by traditional processes:
• Workpiece strength and hardness very high, >400HB
• Workpiece material too brittle, glass, ceramics, heat-
treated alloys
• Workpiece too slender and flexible, hard to clamp
• Part shape complex, long and small hole
• Special surface and dimensional tolerance requirements

4. 4
Typical Parts
 Skin panel for missiles and aircraft
 Turbine blades, nozzles, sheet metal,
small-diameter deep holes, dies, thick
metallic and nonmetallic parts

5. 5
Chemical Machining
(Chem Milling)
 Chemicals are used to dissolve
material
 Masks are used to control attack
 Most common use is circuit boards
and plates for printing (Sunday
comics and rotogravure)
 Cutting speed of 0.0025-0.1
mm/minute – very slow

6. 6
Chemical Machining

7. 7
Electrochemical Machining
(ECM)
 Combines chemical attack and electrical attack
 High material removal rate
 Masking is used to control attack
 Conforming electrodes are to control shape
 Commonly used for aircraft parts such as airfoil
shapes
 Normally followed by abrasive finishing or laser
peening to remove partially adhering particles
 Works with a wide variety of metals

8. 8
Electrochemical Machining

9. 9
Electrical Discharge
Machining (EDM)

10. 10
Electrical Discharge
Machining
 Successive electric arcs melt tiny droplets
from surface of workpiece
 Frozen droplets must be flushed away
 Electrodes are made from graphite,
copper or copper-tungsten alloy
 Material removed from electrode by arc
 Recast layer of approximately 0.001” in
depth left on surface
 Secondary process such as chemical
machining used to remove recast layer

11. 11
Wire EDM

12. 12
Wire EDM
 Uses fine brass wire
 Wire is used once
 Easily computer controlled
 Cutting path must contain straight lines
 Slow cutting speed
 Wire breakage is a problem
 Shallower recast layer than conventional EDM

13. 13
Laser Beam Machining

14. 14
Laser Beam Machining
 Direct laser beam against surface of
workpiece, as in laser welding
 Successive pulses from laser gun vaporize
tiny bits of workpiece
 Location of laser beam controlled by
computer
 Workpiece need not be conductive
 Cuts are tapered
 Gotta trap overshoot from laser beam

15. 15
Laser Beam Machining (cont)
 Produces large remelt zone
 Can produce holes as small as 0.0002”
diameter
 Can produce deep holes
 Used to produce cooling holes in
blades/vanes for jet engines

16. 16
Electron Beam Machining
 Workpiece placed in vacuum chamber
 High-voltage electron beam directed
toward workpiece
 Energy of electron beam melts/
vaporizes selected region of workpiece
 Electron beam moved by deflection coils
 Similar process to EB welding

17. 17
Electron Beam Machining

18. 18
Plasma Arc Cutting
 Plasma is a stream of ionized gas
 Typical temperatures are very high
 Same process as plasma welding, without filler
metal
 Torch movement controlled by computer
 Power requirements depend on material being
cut, plus depth of cut
 Recast layer is deeper than with other processes

19. 19
Ultrasonic Machining
 Abrasive slurry flows over top of
workpiece (loose particles)
 Cutting tool vibrated by ultrasonic energy
 Abrasive particles between tool and
workpiece do the machining
 Works well with hard, brittle workpieces

20. 20
Water Jet Machining
 Narrow jet of water directed, at high
pressure and velocity, against surface of
workpiece
 Jet of water erodes surface of workpiece,
thereby cutting workpiece
 Computer control to achieve shape

21. 21
Water Jet Machining

22. 22
Abrasive Jet Machining (Dry)
 Similar to sand blasting, except that a
very narrow jet of air/abrasive particles
achieves localized cutting
 Computer used to position jet

23. 23
Abrasive Jet Machining

24. 24
Nanofabrication Methods
 Typically used in the semiconductor
industry
 Combines the lithography technique of
chemical machining with an atomic force
microscope
 May incorporate plasma cutting, reduced
to nano scale

25. 25
Economics of Advanced Machining
Processes
 High cost of equipment, which typically
includes computer control
 May use hard tooling, soft tooling, or both
 Low production rates
 Can be used with difficult-to-machine
materials
 Highly repeatable
 Typically requires highly skilled operators

26. 26
Cincinnati Area Advanced
Machining Companies
 Graphel – Wire EDM and Electrodes
 Sermatech-Lehr Precision – Electrochemical
Machining
 Andrews Laser Works – Laser Cutting, Welding and
Drilling
 Meyer Tool – Laser Drilling and EDM
 Barnes Aerospace – EDM Grinding of Honeycomb
 Cincinnati, Inc – Laser and Plasma Arc Machines
 Enginetics – EB Welding
 Elano – Electrochemical Machining