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
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
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
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
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
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
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
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