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Advanced Machining
Processes
Manufacturing
Processes
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Outline
Chemical Milling
Photochemical Blanking
Electrochemical Machining
Pulsed Electrochemical Machining
Electrochemical Grinding
Electrical-Discharge Machining
Electrical-Discharge Grinding
Electrical-Discharge Wire Cutting
Laser-Beam Machining
Electron Beam Machining
Plasma Arc Cutting
Water Jet Machining
Abrasive Water Jet Machining
Abrasive Jet Machining
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Examples of Parts
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Chemical Milling
Produces shallow cavities on a
workpiece, usually to reduce
weight
The area affected by the
chemical reagent is controlledby masking or by partial
immersion
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Chemical Milling
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Chemical Milling
Procedure:
1. Relieve residual stresses to
prevent warping2. Clean the material surface
3. Apply masking material
4. Remove the masking on regions
that require etching
5. Apply the reagents
6. Wash the part
7. Remove remaining masking8. Additional finishing or chemical
milling procedures may be used
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Photochemical Blanking
Uses chemicals and
photographic processes to
remove material, usually froma thin sheet
Can produce complex shapes onmetals as thin as .0025 mm
without forming burrs
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Photochemical Blanking
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Examples of Parts
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Photochemical Blanking
Procedure:
1. Prepare the design at amagnification of up to 100x; make
a photographic negative andreduce it to the size of the part
2. Coat the blank withphotosensitive material
3. Place the negative over the partand expose it to ultraviolet light toharden the exposedphotosensitive coating
4. Dissolve the unexposed coating
5. Apply the chemical reagent6. Remove the masking and wash
the part
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Chemical Machining
Design Considerations:
- Avoid sharp corners, deep narrowcavities, steep tapers, foldedseams and porous workpieces
- Undercuts may develop
- Most of the workpiece should beshaped by other processes tospeed production
- Variations may occur dependingonhumidity and temperature
- Computerized designs must beconverted to a format compatiblewith the photochemical artworkequipment
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Electrochemical
MachiningUses an electrolyte and electrical
current to ionize and remove
metal atoms
Can machine complex cavities inhigh-strength materials
Leaves a burr-free surface
Not affected by the strength,hardness or toughness of thematerial
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Electrochemical
Machining
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Electrochemical
Machining
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Electrochemical
MachiningDesign Considerations:
- The electrolyte erodes away
sharp profiles
- It is difficult to control
electrolyte flow; irregular
cavities may not be formedaccurately
- Allow for small taper in holes
made this way
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Pulsed Electrochemical
MachiningA form of electrochemical
machining; the current is
pulsed to eliminate the needfor high electrolyte flow
Improves fatigue life of the part
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Electrochemical
GrindingUses a rotating cathode
embedded with abrasive
particles for applicationscomparable to milling, grinding
and sawing
Most of the metal removal is
done by the electrolyte,
resulting in very low tool wear
Adaptable for honing
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Electrochemical
Grinding
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Electrochemical
GrindingDesign Considerations:
(in addition to those for
electrochemical machining)
- Avoid sharp inside radii
- Flat surfaces to be ground
should be narrower than thewidth of the grinding wheel
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Electrical-Discharge
MachiningUses a shaped electrode and
electric sparks to remove
metal; discharges sparks atabout 50-500 kHz
A dielectric (nonconductive) fluid
removes debris and acts as aninsulator until the potentialdifference is high enough
Can be used on any material thatconducts electricity
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Electrical-Discharge
Machining
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Electrical-Discharge
Machining
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Electrical-Discharge
MachiningDesign Considerations:
- Design parts so that the
electrodes can be madeeconomically
- Avoid deep slots and narrow
openings- Do not require very fine
surface finish
- Most of the material removalshould be done by other
processes to speed production
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Electrical-Discharge
GrindingThe grinding wheel lacks
abrasives and removes
material by electricaldischarges
Can be combined withelectrochemical grinding
Can be used for sawing, in whichthe saw has no teeth
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Electrical-Discharge
Wire CuttingThe wire moves through the
workpiece like a band saw,
removing material by electricaldischarge
Dielectric fluid is applied to thework area
The wire is generally used onlyonce; it is inexpensive
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Electrical-Discharge
Wire Cutting
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Electrical-Discharge
Wire Cutting
Example of a wire EDM machine
Courtesy of Edison Industrial Service Center
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Electrical-Discharge
Wire Cutting
Example of a wire EDM machine
Courtesy of Edison Industrial Service Center
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Electrical-Discharge
Wire Cutting
Example of a wire used for an EDM machine
This wire has been used; the wave pattern was
formed during take-up
Courtesy of Edison Industrial Service Center
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Electrical-Discharge
Wire Cutting
Example of cores removed from a part using wire
EDM to create the cavity in a high-pressure nozzleHoles were drilled in the interiors so that the wire
could be strung through
Courtesy of Edison Industrial Service Center
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Laser-Beam Machining
Uses a concentrated beam of
light to vaporize part of the
workpiece
Usually produces a rough
surface with a heat-affectedzone
Can cut holes as small as .005mm with depth/diameter ratios
of 50:1
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Laser-Beam Machining
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Laser-Beam Machining
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Laser-Beam Machining
Example of a part cut by laser-beam machining
Splatter marks appear where the laser first cuts into
the material
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Laser-Beam Machining
Design Considerations:
- Non-reflective workpiece
surfaces are preferable
- Sharp corners are difficult to
produce; deep cuts produce
tapers- Consider the effects of high
temperature on the workpiece
material
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Electron Beam
MachiningVaporizes material using
electrons accelerated to 50-
80% the speed of light
Produces finer surface finish and
narrower cut width than otherthermal cutting processes
Requires a vacuum; generateshazardous X rays
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Electron Beam
Machining
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Electron Beam
Machining
An electron beam in a very low-pressure
atmosphere of helium
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Plasma Arc Cutting
Uses plasma (ionized gas) to
rapidly vaporize material
Material removal rates are much
higher than those for laser
beam machining and electronbeam machining; produces
good surface finish and thin cut
width
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Plasma Arc Cutting
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Plasma Arc Cutting
Close-up view of a plasma arc
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Plasma Arc Cutting
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Electron Beam Machining
and Plasma Arc CuttingDesign Considerations:
(in addition to those for laser-
beam machining)
- Parts should match the size of
the vacuum chamber
- Consider manufacturing thepart as a number of smaller
components
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Water Jet Machining
A pressurized jet of water cuts a
groove in the material
Effective for many nonmetallic
materials
Cuts can be started at any
location; does not produce
heat; produces very littleburring
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Water Jet Machining
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Water Jet Machining
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Abrasive Water Jet
MachiningThe water jet contains abrasive
particles; this increases the
material removal rate
Can cut metallic, nonmetallic,
and advanced compositematerials
Suitable for heat-sensitivematerials
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Abrasive Jet Machining
A high-speed jet of dry air,
nitrogen or carbon dioxide
carries abrasive particles
Good for cutting hard or brittle
materials
Can be used for deburring,
cleaning, or removing oxides orsurface films
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Abrasive Jet Machining
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Summary
Advanced machining processes
offer alternatives where
conventional procedures wouldbe insufficient or uneconomical
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The End