Advanced machining processes

Advanced MachiningAdvanced Machining
ProcessesProcesses
ManufacturingManufacturing
ProcessesProcesses
GOPINATH.GGOPINATH.G
MECHANICALMECHANICAL

OutlineOutline
Chemical MillingChemical Milling
Photochemical BlankingPhotochemical Blanking
Electrochemical MachiningElectrochemical Machining
Pulsed Electrochemical MachiningPulsed Electrochemical Machining
Electrochemical GrindingElectrochemical Grinding
Electrical-Discharge MachiningElectrical-Discharge Machining
Electrical-Discharge GrindingElectrical-Discharge Grinding
Electrical-Discharge Wire CuttingElectrical-Discharge Wire Cutting
Laser-Beam MachiningLaser-Beam Machining
Electron Beam MachiningElectron Beam Machining
Plasma Arc CuttingPlasma Arc Cutting
Water Jet MachiningWater Jet Machining
Abrasive Water Jet MachiningAbrasive Water Jet Machining
Abrasive Jet MachiningAbrasive Jet Machining

Examples of PartsExamples of Parts

Produces shallow cavities on aProduces shallow cavities on a
workpiece, usually to reduceworkpiece, usually to reduce
weightweight
The area affected by theThe area affected by the
chemical reagent is controlledchemical reagent is controlled
by masking or by partialby masking or by partial
immersionimmersion

Procedure:Procedure:
1.1. Relieve residual stresses toRelieve residual stresses to
prevent warpingprevent warping
2.2. Clean the material surfaceClean the material surface
3.3. Apply masking materialApply masking material
4.4. Remove the masking on regionsRemove the masking on regions
that require etchingthat require etching
5.5. Apply the reagentsApply the reagents
6.6. Wash the partWash the part
7.7. Remove remaining maskingRemove remaining masking
8.8. Additional finishing or chemicalAdditional finishing or chemical
milling procedures may be usedmilling procedures may be used

Uses chemicals andUses chemicals and
photographic processes tophotographic processes to
remove material, usually fromremove material, usually from
a thin sheeta thin sheet
Can produce complex shapes onCan produce complex shapes on
metals as thin as .0025 mmmetals as thin as .0025 mm
without forming burrswithout forming burrs

Procedure:Procedure:
1.1. Prepare the design at aPrepare the design at a
magnification of up to 100x; makemagnification of up to 100x; make
a photographic negative anda photographic negative and
reduce it to the size of the partreduce it to the size of the part
2.2. Coat the blank withCoat the blank with
photosensitive materialphotosensitive material
3.3. Place the negative over the partPlace the negative over the part
and expose it to ultraviolet light toand expose it to ultraviolet light to
harden the exposedharden the exposed
photosensitive coatingphotosensitive coating
4.4. Dissolve the unexposed coatingDissolve the unexposed coating
5.5. Apply the chemical reagentApply the chemical reagent
6.6. Remove the masking and washRemove the masking and wash
the partthe part

Chemical MachiningChemical Machining
Design Considerations:Design Considerations:
- Avoid sharp corners, deep narrowAvoid sharp corners, deep narrow
cavities, steep tapers, foldedcavities, steep tapers, folded
seams and porous workpiecesseams and porous workpieces
- Undercuts may developUndercuts may develop
- Most of the workpiece should beMost of the workpiece should be
shaped by other processes toshaped by other processes to
speed productionspeed production
- Variations may occur dependingVariations may occur depending
onhumidity and temperatureonhumidity and temperature
- Computerized designs must beComputerized designs must be
converted to a format compatibleconverted to a format compatible
with the photochemical artworkwith the photochemical artwork
equipmentequipment

ElectrochemicalElectrochemical
MachiningMachining
Uses an electrolyte and electricalUses an electrolyte and electrical
current to ionize and removecurrent to ionize and remove
metal atomsmetal atoms
Can machine complex cavities inCan machine complex cavities in
high-strength materialshigh-strength materials
Leaves a burr-free surfaceLeaves a burr-free surface
Not affected by the strength,Not affected by the strength,
hardness or toughness of thehardness or toughness of the
materialmaterial

MachiningMachining

MachiningMachining
- The electrolyte erodes awayThe electrolyte erodes away
sharp profilessharp profiles
- It is difficult to controlIt is difficult to control
electrolyte flow; irregularelectrolyte flow; irregular
cavities may not be formedcavities may not be formed
accuratelyaccurately
- Allow for small taper in holesAllow for small taper in holes
made this waymade this way

Pulsed ElectrochemicalPulsed Electrochemical
MachiningMachining
A form of electrochemicalA form of electrochemical
machining; the current ismachining; the current is
pulsed to eliminate the needpulsed to eliminate the need
for high electrolyte flowfor high electrolyte flow
Improves fatigue life of the partImproves fatigue life of the part

GrindingGrinding
Uses a rotating cathodeUses a rotating cathode
embedded with abrasiveembedded with abrasive
particles for applicationsparticles for applications
comparable to milling, grindingcomparable to milling, grinding
and sawingand sawing
Most of the metal removal isMost of the metal removal is
done by the electrolyte,done by the electrolyte,
resulting in very low tool wearresulting in very low tool wear
Adaptable for honingAdaptable for honing

GrindingGrinding

GrindingGrinding
(in addition to those for(in addition to those for
electrochemical machining)electrochemical machining)
- Avoid sharp inside radiiAvoid sharp inside radii
- Flat surfaces to be groundFlat surfaces to be ground
should be narrower than theshould be narrower than the
width of the grinding wheelwidth of the grinding wheel

Electrical-DischargeElectrical-Discharge
MachiningMachining
Uses a shaped electrode andUses a shaped electrode and
electric sparks to removeelectric sparks to remove
metal; discharges sparks atmetal; discharges sparks at
about 50-500 kHzabout 50-500 kHz
A dielectric (nonconductive) fluidA dielectric (nonconductive) fluid
removes debris and acts as anremoves debris and acts as an
insulator until the potentialinsulator until the potential
difference is high enoughdifference is high enough
Can be used on any materialCan be used on any material
that conducts electricitythat conducts electricity

MachiningMachining

MachiningMachining
- Design parts so that theDesign parts so that the
electrodes can be madeelectrodes can be made
economicallyeconomically
- Avoid deep slots and narrowAvoid deep slots and narrow
openingsopenings
- Do not require very fineDo not require very fine
surface finishsurface finish
- Most of the material removalMost of the material removal
should be done by othershould be done by other
processes to speed productionprocesses to speed production

GrindingGrinding
The grinding wheel lacksThe grinding wheel lacks
abrasives and removesabrasives and removes
material by electricalmaterial by electrical
dischargesdischarges
Can be combined withCan be combined with
electrochemical grindingelectrochemical grinding
Can be used for sawing, in whichCan be used for sawing, in which
the saw has no teeththe saw has no teeth

Wire CuttingWire Cutting
The wire moves through theThe wire moves through the
workpiece like a band saw,workpiece like a band saw,
removing material by electricalremoving material by electrical
dischargedischarge
Dielectric fluid is applied to theDielectric fluid is applied to the
work areawork area
The wire is generally used onlyThe wire is generally used only
once; it is inexpensiveonce; it is inexpensive

Example of a wire EDM machine
Courtesy of Edison Industrial Service Center

Example of a wire used for an EDM machine
This wire has been used; the wave pattern was
formed during take-up

Example of cores removed from a part using wire
EDM to create the cavity in a high-pressure nozzle
Holes were drilled in the interiors so that the wire
could be strung through

Uses a concentrated beam ofUses a concentrated beam of
light to vaporize part of thelight to vaporize part of the
workpieceworkpiece
Usually produces a roughUsually produces a rough
surface with a heat-affectedsurface with a heat-affected
zonezone
Can cut holes as small as .005Can cut holes as small as .005
mm with depth/diameter ratiosmm with depth/diameter ratios
of 50:1of 50:1

Example of a part cut by laser-beam machining
Splatter marks appear where the laser first cuts into
the material

- Non-reflective workpieceNon-reflective workpiece
surfaces are preferablesurfaces are preferable
- Sharp corners are difficult toSharp corners are difficult to
produce; deep cuts produceproduce; deep cuts produce
taperstapers
- Consider the effects of highConsider the effects of high
temperature on the workpiecetemperature on the workpiece
materialmaterial

Electron BeamElectron Beam
MachiningMachining
Vaporizes material usingVaporizes material using
electrons accelerated to 50-electrons accelerated to 50-
80% the speed of light80% the speed of light
Produces finer surface finish andProduces finer surface finish and
narrower cut width than othernarrower cut width than other
thermal cutting processesthermal cutting processes
Requires a vacuum; generatesRequires a vacuum; generates
hazardous X rayshazardous X rays

MachiningMachining

MachiningMachining
An electron beam in a very low-pressure
atmosphere of helium

Uses plasma (ionized gas) toUses plasma (ionized gas) to
rapidly vaporize materialrapidly vaporize material
Material removal rates are muchMaterial removal rates are much
higher than those for laserhigher than those for laser
beam machining and electronbeam machining and electron
beam machining; producesbeam machining; produces
good surface finish and thin cutgood surface finish and thin cut
widthwidth

Close-up view of a plasma arc

Electron Beam MachiningElectron Beam Machining
and Plasma Arc Cuttingand Plasma Arc Cutting
(in addition to those for laser-(in addition to those for laser-
beam machining)beam machining)
- Parts should match the size ofParts should match the size of
the vacuum chamberthe vacuum chamber
- Consider manufacturing theConsider manufacturing the
part as a number of smallerpart as a number of smaller
componentscomponents

A pressurized jet of water cuts aA pressurized jet of water cuts a
groove in the materialgroove in the material
Effective for many nonmetallicEffective for many nonmetallic
materialsmaterials
Cuts can be started at anyCuts can be started at any
location; does not producelocation; does not produce
heat; produces very littleheat; produces very little
burringburring

Abrasive Water JetAbrasive Water Jet
MachiningMachining
The water jet contains abrasiveThe water jet contains abrasive
particles; this increases theparticles; this increases the
material removal ratematerial removal rate
Can cut metallic, nonmetallic,Can cut metallic, nonmetallic,
and advanced compositeand advanced composite
materialsmaterials
Suitable for heat-sensitiveSuitable for heat-sensitive
materialsmaterials

A high-speed jet of dry air,A high-speed jet of dry air,
nitrogen or carbon dioxidenitrogen or carbon dioxide
carries abrasive particlescarries abrasive particles
Good for cutting hard or brittleGood for cutting hard or brittle
materialsmaterials
Can be used for deburring,Can be used for deburring,
cleaning, or removing oxidescleaning, or removing oxides
or surface filmsor surface films

SummarySummary
Advanced machining processesAdvanced machining processes
offer alternatives whereoffer alternatives where
conventional procedures wouldconventional procedures would
be insufficient or uneconomicalbe insufficient or uneconomical

Advanced machining processes

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Advanced machining processes