MECH152-L24-1 (1.0) - 1
Tertiary Manufacturing Processes
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Tertiary Manufacturing Processes
• Grinding and Abrasive Processes
– Grinding
– Honing, Lapping, Super-finishing, Polishing
and Buffing
• Non-traditional Machining and Thermal
Cutting Processes
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Mechanical Energy Processes
Electrochemical Machining Processes
Thermal Energy Processes
Chemical Machining
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Grinding
Grinding – material removal by an abrasive
bonded grinding wheel rotating a high
speed.
Grinding Wheel – basic parameters:
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Abrasive material
Grain size
Bonding material
Wheel grade
Wheel structure
http://www.youtube.com/watch?v=RnTNqSccW-M&feature=PlayList&p=3AFB507B668AF162&index=41
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Grinding Wheel
• Abrasive materials
– Aluminum oxide: grinding ferrous and highstrength alloys (Knoop hardness ~ 2100)
– Silicon carbide: grinding aluminum, brass, and
stainless steel, cast irons and certain ceramics
(Knoop hardness ~ 2500)
– Cubic boron nitride: grinding hardened steels
and aerospace alloys (Knoop hardness ~ 5000)
– Diamond: grinding ceramics, cemented
carbides, and glass (Knoop hardness ~ 7000)
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Grinding Wheel
Grain size – size of the abrasive particles
Typical grain size: 8-250 (mesh size: lines/in)
Grit size 8: coarse grain – for harder material
Grit size 250: fine grain – for soft material, and for
lapping and superfinishing
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Grinding Wheel
Bonding materials – requires strength,
toughness, hardness, and temperature
resistance.
Vitrified bond: baked clay and ceramics, most
common
Silicate: low heat generation, tool grinding
Rubber: flexible, cutoff operation
Resin: thermosets, rough grinding and cuttoff
Shellac: Varnish, strong but not rigid, good finish
Metallic: Usually bronze, diamond of cubic boron
nitride wheels
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Grinding Wheel
Wheel structure and Wheel grade
Wheel structure – relative spacing of the abrasive
grains in the wheel
Vg+ Vb+ Vp = 1.0
Vg - proportion of abrasive grain in the wheel
Vb - proportion of bond material in the wheel
Vp - proportion of pores in the wheel
Wheel grade – bond strength between abrasive
grits, largely depending on Vb. Grade is
measured on a scale between soft (A) and hard
(Z).
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Grinding Wheel Specification
Wheel specification: 30A46H6VXX
30 – Prefix (manufacturer’s symbol for abrasive, optional)
A – Abrasive type (A – aluminum oxide, C – silicon carbide,
etc.)
46 – Grain size (coarse = 8,10,12,14,16,20,24; medium =
30,36,46,54,60; fine = 70,80,…,180; very fine =
220,240,….,600)
H – Grade (A = soft, M = medium, Z = hard)
6 – Structure (1 = very dense, 15 = very open)
V – bond type (B-resinoid, E-shellac, R-rubber, S-silicate, Vvitrified)
XX – Manufacturer’s record (optional)
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Grinding Wheel Specification
Wheel specification: XXD150PYYMZZ1/8
XX – Prefix (manufacturer’s symbol for abrasive, optional)
D – Abrasive type (D – diamond, B – cubic boron nitride)
150 – Grain size (coarse = 8,10,12,14,16,20,24; medium =
30,36,46,54,60; fine = 70,80,…,180; very fine =
220,240,….,600)
P – Grade (A = soft, M = medium, Z = hard)
YY – Concentration (manufacturer’s designation)
M – Bond type (B-resin, M-metal, V-vitrified)
ZZ – Bond modification (manufacturer’s notation)
1/8 – Depth of abrasive (in inches or mm)
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Grinding Wheel Configurations
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Grinding Analysis
Material removal rate, MRR
= vwwd
vw = work speed
w = cutting width
d = depth of cut
Specific energy = Fcv / vwwd
Fc = cutting force
v = wheel speed
Improving surface finish:
Increasing wheel speed
and/or wheel surface grit
density
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Grinding Process
• Specific energy is much greater than
conventional machining
• Most of the energy in grinding results in
high work surface temperature
• Workpiece temperature can be lowered by
grinding fluid.
http://www.efunda.com/processes/machining/grind.cfm
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Surface Grinding
http://www.witherstool.com/surfacegrinding.html
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Cylindrical Grinding
http://www.youtube.com/watch?v=bhjuM85fx8c
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Centerless Grinding
http://www.youtube.com/watch?v=k557Zoeu38s&NR=1
http://www.youtube.com/watch?v=K_E7lZMkuw4&feature=related
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Related Abrasive Processes
• Honing – round hole
• Lapping – flat or slightly spherical surface
• Superfinishing – flat surface, external
cylinder
• Polishing – Miscellaneous shapes
• Buffing - Miscellaneous shapes
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Surface Roughness Values
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Honing
Honing speed typically 0.3 – 3 m/s
Grit size typically 30 – 600
http://www.youtube.com/watch?v=3O0XnA_fwyU
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Lapping
For production of surface of extreme accuracy and
smoothness
Fluid suspended abrasive particles between workpiece
and lapping tool having the shape of the workpiece
http://www.youtube.com/watch?v=GZY3UU8a2U8
Grit size 300 - 600
http://www.youtube.com/watch?v=Ao9s4VCFaOc
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Superfinishing
Similar to honing
Shorter stroke ~ 4.5 mm up to 1500 strokes / minute
Lower pressure between tool and workpiece
http://www.youtube.com/watch?v=RiNmLHBR7dk
Lower work speed ~ 0.25 m/s
Smaller grit size ~ up to 1000
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Polishing
• Polishing
– Removing scratches and burrs by means of
abrasive grains attached to a polishing wheel
rotating at high speed of around 38 m/s.
– Abrasive grains are glued to the outside
periphery of flexible wheel.
– Grit size ranges from 20 to 120.
http://www.youtube.com/watch?v=wcYFOH09_w4
http://www.youtube.com/watch?v=Xkm4KRJQV2s&feature=related
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Buffing
Buffing
– Similar to polishing but used to form high
luster surface
– Wheels are softer
– Very fine grit size mixed in buffing compound
– Speed – 40 to 85 m/s
– Perform manually
http://www.youtube.com/watch?v=lIsc1nDzLak
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Non-traditional Machining and
Thermal Cutting Processes
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•
•
•
Mechanical Energy Processes
Electrochemical Machining Processes
Thermal Energy Processes
Chemical Machining
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Mechanical Energy Processes
• Ultrasonic Machining
• Water Jet Cutting
• Abrasive Jet Machining
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Ultrasonic Machining
Ultrasonic machining
Abrasive slurry driven over the workpiece by an
ultrasonic vibration tool at about 20kHz
Amplitude vibration of 0.076mm
Tool materials – soft steel and stainless steel
Abrasive materials – boron nitride, boron carbide,
aluminum oxide, silicon carbide, diamond
Grit size – 100 to 2000
Gap size – about 2 times grit size
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Ultrasonic Machining
The grit size determines the surface finish
The concentration of abrasive in the water-based slurry
is between 20% to 60%.
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Water Jet Cutting
Uses a fine, high-pressure water jet
to cut the workpiece
Diameter of nozzle – 0.1~0.4 mm
Water jet pressure – 400 MPa
Nozzle material – sapphire, ruby or
diamond
Filtration system to separate swarf
Process parameters – standoff distance
(3.2 mm), nozzle diameter, jet
pressure, and feed rate (5 mm/s – 500
mm/s)
Not suitable for brittle materials
http://www.youtube.com/watch?v=tJYSn9yDSzg
http://www.youtube.com/watch?v=XNGrVxQFrdI
http://www.youtube.com/watch?v=_iqJouVi4NU
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Abrasive Jet Machining
Abrasive water jet cutting
Abrasive particles, aluminum oxide, silicon oxide,
added to the jet stream to facilitate cutting
Grit size: 60 -120
Nozzle diameter: 0.25 – 0.63 mm
Abrasive jet machining
High velocity gas jet with abrasive materials
Dry gas (air, nitrogen, carbon dioxide, and helium)
at 0.2 to 1.4 MPa
Nozzle diameter – 0.075 to 1 mm
Jet velocity – 2.5 to 5 m/s
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Electrochemical Machining Processes
• Electrochemical machining
• Electrochemical deburring and grinding
MECH152-L24-1 (1.0) - 30
Electrochemical Machining (ECM)
Removes metal from an electrically
conductive workpiece by anodic dissolution
Workpiece (anode) is formed by electrode tool
(cathode) at close proximity, setting up an
electrolytic action or a deplating operation
The electrolyte flows rapidly to remove the
deplated material
Tool material – copper, brass or stainless steel
Feed rate of tool = metal removal rate
http://www.youtube.com/watch?v=oxJf5B2LnFY
http://www.youtube.com/watch?v=Z_U_ZZty5Ns&feature=related
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Electrochemical Machining (ECM)
Material specific cons tan t  Voltage
MRR 
Electrode gap  Electrolyte resistivity
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Electrochemical Machining (ECM)
Typical electrode gap distance = 0.075 to 0.75 mm
Electrolyte – water plus salt (NaCl or NaSO3)
Removed work material is in the form of micro
particles which require separation and handling
Voltage in ECM is kept relatively low to avoid
arcing across the gap.
Applies to hard metal or complex work geometry
components for good finish
Low tool wear
Electrochemical
Deburring and Grinding
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Electrochemical deburring (ECD)
Adapting ECM for deburring and rounding sharp
corners on metal parts
http://www.youtube.com/watch?v=wDOXQkHvl4g&feature=PlayList&p=3AFB507B668AF162&index=32
Electrochemical
Deburring and Grinding
Electrochemical grinding
(ECG)
A rotating grinding wheel
with conductive bonding
material to augment anodic
dissolution of metal
workpiece surface
Deplating 95%
Grinding 5%
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Thermal Energy Processes
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Electric Discharge Machining
Electron Beam Machining
Laser Beam Machining
Arc Cutting Processes
Oxyfuel Cutting Processes
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Electric Discharge Machining
(EDM)
Metal removal is
effected by pulsating
electric arcing from a
formed electrode tool
acting as a cathode. The
workpiece anode is
separated from the tool
by a small gap filled
with dielectric fluid.
The dielectric fluid
ionized along the path
of discharge.
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Electric Discharge Machining
(EDM)
Material melted by the
discharge and removed by
the flowing dielectric.
Metal removal is increased
by higher frequency and
higher current.
Best surface finish obtained
by higher frequency and
low current.
Overcut in EDM is
produced when electrical
discharges occur at the
sides of the tool and at the
end.
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Electric Discharge Machining (EDM)
Tool wear occurs with high spark temperature.
The work material removal versus tool wear ratio is
between 1 to 100
Electrode material - graphite, copper, brass, copper
tungsten, etc.
Hardness and strength of the work material do not
affect the process, while the melting point is a
governing factor.
Dielectric fluids include hydrocarbon oils, kerosene,
and distilled or deionized water.
Used for tool fabrication and parts production.
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Electric Discharge Machining (EDM)
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Electric Discharge Wire Cutting
http://www.youtube.com/watch?v=Sr0kC3eRIC8&feature=PlayList&p=3AFB507B668AF162&index=36
Special form of EDM using a small-diameter
wire as the electrode to cut a narrow kerf in
the work.
Workpiece is fed continuously and slowly past the
wire to achieve the cutting path
Wire diameter – 0.076 to 0.3 mm
Wire material – brass, copper, tungsten, and
molybdenum.
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Electric Discharge Wire Cutting
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Electron Beam Machining
High velocity stream of
electrons focused on the
workpiece surface to
weld, cut or heat-treat it
Conducted in vacuum
Beam diameter down to
0.025 mm
Hole depth-to-diameter –
100:1
Thicknees: 0.25 to 6.3 mm
No tool wear
http://www.youtube.com/watch?v=fDYuSleApiQ
http://www.youtube.com/watch?v=qBOoyfuO5rM&feature=related
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Laser Beam Machining
Laser to remove material
by vaporization and
ablation
Types of lasers – carbon
dioxide gas lasers and
YAG lasers
Drilling, slitting, slotting,
scribing, and marking
Hole size down to 0.025
mm
Unlimited workpiece
material
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Arc Cutting Processes
Electric arcing between an electrode and the
workpiece to generate intense heat for
welding or cutting metal
Plasma arc cutting –
Plasma is a superheated, electrically ionized gas
(nitrogen, argon-hydrogen, or mixture)
Secondary gas to confine the arc and clean the kerf
Temperature – 10,000 to 14,000C
Nozzle is water cooled
CNC operation possible
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Arc Cutting Processes
Plasma arc cutting –
Maximum workpiece
thickness – 150 mm
Maximum feed rate – 0.182
m/s
Rough cutting surface and
metallurgical damage
http://www.youtube.com/watch?v=n2XmlFNc7L4&feature=related
http://www.youtube.com/watch?v=mJJydOxHwZU&feature=related
http://www.youtube.com/watch?v=cE_TKqD2oB4&feature=related
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Oxyfuel Cutting Processes
Flame cutting using energy from exothermic
reaction of the metal with oxygen
Fuels include acetylene, propylene, and
propane.
http://www.youtube.com/watch?v=1XDHC0_K7sI
http://www.youtube.com/watch?v=ksM5KNjQxkU
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Chemical Machining
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Chemical Milling
Chemical Blanking
Chemical Engraving
Photochemical Machining
Tolerance as close as 0.0025 mm
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Chemical Milling
Sequence of processing steps in chemical milling (1) clean raw part, (2) apply maskant, (3) scribe, cut, and peel the
maskant from areas to be etched, (4) etch, and (5) remove maskant and clean to yield finished part.
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Chemical Blanking
Sequence of processing steps in chemical blanking (1) clean raw part, (2) apply resist (maskant) by painting through
screen, (3) etch (shown partially etched), (4) etch (completed), and (5) remove resist and clean to yield finished part.
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Chemical blanking
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Chemical Engraving
• Process similar to the other chemical
processes except:
– Filling to apply paint or other coating into the
recessed area
– Panel immersed in a solution to dissolves the
resist but not the coating material
– Resist is removed highlighting the coating
pattern
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Photochemical Machining (PCM)
Sequence of processing steps in photochemical machining (1) clean raw part, (2) apply resist (maskant) by dipping,
spraying, or painting, (3) place negative to resist, (4) expose to ultraviolet light, (5) develop to remove resist from areas
to be etched, (6) etch (shown partially etched), (7) etch (completed), (8) remove resist and clean to yield finished part.
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Application Considerations
Very small holes below 0.125 mm diameter. (Laser beam
machining, LBM)
Holes with large depth-to-diameter ratio, d/D>20. (ECM or
EDM)
Holes that are not round (ECM or EDM)
Narrow slots in slabs or plates (ECM, LBM, EDM, water
jet, abrasive jet)
Micromachining (PCM, LBM, EBM)
Shallow pockets and surface details in flat parts (Chemical
machining)
Special contoured shapes for mold and die applications
(EDM or ECM)
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Application Considerations
Special shapes for which the non traditional processes are appropriate (a) very small diameter holes, (b) holes with
large depth-to-diameter ratios, (c) nonround holes, (d) narrow, non-straight slots, (e) pockets, and (f) die sinking
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Materials Consideration
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Machining Characteristics
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Design for Manufacturing
• Part Drawing
• Select stock
• Process Plan
– Check tolerances and datum
– Select process
• Set up
• Fixture
• Process conditions
– Measurement
• Packaging
• Maintenance