ME 330
Manufacturing Processes
CUTTING PROCESSES
Overview of processes
Cutting processes
Principle of the process
Structure and configuration
Process modeling
Defects
Design For Manufacturing (DFM)
Process variation
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Major cutting processes
 Mechanical processes
Bulk
1. Machining and grinding (will be covered in later classes)
2. Shearing, blanking, and punching (sheet metalworking
operations)
3. Ultrasonic machining (USM)
4. Water jet cutting (WJC or hydrojet)
5. Abrasive water jet cutting (AWJC or abrasive hydrojet)
For sheet and plate
Definition of sheets and plates
Sheets: thickness is 1/64” (0.04 mm) to 1/4” (6 mm).
Plates: thickness is greater than: 1/4” (6mm)
Principle of the process
Structure and configuration
Process modeling
Defects
Design For Manufacturing (DFM)
Process variation
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Principle of cutting for sheets and plates:
There is a shear stress induced on the surface of the cross section
area of plates or sheets. The shearing stress causes the fracture of
two parts.
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Principle of the process
Structure/Configuration of the operation
Process modeling
Defects
Design For Manufacturing (DFM)
Process variation
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Shearing, Blanking, and Punching
Three principal configurations in press working
that cut sheet metal:
 Shearing
 Blanking
 Punching
Different configurations of the
manufacturing system or machine to
generate shear stress, and they share
the same principle of cutting.
Shearing Operation
(a) Side view of the operation; (b) front view of the operation,
equipped with inclined upper cutting blade
Blanking and Punching
 Blanking (a) - sheet metal cutting to separate piece (called a
blank) from surrounding stock
 Punching (b) - similar to blanking except cut piece is scrap, called
a slug
Shearing, Blanking, and Punching
Generic configurations: punch, die, work piece
Shearing
Generic configurations: punch, die, work piece
Punch and Die in blanking and punching
Components of a punch
and die for a punch
operation
Punch
Die
Components of a punch
and die for a blanking
operation
Cost of tooling is concern
 The cost for tooling is even higher than the
press machine in itself.
 Punch and die may need frequently change
due to wear, which is a part of the reasons for
the high cost of tooling.
Non-traditional Cutting Processes
Cutting force is not generated by solid state force
such as solid punch and solid die.
Non-traditional Processes: why
 Newly developed metals and non-metals with special
properties that make them difficult or impossible to cut
or machine by the solid force approach.
 Complex part geometries that cannot readily be
accomplished by conventional cutting and machining.
 Avoid surface damage that often accompanies with the
conventional machining and cutting.
Principle of the process
Structure and configuration
Process modeling
Defects
Design For Manufacturing (DFM)
Process variation
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Major cutting processes
 Mechanical processes
1. Machining and grinding (will be covered in later classes)
2. Shearing, blanking, and punching (sheet metalworking
operations)
3. Ultrasonic machining (USM)
4. Water jet cutting (WJC or hydrojet)
5. Abrasive water jet cutting (AWJC or abrasive hydrojet)
Water Jet Cutting (WJC) or Hydro-jet Cutting
 Uses high pressure, high velocity stream of water directed at work surface
for cutting
The punch
is a water
stream
WJC & Applications
 Usually automated by CNC or industrial robots to manipulate
nozzle along desired trajectory.
 Water also acts as a cooling agent.
 Can cut complex shaped parts.
 Used to cut narrow slits in flat stock such as plastic, textiles,
composites, floor tile, carpet, leather, and cardboard.
 Not suitable for brittle materials (e.g., glass).
Intensity of water-jet is not enough, as opposed to the solid force,
to make a clear-cut. The material tends to spreading around.
Abrasive Water Jet Cutting (AWJC)
 Abrasive particles are added to jet stream for quicker
cutting, which increases the intensity of water jet so that
the high force can be created.
 Suitable to cut metals.
 Slower than laser cutting, but produces a cleaner finish.
 Note that the water jet cut is tapered.
Major cutting processes
 Thermal Energy Processes
1.
2.
3.
4.
5.
Ram electric discharge machining (Ram EDM)
Wire electric discharge machining (Wire EDM)
Electron beam machining (EBM)
Laser beam machining (LBM)
Plasma arc cutting (PAC) or plasma arc machining
(PAM)
6. Air carbon arc cutting
7. Oxyfuel Cutting (OFC) or flame cutting
Principle of the process
Structure and configuration
Process modeling
Defects
Design For Manufacturing (DFM)
Process variation
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Electric Discharge Machining (EDM)
EDM Operation
 One of the most widely used non-traditional processes
 Shape of a finished work surface produced by a shape of electrode
tool
 Can be used only on electrically conducting work materials
 Requires dielectric fluid, which creates a path for each discharge as
fluid becomes ionized in the gap.
 Metal is melted/vaporized by the series of electrical discharges
 Can be very precise and produces a very good surface finish
Work Materials in EDM
 Work materials must be electrically conducting
 Hardness and strength of work material are not
factors in EDM
 Material removal rate depends on melting point of
work material
Principle of the process
Structure and configuration
Process modeling
Defects
Design For Manufacturing (DFM)
Process variation
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Wire EDM
 Special form of EDM uses small diameter wire as electrode to cut a
narrow kerf in work
Operation of Wire EDM
 Work is fed slowly past wire along desired cutting path.
 CNC used for motion control.
 While cutting, wire is continuously advanced between supply
spool and take-up spool to maintain a constant diameter.
 Dielectric fluid is required.
 Applied using nozzles directed at tool-work interface or
submerging work part
Wire EDM Applications
 Ideal for stamping die components
 Since kerf is so narrow, it is often possible to fabricate
punch and die in a single cut
 Other tools and parts with intricate outline shapes,
such as lathe form tools, extrusion dies, and flat
templates
Dental part cut from
nitinol material by
wire EDM
Laser Beam Machining (LBM)
 Uses the light energy from a laser to remove material by
vaporization and ablation
The punch
is a light
beam
LBM Applications
 Drilling, slitting, slotting, scribing, and marking
operations
 Drilling small diameter holes - down to 0.025 mm (0.001
in)
 Generally used on thin stock
 Work materials: metals with high hardness and strength,
soft metals, ceramics, glass and glass epoxy, plastics,
rubber, cloth, and wood
Plasma Arc Cutting (PAC)
 Uses plasma stream operating at very high temperatures to
cut metal by melting
The punch
is a plasma
arc
Operation of PAC
 Plasma = a superheated, electrically ionized gas
 PAC temperatures: 10,000C to 14,000C (18,000F to
25,000F)
 Plasma arc generated between electrode in torch and
anode work piece
 The plasma flows through water-cooled nozzle that
constricts and directs stream to desired location
Applications of PAC
 Most applications of PAC involve cutting of flat metal sheets
and plates.
 Hole piercing and cutting along a defined path.
 Comparable to laser cutting, but cuts are usually is more
coarse.
 Can cut any electrically conductive metal.
 Most frequently cut metals: carbon steel, stainless steel,
aluminum.
Important: Water Jet, Laser, Plasma
 Need to start the cut away from the wanted cut to
prevent a rough surface irregularity where the cut
starts
Starting cut
Wanted cut
Summary of Cutting Processes for Sheets and
Plates in terms of Quality & Cost
Wire EDM
Machining
Quality
(In terms of
tolerances &
surface finish
Water Jet
Laser
Punching/
Blanking
Plasma
Cost
Comparison: sheet and plate cutting
1. Plasma
2. Laser
3. Waterjet
Comparison: sheet and plate cutting
Main criteria for comparison:
1. Materials
2. Cost
3. Quality
4. Productivity
Comparison: sheet and plate cutting
Processes
Material
Plasma
All electrically Gauge to 2 in
conductive
materials
Laser
A variety of
materials
Waterjet
A variety of
materials,
usually soft
material
Cost: decided by the speed.
Thickness
¼ in and
thinner
Quality
Cost
Note
Poor
Low
Need high
power
Middle
Middle
Problem
with
reflective
materials
Highest
High
Major cutting processes
 Electrochemical process:
1. Electrochemical Machining (ECM)
Principle of the process
Structure and configuration
Process modeling
Defects
Design For Manufacturing (DFM)
Process variation
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Electrochemical Machining (ECM)

Material removal by anodic dissolution, using electrode (tool) in close
proximity to work but separated by a rapidly flowing electrolyte
(-)
(+)
Electrochemical Machining (ECM)

Material removal by anodic dissolution, using electrode (tool) in close
proximity to work but separated by a rapidly flowing electrolyte
.
Electrochemical Machining (ECM) Processes
 Electrical energy used in combination with chemical
reactions to remove material
 Reverse of electroplating
 Work material must be a conductor
 Processes:
1. Electrochemical machining (ECM)
2. Electrochemical deburring (ECD)
3. Electrochemical grinding (ECG)
ECM Operation
 Material is depleted from anode workpiece (positive pole)
and transported to a cathode tool (negative pole) in an
electrolyte bath
 Electrolyte flows rapidly between two poles to carry off
depleted material, so it does not plate onto tool
 Electrode materials: Cu, brass, or stainless steel
 Tool has inverse shape of part
– Tool size and shape must allow for the gap
General benefits to manufacture parts by cutting from
sheets and plates:






Fast to manufacture
Parts are low in cost
Helps drive costs for assembled products down
From low to high quantities
Simple to complex parts
Parts can later be formed (bent) to make more
complex shapes
Summary
 Sheet and plate cutting. Sheet and plate can be further
processed by bending, forming, and drawing.
 Principle of cutting.
1.
2.
3.
Shear stress principle (solid force, water-jet)
Electric or light or plasma energy to thermal energy
Electric-chemical effect
 Structure and configuration of each principle.
 Mechanical process (blanking/shearing/punching, waterjet),
Thermal process (EDM, Laser, Plasma), Chemical (ECM).
 Constraints, pros and cons of each cutting process.