ME 330Manufacturing Processes

CUTTING PROCESSES

Overview of processes

Cutting processes

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Principle of the process

Structure and configuration

Process modeling

Defects

Design For Manufacturing (DFM)

Process variation

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)

For sheet and plate

Bulk

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)

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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

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 PunchingGeneric configurations: punch, die, work piece

ShearingGeneric configurations: punch, die, work piece

Components of a punch and die for a blanking operation

Punch and Die in blanking and punching

Components of a punch and die for a punch operation

Die

Punch

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.

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Principle of the process

Structure and configuration

Process modeling

Defects

Design For Manufacturing (DFM)

Process variation

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)

Uses high pressure, high velocity stream of water directed at work surface

for cutting

Water Jet Cutting (WJC) or Hydro-jet 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. Ram electric discharge machining (Ram EDM)2. Wire electric discharge machining (Wire EDM)3. Electron beam machining (EBM)4. Laser beam machining (LBM)5. Plasma arc cutting (PAC) or plasma arc machining

(PAM)6. Air carbon arc cutting7. Oxyfuel Cutting (OFC) or flame cutting

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Principle of the process

Structure and configuration

Process modeling

Defects

Design For Manufacturing (DFM)

Process variation

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

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Principle of the process

Structure and configuration

Process modeling

Defects

Design For Manufacturing (DFM)

Process variation

Special form of EDM uses small diameter wire as electrode to cut a narrow kerf in work

Wire EDM

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

Uses the light energy from a laser to remove material by vaporization and ablation

Laser Beam Machining (LBM)

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

Uses plasma stream operating at very high temperatures to cut metal by melting

Plasma Arc Cutting (PAC)

The punch is a plasma arc

Operation of PAC

Plasma = a superheated, electrically ionized gas

PAC temperatures: 10,000C to 14,000C (18,000F to

25,000F)

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

Quality

(In terms of tolerances & surface finish

Cost

Punching/ Blanking

Plasma

Water Jet

Wire EDM

Machining

Laser

Comparison: sheet and plate cutting

1. Plasma2. Laser3. 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 Thickness Quality Cost Note

Plasma All electrically conductive materials

Gauge to 2 in Poor Low Need high power

Laser A variety of materials

¼ in and thinner

Middle Middle Problem with reflective materials

Waterjet A variety of materials, usually soft material

Highest High

Cost: decided by the speed.

Major cutting processes

Electrochemical process:

1. Electrochemical Machining (ECM)

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Principle of the process

Structure and configuration

Process modeling

Defects

Design For Manufacturing (DFM)

Process variation

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)

.

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. Shear stress principle (solid force, water-jet)2. Electric or light or plasma energy to thermal energy3. 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.