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MANUFACTURINGPROCESSES:

NONTRADITIONAL (OR)

UNCONVENTIONAL

MACHINING

Manufacturing System Team Teaching

Industrial Engineering ITSWeek 12

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Introduction

Conventional -> sharp cutting tool to form achip from the work -> Material RemovalProcess.

Traditional machining: turning, milling,drilling, grinding, etc.

Non conventional -> Other technique for

remove excess material by various technique(not using sharp tool) -> other energy :chemical, mechanical, electrical and therma

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Classification of non tradional

machining

Mechanical: Different from conventional.

Erotion of the work material by a high velocity

stream of abrasive or fluid (or both) is the

typical form of mechanical action in theseprocesses.

Electrical: these nontraditional processes use

electrochemical energy to remove material: themechanism is the reverse of electroplating

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Classification of non tradional

machining

Thermal : Use thermal energy (converted from

electrical energy) to cut or shape the workpart.

Usually gapplied to a very small portion of the

work causing portion to be removed by fusion/vaporization of the material.

Chemical: Chemicals selectively remove

material from portions of workpart, while otherportions of the surface are protected by mask

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Why Nontraditional Processes?

New Materials (1940s)

Stronger

Tougher

Harder Applications

Cut tough materials (above400 HB.)

Finish complex/unusualsurface geometry

Surface finishrequirements/avoid surfacedamage due ot rise of T or

residual stress

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6

Mechanical Energy Process

Ultrasonic machining (USM)

Water jet cutting

Abrasive water jet cutting

Abrasive jet machining

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Mechanical : USM

Ultrasonic Machining -

Cutting action is

accomplished with an

abrasive slurry which isdriven by a tool vibrating at

high frequency. The tool is

the exact shape of the

desired shape to be cut intothe work.

Applications (coining

operations,

slots, blind holes, irregular

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Tool material: soft steel, stainless steel

Abrasive material: boron nitride, boron

carbide, aluminium oxide, silicon carbide, etc

Material : brittle and hard (glass, ceramics,

carbides)

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MECHANICAL: WATER JET MACHINING

(WJC)

Water jet acts like a saw and cuts a narrow groovein the material.

Pressure level of the jet is about 400MPa.

Advantages- no heat produced- cut can be started anywhere without the

need for predrilled holes- burr produced is minimum- environmentally safe and friendly

manufacturing.Applicationused for cutting composites, plastics,

fabrics, rubber, wood products etc. Also used in

food processing industry.

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MECHANICAL: WATER JET MACHINING

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WATER JET MACHINING

M h i l

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Mechanical:

Abrasive Water-Jet Cutting (AWJC)

Similar to sandblasting

Process utilizes a high velocity stream of water mixed with an

abrasive as the cutting tool

Forces the mixture through a nozzle with a hole diameter of

.0040 - .012

System pressures range from 30,000 - 50,000 psi

Used to cut a variety of materials from wood to tool steel (not

for brittle material)

Cutting rate - Alum. Plate - 150 in/min.

One disadvantage to note

Tolerances typically (+/- .01)

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MECHANICAL:Abrasive Jet

Machining (AJM)

In AJM a high velocity jet of dry air/ stream of

gas, nitrogen or CO2 containing abrasive

particles (aluminium oxide, silicon carbide) isaimed at the work piece.

The impact of the particles produce sufficient

force to cut small hole or slots, deburring,

trimming and removing oxides and other surface

films.

Usually for finishing process

For brittle and hard material (glass, silicon, etc) ,

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ABRASIVE JET MACHINING

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Abrasive Waterjet and

Waterjet Part Examples

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Chemical Machining

Material removal occursthrough contact witha strong chemicaletchant.

Chemical milling Chemical blanking Chemical

engraving

Photochemicalmachining

Steps:

Cleaningto ensure materialwill be removed uniformly fromthe surface to be etched

Masking - a maskant (protectivecoating/chemically resistance)applied to certain portion of thepart surface that are not to beetched

Etchingmaterial revoval byimmerse the material in anetchant that attack part surfacethat are not masked

Demasking - maskant removedfrom the part

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Maskant Process

CUT AND PEEL :

Maskant is applied overentire part by dipping,painting, or spraying

After maskant hardens, it iscut by hand using ascribing knife and peeledaway in areas of worksurface to be etched

Used for large workparts,low production quantities,and where accuracy is nota critical factor

PHOTOGRAPH RESIST :

Masking materials containphotosensitive chemicals

Maskant is applied to worksurface and exposed to lightthrough a negative image ofareas to be etched

These areas are then removedusing photographic developingtechniques

Remaining areas are vulnerableto etching

Applications:

Small parts are produced in highquantities

Fabrication of integrated circuitsand printed circuit cards

SCREEN RESIST :

Maskant applied by silk

screening methods

Maskant is painted through a

silk or stainless steel meshcontaining stencil onto surface

areas that are not to be etched

Applications:

Between other two masking

methods

Fabrication of printed circuit

boards

Materials: neoprene, polyvinylchloride, polyethylene, and other polymers

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Chemical Machining(CM)

Oldest nontraditional machining process.

Material is removed from a surface by chemical dissolution using

chemical reagents or etchants like acids and alkaline solutions.

Types of chemical machining1. chemical Milling (chem-mill)

By selectively attacking different areas of work piece

with chemical reagents shallow cavities can be produced on

plates, sheets, forging and extrusion. Use largely in theaircraft industry, to remove material from wing and fuselage

panels for weight reduction

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1. CHEMICAL MILLING

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2. chemical blanking

It is similar to blanking in sheet metals

except material is removed by chemical

dissolution rather than by shearing.

Used in bur free etching of printed circuit

boards, decorative panels etc.

To cut very thin sheet metal (0.025 mm thick) or

intricate cutting patern

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3. Photochemical Machining

(PCM)

Chemical machining in which the photoresist

method of masking is used

Employed in metal working when close tolerances

/ intricate pattern required

Use extensively in electronic industry (circuitdesign, semiconductor wafers)

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Electrochemical Machining

(ECM)

Reverse of electroplating

An electrolyte acts as a current carrier and highelectrolyte movement in the tool-work-piece gap

washes metal ions away from the work piece(anode) before they have a chance to plate onto the tool (cathode).

Toolgenerally made of bronze, copper, brass

or stainless steel. Electrolytesalt solutions like sodium chloride

or sodium nitrate mixed in water.

PowerDC supply of 5-25 V.

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Advantages of ECM

Process leaves a burr free surface.

Does not cause any thermal damage to the

parts.

Lack of tool force prevents distortion of parts.

Capable of machining complex parts and hard

materials

ECM systems are now available as

Numerically Controlled machining centers with

capability for high production, high flexibility and

high tolerances.

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ELECTROCHEMICAL MACHINING

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ELECTROCHEMICAL GRINDING

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Electrochemical Grinding (ECG)

Combines electrochemical machining with

conventional grinding.

The equipment used is similar to conventional

grinder except that the wheel is a rotatingcathode with abrasive particles. The wheel is

metal bonded with diamond or Al oxide

abrasives.

Abrasives serve as insulator between wheel andwork piece. A flow of electrolyte (sodium nitrate)

is provided for electrochemical machining.

Suitable in grinding very hard materials where

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Thermal

Material removal processes based on

thermal energy are characterized by very

high temperatureshot enough toremove material by fusion or vaporation

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Electrical discharge machining

(EDM) Based on erosion of metals by spark discharges.

EDM system consist of a tool (electrode) and work piece,

connected to a dc power supply and placed in adielectric fluid.

when potential difference between tool and work piece is

high, a transient spark discharges through the fluid,

removing a small amount of metal from the work piecesurface.

This process is repeated with capacitor discharge rates

of 50-500 kHz.

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dielectric fluidmineral oils, kerosene, distilled and

deionized water etc.

role of the dielectric fluid

1. acts as a insulator until the potential is sufficientlyhigh.

2. acts as a flushing medium and carries away the

debris.

3. also acts as a cooling medium. Electrodesusually made of graphite.

EDM can be used for die cavities, small diameter deep

holes,turbine blades and various intricate shapes.

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EDM

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Wire EDM

This process is similar to contour cutting with a band

saw.

a slow moving wire travels along a prescribed path,

cutting the work piece with discharge sparks.

wire should have sufficient tensile strength and fracture

toughness.

wire is made of brass, copper or tungsten. (about

0.25mm in diameter).

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WIRE EDM

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Laser beam machining (LBM)

In LBM laser is focused and the work piecewhich melts and evaporates portions of the workpiece.

Low reflectivity and thermal conductivity of the

work piece surface, and low specific heat andlatent heat of melting and evaporationincreases process efficiency.

application - holes with depth-to-diameter ratios

of 50 to 1 can be drilled. e.g. bleeder holes forfuel-pump covers, lubrication holes intransmission hubs.

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LASER BEAM MACHINING

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Electron beam machining (EBM)

similar to LBM except laser beam is replaced by

high velocity electrons.

when electron beam strikes the work piece

surface, heat is produced and metal isvaporized.

surface finish achieved is better than LBM.

Used for very accurate cutting of a wide varietyof metals.

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ELCTRON BEAM MACHINING

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