non traditional process

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Non Traditional Manufacturing Processes

Introduction

Non-traditional manufacturing processes is defined as a group of processes that remove

excess material by various techniques involving mechanical, thermal, electrical or chemical

energy or combinations of these energies but do not use a sharp cutting tools as it needs to be

used for traditional manufacturing processes.

Extremely hard and brittle materials are difficult to machine by traditional machining

processes such as turning, drilling, shaping and milling. Non traditional machining processes,

also called advanced manufacturing processes, are employed where traditional machining

processes are not feasible, satisfactory or economical due to special reasons as outlined

below.

Very hard fragile materials difficult to clamp for traditional machining

When the worpiece is too flexible or slender

When the shape of the part is too complex

!everal types of non-traditional machining processes have been developed to meet extra

required machining conditions. When these processes are employed properly, they offer

many advantages over non-traditional machining processes. "he common non-traditional

machining processes are described in this section.

Electrical Discharge Machining (EDM)

Electrical discharge machining #E$%& is one of the most widely used non-traditional

machining processes. "he main attraction of E$% over traditional machining processes such

as metal cutting using different tools and grinding is that this technique utilises thermoelectric

process to erode undesired materials from the worpiece by a series of discrete electrical

spars between the worpiece and the electrode. ' picture of E$% machine in operation is

shown in (igure ).

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(igure )* Electrical discharge machine

"he traditional machining processes rely on harder tool or abrasive material to remove the

softer material whereas non-traditional machining processes such as E$% uses electrical

spar or thermal energy to erode unwanted material in order to create desired shape. !o,

the hardness of the material is no longer a dominating factor for E$% process. '

schematic of an E$% process is shown in (igure +, where the tool and the worpiece are

immersed in a dielectric fluid.

(igure +* !chematic of E$% process

E$% removes material by discharging an electrical current, normally stored in a capacitor

ban, across a small gap between the tool #cathode& and the worpiece #anode& typically in

the order of volts)amps.

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http://www.answers.com/topic/electrical-discharge-machine-jpg


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Application of EDM

"he E$% process has the ability to machine hard, difficult-to-machine materials. /arts with

complex, precise and irregular shapes for forging, press tools, extrusion dies, difficult internal

shapes for aerospace and medical applications can be made by E$% process. !ome of the

shapes made by E$% process are shown in (igure 0.

(igure 0* $ifficult internal parts made by E$% process

Working principle of EDM

's shown in (igure ), at the beginning of E$% operation, a high voltage is applied across

the narrow gap between the electrode and the worpiece. "his high voltage induces an

electric field in the insulating dielectric that is present in narrow gap between electrode and

worpiece. "his cause conducting particles suspended in the dielectric to concentrate at the

points of strongest electrical field. When the potential difference between the electrode and

the worpiece is sufficiently high, the dielectric breas down and a transient spar discharges

through the dielectric fluid, removing small amount of material from the worpiece surface.

"he volume of the material removed per spar discharge is typically in the range of ) -1to )-

1mm0.

"he material removal rate, %22, in E$% is calculated by the following foumula*

MRR = 40 I / Tm1.23 (cm3/min)

Where,Iis the current amp,

Tmis the melting temperature of worpiece in 3

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Advantages of EDM

"he main advantages of $% are*

4y this process, materials of any hardness can be machined5

No burrs are left in machined surface5

6ne of the main advantages of this process is that thin and fragilebrittle components

can be machined without distortion5

3omplex internal shapes can be machined

Liitations of EDM

"he main limitations of this process are*

"his process can only be employed in electrically conductive materials5

%aterial removal rate is low and the process overall is slow compared to conventional

machining processes5

7nwanted erosion and over cutting of material can occur5

2ough surface finish when at high rates of material removal.

Dielectric fluids

$ielectric fluids used in E$% process are hydrocarbon oils, erosene and deionised water.

"he functions of the dielectric fluid are to*

'ct as an insulator between the tool and the worpiece.

'ct as coolant.

'ct as a flushing medium for the removal of the chips.

"he electrodes for E$% process usually are made of graphite, brass, copper and copper-

tungsten alloys.

$esign considerations for E$% process are as follows*

$eep slots and narrow openings should be avoided.

"he surface smoothness value should not be specified too fine.

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2ough cut should be done by other machining process. 6nly finishing operation

should be done in this process as %22 for this process is low.

Wire EDM

E$%, primarily, exists commercially in the form of die-sining machines and wire-cutting

machines #Wire E$%&. "he concept of wire E$% is shown in (igure 8. 9n this process, a

slowly moving wire travels along a prescribed path and removes material from the

worpiece. Wire E$% uses electro-thermal mechanisms to cut electrically conductive

materials. "he material is removed by a series of discrete discharges between the wire

electrode and the worpiece in the presence of dieelectirc fluid, which creates a path for each

discharge as the fluid becomes ioni:ed in the gap. "he area where discharge taes place is

heated to extremely high temperature, so that the surface is melted and removed. "he

removed particles are flushed away by the flowing dielectric fluids.

"he wire E$% process can cut intricate components for the electric and aerospace industries.

"his non-traditional machining process is widely used to pattern tool steel for die

manufacturing.

(igure 8* Wire erosion of an extrusion die

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"he wires for wire E$% is made of brass, copper, tungsten, molybdenum. ;inc or brass

coated wires are also used extensively in this process. "he wire used in this process should

posses high tensile strength and good electrical conductivity. Wire E$% can also employ to

cut cylindrical ob


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!heical Machining (!M)

Introduction

3hemical machining #3%& is the controlled dissolution of worpiece material #etching& by

means of a strong chemical reagent #etchant&. 9n 3% material is removed from selected areas

of worpiece by immersing it in a chemical reagents or etchants5 such as acids and alaline

solutions. %aterial is removed by microscopic electrochemical cell action, as occurs in

corrosion or chemical dissolution of a metal."his controlled chemical dissolution will

simultaneously etch all exposed surfaces even though the penetration rates of the material

removal may be only .+=.) mmmin. "he basic process taes many forms* chemical

milling of pocets, contours, overall metal removal, chemical blaning for etching through

thin sheets5 photochemical machining #pcm& for etching by using of photosensitive resists in

microelectronics5 chemical or electrochemical polishing where wea chemical reagents are

used #sometimes with remote electric assist& for polishing or deburring and chemical


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"teps in cheical illing

2esidual stress relieving* 9f the part to be machined has residual stresses from the

previous processing, these stresses first should be relieved in order to prevent warping

after chemical milling.

/reparing* "he surfaces are degreased and cleaned thoroughly to ensure both good

adhesion of the masing material and the uniform material removal.

%asing* %asing material is applied #coating or protecting areas not to be etched&.

Etching* "he exposed surfaces are machined chemically with etchants.

$emasing* 'fter machining, the parts should be washed thoroughly to prevent

further reactions with or exposure to any etchant residues. "hen the rest of the

masing material is removed and the part is cleaned and inspected.

Applications#

3hemical milling is used in the aerospace industry to remove shallow layers of material from

large aircraft components missile sin panels #(igure @&, extruded parts for airframes.

(igure @* %issile sin-panel section contoured by chemical milling to improve the

stiffness- to- weight ratio of the part #>alpa


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Electrocheical Machining (E!M)

Introduction

Electrochemical machining #E3%& is a metal-removal process based on the principle of

reverse electroplating. 9n this process, particles travel from the anodic material #worpiece&

toward the cathodic material #machining tool&. ' current of electrolyte fluid carries away the

deplated material before it has a chance to reach the machining tool. "he cavity produced is

the female mating image of the tool shape.

(igure A* E3% process

!imilar to E$%, the worpiece hardness is not a factor, maing E3% suitable for machining

difficult-to =machine materials. $ifficult shapes can be made by this process on materials

regardless of their hardness. ' schematic representation of E3% process is shown in (igure

A. "he E3% tool is positioned very close to the worpiece and a low voltage, high amperage

$3 current is passed between the worpiece and electrode. !ome of the shapes made by

E3% process is shown in (igure B.

(igure B* /arts made by E3%

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Advantages of E!M

"he components are not sub


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$ltrasonic Machining ($"M)

Introduction

7!% is mechanical material removal process or an abrasive process used to erode holes or

cavities on hard or brittle worpiece by using shaped tools, high frequency mechanical

motion and an abrasive slurry. 7!% offers a solution to the expanding need for machining

brittle materials such as single crystals, glasses and polycrystalline ceramics, and increasing

complex operations to provide intricate shapes and worpiece profiles. 9t is therefore used

extensively in machining hard and brittle materials that are difficult to machine by traditional

manufacturing processes. "he hard particles in slurry are accelerated toward the surface of

the worpiece by a tool oscillating at a frequency up to ) >C: - through repeated

abrasions, the tool machines a cavity of a cross section identical to its own. ' schematic

representation of 7!% is shown in (igure ).

(igure )* !chematic of ultrasonic machine tool

7!% is primarily targeted for the machining of hard and brittle materials #dielectric or

conductive& such as boron carbide, ceramics, titanium carbides, rubies, quart: etc. 7!% is a

versatile machining process as far as properties of materials are concerned. "his process is

able to effectively machine all materials whether they are electrically conductive or insulator.

(or an effective cutting operation, the following parameters need to be carefully considered*

"he machining tool must be selected to be highly wear resistant, such as high-carbon

steels.

"he abrasives #+-1 m in dia.& in the #water-based, up to 8F solid volume& slurry

includes* 4oron carbide, silicon carbide and aluminum oxide.

Applications

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Laser%&ea Machining (L&M)

Introduction

Gaser-beam machining is a thermal material-removal process that utili:es a high-energy,

coherent light beam to melt and vapori:e particles on the surface of metallic and non-metallic

worpieces. Gasers can be used to cut, drill, weld and mar. G4% is particularly suitable for

maing accurately placed holes. ' schematic of laser beam machining is shown in (igure )+.

$ifferent types of lasers are available for manufacturing operations which are as follows*

36+#pulsed or continuous wave&* 9t is a gas laser that emits light in the infrared

region. 9t can provide up to + W in continuous-wave mode.

Nd*H'I* Neodymium-doped Httrium-'luminum-Iarnet #H0'l6)+& laser is a solid-

state laser which can deliver light through a fibre-optic cable. 9t can provide up to

W power in pulsed mode and ) W in continuous-wave mode.

(igure )+* Gaser beam machining schematic

Applications

G4% can mae very accurate holes as small as . mm in refractory metals ceramics, and

composite material without warping the worpieces. "his process is used widely for drilling

and cutting of metallic and non-metallic materials. Gaser beam machining is being used

extensively in the electronic and automotive industries.

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Laser 'ea cutting (drilling)

9n drilling, energy transferred #e.g., via a Nd*H'I laser& into the worpiece melts the

material at the point of contact, which subsequently changes into a plasma and leaves

the region.

' gas


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Advantage of laser cutting

No limit to cutting path as the laser point can move any path.

"he process is stress less allowing very fragile materials to be laser cut without any

support.

Very hard and abrasive material can be cut.

!ticy materials are also can be cut by this process.

9t is a cost effective and flexible process.

Cigh accuracy parts can be machined.

No cutting lubricants required

No tool wear

Narrow heat effected :one

Liitations of laser cutting

7neconomic on high volumes compared to stamping

Gimitations on thicness due to taper

Cigh capital cost

Cigh maintenance cost

'ssist or cover gas required

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Water et !utting

Introduction

Water


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Advantages of ater *et cutting

"here is no heat generated in water


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A'rasive Water+et !utting

Introduction

'brasive water


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Applications

'brasive water


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!urface finish degrades at higher cut speeds which are frequently used for rough

cutting.

"he ma


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(igure )@* !teel gear and rac cut with an abrasive water


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,eferences

2. %anufacturing Engineering and "echnology (ifth Edition - !erope >alpa

non traditional process

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