Manufacturing Lecture2

7/29/2019 Manufacturing Lecture2

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UEET 601

Modern Manufacturing

Introduction to manufacturingprocesses


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Metal Casting


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Casting Process

Involves flow of molten metal into mold

cavity - cavity has a shape of the finished partmachined into it. Melt is allowed to cool andsolidify. Final product removed from mold.

Important considerations:flow of melt into cavity

solidification and cooling of metal in the mold

influence of the type of mould material

Typical applications:

Engine blocks/components, pump housings,brake rotors and drums, complex shapes


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Flow of Melt in the Mold

Melt is poured into mold cavity through a POURING CUP

Melt flows through the GATING SYSTEM which consistsof:

Sprue:- vertical channel through which melt flows downward

Runners - channels that carry melt from sprue into cavity

Gate - part of the runner through which melt enters cavity

Risers - reservoirs that supply melt and preventshrinkage during solidification


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Casting ProcessesExpendable Mold

Sand casting

Shell molding

Lost foam process

Lost wax(investmentcasting)

Permanent Mold

Die casting

Centrifugal casting


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Forming and Shaping

Processes


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Forming Processes: - involve processes that deformthe initial material plastically into a final material -sometimes through various stages

In both processes, product can be discrete (e.g. aconnecting rod) or continuous (e.g. sheet metal)

Workability - refers to bulk deformation processes.

Forces applied are predominantly compressive (e.g.forging). To be studied : Rolling and Forging

Formability - refers to sheet forming processes inwhich forces applied are predominantly tensile (e.g.

tube drawing). To be studied : Extrusion and SheetMetal Forming


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Rolling Processes


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Introduction

Process that reduces thickness or changes the cross

section of a long work-piece by application ofcompressive forces through a set of rolls.

Can be done when the workpiece is cold - COLDROLLING or when hot (above recrystallizationtemperature) - HOT ROLLING

Work-piece

Rolls


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Flat Rolling

A sheet or block or strip stock is introduced

between rollers and then compressed andsqueezed. Thickness is reduced. The amountof strain (deformation) introduced determinesthe hardness, strength and other materialproperties of the finished product.

Used to produce sheet metals predominantly


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Other Rolling Processes

Shape or Profile Rolling: - Straight, longstructural parts produced with various crosssectional shapes. Profile roles or rollcombinations used to achieve this

Thread Rolling: - used for making externalthreads. A die with the thread profile, is pressedon to a rotating work-piece.


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Forging Processes


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Introduction

Forging - metal is heated and is shaped by plasticdeformation by suitably applying compressive force;hammer blows using a power hammer or a press.

Forgings yield parts that have high strength toweight ratio - thus are often used in the design of

aircraft frame members.A Forged metal can result in the following: -

Decrease in height, increase in section - open die forging

Increase length, decrease cross-section, called drawing out.

Decrease length, increase in cross-section on a portion ofthe length - upsetting

Change length, change cross-section, by squeezing inclosed impression dies - closed die forging. This results in

favorable grain flow for strong parts


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Types of forging processes

Open Die Forgings / Hand ForgingsE.g. traditional blacksmith

Heading - Upsetting process that increasescross-section by compressing a portion of the

length (hot or cold)

this is used in making heads on bolts and fasteners,valves and other similar parts


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Impression Die and Closed Die Forgings

Example alloy ream

Coining

Types of forging processes


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Extrusion and Drawing

Processes


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Extrusion

Process by which long straight metal parts can beproduced.

Cross-sections that can be produced vary from solidround, rectangular, to L shapes, T shapes, tubesand many other different types

Done by squeezing metal in a closed cavity througha die using either a mechanical or hydraulic press.

Extrusion produces compressive and shear forces inthe stock.

No tension is produced, which makes highdeformation possible without tearing the metal.

Can be done Hot or cold


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Direct or Forward - round billet forcedthrough die opening

most common of theextrusion processes inindustrythe billet is upsetted in thecontainer, so that it assumesthe bore diameter of thecontainerit is then pressed by thestem through the die there is relative motionbetween block and container- FRICTION. Use lubricants


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Indirect Extrusion - Reverse or backwardextrusion- Die moves towards billet

Billet also upsetted first inthe containera dummy block used to

lock the container from onesidea hollow stem pushes dieinto the billet OR dummy

block and container maypush billet through die andhollow container (smallerfriction)


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Hydrostatic Extrusion - billet is smaller, chamber filledwith a fluid -HYDROSTATIC FLUID

container space is sealedpressure is transmitted by ram (orstem)

during extrusion the does nottouch the billetless friction between billet andcontainer


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Impact Extrusion - Blank or slug is extruded backwardby impact force to form a thin walled tube

used for hollow shapes

usually performed on a high-

speed mechanical press - punch

descends at a high speed and

strikes the blank, extruding it

upwards

performed cold; considerable

heating results from the high-

speed deformation

restricted to softer metals such as

lead, tin, aluminum and copper

used to produce medicine and

toothpaste tubes


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Drawing

X section of material reduced by pulling

through dieSimilar to extrusion except material is under

TENSILE force since it is pulled through the die

Various types of sections : - round, square, profilesTube Drawing: - Utilizes a special tool called a

MANDREL is inserted in a tube hollow section to draw aseamless tube

Mandrel and die reduce both the tube's outsidediameter and its wall thickness. The mandrel alsomakes the tube's inside surface smoother


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Sheet Metal Forming


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Introduction

Involves methods in which sheet metal is cut

into required dimensions and shape; and/orforming by stamping, drawing, or pressing tothe final shape

A special class of metal forming where thethickness of the piece of material is smallcompared to the other dimensions

Cutting into shape involve shear forcesForming Processes involve tensile stresses


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Shearing

Process for cutting sheet metal to size out of a

larger stockShears are used as the preliminary step in

preparing stock for stamping processes, or

smaller blanks for CNC presses.Sheet is cut by subjecting it to a shear stress


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Bending

Bending is a process by which metal can be

deformed by plastically deforming thematerial and changing its shape

Flexible; different shapes can be produced

Standard die sets can be used to produce awide variety of shapes


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Other Bending Processes:

Press brake bending - used to form for example

seam jointsRoll bending

Beading

Flanging, dimpling, hemming


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Deep Drawing

In deep drawing, a blank of sheet metal is

restrained at the edges by BLANKHOLDER,and the middle section is forced by a punchinto a die to stretch the metal into a cupshaped drawn part. This drawn part can becircular, rectangular or otherwise


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Stamping

Variety of operations e.g. punching, blanking,embosing, coining


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Others:

Roll bending

BeadingFlanging

Roll forming

Tube bending and forming


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Processing of PowderMetals, Ceramics and

Glass

Powder Metallurgy (P/M)


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Powder Metallurgy (P/M)Process by which metal parts are made by compacting

fine metal powders in a die and heating without melting

(SINTERING)Produces mostly NET shapes

Most commonly used metal powders are iron, copper,aluminum, tin, nickel, titanium, and refractory alloys

Major attraction of P/M is the ability to fabricate highquality parts with complex shapes to close tolerances inan economical manner; highly porous parts, precisionparts of high performance as well as compositematerials can be produced by P/M

Process consists of:

1-Powder production 2-Blending 3-Compaction

4-Sintering 5-Finishing operations

l f /


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Applications of P/M

Tungsten lamp filaments, dental fillings, oil lessbearings, automotive transmission gears,electrical contacts, orthopedic implants, hightemperature filters, aircraft brake pads andlanding gear, impellers in APUs

i f C i


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Processing of Ceramics

Generally procedure involves:

Crushing/grinding (Comminution) material into veryfine particles

Mixing with additives to impart certain characteristics

Shaping

Drying

Firing

F i d Sh i f Gl


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Forming and Shaping of Glass

Process involves: -

MeltingShaping in Molds or other devices

Strength improvements obtained by chemical

and thermal treatments or by laminating with athin plastic (Auto glass)

Types of Products:

- sheet or plate

- rods and tubes

- discrete products (e.g. bottles)

- glass fibers (for composite reinforcement)

M th d f P i


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Methods of Processing: -

a) Flat sheet plate

Drawing - molten glass drawn through a pair of rolls

Rolling - molten glass squeezed between rolls

Float method - molten glass floats into a bath ofmolten tin under controlled atmosphere; then drawn

out by a set of rolls. Smooth surface finish

b) Tubes and Rods -

Tube: -Molten glass wrapped around a mandrel

(hollow or conical) and drawn by a set of rolls; air isblown through the mandrel to prevent tube wall fromcollapsing

Rod: - Similar except no mandrel.

) Gl Fib


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c) Glass Fibers: -

Long fibers - drawing through multiple orificesin heated platinum plates at high speeds

Short fibers - molten glass fed into rotatinghead - CENTRIFUGAL SPRAYING

d) Discrete parts: - Several methods.

Blowing - used to manufacture thin walledproducts such as bottles or flasks

Pressing :- Molten glass pressed into shape in

a moldCentrifugal casting or spinning : -centrifugal

force forces molten glass onto rotating moldwalls and cools into shape


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Processing of Polymers and

Composite Materials


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Polymers1. Casting molten polymer allowed to solidify

inside a mold cavity to acquire the desiredshape. For thermosets, additional curingmay be necessary. Examples: thermoplasticsheets & plates thermoset lenses, gears

2. Blow Molding- used to make thermoplasticbottles and hollow sections. Startingmaterial is a a round heated solid-bottomhollow tube preform. Preform inserted

into two die halves and air is blown insideto complete the process


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Blow molding process


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3. Compression Molding thermoset granules

are compressed in a heated mold to shaperequired. Examples: plugs, pot handles,dishware


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4. Transfer Molding similar to compressionmolding except thermosetting charge is

forced into a heated mold cavity using a ramor plunger. Examples: electrical switchgear,structural parts

5. Cold Molding charge is pressed into shape

while cold then cured in an oven.Economical but usually poor surface finish

6. Injection Molding Most widely used process.Suitable for high production ofthermoplastics. Charge fed from a hopper isheated in a barrel and forced under highpressure into a mold cavity. Several types.

Variety of parts can be made.


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Example of an injection molding system


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7. Extrusion Similar to injection molding

except long uniform sections are producede.g. pipes, rods, profiles


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8. Thermoforming Sheet material heated toworking temperature then formed into

desired shape by vacuum suction or pressure.Suitable for large items such as bath tubs


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9. Rotational Molding used to formhollow seamless products such as bins.

Molten charge is rotated in a mold intwo perpendicular axes simultaneously,or rotated while tilting.

10. Foam Molding Foaming agent iscombined with the charge to releasegas, or air is blown into mixture whileforming. Used to make foams. Amount

of gas determines the density


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11. Others-

-Calendaring: molten plastic forced between

two counter-rotating rolls to produce verythin sheets e.g. polyethylene sheets

-Spinning: modified form of extrusion inwhich very thin fibers or yarns are produced

-Machining: material removal process such asdrilling, turning, thread cutting. E.g. nylonfasteners. In general thermoplastics have

poor machinability.


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Composite Materials

Processing requires care and several methods

Safety and environmental concern over the dustgenerated from particles

For good bonding with matrix, fibers are surface

treated by impregnation - SIZINGWhen impregnation is carried out as a separate

step, several types of partially cured sheets canbe produced:

Prepreg: - Reinforcing material aligned andimpregnated with resin prior to the molding processand cured by the application of heat. Example F14horizontal stabilizer.


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Sheet Molding Compound (SMC) - continuous strandsof fibers cut into short strands then deposited inrandom directions over layer of polymer resin., a

second layer of resin deposited on top and materialpressed between rolls. Allowed to mature undercontrolled temperature and humidity

Bulk molding compounds (BMC) - material is bulky or

shaped like a billet, but processing similar to SMCThick Molding compound (TMC) - combines

characteristics of BMC and SMC.

Methods of Processing include Molding, Filament

Winding, Pultrusion, Pulforming


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Molding: - Several types of molding processes:

Compression molding: - composite material compressedunder heat in a mold

Vacuum-bag molding: - prepregs laid in a mold to formdesired shape, then covered with plastic bag. Pressureto form is obtained by applying a vacuum to the bag

Contact molding: - Uses a single mold to make shapes

like boats. Lay-up of prepreg may be manual usingrollers and brushes - HAND LAY-UP or by SPRAY LAY-UP

Resin Transfer Molding :- Resin mix forced into moldcavity that is filled with reinforcement, through a pump

Transfer/injection Molding:- combines transfer andinjection molding in an automated process


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Filament Winding:- involves winding a resin-saturated strand of reinforcing filament around arotating mandrel until desired thickness isobtained. Used for axisymmetric parts - pipes,storage tanks; asymetric parts - aircraft fuselage,propeller blades


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Pultrusion:- fibers are brought together overrollers, dipped in resin and drawn through aheated die. A continuous cross section compositepart emerges on the other side. Very applicablefor long shapes with uniform sections such asrods, or even pipes


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Pulforming:- used to make continuos productsnot necessarily having uniform cross section.

After pulling through a polymer bath, compositeis cured inside to heated die halves into requiredshape.


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Rapid Prototyping


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Prototype is a new examinable product,usually still under development; required fortests and evaluation

Rapid Prototyping is a new technologywhich speeds up the process of product

developmentUsually, new physical model can be builtfrom a CAD file in a matter of hours

There are three basic types:

SubtractiveAdditiveVirtual


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Subtractive Processes

Uses computer based technologies in design,drafting and manufacturing to speed up processof the production of prototype

Requires software that can translate CAD data

into format usable for manufacturing and CNCsoftware

Used only when shape verification of prototype isneeded - a soft material like wax is used tomanufacture the prototype by any conventionalor non-conventional method


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Additive ProcessesParts are built in layers (or slices)Five basic steps:-

Create a CAD model of the design

Convert the CAD model to STL (stereolithography) format

Slice the CAD model to STL format

Model constructed one layer on top of another

Cleaning and finishing operations

There are several types


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Types of RR processes

Fused Deposition Modeling (FDM) Stereolithography Selective Laser Sintering

Solid-Base Curing (Solid Ground Curing)

Laminated Object Manufacturing (LOM)

Limited design restrictions -- can produce any thing


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Limited design restrictions can produce any thingthat can be designed on a CAD application

Automatic scaling -- accurately scales part to fit insidemachine production space

Disadvantages

Limited material -- works with only a few plastics andceramics

Limited size

High Cost of actual machine


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Virtual Prototyping

Uses advanced software to render CADdesign features for simulation and

analysis (no prototype built)Examples - Boeing 777 production - there

was no prototype built.

Applications of Rapid


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Applications of Rapid

Prototyping

Production of finished items - only viablefor polymeric materials

Shape verification of models

Simulation and analysis of products duringdesign stage

Rapid tooling: - RP models used as a

pattern to create a mold quickly or usesthe RP process directly to fabricate a toolfor a limited volume of prototypes.


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Material Removal Processes

Introduction


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Introduction

Involves shaping of parts by material

removal processCan range from a simple operation such

as sawing off a riser to complex

operations involving Computer controlledmachines

Categories:-

Cutting -single point or multi-point toolAbrasive processes

Advanced processes - ECM, EDM, EBM, LBM,e.t.c.

Common Types of Metal Cutting


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yp gProcesses

Turning Milling Drilling


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Tool MaterialsCarbon and Medium Alloy Steels

High Speed Steel

Carbides

Ceramics (cermets)Diamonds

Cutting Fluids


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Cutting Fluids

Essentially a coolant or lubricant or both

Cutting fluids accomplish the following:-Reduce friction and wear - improve tool life and

surface finish

Reduce forces and hence power for cutting

Cool work-tool interface, thus reducing thermaldistortion

Wash away chips

Protects machined surface from corroding

Types of coolants : - Oils, emulsions,synthetics, vegetable oils


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Advanced Machining

Processes

Introduction


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Introduction

Advanced machining methods - also referred to

as non-traditional machining methodsHave been developed to complement traditional

machining processes (TM) in situations where it

is not feasible to use TM methods: -work material too hard or brittleworkpiece too flexible to hold

part shape too complex

surface finish and dimensional requirements toorigorous

temperatures and residual stresses involvedundesirable


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Common Types

Chemical Machining - Selective chemicalattack/etching on a metallic material surfaceusing selected chemical reagents or ETCHANTS

Photo-Chemical Machining (PCM)- also knownas Photo Etching - used to produce precisionparts and decorative items, mainly sheets andfoils.

Laser Beam Machining -source of energy is alaser beam


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Common Types

Electrochemical machining (ECM) - Reverse ofelectroplating in which metal is selectively removed fromthe anode by electrolytic action of a specially shapedcathode tool

Electric discharge machining (EDM), also calledelectrodischarge or spark-erosion machining -

EDM works by eroding material in the path ofelectrical discharges that form an arc between a

shaped electrode tool and the workpiece.Workpiece is immersed in a dielectric fluid which also

acts to flush away debris


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Welding and Joining Processes


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Introduction

Joining processes fall into three differentcategories:welding

adhesive bonding

mechanical fastening

Welding processes can be divided intothree categories:

fusion welding

solid state welding

non-fusion welding


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Fusion Welding: -heat is applied to melt metal locally at joint

the joint is allowed to solidify and fuse

source of heat can be an electrical arc or a flame

filler material may be required to fill the gap.

Fusion Welding Processes


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Types of fusion welding processes 1. Oxyfuel (gas) weldingSource of heat is a gaseous fuel combined with O2Fuels : -

acetylene (oxyacetylene welding - the most common)

others (mostly used for cutting - propane, hydrogen, MAPP,propylene, natural gas)

when mixed together in correct proportions within a hand-heldtorch or blowpipe, a relatively hot flame is produced with atemperature of about 3,200 deg.C.


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Types of fusion welding processes

2. Arc - Welding ProcessesHeat source is from an electrical arc

electrode can be consumable (also acts as filler)

or non-consumable (separate filler is required)there are several types of arc welding processes

shielded metal arc (consumable electrode)

gas shielded processes TIG (non - consumable), MIG(consumable)

submerged arc welding

flux-cored arc welding

Plasma arc welding


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Other Welding Processes


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Solid State welding

Ultrasonic welding - used for both metallic and non-metallic

processes especially thin sheets; used extensively in plastics

Resistance welding - commonly used in sheet metals; verypopular in automotive body assembly

Brazing and Soldering

Other Joining Processes

Adhesive bonding - a wide variety

Mechanical fasteners - bolts, rivets, screws, etc


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Oxy-Fuel Cutting

Arc cutting

Plasma cutting

Metal cutting processes


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Brazing and Soldering

Non-fusion joining processesDissimilar materials can be joined

Brazing is done when two metals, which

are not melted, are joined with a thirdmetal that melts at temperatures above840 deg F.

Soldering occurs when two metals, whichare not melted, are joined by a thirdmetal having a melting point below840deg. F

Methods of brazing


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Methods of brazing

Torch

furnace

induction

resistance

deep brazing

Applications of brazing


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Automotive

air conditioner heat exchangerheater heat exchanger

radiator core (engine heat exchanger)

Fuel rail for injectors

pollution control stainless tubing

Aerospace

jet engine parts

rocket engines

Plumbing

faucets

larger piping in multistory buildings

Soldering


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Occurs when two metals, which are not

melted, are joined by a third metal havinga melting point below840 deg. F

Biggest advantage: minimum warpage

and minimal disturbance of the heattreatment of the parent metal

Typical fillers: Tin-lead (most common)

Tin-zinc

Lead-silver

Tin-silver (electronics)

Tin-bismuth (electronics)

Types of Soldering


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Procedures

Soldering IronsTorch soldering

Dip soldering

Wave solderingOven soldering

Resistance soldering

Induction soldering

Infrared soldering

Applications of Soldering


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Applications of Soldering

Soldering is used for the following desired

characteristics:leakproof joints

neatness

low-resistance electrical joint

sanitation

Soldered joint is not as strong as a brazed

or welded joint

Soldered assemblies must be kept at low

operating temperatures to prevent the

soldered joint from failing

Manufacturing Lecture2

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