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1The Exponent Group of Journals For General Engineering, Volume 4, Number 4, Sep 2016 - Nov 2016

Volume: 4 - Number 4 Sep 2016 - Nov 2016

ContentsStudy of Heat Umesh Wadyekar 4 Exchangers Overview of Vishwajeet Birajdar 9 Manufacturing Process Manufacturing Prasad Magar 14 Process - Milling

Technology of Anil Thakur 22 Pre-Treatment of Textile

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Editorial

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Editorial Dear readers

With great pleasure we are handing over this fourth issue of Volume IV of Journal on General Engineering.

We all are aware of importance of radiators in car . Radiator is a type of heat exchanger. Heat exchanger is a device , which is used for transferring heat from onefluidtoanotherthroughaseparatingwall.Theseare extensively used in chemical, food and process industries.Inourfirstarticlewewillstudythevarioustypes heat exchangers that are being used today. Every year road traffic accidents take away lives of1.2 million people worldwide. India accounts for about 10% of these i.e about hundred and twenty thousand lives. Most of the casualties take placedue to slamming of chest in head –on collisions. Air bags are designed to keep occupants head, neck, and chest safe, from slamming into the dash, steering wheel,orwindshieldinafront-endcrash,inafractionof second. Air bags are fabric bags that are filledquicklywithagastoprovidesupplementprotectionfor vehicle passengers during some collisions. Our second article is giving very important informationon these life saving Air Bags in automobiles Manufacturingandworkshoppracticeshavebecomeimportant in the industrial environment, to produce products for the service of mankind.

Manufacturing technology provides the tools that enable production of all manufactured goods.Thusmanufacturing process really represents adding

valuetoarawmaterialandcreationofwealth.Ourarticle on Overview of manufacturing processesmainly aims to give very good information onmanufacturing as a whole , and help readers to select proper manufacturing process. Further we are discussing, in details a very well known and popular machining process of milling in ournextarticle.Articlegivesfull informationaboutvarious types of milling machines and variety of milling cutters ,tools being used in the industries,today. In our earlier issues of Engineering journal , we have seenhow textilesaregettingcoloredordyedor printed. Who will like to wear a poorly dyed shirts and dresses ?. For the good quality of dyeing, pretreatment is very essential. Pretreatment is aheartofprocessingoftextile.Inpretreament,alltheimpurities are removed and fabric is brought to astage where it is more absorbent and white and can be easily processed further. We will study , how this pre-treatment is acuallyachieved inourarticleonPre-treatmentofTextiles. Hope you are finding the articles in the journal,interestingandinformative.Weanxiouslyawaityourcontributionandfeedbacktomakethisjournalmoreinterestingandmeaningfultoallofus.


4 The Exponent Group of Journals For General Engineering, Volume 4, Number 4, Sep 2016 - Nov 2016

Study of Heat Exchangers

- Umesh Wadyekar E-mail: [email protected]

Introduction - We all are aware of radiators in car . The incoming air is used to cool the cooling media of the engine. Radiator is a type of heat exchanger. Heat exchanger is a device , which is used for transferring heat from onefluidtoanotherthroughaseparatingwall .Theseareextensivelyused inchemical, foodandprocessindustries.Theyoperateatvarioustemperatureandpressureconditions.Fluidsusedalsovary.Hencetheseheatexchangersneedtobedesignedcarefullytosuittheneed.Inthisarticlewewillstudythevariousheatexchangers that are being used today.



Fig no 1– Various categories of Heat exchangers

Heatexchangers canbeclassifiedaccordingtotheprocessofheattransfer,mechanicalconstructionandprincipalmaterialofconstruction.Theclassificationis not rigid , and some of the heat exchangers may fall under more than one category.There are many types of Heat Exchangers . Few of them are as shown above in Fig 1

Types of Heat Exchangers 1. Double pipe Heat exchanger This is used particularly when the flow rates arelow, and when the temperature range is relativelyhigh.Inthistypeonefluidflowsinsideapipe,whilesecond fluid flows either co -or counter-currentlyin the annulus between a large pipe and the outer side of the inner pipe carrying the first fluid. Thecomponents of the heat exchanger unit consists of concentricpipes,connectingteesandreturnbends.

Figno2–DoubletypeHeatexchangerschematic

Fig no 3 Double pipe Heat exchanger 2. Shell and Tube type heat exchanger These are most widely used types of heat exchangers. The equipment consists of a number of parallel tubes enclosedinarelativelyclosefittingcylindricalshell.Onefluidflowsinsidethetubeandiscalledtubesidefluid,theotherflowsoutsidethetubesandiscalledtheshellsidefluid.Ifnoneofthefluidcondensesorevaporates the unit is called as “heat exchanger”. If one of the fluids, either in the shell in the tubecondenses, the unit is called as “condenser” or as a “heater”, depending on whether the primary purpose of theunit is to condenseonefluidor toheat theother. Similarly if one of the fluids evaporates, theunit is designated as an “evaporator’ or as a “cooler”, depending on whether the primary purpose is to evaporate one fluid or to cool the other. In thecase of vapour in –tube condensers, the vapour distribution isuniform,pressuredrop is reasonableand vapour sub-cooling is readily accomplished. For serviceathighvacuumconditions,horizontalvapourin-shell condenser is a preferred design, because at high vacuum the vapour lines are large, vapour temperatures are usually high and condensate sub-cooling is not too important. Few types are as shown below.

Fig no 4 Fixed Tube sheet type Heat Exchanger



Figno5OutsidepackedfloatingheadHeatExchanger

Figno6.FloatingheadHeatExchanger

Fig no 7. U-Bundle type Heat Exchanger

Fig no 8. Reboiler with internal U Bundle 3. Special types of Heat Exchangers These are used in special cases where the standard formsoftubularexchangersareunsatisfactory. Pipe coils – These coils of spiral or helical shape are used for cooling purposes, especially at high temperature and pressure applications. Such coilsare immersed in a tank of water or sprayed with water. The pressure drop in the coil is high, but the constructionissimpleandlessexpensive.

Fig no 9 Coil made out of copper tubes



Figno10.HeatingCoilmadewithSS316Tubes M/S. Dalal Engineering Pvt Ltd.

1. Spiral heat exchanger This consists of two plates, spirally wound one inside the other on a split mandrel, each turn being separatedbyspacerstuds,flashweldedtotheplatesbeforewinding.Afterwindingalternatepairsofplatesare edge welded to form two channels, each open at one side and welded at the other. The last turn of the spiral forms the shell of the cylindrical spiral body, endsofwhichareclosedbyendcovers.Thehotfluidentersatthecentre,flowsthroughtheinnerpassageandleavesattheperiphery.Thecoldfluidentersattheperiphery,flowsthroughtheouterpassage,andleavesatthecentre.Thetwofluidsthusflowintruecounter current in between curved surfaces, giving excellent flow characteristics. The curved channelgives a constantly changing angle of incidence to the particlesthatmay,inconventionalexchangers,causefouling. The spiral heat exchanger is used for highly fouling and corrosive liquids.

Fig no 11. Spiral coil for Heat Exchanger

Fig no 12 Spiral coiled Heat Exchanger 2. Plate type heat exchanger

This is constructed by a series of corrugated parallel plates held firmly together between frames. Theheat transfer surfaces consist of the adjacent plates. Gasket cemented to the plates help to form separate channelsforthetwofluids.Thetwoliquidstravelincountercurrentdirectionsandtheheattransfertakesplacethroughtheplate.Headersconnectingthetwoliquids connect the alternate plate compartments through corner plates. The whole assembly is bolted together with stay bolts and end plates. This has the advantage of being able to increase the area by adding extra plates. The advantages are high rates of heat transfer, low pressure drop and easy cleaning and replacement of plates. This type of exchanger is used in food , dairy and other industries where even the slightest contaminationof the products due to



leak cannot be tolerated.

Fig no 13 Plate type Heat Exchanger

3. Finned tube heat exchanger Incaseofheatingairorgas,wheretheheattransfercoefficientsarelow,thesurfaceareacanbeincreasedby use of fins either in transverse or longitudinalforms.Transversefinnedtubesareusedforcoolingprocess streams by air. Longitudinal finned tubesunit are used at high temperature and high pressure service, where heat transfer rates are low.

Fig no 14 Finned type Heat Exchanger

Fig no 15. Finned type Heat Exchanger with enclosures

4. Graphite heat exchangers

Carbon& graphic areused inmany applications intheconstructionofchemicalequipment,sincethesematerials are stable over a wide range of temperature & are chemically resistant to most corrosive agents. Graphite has a high thermal conductivity. Due totheir low tensile strength&brittleness, techniquesin design & fabrication of these materials differfrom those employed for metals. Several types of graphite exchangers are made. In the normal types, the exchanger is made of the shell, & in the tube type,with graphite tubes & tube sheet.The cubic or rectangular block heat-exchanger consist of graphite block perforated with rows of parallel holes for conveying the two fluids. The graphic blocks aremade from a series of accurately machined plates of graphite laminated together & bonded with thermosettingresins.Headersareboltedtothefourfaces of the graphite block for supply & discharge of thefluids.Inacylindricalblockofgraphite,holescanbedrilled& theseblockscanbemulti-stocked inacylindrical steel shell that has gland fittings. Theseunits have been designed for use as evaporators & re-boilers. In another design known as the cartridge block exchanger, a graphite core & process headers are housed in a cylindrical steel shell. The graphite core is performedwith holes for the process fluid,opening into headers at each end.



Fig no 16 . Graphite Heat Exchanger Wehavestudiedconstructionofvariousheatexchangers.Innextissuewewillstudythedesignaspectsofthese heat exchangers. References 1. Mahajan,K.K., Design of Process equipment, Pressure Vessel Handbook Publishing Co.USA-1979. 2. RubinF.L.‘PracticalHeatExchangerDesign’ChemEngProg.64(12),44-19683. VaradarajuluR.‘HaveaLookatShellandTubeHeatExchangers’Chem,AgeofIndia,27(5),479(1976)4. TubularHeatExchangersManufacturersAssociation–TEMA-1998



Overview on Manufacturing Processes

- Vishwajeet BirajdarE-mail: [email protected]

PREFACE: Manufacturingandworkshoppracticeshavebecomeimportant in the industrial environment to produce products for the service of mankind. The knowledge of manufacturing practices is highly essential forall engineers and technocrats for familiarizingthemselves with modern concepts of manufacturing technologies.Thebasicneedistoprovidetheoreticalandpracticalknowledgeofmanufacturingprocessesand workshop technology to all the engineers. This article coversmanufacturing processes/technology,workshoptechnologyandworkshoppractices.

INTRODUCTION: Manufacturingisthebackboneofanyindustrializednation.Manufacturingandtechnicalstaffinindustrymust know the various manufacturing processes, materials being processed, tools and equipment for manufacturing different components or productswithoptimalprocessplanusingproperprecautionsandspecifiedsafetyrulestoavoidaccidents.Besideabove, all kinds of the future engineers must know thebasicrequirementsofworkshopactivitiesinterm of man, machine, material, methods, money and other infrastructure facilities needed to bepositioned properly for optimal shop layouts orplant layout and other support services effectivelyadjusted or located in the industry or plant within a well-plannedmanufacturingorganization. The complete understanding of basic manufacturing processesandworkshoptechnologyishighlydifficultforanyonetoclaimexpertiseoverit.

The study deals with several aspects of workshops practices also for imparting the basic workingknowledge of the different engineering materials,tools, equipment, manufacturing processes, basic

concepts of electromechanical controls of machine tools, production criteria’s, characteristics andusesof various testing instruments and measuring orinspecting devices for checking components orproducts manufactured in various manufacturing shops in an industrial environment. It also describes and demonstrates the use of different hand tools(measuring,marking,holdingand supporting tools,cutting etc.), equipment, machinery and variousmethods of manufacturing that facilitate shaping or forming thedifferentexisting rawmaterials intosuitable usable forms.

It deals with the study of industrial environment which involves thepractical knowledge in the areaofferrousandnon-ferrousmaterials,theirpropertiesand uses. It should provide the knowledge of basic workshopprocessesnamelybenchworkandfitting,sheet metal, carpentry, pattern making, mouldmaking, foundry, smithy, forging, metal working and heat treatment, welding, fastening, machine shop, surface finishing and coatings, assemblinginspectionandqualitycontrol.Itemphasizesonbasicknowledge regarding composition, properties anduses of different rawmaterials, various productionprocesses, replacement of or improvement over a large number of old processes, new and compact designs, better accuracy in dimensions, quickermethodsofproduction,bettersurfacefinishes,morealternatives to the existing materials and toolingsystems, automatic and numerical control systems,highermechanizationandgreateroutput.

Definition of Manufacturing Technology: • Manufacturing technology provides the tools

that enable production of all manufacturedgoods. These master tools of industry magnify the effort of individual workers and give anindustrialnationthepowertoturnrawmaterials



into the affordable, quality goods essential totoday’s society.

• Thus manufacturing process really represents adding value to a rawmaterial and creation ofwealth.

Manufacturing processes refers to science and technology of manufacturing products effectively,efficiently, economically and environment-friendlythrough • Applicationofanyexistingmanufacturingprocess

and system • Proper selection of input materials, tools,

machines and environments. • Improvement of the existing materials and

processes • Development of new materials, systems,

processes and techniques

All such manufacturing processes, systems, techniques have to be

• Technologically acceptable • Technically feasible • Economically viable • Eco-friendly

Manufacturing Science and technology are growing exponentiallytomeetthegrowingdemandsfor;

1. Increaseandmaintenanceofproductivity,qualityandeconomyspeciallyinrespectofliberalisationandglobalcompetitiveness

2. Making micro and ultra-precision components for the modern electronics, computers and medical applications

3. Processingexoticmaterials,comingupwithrapidand vast advent of science and technology like aerospace and nuclear engineering.

Advance manufacturing engineering involves the following concepts—

1. Process planning. 2. Process sheets. 3. Route sheets. 4. Tooling. 5. Cuttingtools,machinetools(traditional,numerical

control(NC),andcomputerizednumericalcontrol(CNC).

6. Jigs and Fixtures. 7. Dies and Moulds. 8. ManufacturingInformationGeneration.9. CNC part programs. 10. Robot programmers. 11. Flexible Manufacturing Systems (FMS), Group

Technology (GT) and Computerintegratedmanufacturing(CIM).

CLASSIFICATION OF MANUFACTURING PROCESSES: For producing of products materials are needed. It isthereforeimportanttoknowthecharacteristicsofthe available engineering materials. Raw materials used manufacturing ofproducts, tools, machines and equipment in factories or industries are extracted from ores.

The ores are suitably converted into a molten form byreducingorrefiningprocessess.Thismoltenmetalis poured into moulds for providing commercial castings,calledingots.Suchingotsarethenprocessedin rolling mills to obtain market form of material supply in form of bloom, billets, slabs and rods.

These forms of material supply are further subjected tovariousmanufacturingprocessesforgettingusablemetalproductsofdifferentshapesandsizesinvariousmanufacturing shops. All these processes used in



manufacturing concern for changing the ingots into usable products may be classified into six majorgroups as primary shaping processes, secondary machining processes, metal forming processes, joining processes, surface finishing processes andprocesseseffectingchange inproperties.Thesearediscussed as under. 1. Primary Shaping Processes: Primary shaping processes are manufacturing of a product from an amorphous material. Some processes produces finish products or articles intoits usual form whereas others do not, and require furtherworkingtofinishcomponenttothedesiredshapeandsize.

Castings need re-melting of scrap and defectiveingots in cupola or in some othermelting furnaceand then pouring of the molten metal into sand or metallicmouldstoobtainthecastings.Thustheintricate shapes can be manufactured. Typical examplesoftheproductsthatareproducedbycastingprocess are machine beds, automobile engines, carburetors, flywheels etc. The parts producedthrough these processes may or may not require to undergofurtheroperations.

Some of the important primary shaping processes is:

1. Casting,2. Powder metallurgy, 3. Plastictechnology,4. Gascutting,5. Bending and 6. Forging. 2. Secondary or Machining Processes: As large number of components require further processing after the primary processes. Thesecomponents are subjected to one or more number ofmachiningoperationsinmachineshops,toobtainthe desired shape and dimensional accuracy on flat and cylindrical jobs. Thus, the jobs undergoingthese operations are the roughly finished productsreceived through primary shaping processes. The process of removing the undesired or unwanted material from the workpiece or job or component toproducea required shapeusinga cutting tool isknown as machining. This can be done by a manual process or by using a machine called machine tool

(traditionalmachinesnamelylathe,millingmachine,drilling,shaper,planner,slotter).Inmanycasestheseoperations are performed on rods, bars and flatsurfaces in machine shops.These secondary processes are mainly required for achieving dimensional accuracy and a veryhigh degree of surface finish.The secondary processes require the use of one or more machine tools, various single or multi-point cutting tools (cutters), job holding devices,markingandmeasuringinstruments,testingdevicesand gauges etc. for getting desired dimensionalcontrol and required degree of surface finish onthe workpieces. The example of parts produced by machining processes includes hand tools machine tools instruments, automobile parts, nuts, bolts and gears etc. Lot of material is wasted as scrap in the secondary or machining process. Some of the common secondary or machining processes are— 1. Turning, 2. Threading, 3. Knurling, 4. Milling, 5. Drilling, 6. Boring, 7. Planning, 8. Shaping, 9. Slotting,10. Sawing, 11. Broaching, 12. Hobbing, 13. Grinding, 14. Gearcutting,15. Threadcuttingand16. Unconventional machining processes namely

machiningwithNumericalControl(NC)machinestools or Computer Numerical Control (CNC)machines tools using ECM, LBM, AJM, USM setups etc.

3. Metal Forming Processes: Forming processes encompasses a wide variety of techniques, which make use of suitableforce, pressure or stresses, like compression, tension and shear or their combination to cause a permanentdeformationoftherawmaterialtoimpartrequiredshape. These processes are also known as mechanical workingprocessesandaremainlyclassifiedintotwomajor categoriesi.e., hot working processes and cold working processes. In these processes no material isremoved; however, it is deformed and displaced



using suitable stresses like compression, tension, and shear or combined stresses to cause plasticdeformation of the materials to produce requiredshapes.Suchprocessesleadtoproductionofdirectlyusablearticleswhich includekitchenutensils, rods,wires,rails,colddrinkbottlecaps,collapsibletubesetc. Some of the important metal forming processes are: Hot working Processes 1. Forging, 2. Rolling, 3. Hot spinning, 4. Extrusion, 5. Hot drawing and 6. Hot spinning. Cold working processes 1. Cold forging, 2. Cold rolling, 3. Cold heading, 4. Cold drawing, 5. Wire drawing, 6. Stretch forming, 7. Sheet metal working processes such as piercing,

punching, lancing,notching, coining, squeezing,deep drawing, bending etc.

4. Joining Processes: Many products observed in day-to-day life, are commonlymadebyputtingmanypartstogethermaybe in sub-assembly. For example, the ball pen consists of a body, refill, barrel, cap, and refill operatingmechanism. All these parts are put together to form the product as a pen.

More than 1000 parts are put together to make varioussub-assembliesandfinalassemblyofcaroraeroplane. A complete machine tool may also require to assemble more than 100 parts in various sub-assemblyorfinalassembly.Theprocessofputtingtheparts together to form the product, which performs thedesiredfunction,iscalledassembly.Anassemblyof parts may require some parts to be joined together using various joining processes. But assembly should not be confused with the joining process. Most of the products cannot be manufactured as single unit they aremanufacturedasdifferentcomponentsusingoneor more of the above manufacturing processes, and

these components are assembled to get the desired product.

Joiningprocessesarewidelyusedinfabricationandassembly work. In these process two or more pieces of metal parts are joined together to produce desired shapeandsizeoftheproduct.Thejoiningprocessesarecarriedoutbyfusing,pressing,rubbing,riveting,screwingor any other means of assembling. These processes are used for assembling metal parts andin generalfabricationwork.Suchrequirementsusuallyoccur when several pieces are to be joined together to fabricate a desired structure of products. These processesareuseddevelopingsteamorwater-tightjoints. Temporary, semi-permanent or permanent type of fastening to make a good joint is generally created by these processes. Temporary joining of components can be achieved by use of nuts, screws and bolts. Adhesives are also used to make temporary joints. Some of the important and common joining processes are: 1. Welding(plasticorfusion),2. Brazing,3. Soldering, 4. Riveting,5. Screwing, 6. Pressfitting,7. Sintering, 8. Adhesive bonding, 9. Shrinkfitting,10. Explosive welding, 11. Diffusionwelding,12. Keysandcottersjoints,13. Coupling and 14. Nut and bolt joints. 5. Surface Finishing Processes:

Surfacefinishingprocessesareutilizedforimpartingintended surface finish on the surface of a job. Byimparting a surface finishing process, either a verynegligible amount of material is removed or added to the surface of the job. These processes should not be mis-understood as metal removing processes in any case as they are primarily intended to provide a good surfacefinishoradecorativeorprotectivecoatingonto the metal surface. Surface cleaning process is also calledasasurfacefinishingprocess.



Some of the commonly used surface finishingprocesses are:

1. Honing, 2. Lapping, 3. Superfinishing,4. Belt grinding, 5. Polishing, 6. Tumbling, 7. Organicfinishes,8. Sanding, 9. deburring, 10. Electroplating,11. Buffing,12. Metalspraying, 13. Painting,14. Inorganiccoating,15. Anodizing,16. Sherardizing,17. Parkerizing,18. Galvanizing,19. Plasticcoating,20. Metalliccoating,21. Anodizingand22. Sandblasting.

Processes Effecting Change in Properties Processeseffectingchangeinpropertiesaregenerallyemployed to provide certain specific properties tothe metal work pieces for making them suitable for particularoperationsoruse.

Someimportantmaterialproperties likehardening,softening and grain refinement are needed to jobsand hence are imparted by heat treatment. Heat treatments affect the physical properties and also

make a marked change in the internal structure of the metal. Similarly themetal formingprocesseseffecton the physical properties ofwork pieces Similarlyshotpeeningprocess, imparts fatigue resistance towork pieces.

A few such commonly used processes are given as under:

1. Annealing, 2. Normalising, 3. Hardening, 4. Case hardening, 5. Flame hardening, 6. Tempering, 7. Shot peeing, 8. Grainrefiningand9. Age hardening.

Inaddition,somealliedmanufacturingactivitiesarealsorequiredtoproducethefinishedproductsuchasmeasurement and assembly.

We will study each manufacturing process in details, incontinuationtothis.

References 1. Manufacturing Processes – Book by Mr. Rajendra 2. www.google.com 3. www.wikipedia.org



Manufacturing Processes -- Milling

- Prasad MagarE-mail: [email protected]

In any type of machining process, a piece of raw materialiscutintoadesiredfinalshapeandsizebyacontrolled material-removal process. Inthisarticle,weshallseedetailsofamanufacturingprocess which is known as Milling Process.

Milling is the machining process of using rotary cutters(CutterwhichhasROUNDPeripheralshape)toremovematerialfromaworkpiecebymoving(orfeeding)inadirectionatananglewiththeaxisofthetool.Itcoversawidevarietyofdifferentoperationsand machines, on scales from small individual parts tolarge,heavy-dutygangmillingoperations.Itisoneof the most commonly used processes in industry and machine shops today for machining parts to precisesizesandshapes.

Millingoperation

Milling is the most common form of machining, a material removal process, which can create a variety offeaturesonapartbycuttingawaytheunwantedmaterial. The milling process requires a milling machine,workpiece,fixture(toholdtheworkpiecein the position), and a cutter. The workpiece is apiece of pre-shaped material that is secured to the fixture,which itself isattachedtoaplatform insidethemillingmachine.Thecutterisacuttingtoolwithsharp teeth that is also secured in the milling machine and rotates at high speeds. By feeding the workpiece intotherotatingcutter,materialiscutawayfromthisworkpiece in the form of small chips to create the desired shape.

Milling is typically used to produce parts that are not axially symmetric and have many features, such as holes, slots, pockets, and even three dimensional surface contours. Parts that are fabricated completely throughmilling often include components that areused in limited quantities, perhaps for prototypes,such as custom designed fasteners or brackets. Another application of milling is the fabrication oftooling for other processes. For example, three-dimensional molds are typically milled. Milling is also commonly used as a secondary process to add



orrefinefeaturesonpartsthatweremanufacturedusingadifferentprocess.Duetothehightolerancesandsurfacefinishesthatmillingcanoffer,it isidealfor adding precision features to a part whose basic shape has already been formed.

Milling Machine Process: Millingisacuttingprocessthatusesamillingcutterto remove material from the surface of a workpiece. Themillingcutterisarotarycuttingtool,oftenwithmultiplecuttingpoints.Asopposedtodrilling,wherethetoolisadvancedalongitsrotationaxis,thecutterin milling is usually moved perpendicular to its axis so that cutting occurs on the circumference of thecutter.Asthemillingcutterenterstheworkpiece,thecuttingedges(flutesorteeth)ofthetoolrepeatedlycut into and exit from the material, shaving offchips (swarf) from the workpiece with each pass.Thecuttingaction is sheardeformation;material ispushedoff theworkpiece intiny clumps thathangtogethertoagreaterorlesserextent(dependingonthematerial)toformchips.Thismakesmetalcuttingsomewhat different (in its mechanics) from slicingsoftermaterialswithablade.

The milling process removes material by performing many separate, small cuts. This is accomplished by usingacutterwithmanyteeth,spinningthecutterat high speed, or advancing the material through thecutterslowly;mostoftenitissomecombinationof these three approaches. The speeds and feeds used are varied to suit a combination of variables.The speed at which the piece advances through the cutteriscalledfeedrate,orjustfeed;itismostoftenmeasuredinlengthofmaterialperfullrevolutionofthecutter.



Milling Product History:

Millingmachinesevolvedfromthepracticeofrotaryfiling—thatis,runningacircularcutterwithfile-liketeeth in the headstock of a lathe Machine. Rotaryfilingand,later,truemillingweredevelopedtoreducetimeandeffortspenthand-filing.Thefullstory of milling machine development may never be known, because much early development took place in individual shops where few records were kept for posterity. However, the broad outlines are known, as summarized below. From a history-of-technology viewpoint, it is clear that the naming of

this new type of machining with the term “milling” was an extension from that word’s earlier senses of processing materials by abrading them in some way (cutting,grinding,crushing,etc.). Rotary filing long predatedmilling. A rotary file byJacques de Vaucanson, circa 1760, is well known. It is clear thatmillingmachines as a distinct class ofmachine tool (separate from lathes running rotaryfiles)firstappearedbetween1814and1818.

This milling machine was long credited to Eli Whitney and dated to circa 1818. From the 1910s through the 1940s, this version of its provenance was widely published. In the 1950s and 1960s, various historians of technology mostly discredited the view ofthismachineasthefirstmillerandpossiblyevenofWhitney as its builder.Nonetheless, it is still animportant early milling machine, regardless of its exact provenance.

The Middletown milling machine of circa 1818, associated with Robert Johnson and Simeon North



The milling machine built by James Nasmyth between 1829 and 1831 for milling the six sides of a hex nut usinganindexingfixture.

A typical Lincoln miller. The configuration wasestablishedinthe1850s.(ThisexamplewasbuiltbyPratt&Whitney,probably1870sor1880s.)

Brown & Sharpe’s groundbreaking universal milling machine, 1861

A typical universal milling machine of the early 20th century. Suitable for tool room, jobbing, or productionuse.

Types of Milling Machines:

Millingmachinesareamongthemostversatileanduseful machine tools due to their capabilities to



performavarietyofoperations.Theycanbebroadlyclassifiedintothefollowingtypes:

• Column and knee type of milling machines • Bed type • Rotary table • Tracer controlled

Column & Knee type Milling Machines: Usedforgeneralpurposemillingoperations,columnand knee type milling machines are the most common milling machines. The spindle to which the milling cutter ismaybehorizontal (slabmilling)orvertical(faceandendmilling).

The basic components are: • Work table, on which the workpiece is clamped

using the T-slots. The table moves longitudinally with respect to the saddle.

• Saddle, which supports the table and can move

transversely. • Knee, which supports the saddle and gives the

tableverticalmovementsforadjustingthedepthof cut.

• Overarm in horizontal machines, which isadjustable to accommodate different arborlengths.

• Head, which contains the spindle and cutterholders. In vertical machines the headmay befixedorverticallyadjustable.

Bed Type Machines: In bed type machines, the work table is mounted directly on the bed, which replaces the knee, and can move only longitudinally. These machines have high stiffnessandareusedforhighproductionwork.

Planer Machines: Planer machines are similar to bed type machines butareequippedwithseveralcuttersandheadstomill various surfaces.

Rotary Table Machines: Rotarytablemachinesaresimilartoverticalmillingmachines and are equipped with one or more heads todofacemillingoperations



Tracer Controlled Machines

Tracer controlled machines reproduce parts from a mastermodel.Theyareusedintheautomotiveandaerospace industries from machining complex parts and dies. Computer Numerical Control(CNC) Machines

: Various milling machine components are being replaced rapidly with computer numerical control (CNC)machines. Thesemachine tools are versatileand are capable of milling, drilling, boring and tapping withrepetitiveaccuracy.

Operations on the Milling Machine:There aremany types of themilling operation buttolimitthesizeofthisarticle,weshallseehowtheoperationisperformedonaWorkpiece: Plain Milling Operation:



Face Milling:

Straddle Milling Operation:

Saw milling Operation:

Gang Milling:

Form Milling:



End Milling:

Profile Milling machine:

Pocket Milling and Contour Milling:

References: • https://en.wikipedia.org/wiki/Milling

(machining)• http://www.custompartnet.com/wu/milling• http://www.hnsa.org/wp-content/

uploads/2014/07/milling-machine.pdf • http://www.sandvik.coromant.com/en-gb/

knowledge/milling/application_overview/face_milling/general_face_milling

• http://www.egr.msu.edu/~pkwon/me478/operations.pdf



Technology of Pre-treatment of Textile

- Anil S. Thakur E-mail: [email protected]

SYNOPSIS : Pretreatment is a heart of processing of textile. Inpretrement,alltheimpuritiesareremovedandfabricis brought to a stage where it is more absorbent and white and can be easily processed further. The processwhichisdonetomakethetextilematerialssuitablefordyeingandprinting.Suchassingeing,desizing,scouring,bleachingetc.

INTRODUCTION :

Natural fibers and synthetic fibers contain primaryimpuritiesthatarecontainednaturally,andsecondaryimpurities thatareaddedduringspinning ,knittingandweavingprocesses.Textilepre-treatmentistheseries of cleaning operations. All impurities whichcause adverse effect during dyeing and printing isremoved in pre-treatment process.

Pre-treatmentprocesses includedesizing, scouring,and bleaching which make subsequent dyeing and softeningprocesseseasy.Unevendesizing,scouring,and bleaching in the pre-treatment processes might cause drastic deterioration in the qualitiesof processed products, such as uneven dyeing and decrease in fastness. All the processes of this stream are carried out in aqueous state or aqueous medium. The main processesofthissectioninclude: • Singeing • Desizing• Scouring • Bleaching • Mercerizing

FlowchartofPre-treatmentonCottonFabric:

SINGEING : Theverb‘singe’literallymeans‘toburnsuperficially’.Technically, singeing refers to the burning-off ofloose fibres not firmly bound into the yarn and orfabric structure. Singeing is an important part of pre-treatment.Thisistheburningoffofprotrudingfibreends from the surface of the fabric. Singeing is the process of removing the hairs of fabricsor fibers. Insingeingprocess,weuse threetechnique applied to it. At the end of this process, we willfind,thatthefabricsissmootherthanbeforeandthe fabrics wet ability is increased. Technique of Singeing: 1. Gas flame singeing : The fabric passes over

burningflametoburnhairsoffabric.



2. Roller singeing : The fabric passes over the heated rotary copper cylinders.

3. Hot plate singeing : The fabric is passed over the heated plates at speed of 150 to 250 yards/min.

Singeing Process is as follows: • To produce a smooth surface finish on fabrics

madefromstaplefibersfirst thefabricsurfacesare brushed lightly to raise the unwanted fiberends.

• Then the fabrics is singed with or passed over heated copper plates or gas flames. The fibreendsburnoff.

• As soon as the fabric leaves the singeing area, it entersawaterbathordesizingbath.Thisstopsany singeing after glow or sparks that mightdamage the cloth.

Singeing Machine

DESIZING : Desizingistheprocessofremovingthestarchorsizethecoveringthewarpyarnusingenzyme,oxidizingagent , or other chemicals .

Thereare three typesof technique indesizing andfourmethodofdesizingthathasbeenused.

Objectives Of Desizing : Toeliminatethewaterrepellentnatureofsizedcloth.To increase the absorbency. To reduce the consumption of chemicals insubsequent process.

Techniques of Desizing : WaterInsolubleSizes:Removalofstarchbasedsizingagents.Starch Based : Removal of water soluble and insoluble sizes.Mixture of Starch Based And Water Soluble Type : Removalofwatersolublesizes.

DesizingMethods : EnzymaticDesizingOxidativeDesizingAcidSteeping/DesizingRotSteepingDesizingDesizingwithHotcausticsodatreatmentHot washing with detergentRemovalofwatersolublesizesAtmosphericPlasmaDesizing

Enzymatic Desizing : The hydrolysis of starch using enzymes underparticularconcentration,temperatureanddurationiscalledenzymaticdesizing.Enzymatic desizing is themost widely experiencedmethodtodesizethestarch.Advantages :No usage of aggressive chemicals .Nodamagetothefibre.Widevarietyofapplicationprocesses.Disadvantages :Lower additional cleaning effect towards otherimpurities.Noeffectoncertainstarches(eg.tapiocastarch)

Oxidative Desizing : It is used to remove non-starch sizes that don’tdissolve in water.Avarietyofoxidantcanbeappliedafterpaddingthehydrogenperoxide(H2O2)andsteamfor2to3mins.The advantage of oxidative desizing aresupplementary cleaning effect , effectiveness fortapiocastarchesbutoxidizingagentsmaydamagetofibres.

Acid Desizing : Coldsolutionsofdilutesulphuricacidorhydrochloricacidareutilizedtodegradestarchandothersizes.However this method has also disadvantage of bad



affectingthecellulosicfibresincottonfibres.

Caustic Soda Desizing : In this method fabric containing starch would be expanded under the hot solution of sodiumhydroxide(causticsoda).Caustic sodadissolves starchand foam layerwhichcan be separated.Padding the fabric in alkali and stacked under 60 to80degreeCelsiusfor6to12hours,thedesizingprocesscanbefinished.

DesizingofFabric

SCOURING :Scouring is the process by which all the natural and additive impurities such as oil,wax,fat ,hand dustetc. are removed to produce hydrophilic and clean textilematerial.Itisoneofthevitalprocessesofwetprocessing.

Objectives of Scouring : • To make the fabric highly hydrophilic • Toremoveimpuritiessuchasoils,waxes,gum,

husks as nearly possible.• To increase absorbency of fabric or textile

materials without physical and chemical damage• To produce clean material by adding alkali • To make the fabric ready for next process

• To remove non-cellulosic substance in case of cotton.

Scouring process depends on : • Type of Yarn • Colour of Yarn • Cleanliness of Yarn • Twist and Count of Yarn • ConstructionOfFabric• Shade Percentage and Type of Shade of Finished

Product

Chemicals Used In Scouring Process :

Form of Scouring: 1. Yarn Scouring: • Hank form • Package form • Continuoussheetwarpform. 2. Fabric scouring:• Open width form.JiggerPad batchProgressive jig • Ropr form:KierWasher Scouring Process : Batch processSemi-continuousprocessDiscontinuousprocessModern process



Scouring methods of Cotton : Generally,therearetwoprinciplemethodsofcottonscouring :Discontinuous(Kierboilingprocessorwinchdyeingmachine)Continuous(ScouringinJorLbox)

Main parts of Kier Boiler : Cylindrical vesselMixing tankMultitubularheatexchangerPerforatedfalsebottomCirculartube(sprayliquoronfabric)

Process : The working process in J box can be divided into four units : 1. Impragnationbox2. Pre-heater 3. J-box 4. Washing unit

BLEACHING : Bleaching is chemical treatment employed for the removal of natural colouring matter from thesubstrate. The source of natural colour is organic compounds with conjugated double bonds, by doing chemical bleaching the discoloration takesplace by breaking the chromophore , most likely destroying the one or more double bonds with in this conjugated system. The material appears whiter afterthebleaching.



Aims of Bleaching can be described as follows : • Removalofcolouredimpurities• Removal of seed coats • Minimumtenderingoffibre• Technicallyreliableandsimplemodeofoperation• Lowchemicalandenergyconsumption• Increasing the degree of whiteness Bleaching Agent : A bleaching agent is a substance that can whiten or decolorize other substances. Bleaching agentsessentiallydestroychromophores(therebyremovingcolour) via the oxidation or reduction of theseabsorbinggroups.Thusbleachescanbeclassifiedaseitheroxidizingagentsorreducingagents. Oxidative Bleaching : The bleaching agent is chemical reagent which decomposes in alkali solution and produce activeoxygen. The active oxygen is in fact the intrinsicbleaching agent as it will further destroy partly or completelythecolouringmatterpresentinthetextilematerial. Reductive Bleaching :ThebleachingagentwilldestroythecolouringmatterbyreductivereactionofSO2 Bleaching Agents :

Auxiliaries used for bleaching : • Stabilizers• Activators• Wettingagents/detergents• Sequestering agents • Anti-corrosionagents Comparison of Bleaching Efficiency :

pHTemp.Time.WaxAshFluidity%Reflect.(DegreeCelsius)

NaOCL 11 40 2h 0.23 0.05 6.2 83NaClO2 3.8 98 2h 0.21 0.02 6.0 86H2O2 10.5 90 2h 0.09 0.41 5.1 90 Mercerizing :Mercerizing is one of themost important finishingprocesses of cotton with a strong caustic alkalisolution in order to improve the lustre, hand andother properties . It imparts gloss to the fibre,increases its hygroscopicity, strength and improves dyeaffinity.Mercerizingimprovesthereactionswitha varietyof chemicals andelongationof thefibredandalsoimprovesthestabilityofform.Mercerizingprocess consists in treatment of cellulosic materials with concentrated solutions of caustic soda at atemperature of 15 to 18 degree Celsius Purpose of Mercerizing : • To improve the lustre • To improve the strength • To improve the dye uptake and moisture regain

Effect of Mercerization: Improve Lustre.Increase ability to absorb dye.Improvereactionwithaverityofchemicals.Improvestrength/elongation.Improve smoothness.It has been shown that the increase in the lustre occursbecauseofaneffect.Thecottonfibredoconvoiuted.Thecross-sectionalshapechanges.



Different Mercerizing Machinery / Technology : • Knittedfabricmercerizingm/c.• Wovenfabricmercerizingm/c.• Automatic hank yarn mercerizing m/c.

Chainless–paddlesmercerizingm/c.• Clipmercerizingm/c.• Openwidthfabricmercerizingm/cwithcaustic

recovery unit.

Factors Of Mercerizing : Inmercerizingfollowingareimportantparameters:

1. Temperature 2. Tension 3. Time

LustreofYarnAfterMercerizing

MercerizingMachine

Steps in Pre-treatment Process of Cotton and Natural Fibres: Majorstepsinvolvedintextilepre-treatmentare, 1. Singeing 2. Desizing,3. Scouring, 4. Mercerization5. Bleaching. Steps in Pre-treatments for Wool: 1. Raw wool scouring; aqueous and/ or solvent

washing 2. Carbonizing3. Scouring(desizing)4. Fulling/crabbing/thermofixing5. Easy-care treatments 6. Anti-feltinganti-shrinkingtreatments7. Wool Bleaching Steps in Pre-treatment of Silk: To prepare a silk yarn for dyeing and silk fabrics for dyeing and printing, it is necessary to partially orcompletely remove sericin, as well as natural oils and organicimpurities.Dependingonthepercentageofsericinremovedduringscouring(sericinispresentinrawsilk inaratiobetween20%to25%),theend-productisdefinedasunscoured(usedonlyforshirtsandsuits),`souple’ordegummed.1. Degumming



2. Scouring 3. Bleaching Pre-treatmentOfSyntheticTextileMaterials:

Althoughmotsofthesyntheticsdonotneedtobegivenaverystrongpre-treatmenthoweverthepossiblestepsinpre-treatmentofsyntheticsare 1. Desizing2. Heatsetting3. Washing 4. Bleaching if necessary. Conclusion :

References : 1. www.google.com 2. TechnologyofTextileProcessingByProf.V.A.Shenai

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