LATEST TRENDS IN MACHINING - Drishtikona

ILLUSTRATIONSSECTION 11.1 John Wilkenson’s cylinder bore mill1.2 An early lathe1.3 J. R. Brown’ first universal milling machine, 18621.4 A machine shop as it looked in1890.1.5 Charles H. Norton’s cylindrical grinder, 19001.6 Fellows’ gear shaping machine, 1897SECTION 152.162.172.182.192.202.212.222.23Deviations in basic workpieces with design changeTime cycle reduction over yearsNarrowing tolerance over last decadesConventional horizontal front loading chuckerCo-axial horizontal turning centers and sub-spindle turningmachinesAn inverted vertical CNC turning chuckerA unique combination of inverted and conventional spindleorientationA 4-axis CNC lathe with twin turretA center drive CNC lathe for simultaneous machining at bothendsTime analysis of two kinds of machining :single spindle andten-spindle headA transfer line with CNC machining center modulesAgile rotary-index machining setupIntegral spindle motor designConventional spindle drive VS. integral spindle motorA water-cooled spindle housingAn advance linear way design with roller bearingsAdvance ball screw and roller screwA Linear motor drive vs. a ballscrew driveModular concept in machine tool designVarious inaccuracies requiring regular monitoringTomb stone for vertical machining centerA typical quick-change fixtureGantry load/unload system for a machining lineVI

SECTION 33.1Relation between hardness and toughness of different toolmaterials3.2Some latest insert with optimized top form geometry3.3Conventional flute vs. conventional flute3.4Conventional vs. helical drill point3.5Delta, SE, and Hosoi points on carbide drills3.6Oil hole drills following helix of flutes vs. conventional straightoil hole3.7Proprietary 4-facet overlapping radius split point for steel andaluminum3.8Rapid feedback through bus coupling for high speed tapping.3.9Thrilling process- a combination of different processes3.10 Schematic working of Tornado tool3.11 Some typical multi-layer coatings3.12 Hardness of selected coating materials3.13 Equivalent toolholder sizes of HSK and V-taper3.14 HSK toolholders and clamping system3.14 Some alternatives to HSK toolholder for high speed machining3.15 Different styles of toolheads for automatic clamping mechanism3.17 Sandvik Capto- and Kennametal KM cutting heads3.18 Modular tooling system with cutting units and adapters (left),extensions or reducers (center), and clamping units (right)SECTION 44.14.24.34.44.54.6Conventional, High speed, and High velocity machiningCutting force reduction with increasing speedChip formation in metal cuttingKennametal’s cutter body for supersonic speedGang tooled high performance latheSome typical applications of hard turningSECTION 55.15.25.35.45.5Wide and multi- wheel vs. CNC single wheel grindingA CNC multi-surface turret type internal grinderAnother multi-surface grinding set-up for a transmission gearDifferent grinding cyclesSingle point grindingSECTION 66.1Kinematics of Variax machine tool from Giddings & Lewis6.2A balancing system integrated on the machine tool’s spindleVII

ANNEXURE – AA1.1 Hole diagrams of a cylinder blockA1.2 Some variants of head-changersA1.3 Heller’s FST systemA1.4 A MAPAL multi-cut precision boring toolA1.5 A conventional honing tool with honing movement and honing effectA2.1A2.2A2.3A2.4Hole diagrams of a typical cylinder headA tooling to finish machine valve seat and valve guide boresConventional camboring tooling systemA MAPAL fine camboring systemA3.1A3.2A3.3A3.4A3.5A3.6Crankshaft milling methodsInternal crankshaft millingTurn broaching methodsFillet deep rollingShapes of main and pin bearingsDifferent superfinishing techniquesA4.1A4.2A4.3A 3-step centerless grinding of camshaftDifferent forms of cam profilesMulti-station belt grinding machine’s systematic layoutA5.1A5.2Impact fracture splitting fixtureConventional method vs. fracture splittingVIII

v0micronDegree centigrade3-dimensionalAlternating currentAutomated Guided turingCubic boron nitridecubic centimeter per minuteCo-ordinate Measuring MachineComputer Numerical ControlChemical vapor depositionDirect currentDistributed Numerical ControlDepth of cutElectrical discharge machiningFinite element analysisFinite Element AnalysisGeneral ElectricHigh Efficiency Deep GrindingHuman Machine Interfacehigh speed machininghigh velocity machiningInput/OutputInside diameterInternational Standard Organisationkilogramkilogram force per millimeterkilowattslength/diameterliter per hourLiter per minutelaser-assisted machiningmeters per minutemeters per secondmeter per secondmeter per second2meter/ second2Massachussetts Institute of Technologymillimetermillimeter per revolutionIX

RpmsecSGSGVTAMTTSVVMCmillisecondmillisecondMedium temperature chemical vapor depositionNewtonNumerical ControlNon-Uniform Rational B-SplinesOutside DiameterOriginal Equipment ManufacturerOpen Modular Architecture ControllerPlasma assisted physical vapor depositionPersonal ComputerPolycrystalline diamondProgrammable Logic ControlPhysical vapor depositionAverage roughnessrockwell hardnessRail Guided Vehiclerevolutions per minuteSecondsSilica GelSelf Guided Vehicletemperature- assisted machiningTuned tooling systemvoltsVertical machining centerX

MACHINING - LATEST TRENDSSection 1MACHINE TOOLS - HistoryEarly machine tools, Machine tools of pre-auto era, Grinding wheels anduniversal grinding machines, Gear manufacturing machines, Cutting toolmaterials, Some production machine tools, Evolution of new machine tools,Numerical control and computerized machining.

Latest Trends in MachiningSection 1MACHINE TOOLS - HistoryEarly machine tools, machine tools of pre-auto era, grinding wheels and universal grinding machines,gear manufacturing machines, cutting tool materials, some production machine tools, evolution ofnew machine tools, numerical control and computerized machining.EARLY MACHINE TOOLSThe hand tool became a machine tool, when man first made a rigid, ground-based frame supportingbearings in which either a tool or a work-piece could be rotated on a spindle. An irregular piece of woodor metal fixed upon the spindle could be rotated and made to a perfectly circular form of any diameter bya hand-held tool. Gradually raw material got switched over to cast iron and then steel from wood that wasused earlier. Crucible steel was produced in 1746 in England by Benjamin Huntsman, a maker of clocksand watches. The rolling machinery for working iron originated in Sweden during the 17th century and wasbrought to England soon afterwards. Besson constructed screw cutting lathe in 1579. The machine wascapable of cutting screws of different pitches by using pulleys of different sizes, either right or left hand withcrossed belts. The necessity of boring of cannons resulted in the first heavy metal-cutting technology,which could later be transferred to the boring of cylinders for the reciprocating steam engine after itsdiscovery by James Watt. In 1713, a Swiss named Maritz invented a vertical boring mill accurate enoughto bore gun barrels from a solid casting. In 1758, a remarkable horizontal boring mill was produced by aDutch gun founder, Peter Verbruggen, working with a Swiss engineer named Jacob Ziegler. Boring cylindersand turning pistons for early steam engines presented new problems. A piston during the beginnings of theage of steam engine was considered a good fit if it came within one eighth of an inch of fitting the cylinderbore everywhere. Watt’s first engine called for an 18-inch cylinder, but it took five years to successfullyproduce the cylinder by John Wilkenson (Fig 1.1). In1776, Watt wrote about this boring mill- “Mr. Wilkensonhas improved the art of boring cylinders sothat I promise upon a 72-inch cylinder beingnot further from absolute truth than thethickness of a thin sixpence in the worst part.”Fig.1.1 John Wilkenson’s cylinder boring mill, 17762By 1792, the making of screws with latheshad progressed to the factory stage.Sometime after 1800, Maudslay introducedthe all-metal lathe with lead screw, changewheels and compound slide rest. In 1805,he came out with his micrometer- “LordChancellor” to settle all disputes overaccuracy. In 1818,the copying lathe that wasdesigned by Thomas Blanchard came intogeneral use for turning the stocks of riflesand pistols.

MACHINING - LATEST TRENDSMACHINE TOOLS OF PRE-AUTO ERASThe growth of the market of arms, bicycles and sewing machines led to a rapid expansion of machinetool industry. From lathes, in 1845 Stephen Fitch of Middlefield (Connecticut) designed and built theworld’s first turret lathe. It had long cylindrical turret, which revolved on a horizontal axis and carriedeight tools mounted on spindles, each of which could be advanced as required. The turret carriagewas advanced and the feed applied by a three-armed capstan. Thus eight successive operationscould be rapidly performed without stopping the machine to change tools. The logical development ofthe turret lathe was the fully automatic screw machine. In 1871, Edward G. Parkhurst patented colletchuck and closing mechanism for his screw machine to help it make automatic. The first completelyautomatic turret lathe was designed and built by Christopher Miner Spencer.Fig 1.2 An early Lathe, 1825Fig. 1.3 J.R. Brown’s first universal milling machine, 1862Joshep R. Brown of the firm of Brown & Sharpe designed and built the first truly universal millingmachine that provided solution to the twist drill manufacturing, Fig.1.3. It normally cut right-handspirals, but Brown arranged the change gears’ train so that the machine could cut a left-hand spiral ifdesired. Brown is credited with many machines. He invented and built an automatic linear dividingengine for graduating rules and from it came steel rules, the vernier calipers, hand micrometers andprecision gauges that provided solution for quality production. Brown also devised an improvedform-milling cutter for gear cutting, and in 1855 he built a gear-cutting machine using a formed millingcutter for producing involute teeth. Brown’s cutter had segmental teeth, each of which in cross sectionconformed exactly to the contour of the tooth form required. The face of each tooth was ground forresharpening.3

Latest Trends in MachiningGRINDING WHEELS AND UNIVERSAL GRINDING MACHINESIn 1872, silicate wheels began being produced. A year later, a potter named Sven Pulson made a betterwheel with a mixture of emery and clay, and in 1877, F. B. Norton patented the process. And again, it wasJoseph Brown and his staff who removed the defects in existing grinders and came up with an improved“Universal Grinding Machine” in 1876. On this machine, the workpiece travelled past the wheel instead ofthe wheel traversing the workpiece. The head and tailstock units were mounted on a traversing table.Adjustment of trips at the front of the machine automatically controlled the table travel. For taper grinding,slides at the upper table could be angled by means of an adjusting screw. The guide-ways wereprotected from abrasive dust, and a water coolant was used. This grinder was the parent of allsubsequent precision grinding machines.Henry Leland, who had worked as foreman in the Brown & Sharpe shop, and later became thePresident of the Cadillac Motor Company wrote later about the grinding machine of Brown: “WhatI consider Mr. Brown’s greatest achievement was the Universal Grinding Machine. In developing anddesigning this machine he stepped out on entirely new ground and developed a machine which has enabledus to harden our work first and then grind it with the utmost accuracy.” These new and better grindingmachines facilitated the production of precision gauges and measuring instruments as well as accuratehardened steel cutting tools such as drills, taps, reamers and milling cutters. A machine shop looked likeone shown in Fig. 1.4.Fig. 1.4 A machine shop as it looked in 1890By 1891, an American, Edward G. Acheson, produced a synthetic abrasive of controlled quality byfusing a mixture of carbon and clay in an electric arc furnace. Crystals (silicon carbide) producedwere of a hardness then surpassed only by diamonds. Acheson called his synthetic materialcarborundum. Another American, Charles B. Jacobs, in 1897 produced another synthetic abrasiveby fusing aluminum oxide (bauxite) with small quantities of coke and iron borings and called it alundum.Charles H. Norton secured the rights to this product and became the man responsible for the productiongrinding machine (Fig. 1.5) and better abrasive wheels. First, Norton invented a machine for dynamicallybalancing grinding wheels to make them perfectly balanced. Norton also improved the processes of4

MACHINING - LATEST TRENDSdressing and truing the grinding wheel.Norton then redesigned the Brown &Sharpe Universal Grinding Machineimproving the bearings. By building aheavier, stronger grinding machine,and by using much wider wheels,Norton conceived the technique ofplunge grinding. This new grinder wasnot only applicable to plain grindingbut also made possible form grindingby the use of wheels shaped to thecontours desired. In 1903, CharlesNorton produced a crankshaft journalgrinding machine. A wide wheel wascapable of grinding a journal toFig.1.5 Charles H. Norton’s cylindrical grinder, 1900finished diameter in a single plunge cut.The cycle time of the operation wasreduced to 15 minutes, which previously took five hours of turning, filing and polishing. Henry Fordordered 35 of these machines for his new Model T production plant. Norton is also credited withincorporating its own micrometer in the grinding machine to reduce the workpiece by precisely the desiredamount-say 0.00025 of an inch.GEAR MANUFACTURING MACHINESGear mathematics developed through several centuries without having much practical effect on the waymechanics actually cut gears. Edward Sang produced a treatise in Edinburgh in 1852 that ultimately laidthe groundwork for the generating type of gear cutting.By 1867, William Sellers had exhibited a milling machine gear cutter in which the sequence of automaticmotions was so controlled by stops that the cutter could not advance unless and until the gear blank hadbeen correctly indexed for the next tooth. When all theteeth had been cut, the machine stopped automatically.Then the molding generating cutter was devised. Insteadof indexing the gear blank, the cutter and the gear blankwere given synchronous motions, so that the two werecorrectly meshed together. In 1880, Ambrose Swaseydeveloped one machine that operated on the “describinggenerating” method for Pratt & Whitney.Fig.1.6 Fellow’s gear shaping machine, 1897In 1884, Huge Bilgram of Philadelphia came out with agear shaper working on the molding generating principleto make small bevel gears for the chainless bicycle. In 1898,James E. Gleason invented a machine that generated bevelgears by using a rotary cutter and a combination of motionsrotary, swinging of the cutter carrier, and lateral. Gleason’s5

Latest Trends in Machiningmachine was fully automatic that provided the manufacturing solution to bevel gearing used in differentialdrive. The most advanced gear cutting machine of the molding generating type was Fellows’ gear shaperof 1897 (Fig.1.6) that was invented just in time to produce gears that would be needed for automobiles.Edwin Fellows designed the teeth of his cutter in such a way that one cutter could be used to makegears of any diameter provided the pitch was the same. The only qualification was that its teeth mustbe of the specific helix angle the cutter was designed to produce. To make hardened cutters for hisshaping machine, Fellows created another machine.Hobbing was the last to come. The first attempt to cut gears by using a worm with teeth on it wasmade perhaps by Ramsden in England in 1766. In 1835, Josheph Whitworth produced a machinethat would hob spiral gears. But the hobber did not become practical until Pfauter, working in Germanybuilt a machine with a cutter axis that was not at 900 to the gear axis. There were many problems indeveloping the process, but by 1909, there were at least 24 firms manufacturing gear-hobbing machines.CUTTING TOOL MATERIALSRobert Mushet first produced the improved tool steel in 1868 in England. That proved to be far superiorto carbon steel used for tool earlier. With this new tool steel, John Fowler & Co. of Leeds turned ironshafts in the lathe at the rate of 75 feet per minute, and when machining steel wheels in their boring mill theycould make roughing cuts 1/2 inch deep. Frederick W. Taylor (1856-1915) is credited with the revolutionaryresearch on cutting tool materials. In 1900 Paris Exhibition, Taylor amazed the visitors with chips peelingaway at blue heat from an American lathe while the tip of the cutting tool was red hot.Taylor was the first to carry out methodical experiments with cutting tools that lasted over 26 years andcost over 200,000 - a large R&D expenditure for the time. Mushet’s steel contained 7% tungsten, 2%carbon and 2.5% manganese. Taylor with Maunsel White in the Bethlehem Steel Works discovered thatchromium was an effective substitute for manganese used to give the steel self-hardening character, whilegiving better performance. They then increased both the chromium and tungsten (the tungsten to 14%)and added silicon, which was found to increase shock resistance. They found that if a tool is heated to20000 F (just below fusion point) instead of 15500 F, cutting speed would be increased to 80 to 90 feetper minute (as against 30 feet per minute in earlier case) before failure occurred in the same time. Additionof 0.7% vanadium produced further improvement.But with this radically improved new cutting material, all the existing machine tools were to becomeobsolete. As proof of this, the Ludwig Loewe Company, A.G., a reputable German machine-tool builder,tested the new steel tools in one of their lathes and drilling machines, running them so as to give maximumperformance. In four weeks both machines were reduced to junk! Main drive spindles were twisted;thrust bearings were destroyed; keys fell out of gears and shafts; cast gears were broken and the lubricationsystems proved inadequate. Taylor had not only given the machine designer a new tool but also thespecifications by which its performance could be translated into terms of tool pressure, speed and feed.Cemented tungsten carbide was first produced by Krupps of Essen, Germany in 1926. After the LeipzigFair in 1928, where the carbide tool was demonstrated under working conditions, it was an instantsensation. The introduction of tungsten carbide tools resulted in second machine tool revolution. this newcutting tool material also made po

Manufacturing technology and management techniques, more so the machining concepts have undergone a sea change in last four decades. This book is an attempt to present to the practicing engineers, managers, and research scholars in engineering industry and institutions the latest trends in machining and a glimpse of the future of machining.