Classification, Selection and application of Machine tools

Classification, Selection and application of Machine toolsModule 01 1Production Process - II1Lathe Machines3Production Process - II

3Lathe MachineLathe is a machine, which removes the metal from a piece of work to the required shape &size using turning operations

4Production Process - II

4Lathe OperationsLathes are the oldest machine toolsLathe ComponentsBed: supports all major componentsCarriage: slides along the ways and consists of the cross-slide, tool post, apronHeadstock Holds the jaws for the work piece, supplies power to the jaws and has various drive speedsTailstock supports the other end of the workpieceFeed Rod and Lead Screw Feed rod is powered by a set of gears from the headstock

5Production Process - II5Lathe SpecificationsA lathe is specified by its Swing maximum diameter of the workpieceDistance from headstock and tailstock centersLength of the bedLathes are available in a variety of styles and types of construction powerTypes of lathesBench lathe: Placed on a benchLow powerHand feed operatedToolroom lathes: High precisionEngine lathesAvailable in a wide variety of sizesUsed for a variety of turning operations

6Production Process - II6Types of Lathe MachinesAutomatic LatheA lathe in which the work piece is automatically fed and removed without use of an operator. Cutting operations are automatically controlled by a sequencer of some form.Turret LatheA lathe which has multiple tools mounted on turret either attached to the tailstock or the cross-slide, which allows for quick changes in tooling and cutting operations. Types Ram type and Saddle typeComputer Controlled LatheA highly automated lathe, where both cutting, loading, tool changing, and part unloading are automatically controlled by computer coding.

7Production Process - II7Lathe OperationsTurning: produce straight, conical, curved, or grooved work pieces Facing: to produce a flat surface at the end of the part or for making face grooves.Boring: to enlarge a hole or cylindrical cavity made by a previous process or to produce circular internal grooves.Drilling: to produce a hole by fixing a drill in the tailstock Threading: to produce external or internal threadsKnurling: to produce a regularly shaped roughness on cylindrical surfaces

8Production Process - II876Production Process - II76Types of chucksThree Jaw chuckFor holding cylindrical stock centered.For facing/center drilling the end of your aluminum stock

Four Jaw chuckThis is independent chuck generally has four jaws , which are adjusted individually on the chuck face by means of adjusting screws

10Production Process - II

10Type of ChucksCollet chuck is used to hold small workpieces

Magnetic chucks can be used to hold thin jobs11Production Process - II

11Work Holding Devices12Production Process - II

12Mandrels13Production Process - II

13Lathe Tool GeometryRake anglecontrols direction of chip flowStrength of the toolSide rake angle Bake rake angle controls direction of chip flowCutting edges affects surface finish and tool-tip strengthNose radius affects surface finishMaterial Removal Rate (MRR) is the volume of material removed per unit time

14Production Process - II14Milling Machine

15Production Process - II Definition Components Types Cutting Tools Operations Factors affecting operations Classification of Milling Forces acting during Milling

15IntroductionMilling is the basic process of progressive chip removal to produce a surface.Mill cutters have single or multiple teeth that rotate about an axis, removing material.Often the desired surface in obtained in a single pass of cutter or workpiece with very good surface finish.Milling is particularly well suited and widely used for mass production.More flat surfaces are produced by milling than by any other machining processes.

16Production Process - II16Milling MachinesUsed to produce one or more machined surfaces accurately on workpieceOne or more rotary milling cuttersWorkpiece held on work table or holding device and brought into contact with cutterVertical milling machine most commonHorizontal milling machine handles operations normally performed by other toolsDeveloped in 1860'sMilling process may be vertical, horizontal, angular, or helicalCan be used for milling, drilling, boring, and reamingCan machine in one, two, or three planesX, Y, Z

17Production Process - II17Mill ConstructionMost mills consist of column-and-knee designsThe column is mounted on a base and the spindle mounted on a part extending from the column.The knee which is attached to be base, has vertical movement.The workpiece is mounted on a table with longitudinal movement, and the table is mounted on a saddle with transverse movement, which in turn is set on the knee.Most common of this type mill is the Ram mill which has a motor and pulley system mounted on the top of the column.

18Production Process - II18Horizontal Milling Machine

19Production Process - II19Vertical Milling Machine

20Production Process - II20Milling Machine Cutting Tools

21Production Process - II21Fundamental ClassificationMilling is classified in two categories:Peripheral milling (also called Slab milling) - the surface is generated by teeth located on the periphery of the cutter body. The surface is parallel with the axis of rotation of the cutter. End milling: also called face milling, the surface generated is at a right angle to the cutter axis. Material is removed by the outer edge of the teeth and the face portion providing finishing action.

22Production Process - II22Types of OperationsFace millingEnd millingSlab MillingKeyway cuttingDovetail cuttingT-slot and circular slot cuttingGear cuttingDrillingBoringJig boring

Straddle MillingGang MillingForm Milling Profile MillingCam MillingThread Milling23Production Process - II

23Factors Affecting the Efficiency of a Milling OperationCutting speedToo slow, time wastedToo fast, time lost in replacing/regrinding cuttersFeedToo slow, time wasted and cutter chatterToo fast, cutter teeth can be brokenDepth of cutSeveral shallow cuts wastes time

24Production Process - II24Milling Machine SelectionWhen purchasing or using a milling machine, consider the following issues:Spindle orientation and rpmMachine capability (accuracy and precision)Machine capacity (size of workpieces)Horsepower available at spindle (usually 70% of machine horsepower)Automatic tool changing

25Production Process - II25Up Milling (Convnetional Milling) Vs Down Milling26Production Process - II

26Up Milling or Conventional MillingThe cutter rotates against the direction of feed of the workpeice.The Chip is very thin at the beginning and increased along its length.The cutter tends to push the work along and lift it upwards from the table. The action tends to loosen the workpiece from the fixture.In the up milling, chips can be carried into the newly machined surface, causing the surface finish to be poorer than in down milling27Production Process - II27Down MillingThe cutter rotates in the same direction as the direction of feedAdvantage:The work piece is pulled into the cutter, eliminating any effects from looseness of the work table feed screw.There is less tendency for the machined surface to show toothmarks, and the cutting process is smoother, with less chatter.The cutting force tends to hold the workpiece against the machine table, permitting lower clamping force.Disadvantage:The maximum chip thickness is at the point of tooth contact with the work piece. Dulling the teeth more quickly, especially for workpiece with a hard surface.

28Production Process - II28Milling Surface ForcesMilling is an interrupted cutting process .Impact loadingCyclic heatingCycle cutting forcesAs show in the figure below, the cutting force, Fc, builds rapidly as the tool enters the work at A and progresses to B, peaks as the blade crosses the direction of feed at C, decreases to D, and then drops to zero abruptly upon exit.

29Production Process - II

29Drilling Machines31Production Process - IIDefinitionTypes of drilling machineParts of drilling machineOperationsDrill tool

31Drilling Machine DefinitionPrimarily used for creating holes in workpieces, quickly and at low cost.The hole is generated by the rotating edge of the cutting tool know as drill.As the machine exerts vertical pressure to create a hole, it is called as Drill Press.First drills created be Egyptians in 1200 BC.32Production Process - II

32Drilling Machine TypesPortable drilling machineSensitive drilling machineBench mountingFloor mountingUpright drilling machineRound column sectionBox column sectionRadial drilling machinePlain Semi-universalUniversalGang drilling machineMultiple spindle drilling machineAutomatic drilling machineDeep hole drilling machineVertical Horizontal33Production Process - II

33Drilling Machine PartsBase ColumnTableDrill HeadSpindle drive and feed mechanismWork holding devicesT-bolt and clampsDrill press viceV-blockAngle plateTool holding devicesSleeveChucksSockets34Production Process - II

34Drilling Machine OperationsDrillingReamingBoringCounter-boringCounter-sinkingSpot FacingTappingLappingGrindingTrepanning

35Production Process - II

35Drill ToolA drill is a fluted cutting tool used to create or enlarge a hole in a solid materialTypes of Drill toolFlat or spade drillStraight fluted drillTwo-lip twist drillTaper shank core drillOil tube drillCenter drillIn metric system: 0.2 mm to 100 mm diametersIn British system:Numbers: 1 (0.228 inch) to 80 (0.0135 inch) by steps of 0.002 inchLetters: A (0.234 inch) to Z (0.413 inch) by steps of 0.010 inchFractional: 1/64 inch to 5 inch in steps of 1/64 inch36Production Process - II36Drill Tool Types37Production Process - II

Grinding Machine

39Production Process - II

39Grinding MachineDefinition:It is a metal cutting operation performed by means of a rotating abrasive wheel that acts as a cutting tool.It is used to finish workpieces which must show a high surface quality, accuracy of shape and dimension.It usually removes about 0.25 to 0.50 mm of metal in most operations and the accuracy in dimensions is in the order of 0.000025 mm.Kinds of grinding:RoughPrecision

40Production Process - II40Rough & Precision GrindingRough GrindingFloor stand and bench grindersPortable and flexible shaft grindersSwing frame grindersAbrasive belt grindersPrecision GrindingCylindrical grindersInternal grindersSurface grindersTool and cutter grindersSpecial grinding machines41Production Process - II41Classification of GrindingExternal cylindrical grindingInternal cylindrical grindingSurface grindingForm grinding

According to use of coolantWet GrindingDry Grinding

Snagging: Type of grinding where considerable amount of metal is removed without regard to the accuracy of the finished surface, e.g. Removing excess metal on welds, risers on castings, imperfections on steel billets, etc.42Production Process - II42Parts of the Grinding WheelAbrasivesNatural: Sandstone/solid quartz, emery(Aluminum Oxide 55 to 65%), corundum(Aluminum Oxide 75 to 95%) and diamondArtificial: Silicone Carbide (SiC)Aluminum Oxide (Al2O3)Bonds and Bonding ProcessesVitrified bonding processSilicate bonding processShellac bonding processResinoid bonding processRubber bonding processOxy-chloride bonding process

43Production Process - II43Broach Tool

45Production Process - II45Broach Tool46Production Process - II

46Broach Tool

47Production Process - II47Broach ToolDefinition: a broach is multi-point cutting tool consisting of a bar having a surface containing a series of cutting teeth or edges, which gradually increase in size from the starting end to the rear end.Application: used for cutting serrations, splines, gun rifling and keyways. Types: Push TypePull TypeClassification according to machining:Internal or hole broachingSurface broaching48Production Process - II48Broaching MachineDefinition: The machine consists of a work holding fixture, a broach tool, a drive mechanism and a suitable supporting frame.

TypesHorizontalVertical Surface Continuous

Broach Material: 18-4-1 Tungsten-chromium-vanadium steelCarbide steels49Production Process - II49Advantages and LimitationsAdvantagesRate of production is very high.Little skill is required to perform a broaching operationHigh accuracy and excellent surface finish is possible.Both roughing and finishing cuts are completed in one pass of the tool.Lubrication process is simpler.LimitationsHigh tool cost.Very large workpieces cannot be broachedThe surfaces to be broached should not have obstructions.Parts must be capable of being rigidly clamped and withstand high forces occurring during cutting process.50Production Process - II50Lapping Machines52Production Process - II

52Lapping MachinesLapping is an abrading process that is used to produce:Geometrically true surfacesCorrect minor surface imperfectionsImprove dimensional accuracyProvide very close fit between 2 contact surfacesThe lapping machine consists of:Abrasive powders Emery, corundum, iron oxide, chromium oxide, etc. mixed with oil or special pastes Laps shoes or quills which are rubbed against the workpieces made of soft CI, brass, copper, lead or soft steelFeed Mechanism By hand or machine53Production Process - II53Lapping MachinesProcedureIn this machine the lap is charged (embedded) with abrasive material and rubbed against the workpiece. When the lap is once charged, it should be used without applying more abrasive until it ceases to cut.Laps motion is usually rotary or reciprocating.TypesHand or ManualMachine or AutomaticFinishing Thickness0.005 to 0.01 mm54Production Process - II54Lapping Machines Types and ApplicationsVertical Axis Lapping MachinesFlat or round surfacesCenter-less Lapping MachinePiston PinsBearing racesCupsValve tappetsShaftsAbrasive Belt Lapping MachinesBearingsCams55Production Process - II55Honing Machines

56Production Process - II56Honing Machines57Production Process - IIHoning is a grinding or abrading process, done mostly for finishing round holes.It is done by means of bonded abrasive stones called hones.The cut is between 0.25 to 3 mm.It is used to correct out roundness imperfections, taper, tool marks and axial distortions.

57Honing MachinesTool Materials Common abrasive and bonding materials impregnated with sulphur, resin or wax to improve cutting action.Honed materials plastics, silver, aluminum, brass, CI, hard steel and cemented carbides.Manual and automaticProcedureWorkpiece is held firmly and tool is rotated inside the hole to be finished.Honing stones are attached to holders in regular spaced intervals.Coolants are used to keep temperatures low and flush away chips.

58Production Process - II58Honing MachinesA honing machine rotates and reciprocates the hone inside holes being finished.TypesVerticalHorizontalHoning can be done on lathe, drill press etc., but better results are obtained by honing machines for production work.Applications:Gun barrelsLarge boresCar crankshaft journals59Production Process - II59Shaping Machines61Production Process - II

61Shaping MachinesDefinition:The shaper is a reciprocating type of machine tool.Surfaces(primarily flat) are produced, which may be horizontal, vertical or inclined.1836 James NasmythTypes:According to type of mechanism for giving reciprocating motion to the ramCrank typeGeared typeHydraulic type

62Production Process - II62Shaping MachinesTypesAccording to position and travel of ramHorizontal typeVertical typeTravelling head typeAccording to type of design of the tableStandard shaperUniversal ShaperAccording to the type of cutting strokePush typeDraw type

63Production Process - II63Shaping MachineParts of a Shaper:BaseColumnCross-railSaddleTableRamTool-headShaper Size:Stroke Length 175 to 900 mmDrive type belt drive or individual motor drivePower inputFloor space required, weight, amount of feed, etc.

64Production Process - II64Shaping MachineShaper OperationsMachining horizontal surfaceMachining vertical surfaceMachining angular surfaceCutting slots, grooves and keywaysMachining irregular surfacesMachining splines or cutting gearsShaper Tools:Roughing toolFinishing toolSide facing toolDovetail cutting toolParting or slotting tool

65Production Process - II65Shaper MachineShaper Mechanism:Crank and slotted link mechanismWhitworth quick return mechanismHydraulic shaper mechanismWork Holding Devices:ViseParallelsHold DownsT-bolts and clampsStop pinsToe dogsAngle plateV-blockShaper Centers66Production Process - II66Slotting Machines

67Production Process - II67Slotting Machines68Production Process - II

68Slotting MachineIt is a reciprocating type of cutting machine similar to the shaper and planer machines. The major difference between a shaper and a slotting machine is that, in the slotter the ram holding the tool reciprocates in a vertical axis whereas in the shaper, the ram reciprocates in the horizontal axis.A vertical shaper and a slotter are almost similar.Only difference is that in the vertical shaper, the ram may reciprocate at an angle to the horizontal table.Applications Cutting grooves, keyways and slots.Developed in 1800 by Brunel.

69Production Process - II69Slotting MachineTypesPuncher SlotterPrecision SlotterSlotter Size specified in terms of length of stroke of ram (80-900 mm)Slotting Machine Parts:BaseColumnSaddleCross-slideRotating TableRam and Tool head assemblyRam Drive MechanismFeed Mechanism70Production Process - II70Slotting MachineRam Drive Mechanism TypesWhitworth quick return mechanismVariable speed reversible motor drive mechanismHydraulic drive mechanismSlotter Operations:Machining flat surfacesMachining cylindrical surfacesMachining irregular surfaces and cam machiningMachining slots, keyways and groovesSlotter Tools: Force is acting along the length of the tool.71Production Process - II71Planing Machines

72Production Process - II72Planing Machines73Production Process - IIThe planer is used to produce plane and flat surfaces by a single point cutting tool.It is a very large machine, capable of machining heavy and large workpieces.Here the work which is supported on a table is reciprocated instead of the tool.Developed in 1817 by Richard Roberts

73Planing MachinesTypesDouble housing planerOpen Side PlanerPit PlanerEdge or Plate planerDivided table planerSize: planer is specified by the size of the largest rectangular solid that can reciprocate under the tool. Sizes range from 750 mm to 3000 mm planerPlaning Machine Parts: Bed, Table or plates, Housing or Column or up-right, Cross-rail, Tool head and Driving and feed mechanism74Production Process - II74Planing MachinesPlaner MechanismTable Drive MechanismOpen and cross-belt driveReversible motor driveHydraulic driveFeeding mechanismFriction discElectrical drivePlaner Operations:Planing flat horizontal operationsPlaning Vertical surfacesPlaning at an angle and machining dovetailsPlaning curved surfacesPlaning slots and grooves75Production Process - II75Gear Milling

77Production Process - II77Gear MillingDefinition: It is a simple, economical and flexible method of gear making.Spur Gear, helical, bevel gears and racks can be produced by this method.The quality of gear produced is not high, since the operation of the indexing device is not precise.Hence end milling cutter method is seldom used and only for small quantity production.It is used for producing gears that have low operation speed and deviation in angular motion is not the major concernGear milling gives much better quality results, when form milling cutters are used.78Production Process - II78Gear Hobbing

79Production Process - II79Gear Hobbing

80Production Process - II80Gear Hobbing

81Production Process - II81Gear HobbingIt is a process of generating gear tooth by means of a rotating cutter called a hob.Gear Hobbing is a continuous cutting operationCutting Procedure:The hob and gear blank are connected by means of change gearsInitially the hob is clear of the blankThen it is made to move inwards to obtain required teeth depthThen the hob is fed in a direction parallel with the axis of rotation of the gear.As the gear blank rotates, the teeth are generatedAnd the feed of the hob across the face of the blank extends the teeth to the desired tooth face widthOne rotation of the blank completes the cutting unless the blank has a wide face.

82Production Process - II82Gear HobbingTypes of Hobbing:Axial RadialTangentialAdvantages of Gear Hobbing:Method is versatile, used for production of spur, helical and worm gearsRapid, economical and highly productiveProduces accurate gearsCutter is universalDisadvantagesCannot generate internal gearsNeeds more space for hob approach

83Production Process - II83Hob DesignOutside Diameter, Hole size and number of flutes

Hob Addendum = 1.25 x module (m)Hob Dedendum = 1.25 x module (m)

84Production Process - IIModule mmGeneral purpose solid hobsO.D.Hole SizeNo. of Flutes1 to 1.255022122 to 2.757027103 to 3.58032103.75 to 4.5903295 to 5.510032984Hob DesignDepth of Hob tooth = Addendum + Dedendum = 2.5 x mCorner Radius of hob tooth = (0.25 to 0.3) mRoot Radius of hob tooth = (0.2 to 0.3) mHob Length = 44 mm for m = 1mm = 200 mm for m = 11 mmRake Angle is 0Relief Angle at tooth tip is 9 to 12.85Production Process - II85Gear Shaping

86Production Process - II86Gear Shaping

87Production Process - II87Gear ShapingIn Gear shapers, the cutter reciprocates rapidly.The teeth are cut by the reciprocating motion of the cutterRack type cutter: Cutter needs to be indexed to complete cutting.Rotary pinion type cutter: More productive and more commonHere gear is produced both by the reciprocating motion of the cutter and the rotational motion of both the cutter and the gear blank.The cutter reciprocates at about 100 strokes per minuteBoth Straight and Helical tooth gears can be cut on gear shapers

88Production Process - II88Gear ShapingAdvantages:One Cutter for cutting all spur gears of same module irrespective of the number of teeth.Needs only small clearance recessParticularly suitable for cutting cluster gearsVersatile, can cut almost every type of gearGears produced are very accurateSuitable for medium and batch productionDisadvantages:Cutting takes place during only one half of the strokeSeparate helical guide is required for cutting helical gear89Production Process - II8990Production Process - IIFeatureGear HobbingGear ShapingAccuracyBetter w.r.t tooth spacing and runoutBetter w.r.t tooth formSurface FinishProduces radial flats based on feed rate of hob across workProduces a series of straight lines parallel to axis of gearVersatilityCannot be used for internal gearCan be used for internal gearLimitationHob dia. Limits gear with shoulderGood for helical gear productionRequires very little clearance.Needs guide for helical gearsProduction RateStacking can increase production ratesHigh speed stroking can increase production rates90Gear Shaving

91Production Process - II

91Gear ShavingIn this method a very hard gear is used to remove fine chips from the gear tooth profileIt is usually done for untreated gears.Types:Rotary Type: A rotary shaving cutter is run in a mesh with the gear for finishing purposes. The cutter has a number of peripheral gashes, serrations or grooves to form a series of cutting edges.Rack Type: The cutter is in the form of a rack. During the operation, the gear is rolled in mesh with the cutter. The cutter is reciprocated and at the end of each stroke is fed into the gear.

92Production Process - II92Gear Grinding

93Production Process - II

93Gear GrindingIt is one of the most accurate method of gear finishing.Grindinginvolves the removal of unwanted materials through an abrasionprocess.Types of operationForm grindingHere the grinding wheel is dressed to the form of an involuteIt is similar to the formed cutter used in milling.Generation grindingHere the gear is rolled past the revolving wheelThe finishing is done by the flat face of the wheelDrawbacks: Low production capacity, expensive wheels and skilled labor94Production Process - II94ProblemsCutting SpeedFeed Depth of CutMachining Time95Production Process - II95