M processes notes_8 (1)

Abrasive MachiningAbrasive Machiningand Finishingand Finishing

ManufacturingManufacturingProcessesProcesses

OutlineOutline

UnitsUnitsAbrasivesAbrasivesGrindingGrinding

Grinding WheelsGrinding WheelsGrinding ProcessGrinding Process

Coated AbrasivesCoated AbrasivesBelt GrindingBelt Grinding

HoningHoningLappingLappingOther Finishing OperationsOther Finishing OperationsDeburring ProcessesDeburring Processes

Abrasive MachiningAbrasive Machining


Why a smooth surface?Why a smooth surface?


Why a smooth surface?Why a smooth surface?

Reduction in FrictionReduction in FrictionHeat - BearingsHeat - Bearings

Reduction in WearReduction in WearBushings/BearingsBushings/Bearings

AppearanceAppearanceCar Body, FurnitureCar Body, Furniture

ClearanceClearanceDisk HeadDisk Head

SharpnessSharpnessCutting ToolsCutting Tools


How do we get a smooth How do we get a smooth surface?surface?


How do we get a smooth How do we get a smooth surface?surface?

Remove MaterialRemove MaterialAbrasive MachiningAbrasive Machining

FlattenFlattenBurnishingBurnishing

Fill in VoidsFill in VoidsAdd materialAdd material

PaintPaintFinishFinishWaxWax

UnitsUnits

Meter (m)Meter (m)Centimeter (cm)Centimeter (cm) == .01 m.01 mMillimeter (mm)Millimeter (mm) == .001 m.001 mMicrometer (µm)Micrometer (µm) == 1010-6-6 m mNanometer (nm)Nanometer (nm) == 1010-9-9 m mAngstrom (Ǻ)Angstrom (Ǻ) == 1010-10-10

mm

UnitsUnits

12872000 m meter

10-2 centimeter

10-6 micrometer

10-9 nanometer

10-10 angstrom

AbrasivesAbrasives

AbrasivesAbrasivesSmall, hard nonmetallic Small, hard nonmetallic particles with sharp edges and particles with sharp edges and irregular shapesirregular shapes

Can remove small amounts of Can remove small amounts of material, producing tiny chipsmaterial, producing tiny chips

Abrasive processes can Abrasive processes can produce fine surface finishes produce fine surface finishes and accurate dimensional and accurate dimensional tolerancestolerances

Types ofTypes ofAbrasivesAbrasives

Conventional AbrasivesConventional Abrasivesa. Aluminum oxide (Ala. Aluminum oxide (Al22OO33))

b. Silicon carbide (SiC)b. Silicon carbide (SiC)

SuperabrasivesSuperabrasivesc. Cubic Boron Nitride (cBN)c. Cubic Boron Nitride (cBN)d. Diamondd. Diamond

Abrasives are harder than Abrasives are harder than conventional tool materialsconventional tool materials

Abrasive FactorsAbrasive Factors

- Grain sizeGrain size- Grain shapeGrain shape- HardnessHardness- Friability (tendency to fracture)Friability (tendency to fracture)

Abrasive Hardness and Abrasive Hardness and Thermal ConductivityThermal Conductivity

GrindingGrinding

Example of aExample of aGrinding MachineGrinding Machine

Types of GrindingTypes of Grinding

- Surface GrindingSurface Grinding- Cylindrical GrindingCylindrical Grinding- Internal GrindingInternal Grinding- Centerless GrindingCenterless Grinding- OthersOthers

- Tool and cutter grindersTool and cutter grinders- Tool-post grindingTool-post grinding- Swing-frame grindersSwing-frame grinders- Bench grindersBench grinders

- Creep-Feed GrindingCreep-Feed Grinding

Surface GrindingSurface Grinding

Cylindrical GrindingCylindrical Grinding


http://www.minnesotagrinding.com/ODGrinding400.jpg

Internal GrindingInternal Grinding

Centerless GrindingCenterless Grinding

Creep-Feed GrindingCreep-Feed Grinding

Bonded Abrasives/Bonded Abrasives/Grinding WheelsGrinding Wheels

Bonded AbrasivesBonded AbrasivesMost grinding wheels are made Most grinding wheels are made of abrasive grains held together of abrasive grains held together by a bonding materialby a bonding material

Types of bonding material:Types of bonding material:Vitrified (glass)Vitrified (glass)Resinoid (thermosetting resin)Resinoid (thermosetting resin)RubberRubberMetal (the wheel itself is metal; Metal (the wheel itself is metal; the grains are bonded to its the grains are bonded to its surfacesurface

Grinding Wheel Grinding Wheel ComponentsComponents

Grinding WheelGrinding WheelStructureStructure

Grinding ProcessGrinding Process

GrindingGrinding- Grains have irregular shapes Grains have irregular shapes

and random spacingand random spacing- Average rake angle is very Average rake angle is very

negative (about -60° or lower)negative (about -60° or lower)- Radial positions of grains varyRadial positions of grains vary- Cutting speed is very high (ca. Cutting speed is very high (ca.

600 ft/min)600 ft/min)


Grain forceGrain force ((v/V)√(d/D))(material strength)((v/V)√(d/D))(material strength)

Temperature riseTemperature rise DD1/41/4dd3/43/4(V/v)(V/v)1/21/2

Effects caused by grinding Effects caused by grinding temperature increase:temperature increase:

- SparksSparks- TemperingTempering- BurningBurning- Heat CheckingHeat Checking

Grinding WheelGrinding WheelWearWear

Types:Types:Attritious Grain WearAttritious Grain Wear

Grains develop a wear flatGrains develop a wear flat

Grain FractureGrain FractureNecessary to produce Necessary to produce

sharp sharp grain edgesgrain edges

Bond FractureBond FractureAllows dull grains to be Allows dull grains to be

dislodged from the wheeldislodged from the wheel

Grinding WheelGrinding WheelLoadingLoading

Truing and DressingTruing and Dressing

Cutting FluidsCutting Fluids

- Remove heatRemove heat- Remove chips, grain fragments Remove chips, grain fragments

and dislodged grainsand dislodged grains- Are usually water-based Are usually water-based

emulsionsemulsions- Are added by flood applicationAre added by flood application

Grinding RatioGrinding Ratio

G = G = Volume of material removed Volume of material removed Volume of wheel wearVolume of wheel wear

Vary greatly (2-200 or higher) Vary greatly (2-200 or higher) depending on the type of depending on the type of wheel, grinding fluid, and wheel, grinding fluid, and process parametersprocess parameters

Higher forces decrease the Higher forces decrease the grinding ratiogrinding ratio

GrindingGrinding

Design Considerations:Design Considerations:- Design parts so that they can be held Design parts so that they can be held

securelysecurely- Avoid interrupted surfaces if high Avoid interrupted surfaces if high

dimensional accuracy is required dimensional accuracy is required because they can cause vibrationsbecause they can cause vibrations

- Ensure cylindrical parts are balanced and Ensure cylindrical parts are balanced and thick enough to minimize deflectionsthick enough to minimize deflections

- Short pieces may be difficult to grind Short pieces may be difficult to grind accurately in centerless grinding because accurately in centerless grinding because of limited support by the bladeof limited support by the blade

- Parts requiring high accuracy form Parts requiring high accuracy form grinding should be kept simple to prevent grinding should be kept simple to prevent frequent wheel dressingfrequent wheel dressing

- Avoid small deep or blind holes or include Avoid small deep or blind holes or include a reliefa relief

Ultrasonic MachiningUltrasonic Machining

Uses fine abrasive grains in a Uses fine abrasive grains in a slurry to remove material from slurry to remove material from brittle workpieces by brittle workpieces by microchipping and erosionmicrochipping and erosion

The tool vibrates at 20 kHz and a The tool vibrates at 20 kHz and a low amplitude (.0125-.075 mm) low amplitude (.0125-.075 mm) which accelerates the grains to which accelerates the grains to a high velocitya high velocity

Can create very small holes and Can create very small holes and slotsslots

Rotary Ultrasonic Rotary Ultrasonic MachiningMachining

Uses a rotating and vibrating tool Uses a rotating and vibrating tool to remove material, as in face to remove material, as in face millingmilling

Diamond abrasives are Diamond abrasives are embedded in the tool surfaceembedded in the tool surface

Effective at producing deep Effective at producing deep holes in ceramic parts at high holes in ceramic parts at high MRR MRR


Design Considerations:Design Considerations:- Avoid sharp profiles, corners Avoid sharp profiles, corners

and radii; the slurry erodes and radii; the slurry erodes corners offcorners off

- Allow for slight taper for holes Allow for slight taper for holes made this waymade this way

- Support the exit end of holes Support the exit end of holes being formed with a backup being formed with a backup plate to prevent chipping of the plate to prevent chipping of the holderholder

Coated AbrasivesCoated Abrasives

Coated AbrasivesCoated AbrasivesAbrasive grains are deposited Abrasive grains are deposited on flexible backing; they are on flexible backing; they are more pointed than those in more pointed than those in grinding wheelsgrinding wheels

Common examples: Common examples: sandpaper, emerysandpaper, emery


Belt GrindingBelt GrindingUses coated abrasives in the Uses coated abrasives in the form of a belt; cutting speeds form of a belt; cutting speeds are about 2500-6000 ft/minare about 2500-6000 ft/min

MicroreplicationMicroreplicationAbrasives with a pyramid Abrasives with a pyramid shape are placed in a shape are placed in a predetermined regular pattern predetermined regular pattern on the belton the belt

Belt GrindingBelt Grinding

HoningHoning

Used mainly to improve the Used mainly to improve the surface finish of holessurface finish of holes

Bonded abrasives called Bonded abrasives called stones are mounted on a stones are mounted on a rotating mandrel; also used on rotating mandrel; also used on cylindrical or flat surfaces and cylindrical or flat surfaces and to remove sharp edges on to remove sharp edges on toolstools

HoningHoning

Hole defects correctible by honing

Superfinishing/Superfinishing/MicrohoningMicrohoning

Uses very low pressure and Uses very low pressure and short strokesshort strokes

LappingLapping

Used to enhance surface finish and Used to enhance surface finish and dimensional accuracy of flat or dimensional accuracy of flat or cylindrical surfaces; tolerances are cylindrical surfaces; tolerances are on the order of .0004 mm; surface on the order of .0004 mm; surface finish can be as smooth as .025-.1 finish can be as smooth as .025-.1 μμm; this improves the fit between m; this improves the fit between surfacessurfaces

Abrasive particles are embedded in Abrasive particles are embedded in the lap or carried in a slurrythe lap or carried in a slurry

Pressures range from 7-140 kPa Pressures range from 7-140 kPa depending on workpiece hardnessdepending on workpiece hardness

LappingLapping

Example of aExample of aLapping MachineLapping Machine

2- and 3-Body2- and 3-BodyAbrasionAbrasion

2-body abrasion: grains are embedded in a surface

3-body abrasion: grains move freely between surfaces

Lapping –Lapping –MicrochippingMicrochipping

Clat

Cra

d

ah

Plastic zone

Lateral cracks – remove material

Radial cracks – surface damage

Lapping FinishLapping Finish

Grinding Lapping

Types of LappingTypes of Lapping

Single-sided lapping machine

Types of LappingTypes of Lapping

Upper lap rotation

Lower lap rotation

Rolling cylindrical workpieces

Upper lap rotation

Lower lap rotation

Cylindrical parts

Double-sided lapping

Cylindrical Lapping

Lapping ProcessLapping Process

Examples ofExamples ofLapped PartsLapped Parts

The workpieces made of aluminum oxide were rings The workpieces made of aluminum oxide were rings having 0.5” ID, 0.8” OD and 0.2” thickness. Its high having 0.5” ID, 0.8” OD and 0.2” thickness. Its high hardness promotes a series of applications in hardness promotes a series of applications in mechanical engineering, such as bearings and mechanical engineering, such as bearings and seals. seals.

Initial Ra = 0.65 µmInitial Ra = 0.65 µmFinal Ra (after lapping) = 0.2 µmFinal Ra (after lapping) = 0.2 µm


Hexoloy SiC is a new sintered alpha silicon carbide Hexoloy SiC is a new sintered alpha silicon carbide material designed specifically for optimum performance in material designed specifically for optimum performance in sliding contact applications. It is produced by pressureless sliding contact applications. It is produced by pressureless sintering ultra-pure sub-micron powder. This powder is sintering ultra-pure sub-micron powder. This powder is mixed with non-oxide sintering aids, then formed into the mixed with non-oxide sintering aids, then formed into the desired shapes by a variety of methods and consolidated desired shapes by a variety of methods and consolidated by sintering at temperatures above 2000by sintering at temperatures above 2000 C (3632 C (3632 F). The F). The sintering process results in single-phase, fine-grain SiC sintering process results in single-phase, fine-grain SiC product that is very pure and uniform, with virtually no product that is very pure and uniform, with virtually no porosity. Whether used in corrosive environments, porosity. Whether used in corrosive environments, subjected to extreme wear and abrasive conditions, or subjected to extreme wear and abrasive conditions, or exposed to high temperatures, Hexoloy sintered alpha exposed to high temperatures, Hexoloy sintered alpha silicon carbide outperforms other advanced ceramics. This silicon carbide outperforms other advanced ceramics. This kind of ceramic material is ideal for applications such as kind of ceramic material is ideal for applications such as chemical and slurry pump seals and bearings, nozzles, chemical and slurry pump seals and bearings, nozzles, pump and valve trim and more. pump and valve trim and more.

Initial Ra = 0.053 µmInitial Ra = 0.053 µmFinal Ra (after lapping) = 0.02 µm.Final Ra (after lapping) = 0.02 µm.


Hardened steel W-1. The high content of Carbon allows Hardened steel W-1. The high content of Carbon allows high hardness to be achieved by hardening and also high hardness to be achieved by hardening and also formation of carbide, which gives the high wear resistance. formation of carbide, which gives the high wear resistance. The dimensions for the parts made of W-1 were 0.8”OD The dimensions for the parts made of W-1 were 0.8”OD and 0.4” thickness (as seen in figure 3.3). The initial and 0.4” thickness (as seen in figure 3.3). The initial hardness of the steel was about 10-14 HRC. hardness of the steel was about 10-14 HRC. The parts were heat-treated and, after quenching in oil, the The parts were heat-treated and, after quenching in oil, the resulting hardness was 44 – 48 HRC. The steps followed resulting hardness was 44 – 48 HRC. The steps followed for the heat treatment were: 1) preheat oven to 1425-for the heat treatment were: 1) preheat oven to 1425-15001500F; 2) place part in the oven for ½ hour per inch of F; 2) place part in the oven for ½ hour per inch of thickness; 3) quench the part in oil; 4) test the hardness. thickness; 3) quench the part in oil; 4) test the hardness.

Initial Ra = 0.5 µmInitial Ra = 0.5 µmFinal Ra (after lapping) = 0.1 µm. Final Ra (after lapping) = 0.1 µm.

Other FinishingOther FinishingOperationsOperations

PolishingPolishingProduces a smooth, reflective Produces a smooth, reflective surface finish; done with disks surface finish; done with disks or belts with fine abrasive or belts with fine abrasive grainsgrains

ElectropolishingElectropolishingProduces mirror-like surfaces Produces mirror-like surfaces on metals; the electrolyte on metals; the electrolyte removes peaks and raised removes peaks and raised areas faster than lower areas; areas faster than lower areas; also used for deburringalso used for deburring

Example of a Polishing Example of a Polishing MachineMachine

Examples ofExamples ofPolished PartsPolished Parts

Polished disk drive heads compared to the size of a dime

Polishing ResultsPolishing Results

Magnetic FinishingMagnetic Finishing

Magnetic Float PolishingMagnetic Float PolishingA magnetic field pulls on the A magnetic field pulls on the magnetic abrasive fluid, floating the magnetic abrasive fluid, floating the workpieces and pressing them workpieces and pressing them against a drive shaft; forces are against a drive shaft; forces are very small and controllable so the very small and controllable so the polish is very finepolish is very fine

Magnetic Field Assisted PolishingMagnetic Field Assisted PolishingThe workpiece is rotated on a The workpiece is rotated on a spindle and the magnetic field spindle and the magnetic field oscillates, producing vibrations in oscillates, producing vibrations in the magnetic abrasive fluidthe magnetic abrasive fluid

Magnetic FinishingMagnetic Finishing

Abrasive ProcessAbrasive ProcessCapabilitiesCapabilities

DeburringDeburring

BurrsBurrsThin ridges (usually triangular) Thin ridges (usually triangular) that form on the workpiece that form on the workpiece edges during production; can edges during production; can be detrimental to the part or its be detrimental to the part or its functionfunction

Traditionally removed Traditionally removed manually; can account for up to manually; can account for up to 10% of the part manufacturing 10% of the part manufacturing costcost

Deburring ProcessesDeburring Processes

- Manual (files and scrapers)Manual (files and scrapers)- Mechanical by cuttingMechanical by cutting- Wire brushingWire brushing- Abrasive beltsAbrasive belts- Ultrasonic machiningUltrasonic machining- ElectropolishingElectropolishing- Electrochemical MachiningElectrochemical Machining- Magnetic abrasive finishingMagnetic abrasive finishing- Vibratory FinishingVibratory Finishing- Shot blasting, abrasive blastingShot blasting, abrasive blasting- Abrasive flow machiningAbrasive flow machining- Thermal energy (laser, plasma)Thermal energy (laser, plasma)


Vibratory and Barrel FinishingVibratory and Barrel FinishingAbrasive pellets are placed in a Abrasive pellets are placed in a container with the workpiece; container with the workpiece; the container is vibrated or the container is vibrated or tumbledtumbled

Shot BlastingShot BlastingAbrasive particles are Abrasive particles are propelled at the workpiece at propelled at the workpiece at high velocity by an air jet or a high velocity by an air jet or a wheelwheel


Abrasive Flow MachiningAbrasive Flow MachiningAn putty-like substance with An putty-like substance with abrasive grains is forced around abrasive grains is forced around and through the workpiece; and through the workpiece; especially useful for pieces with especially useful for pieces with internal spaces that cannot be internal spaces that cannot be reached by other meansreached by other means

Thermal EnergyThermal EnergyThe workpiece is exposed to an The workpiece is exposed to an instantaneous combustion reaction; instantaneous combustion reaction; the burrs heat up much more the burrs heat up much more rapidly than the solid part and melt rapidly than the solid part and melt awayaway

SummarySummary

Abrasive processes offer a way Abrasive processes offer a way to increase surface finish and to increase surface finish and dimensional accuracydimensional accuracy

Deburring may be necessary for Deburring may be necessary for proper part fit and functionproper part fit and function

The End

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M processes notes_8 (1)

Technology

Transcript of M processes notes_8 (1)