microsoft powerpoint - lecture6

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MANUFACTURINGMANUFACTURING

PROCESSESPROCESSES

--AMEM 201AMEM 201

Lecture 6Lecture 6:: Machining ProcessesMachining Processes

DR. SOTIRIS L. OMIROU

IntroductionIntroduction

Machine ToolsMachine Tools

Tool MaterialsTool Materials

Cutting FluidsCutting Fluids

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The machining is the most broad technologicalprocess used in manufacturing.

Generaly, in the field of manufacturing, the term ofMachining means removal of material from a raw

material, by cutting small chips, in order to obtainthe desired shape and dimensions for final part.

The machining is strictly necessary when finishedpart has to have very tight tolerances ofdimensions or when the roughness of surfacesneed to be very smooth.

Introduction toIntroduction to MMachiningachining


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Removal of chips, from a raw material, is performedby a cutting tool that need a motion relative to rawmaterial. This motion, named cutting motion, couldbe practically a rotation one or a translation one.

The next two examples will illustrate in a synopsisway the cutting process, the chip removal from a rawmaterial.

First example is related to the case when the cuttingmotion is a rotation one, like in turning machining.The second example is related to the case when thecutting motion is a translation one, like in shaping

machining.


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The raw materialperforms a rotationmotion (cuttingmotion) and toassure the process

continuity the toolperforms atranslation motion(feeding motion)

The raw materialperforms a rotationmotion (cuttingmotion) and toassure the process

continuity the toolperforms atranslation motion(feeding motion)



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The figurepresents ashaping machine.In this case thecutting motion isexecuted by thecutter while theworkpiece (rawmaterial) remainstationary.

The figurepresents ashaping machine.In this case thecutting motion isexecuted by thecutter while theworkpiece (rawmaterial) remainstationary.

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Sloting/Shaping

Turning Milling Drilling

Cutting with Conventional Tools(Single point or multi point cutting tools

having a cleary defined geometry)

Grinding Honning Lapping

Cutting with Non-Conventional Tools(Abrasive tools that have a random

geometru of cutting part)

Traditional machining

Waterjet

Electro/Chemicalerosion

Laserbeam

Ultrasonic

Machining by:

Non-Traditional machining

Machining types(Cutting processes types)

Sloting/Shaping

Turning Milling Drilling

Cutting with Conventional Tools(Single point or multi point cutting tools

having a cleary defined geometry)

Grinding Honning Lapping

Cutting with Non-Conventional Tools(Abrasive tools that have a random

geometru of cutting part)

Traditional machining

Waterjet

Electro/Chemicalerosion

Laserbeam

Ultrasonic

Machining by:

Non-Traditional machining

Machining types(Cutting processes types)

There are many types of machining operation.

A synoptical classification is shown below.



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Definition of MDefinition of Machinachineses

Generally a machineis an equipmentwhich transform atype of energy intoanother type

Generally a machineis an equipmentwhich transform atype of energy intoanother type

Example:

Eolyan Turbine:Transforms the windenergy intomechanical energy

Lathe machine:

Transforms the

electrical energyinto mechanicalenergy

Example:

Eolyan Turbine:Transforms the windenergy intomechanical energy

Lathe machine:

Transforms the

electrical energyinto mechanicalenergy

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DDefinitionefinition of tof thehe MMachineachine tooltool

The machine tool is a processing machine, thatproduces different parts from point of view ofshape accuracy, productivity and otherconditions, using specific technological

process.

Example:

Machine-Tools for chip removal

Machine-Tools for forming processes

The machine tool is a processing machine, thatproduces different parts from point of view ofshape accuracy, productivity and otherconditions, using specific technologicalprocess.

Example:

Machine-Tools for chip removal

Machine-Tools for forming processes


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Classification ofClassification of machinemachine--toolstools

In this respect different criteria are used, like:

The basic operation of chip removal

The automation level

The complexity level

The production volume

The main shape of part that has to be machined

etc.

In this respect different criteria are used, like:

The basic operation of chip removal

The automation level

The complexity level

The production volume

The main shape of part that has to be machined

etc.

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The machineThe machine--toolstools claclasssificationsification upon theupon the

basic operationbasic operation of chip removalof chip removal

The basic operation Machine-tool type

Turning..................... Lathe

Milling....................... Milling machine

Shaping..................... Shaping machine

Grinding..................... Grinding machine

Honing..................... Honing machine

.. ..

Drilling machineDrilling


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Manual Demiautomated

Rigid automation

(Cames)

Flexible automation

(Numerical Control-NC)

Automated

Machine-Tools

with.........Control

Manual Demiautomated

Rigid automation

(Cames)

Flexible automation

(Numerical Control-NC)

Automated

Machine-Tools

with.........Control


level of automationlevel of automation

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1. Conventional Machine-Tools

2. Machining Centers *

* These have:

-NC

-Tools magazine

-Automated tools changer

-Large number of basic operations

1. Conventional Machine-Tools

2. Machining Centers *

* These have:

-NC

-Tools magazine

-Automated tools changer

-Large number of basic operations

The machineThe machine--toolstools clasclasssificationification upon theupon the

level of complexitylevel of complexity


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Small volume production Medium and large volume Mass production

Machine-Tools for


production volumeproduction volume

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1. Machine-Tools forrevolution parts

Example:

Lathes

Turning machiningcenters

Round grindingmachines

1. Machine-Tools forrevolution parts

Example:

Lathes

Turning machiningcenters

Round grindingmachines

2. Machine-Tools forprismatic parts

Example:

Milling machines

Machining centers fordrilling and milling

Planar grindingmachines

2. Machine-Tools forprismatic parts

Example:

Milling machines

Machining centers fordrilling and milling

Planar grindingmachines


main shape of partmain shape of part that has to be machinedthat has to be machined


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The chip removalThe chip removal

Chip removal is a technological

process by that a raw material

is transformed into a final part.

The condition for the existing of chip removal isa relative motion between the raw material andtool. This motion is named effective chip removal

motion and it has the speed V.

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The ECONOMIC Chip removalThe ECONOMIC Chip removal

There is only one speed V for each pair of rawmaterial and tool material, when the chipremoval is done in an economical way.

If the motion is a rotation one, then

V = ( . D . n)/1000 [m/min]

where- D [mm] is part or tool diameter

n [1/min] is the rotation freqeunce

There is only one speed V for each pair of rawmaterial and tool material, when the chipremoval is done in an economical way.

If the motion is a rotation one, then

V = ( . D . n)/1000 [m/min]

where- D [mm] is part or tool diameter

n [1/min] is the rotation freqeunce


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Needed

Outputs:

Machined

part

Inputs:

Rowmaterial

Energy

Infor-

mation Secondary

Outputs:

Heat

Swarfs

NoiseSecondary inputs:

Cooling liquid.....

TheThe BBlocklockDDiagramiagram for afor a MACHINE TOOLMACHINE TOOL

Engine

MACHINE TOOL

PartPartPartPart

Clamping

device

Transfer and

adjusting/transformingmechanisms

Machining process

Engine

ToolToolToolTool

Clamping

device

Transfer andadjusting/

transformingmechanisms

Transfer andadjusting/

transforming

mechanisms

Engine

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Elements of an Effective ToolElements of an Effective Tool

High hardness at elevated temperaturesHigh hardness at elevated temperatures

Wear resistanceWear resistance

Strength to resist bulk deformationStrength to resist bulk deformation

Adequate thermal propertiesAdequate thermal properties

Consistent tool lifeConsistent tool life

Correct geometryCorrect geometry

Chemical stabilityChemical stability

Tool MaterialsTool MaterialsTool MaterialsTool MaterialsTool MaterialsTool MaterialsTool MaterialsTool Materials


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Wide variety of materials andWide variety of materials and

compositions are available to choose fromcompositions are available to choose from

when selecting a cutting toolwhen selecting a cutting tool


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Tool steelsTool steels -- low end of scale. Used to make somelow end of scale. Used to make somedrills, taps, reamers, etc. Low cost equals low tool life.drills, taps, reamers, etc. Low cost equals low tool life.



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High speed steel(HSS)High speed steel(HSS)

Prior to World War II the most common type of lathePrior to World War II the most common type of lathe

bit was made from high speed tool steel. High speedbit was made from high speed tool steel. High speedtooling is atooling is a steelsteel alloyalloy with a predetermined percentagewith a predetermined percentage

ofof tungstentungsten mixed in. There is also amixed in. There is also a hardeninghardening processprocess

that makes high speed tooling very hathat makes high speed tooling very harrd and weard and wear

resistant. These tools are able to withstand high workresistant. These tools are able to withstand high work

temperatures. Tools typically made from high speed aretemperatures. Tools typically made from high speed are

end millsend mills,, drillsdrills,, reamersreamers,, and lathe tool bitsand lathe tool bits..

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Fig. 1: End mill

Fig. 3: Reamer

Fig. 2: Drill

Fig. 4: Lathe tool bit

High speed steel(HSS)High speed steel(HSS)


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CobaltCobalt -- one step above HSS, cutting speeds are generallyone step above HSS, cutting speeds are generally25% higher.25% higher.

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CarbidesCarbides -- Most widely used cutting tool today.Most widely used cutting tool today.Cutting speeds are three to five times faster thanCutting speeds are three to five times faster than

HSS.HSS. Carbides are made by blending micronCarbides are made by blending micron--sizedsized

tungsten carbide andtungsten carbide and cobaltcobalt powders, then pressingpowders, then pressing

the mixture in athe mixture in a moldmold and at a temperature highand at a temperature highenough to cause the cobalt to flow. This process isenough to cause the cobalt to flow. This process is

called "called "sinteringsintering" and the resulting tool is called" and the resulting tool is called

"cemented" carbide."cemented" carbide. In addition to tool composition,In addition to tool composition,

coatings are added to tool materials to increasecoatings are added to tool materials to increase

resistance to wear.resistance to wear.



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CarbidesCarbides


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CeramicsCeramics -- Contain pure aluminum oxide and canContain pure aluminum oxide and cancut at two to three times faster than carbides.cut at two to three times faster than carbides.

Ceramic tools have poor thermal and shockCeramic tools have poor thermal and shock

resistance and are not recommended for interruptedresistance and are not recommended for interruptedcuts. Caution should be taken when selecting thesecuts. Caution should be taken when selecting these

tools for cutting aluminum, titanium, or othertools for cutting aluminum, titanium, or other

materials that may react with aluminum oxide.materials that may react with aluminum oxide.



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InsertsInserts


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InsertsInserts are individual cutting tool withare individual cutting tool withsevered cutting points. They are clamped onsevered cutting points. They are clamped on

tool shanks with locking mechanisms or can betool shanks with locking mechanisms or can be

brazed to the tools. Clamping is preferredbrazed to the tools. Clamping is preferred

method for securing an insertmethod for securing an insert

Carbide Inserts are available in various shapesCarbide Inserts are available in various shapes--

Square, Triangle, Diamond and RoundSquare, Triangle, Diamond and Round

Strength depends on the shapeStrength depends on the shape



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Insert AttachmentInsert AttachmentMethods ofMethods of

attaching insertsattaching inserts

to toolholders :to toolholders :

(a)(a) ClampingClamping

(b)(b) Wing lockpins.Wing lockpins.

(c)(c) Examples ofExamples ofinserts attachedinserts attached

to toolholdersto toolholders

side screws.side screws.

(d)(d) brazedbrazed


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Cutting FluidsCutting FluidsCutting FluidsCutting FluidsCutting FluidsCutting FluidsCutting FluidsCutting Fluids


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Taylor Tool Life EquationTaylor Tool Life Equation

Relationship is credited to F. W. TaylorRelationship is credited to F. W. Taylor

CvTn=

where,

v= cutting speed;

T= tool life;

and n and Care parameters that depend on feed,depth of cut, work material, tooling material, etc


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TWO MAIN CATEGORIES

(a) Water based for cooling

(b) Oil based for lubricating. (low cutting speed)

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