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WEEK-11 OCT 21 ST 2014 2014-2015 SEMESTER-I TA201 Manufacturing Processes
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Page 1: Week11

WEEK -11

O C T 2 1 S T 2 0 1 4

2 0 1 4 - 2 0 1 5 S E M E S T E R - I

TA201Manufacturing Processes

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Announcements: Project Evaluation

TA 201Dr. Shashank Shekhar

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Project Job weightage: 20%; Project report weightage: 5% Project job would be evaluated on the basis of

(a) Innovation(b) Finish(c) Volume of work

Also note that each member of a group need not get the same marks for the project. Individuals will be awarded marks based on their contribution and their ability to answer the questions posed to them. It is suggested that all group members are prepared to describe their work in 5 minutes with emphasis on the important aspects of your project.

Date Time Batch

Nov 10th 2 pm to 4 pm Monday batch

Nov 10th 4.30 pm to 6.30 pm Thursday batch

Nov 11th 2 pm to 4 pm Tuesday batch

Nov 11th 4.30 pm to 6.30 pm Friday batch

Nov 12th 2 pm to 4 pm Wednesday batch

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Higher production ratesConservation of metalGreater strengthFavorable grain orientation

Forging

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Upset Forging

TA 201Dr. Shashank Shekhar

Upset Forging is deformation process in which a cylindrical part is increased in diameter and reduced in length

It can be open-die or close-die forging

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Heading (Upset Forging)

Making of bolt head

TA 201Dr. Shashank Shekhar

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Basic bulk deformation processes: Extrusion

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Dr. Shashank Shekhar

It is a deformation process in which the work metal is forced to flow through a die opening to produced a desired cross-section shape.

Product will have constant cross-section

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Extrusion

Indirect Extrusion

Direct Extrusion

Extrusion

Cold Extrusion

Warm Extrusion

Extrusion

Continuous

Discrete

Physical Configuration

Working Temperature

Process

Classifications of Extrusion

Hot Extrusion

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TA 201Dr. Shashank Shekhar

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Direct Extrusion

Billet is placed in a chamber and forced through a die opening by a hydraulically-driven ram or pressing stem

As the ram approaches the opening, a small portion of the billet remain that cannot be forced through the die opening. This extra portion is called butt, that is separated from the product

Schematic of direct extrusion

Friction is one of the main problem in direct extrusion

Friction problem is aggrevated at high temperature because of presence of oxide layer

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TA 201Dr. Shashank Shekhar

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Direct Extrusion

• Hollow sections are possible using mandrel• As the billet is compressed, the material is forced to flow through

the clearance between the mandrel and the die

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TA 201Dr. Shashank Shekhar

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Indirect Extrusion

• Also called backward extrusion or reverse extrusion• Friction is lower along the container walls• Rigidity of the pressing piston/ram is low because of hollow structure• Limitation in length of extruded parts

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Pressure dependence

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Sheet Metalworking

Forming and related operations performed on metal sheets, strips, and coils

High surface area to volume ratio of starting metal, which distinguishes these from bulk deformation

Often called press working because presses perform these operations

- Parts are called stampings

- Usual tooling: punch and die

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Basic sheet metalworking operation: Shearing

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Shearing, Blanking and Punching

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Sheared edges and effect of clearance

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Clearance:c = ActAc= clearance allowance parameter (~0.045 to 0.075)

Clearance too small requires much larger forces

Clearance too large causes oversized burr

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Cutting Forces

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S= shear strength

TS= tensile strength

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Basic sheet metalworking operation: Bending

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Dr. Shashank Shekhar

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Bend angle is α; Bend radius is measured on the inside surface

Bend allowance: If the bend radius is small, stretching may occur. Stretching or bend allowance can be estimated as follows:

where Ab = bend allowance (in mm)α = bend angle (degrees)R = bend radius (mm)t = stock thickness (mm)Kba = factor to estimate stretching

= 0.33 (if R < 2t)= 0.5 (if R > 2t)

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Springback:When bending load is removed, elastic part of the strain is recovered

where = included angle of sheet metal part (degrees)= included angle of bending tool (degrees)

Bend radius also increases due to elastic recoveryAmount of springback increases with increasing Yield strength and

Elastic Modulus of metalOverbending and Bottoming used to overcome springback

a'

t

''

t

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Bending Force:Depends on

Geometry of punch and die Strength of material Thickness and length of sheet metal

F = bending force (N)TS = tensile strength of material (Mpa)w = width of part in direction of bend axist = stock thicknessD = die opening dimensionKbf = geometry dependent constant (edge bending =0.33;

V-bending = 1.33)

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Basic sheet metalworking operation: Deep Drawing

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I N T R O D U C T I O N

P O W D E R P R O D U C T I O N

C O M P A C T I O N

S I N T E R I N G

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Powder Metallurgy (Chapter 16, 17 Groover)

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Powder Metallurgy: Tungsten Filament

W: Tm=34220C

Powder metallurgy

TA 201Dr. Shashank Shekhar

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Powder Metallurgy: Cermet cutting tools(Ceramic-metal composite)

Microstructure: ceramic particles in metal matrix Cermet-tipped saw blade for long life

Cermet cutting inserts for lathe

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TA 201Dr. Shashank Shekhar

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Powder Metallurgy: Porous Metals

Oil-impregnated Porous Bronze Bearings

Metal filters 26

TA 201Dr. Shashank Shekhar

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Importance of P/M

Versatile and used in numerous industries Eliminates or minimizes machining Minimizes scrap Maintains close dimensional tolerances Permits a wide variety of alloy systems Facilitates manufacture of complex shapes which would be impractical with other processes

Provides excellent part to part repeatability Cost Effective Energy and environmentally efficient

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P/M net-shape gears are common, save machining time

Powder Metallurgy (P/M)

Method:• Make fine metal powders and sort• Mix powders to get “alloy”

• Iron alloys most common, also Bronze• Compaction

• Powder is pressed into a “green compact”• 20,000-100,000psi pressure• Still very porous, ~70% density• May be done cold or warm (higher density)

• Sintering• Controlled atmosphere: no oxygen• Heat to 0.7 to 0.9*Tm• Particles bind together• Part shrinks in size • Density increases, up to 95%• Strength proportional to Density

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TA 201Dr. Shashank Shekhar

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30Conventional powder metallurgy route

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31Powder characterization

Particle size and distribution

Particle shape and structure

Particle surface area

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Methods of Powder Production

Methods of mechanical attrition, to obtainfine particles: (a) roll crushing, (b) ball mill, &(c) hammer milling

Chemical reduction: W powder production (Hydrogen reduction)

Precipitation: Ni, Cu powder production (Cementation)

TA 201Dr. Shashank Shekhar