WEEK-11 OCT 21 ST 2014 2014-2015 SEMESTER-I TA201 Manufacturing Processes
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
2014-15 Semester-I
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
2014-15 Semester-I TA 201Dr. Shashank Shekhar
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Higher production ratesConservation of metalGreater strengthFavorable grain orientation
Forging
2014-15 Semester-I
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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
2014-15 Semester-I
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Heading (Upset Forging)
Making of bolt head
TA 201Dr. Shashank Shekhar
2014-15 Semester-I
Basic bulk deformation processes: Extrusion
TA 201
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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
2014-15 Semester-I
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
2014-15 Semester-I
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
2014-15 Semester-I
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
2014-15 Semester-I 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
2014-15 Semester-I TA 201Dr. Shashank Shekhar
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Pressure dependence
2014-15 Semester-I TA 201Dr. Shashank Shekhar
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2014-15 Semester-I
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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Dr. Shashank Shekhar
2014-15 Semester-I
Basic sheet metalworking operation: Shearing
TA 201
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Dr. Shashank Shekhar
2014-15 Semester-I
Shearing, Blanking and Punching
TA 201Dr. Shashank Shekhar
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2014-15 Semester-I
Sheared edges and effect of clearance
TA 201Dr. Shashank Shekhar
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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
2014-15 Semester-I
Cutting Forces
TA 201Dr. Shashank Shekhar
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S= shear strength
TS= tensile strength
2014-15 Semester-I
Basic sheet metalworking operation: Bending
TA 201
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Dr. Shashank Shekhar
2014-15 Semester-I TA 201Dr. 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)
2014-15 Semester-I TA 201Dr. Shashank Shekhar
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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
2014-15 Semester-I TA 201Dr. Shashank Shekhar
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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)
2014-15 Semester-I
Basic sheet metalworking operation: Deep Drawing
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Dr. Shashank Shekhar
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
Dr. Shashank Shekhar TA 201
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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
2014-15 Semester-I
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
2014-15 Semester-I
Powder Metallurgy: Porous Metals
Oil-impregnated Porous Bronze Bearings
Metal filters 26
TA 201Dr. Shashank Shekhar
2014-15 Semester-I
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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TA 201Dr. Shashank Shekhar
2014-15 Semester-I
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TA 201Dr. Shashank Shekhar
2014-15 Semester-I
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
2014-15 Semester-I
30Conventional powder metallurgy route
TA 201Dr. Shashank Shekhar
2014-15 Semester-I
31Powder characterization
Particle size and distribution
Particle shape and structure
Particle surface area
TA 201Dr. Shashank Shekhar
2014-15 Semester-I
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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