02. ColdHeadingForFastenerManufacture
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Transcript of 02. ColdHeadingForFastenerManufacture
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COLD HEADING
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COLD HEADING
DEFINITION
Metal forging process used for rapidly producing enlarged (upset) sections on a piece of rod or wire held in a die
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PROCESS CHARACTERISTICS
Extrusions without draft
Range of Tolerance: IT6 to 15
Normal range: IT9 to 12 Finished workpieces have improved
Grain structure Mechanical properties
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COLD HEADING
PROCESS CHARACTERISTICS
High productivity
Full quality control
Process monitoring & methods of SPC
High material yield
Reduced material cycle
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PROCESS CHARACTERISTICS
Finished surfaces are smooth withuniform accuracy
All ductile metals
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COLD HEADING
COLD FORGING TECHNIQUES
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COLD HEADING
SINGLE DIE HEADING PROCESS
Cut off, the wire is sheared off in pieceswith same cubic volume as the finalfastener blank shape
Preform, a blow is delivered to the
fastener blank, transforming it into afastener preform, or cone blow
Finish blow, a second blow reforms the
one or preform into the final fastener geometry
Eject, or kick out
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COLD HEADING
STAGES IN FASTENER Mfg.
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MATERIALS
Low carbon steel Low carbon alloy steel. Non-ferrous - Al, Cu, Mg, Pb, Ti, Zn, Sn,
Ni & their alloys
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COLD HEADING
ADVANATAGES
Precision cold forging of materials offersthe net/near net shape production of simpleor complex geometry parts
High accuracy gives savings on account of material & energy (no finish machiningneeded)
CAD can be used to optimize strength toweight ratio
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ADVANTAGES
Yield & break strength increased
Harder surface & more favorablematerial structure
Results in smoother surface, suitable for surface treatment, such as zinc plating
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PRECAUTIONS TO BE TAKENWHILE SELECTING MATERIAL
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PRECAUTIONS TO BE TAKEN WHILESELECTING MATERIAL
The bolt plating material is usually thelimiting factor on maximum service
temperature
Carbon steel & alloy steel are unsatisfactory
(become brittle) at temperatures below -65 F(-54 0C)
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COLD HEADING
DIE DESIGN
FOR
COLD FORGING
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RULE 1
Limit of length of unsupported stock that can be upset in
one blow withoutinjurious bucklingis not more than 3
times the diameter of the bar
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COLD HEADING
RULE 2
Length of the stock more than 3 times bar diameter can be successfully upset in one blow, provided the diameter of the upset
made is not more than 1.5 times bar diameter
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RULE 3
In an upsetrequiring more than3d in length whenthe diameter of the
upset is 1.5d, theamount of unsupported stock
beyond the face of the die must notexceed 1d of the bar
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MATERIALS FOR DIE BLOCKS
Heat resistant
Adequate strength Low wear rateMachinability
Typical material: Carbide
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Volume of the stock required inthe finished forging Size of the stock used
Maximum dimension of thefinished forging Number of blows necessary tocomplete the forging
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DESIGN OF BOLT (CASE STUDY)
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Material Class: 8.8
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Material class 8.8 stands for
8 x 8 = 64 640MPa yield strength
800MPa ultimate tensile strength
Carbon steel with additives (e.g.
Boron, Mn, Cr) quenched & tempered
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Volume of Bolt: 4130 mm 3
Volume of Head: 2945.24 mm 3
Length of wire required: 29 mm
using 13.5 wire
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COLD HEADING
Why 13.5 & not 7.9 wire?
Extrusion ratio with 13.5 = 24.29%
with 7.9 = 90.1%
Permissible limit 70 %
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COLD HEADING
Why 13.5 & not 7.9 wire?
Upset ratio with 13.5 = 70.84%
with 7.9 = 90%
Permissible limit 70 %
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Company visited
Mini Nuts
Bangalore
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CONCLUSION
To conclude we can say that this is a
very cost effective process as comparedto other manufacturing processes for fasteners, as.
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THANK YOU