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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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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 FORGING TECHNIQUES

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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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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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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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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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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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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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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