forming lec 3 deformation system [compatibility mode]

7/30/2019 Forming Lec 3 Deformation System [Compatibility Mode]

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e orma on sys em


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Primary Manufacturing process

Source: Courtesy:E. Paul DeGarmo, P.E, Macmillan

Publ.co.,Inc.N.Y,Collier Macmillan Publ. London,

Davic Associates,Inc 1974


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Plastic Zone

Flow Stress

DeformationRatio,

DeformationRate,

DeformationTemperature,

Other MaterialProperties,

Plastic zone

= - = - = - (dh/h)/(dt) =

V/h, sec-1

act

= a pe cequation,Isotropic

condition etc

Stages for

formability

Machine

Characteristics

Stages,Properties,

Energy

Formability of

materials,defects, state

of stress


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Work Piece Surface Condition

Reaction with Atmosphere,

Reaction with Lubricant

Absorption of detrimental gases

Leading to damaging mechanism

Leads to:

Plasticity getting defeated

End Properties Undesirable


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Tribological Sector in The deformation Zone

FRICTION WEAR LUBRICATION

Tribology

Relative

Velocity

Heat &

Pressure

Function of Pressure,Heat

& Film Strength

Reduce stresses, Facilitate flow, Increase tool life, ensurequality products, reduce production stages etc.


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Tool Pickup

Tool Galling

Dip the thumb in

A simple analogy for toolpickup and galling

The boil is formed.(Tool pickup)

Peeled boilexposes thevirgin skin

(Tool galling)

Septicthumb


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Tool Zone

Tooling should aim to facilitate flow of material. reduce friction,

wear and tool galling.

Tool design should envisage production sequence to ensurecontrolled delegation of load and material flow.

Tool design should envisage cost constraints as well constraints

arisin out of existin machine drive limitations.

Amortization cost should be aimed favorably by metallurgicalconsiderations in terms of evolving methodologies of reducing the

forming stress.

Tool stiffness should be aimed high. Low stiffness pulls down the

total stiffness of the system resulting in less accurate product and

decreasing the forming efficiency.


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C.I.R.P. 5124


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Lower stiffness decreases the productivity.

C = stiffness

m = mass,

then, C/ m = natural fre uenc , n decreases. Thus o eratin fre uenc

e

n

m

c

=

Importance of tool stiffness

has to be reduced to avoid resonance and tool failure.


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Hydraulic press

Hydraulic presswith extrusion dieset up


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Characterization Total Stiffness of Metal Forming System


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QUOTE:

From KURTLANGE

Successof Metal

IMPORTANCE OF TOOL ZONE

Dependson

Tooling.


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F

Upsetting

Before AfterSpn.

LK = F2 /2C

e = elasticdeformation

Stroke, mm

Area under triangle= (1/2) (F) (e).,

C = F/e.,Area becomes

(1/2) (F)(F/C)= F2 /2C = LK

Which is same as spring work

Useful Work, WD

Typical Force Stroke Diagram to enumerate theimportance of Stiffness of Tools


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Spring Loss = LK = F2 / 2C and this increases with lower

stiffness.

IMPORTANCE OF TOOL ZONE

, , d

decreases., the deformation efficiency decreases.


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Clutch&

Flywheel

Formed Part

Mechanical Press Schematic of the Spring System


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Some methods to reduce cutting forces

Courtesy: Hand Book of Metal Forming, Schuler


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Courtesy: Hand Book of Metal Forming, Schuler


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Initial Work

Piece Characteristics

Forming

Forces

Stiffness of

tools, machine

Initial Work Piece

Characteristics

F = f (, , ,,,, )

END PIECE CHARACTERISTICS

Dimensional Positional/Form Surface Materialrror rror rror ropert es rror

Deviation fromNominal Dimn.Eg:base dimn

Position error spring back,

mismtch

Worms/Scores/Scales, orangepeel defect Surface error

Earing,res.stress,notch effect matl.

error


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References

Source: Courtesy : Hand Book of Metal Forming, Kurt Lange,McGraw Hill Publ.,NY, 1985

ICFG Data Sheets, ASM Publ. 1970/75

Compendium of press tools for metal forming, P.Venugopal, IITMadras

forming lec 3 deformation system [compatibility mode]

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