Post on 04-Apr-2018
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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