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Master of Simulation Techniques

Lecture No.5

FineFine BlankingBlanking

Prof. Dr.-Ing. F. Klocke

Structure of the lecture

Blanking

Sheared surface and force

Wear

Blanking processes and blanking too ls

Errors on sheared workp ieces

Fine blanking Comparison to normal b lanking

Process details and degree of d iffi culty

Tool setup and tool materials

Examples of f ine blanking parts

Calculation of blanking processes

analytical calculation method

FEA of fine blanking processes


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Separation processes

Phases in shearing


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Influence of die clearance on the formation of cracks and sheared surfaces

Sheared surface in blanking


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Quality of sheared surface depending on specific die clearance

Components of cutting force in blanking


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Qualitative diagram of cutt ing force in dependence on the cutting way

Reduction of cutting force by modification of tools


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Blanking


Wear



Fine blanking

Comparison to normal b lanking







Forms of wear on cutting punches


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Blanking


Wear



Fine blanking








Open and closed cut in shearing


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Differentiation of blanking and perforating

Sectional image of tool guiding construct ion


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Multi-stage blanking tool

Example for multi-stage punching


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Blanking


Wear



Fine blanking








Geometry errors on blanked parts


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Influence of the specific die clearance on the crack depth


Blanking


Wear











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Comparison blanking - fine blanking

Process sequence of fine blanking


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Animation fine blanking

Comparison of sheared surface in blanking and fine blanking


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Blanking


Wear



Fine blanking








Influence of stress state on the duct ility


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Stress states in the cutting zone in fine blanking

Fine blanked parts


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Fine blanked parts

Characteristics of quality of a fine blanked workpiece


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Correlations of process variables in fine blanking


Blanking


Wear











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Definition of degree of difficulty in fine blanking

Fine blanking of a disc


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Geometry of vee rings

Forces in fine blanking


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Fine blanking of a disc by multi step blanking


Blanking


Wear











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Fine blanked control disc (one step blanking)

Knife of an electric tin opener


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Fine blanking of a clutchdisc

Quality of sheared surface and margin area properties


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Calculation of b lanking process

Analytical calculation method

FEA of (fine)blanking processes

Principals and drawbacks

Advantage over analytical calculation by means of examples

Calculation of blanking process - cutting force

SSS klsF =max

mS Rk 8,0=

maximum cutting force

s :sheet thicknesslS :length of cutting linekS :cutting resistance

approximate calculation withtensile strength


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Calculation of blanking process - cutting energy

( )=gx

SSdxxFW

0

maxSgS FxcW =

cutting energy

x :cutting distanceF

S

:current cutting force

c :correction factorincluding variables likematerial properties,

effective cuttingdistance,

size of die clearance andfriction

Calculation of fine blanking process - vee ring force

mRRRRhlF = 4 approximation value for the vee ring force

lR :length of vee ringhR :overall height of vee ring

Rm:material tensile strength


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Calculation of fine blanking process - counter punch force

GqG qAF =

220

mm

NqG =

270

mm

NqG =

approximation for the counter punch force

Aq :cutting piece surface

qG :specific counter punch force

Value of the specific counter punch force forsmall sized, thin workpieces.

Value of the specific counter punch force forbig, thick workpieces.

Calculation of fine blanking process - cutting force

GStS FFF =

sl

F

A

Fk

S

S

S

SS

== maxmax

m

S

RkC =1

mgSgS RslCslF == 1

9,06,0 1


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Blanking


Wear



Fine blanking








Simulation fine blanking

Simulation of fine blanking offers the opportunity to include:

This leads to the following results:

force over punch travelstress fieldstrain rate field

draw-inspredictionof fracture

flow stress datafriction propertiesthermomechanical coupling

More exact input data can be enclosed:

instead of mgS RslCF = 1

.constRm =


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Simulation fine blanking: Example

mater ial flow

detail


damage


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strain-rate


strain


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Simulation fine blanking: material flow as a function of friction


maximum

principle

stress in

blanking

punch

and

workpiece

forces in

the tool:

blankingdie

blank-

holderblankingpunch

counter-punch


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stresses in the tool

Simulation blanking: Example

workp iece fracture - deleting e lements

detail


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3D-simulation - draw-ins


3D-simulation - strain


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What does the sheared surface look like in b lanking ?

Why is th is surface not completely smooth ?

Please explain the punch force over punch travel for blanking !

Why are blanking tools made of hardened and tempered material ?

Why are sheet metal parts of high quantity m ade preferably throughblanking and not through CNC-wire Electro-erosion ?

What is the maximum st roke frequency of a blanking machine ?

Why is there an increased fraction of smooth surface in f ine blanking incomparison to normal blanking ?

What is the reason behind the diff iculty classes in fine blanking ? Whycan a protruding part be not arbitrarily thin ? Why can a radius not bearbitrarily small ?

Can hardened and annealed materials be used as workpiece material infine blanking ?

What is the maximum plastic s train in fine blanking ?

Questions

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