l05 blanking and fine blanking
TRANSCRIPT
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© WZL/Fraunhofer IPT
Blanking and FineblankingSimulation Techniques in Manufacturing Technology
Lecture 5
Laboratory for Machine Tools and Production Engineering
Chair of Manufacturing Technology
Prof. Dr.-Ing. Dr.-Ing. E.h. Dr. h.c. Dr. h.c. F. Klocke
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Calculation of blanking parts5
Fineblanking4
Shearing3
Requirements on blanking parts2
Introduction1
Outline
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Deep Drawing
Ironing
Spinning
Hydroforming Wire Drawing Pipe Drawing
Collar Forming
Casting Forming Cutting Joining Coating Changing ofMaterial Properties
CompressiveForming
Tenso-
Compressive
Forming
TensileForming
Bend FormingShear
FormingSevering
Translate Twist
Intersperse
Manufacturing Processes
according to DIN 8580ff
Open DieForging
Closed Die
Forging Cold Extrusion Rod Extrusion
Rolling Upsetting
Hobbing
Thread Rolling
Stretch Forming
Extending
Expanding
Embossing
With linearToolMovement
Withrotating ToolMovement
Shearing
Fine Blanking
Cutting with a
single Blade Cutting with
two approaching
Blades Splitting
Tearing
Introduction
Sheet Metal Forming Processes
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Introduction
What is blanking?
Definition:
Mechanical separation of workpieces by a shearing process without formation of chips – if necessary, including additional forming-operations.
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Calculation of blanking parts5
Fineblanking4
Shearing3
Requirements on blanking parts2
Introduction1
Outline
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Requirements on blanking parts
Required quality of blanking parts
surface evenness
smooth sheared zone
cutting burr
rupture zone
draw-in
achievableroughness
angular deviation
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Calculation of blanking parts5
Fineblanking4
Shearing3
Requirements on blanking parts2
Introduction1
Outline
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Shearing - Introduction
Shearing – Introduction
application IT-classification costs output
Shearing
high
rough (IT 11) low high
lowfine (IT 7)
shearedsurface
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Shearing - Characterisation of the process
Open and closed cut in shearing
open cut closed cut
tool flankopen flank
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Shearing - Characterisation of the process
Differentiation of blanking and piercing
blanking piercing
waste
waste
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Shearing - Characterisation of the process
Tool design of shearing
punch
sheet metal
blanking die
u – die clearenceapp. 0,05 x sheet thickness
with:
u = ½·(a – a1)
a – dimension of cutting die
a1 – punch dimension
α – relief angleof cutting die
U
blank holder
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Shearing - Characterisation of the process
Process sequences of shearing
1 2
3 4
charging ofthe punch
elastic& plasticdeformation
shearing& cracking
break through
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Shearing – Achievable accuracy
Errors on sheared workpieces
burr height hG
draw-in height hE
draw-in
shearing zone
rupture zone
tR
hG
hE
crack depth tR
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Shearing – Achievable accuracy
Influence of die clearance on the sheared surfaces
smallclearance
bigclearance
By a small die clearance, distortion wedges are generated by squeezing of the materialbetween two cracks
no formation of distortion wedge
formation of distortion wedge
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Shearing – Achievable accuracy
Quality of sheared surface depending on specific die clearance
s
p e c i f i c d i e
c l e a
r a n c e :
d i e
c l e a
r a n c e
u S
/ s h e e t t h i c k n e s s s
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Shearing – Achievable accuracy
Influence of specific die clearance on crack depth
blanking
specific die clearance us / %
C r a c
k d e p t h
t R
s h e e
t t h i c k n e s s s
Part diameter
da = 30 mm
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Shearing – Achievable accuracy
Relation between burr height and number of cuts
ductilesheet
brittlesheet
burr height
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Shearing - Forces in shearing
Reduction of cutting force by modification of tools
Contact between punch and sheet
slopedcut
planecut
s h
total punch stroke
f o r c e F
0 s 2s 3s
0,3 Fmax
0,6 Fmax
0,9 Fmax
Fmax h = 0 (plane cut)
h = 1/3 s (sloped cut)
h = s (sloped cut)
h = 2s(sloped cut)
=
work s(h=0) = work s(h=2s)
Due to workpiece-bending, sloped cut is only suited for piercing.
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Shearing - Forces in shearing
Reduction of cutting force by modification of tools
conical punchgrooved punchplane cut sloped cut
conical die grooved die punch offset
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Shearing - Forces in shearing
Dependence of quality on shearing strength of carbon steel
carbon concentration tensile strength breaking elongation sheet thickness
die clearance part diameter aspect ratio Die / punch radius
Cutting resistance kS is defined as the cutting force (Fs) referring to the cutting surfacekS = FSmax / AS (with As= ls*s)
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Shearing – Wear
Wear on the punch
wear on shaft area
wear on front facefatigue wear on front face
fatigue wear and wear on frontface especially appear for lowersheet thickness (s < 2 mm)
wear on shaft area
– is caused by friction betweenpunch and sheet in direction ofpunch movement
– appears during cutting of thickersheets (s ≥ 2 mm)
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open cut
Workpiece
Shearing – wear
Influences on wear
Source: reiner, Müller Weingarten, Feintool
Tool Machine
Type of process
tool wear
materialhardnesssurfaceguidancedie clearance
stiffness
kinematics
alloystiffnesshardnessdimensionshape
open cutclosed cut
closed cut
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Shearing – Tool design
Multi-stage blanking tool
4 stageMulti-stage blanking toolfor shearing of rotor- andstator-sheets
stator rotor
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Calculation of blanking parts5
Fineblanking4
Shearing3
Requirements on blanking parts2
Introduction1
Outline
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Fineblanking - Introduction
Fineblanking - Introduction
application IT-classification costs output
shearing
fineblanking
high
rough (IT 11) low high
lowfine (IT 7)
shearedsurface
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Fineblanking – Characterisation of the process
Animation of fineblanking
clamping
plastic deformation
cutting
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fineblankingshearing
1 – cutting die(2 – guiding plate)3 – punch
FS – punch force
1 – cutting die2 – vee ring and
blank holder
3 – punch4 – counter punch
FS – punch forceFR – vee ring and blank
holder forceFG – counter punch
force
Fineblanking – Characterisation of the process
Differences between shearing and fineblanking
die clearance5% 0,5%
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Fineblanking – Details
Geometry of vee rings
thin sheets
thick sheets
sheet thickness s5 – 15 mm
sheet thickness s3 – 5 mm
blank holderwith vee ring
cutting die
• create compression stresses
• prevent horizontal movement of thesheet / material flow
vee ring
cutting line
toothed
inward notch
outward notch
vee ring cutting line
intention:
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Fineblanking - Details
Dependence of workpiece quality on influencing quantities
counter punch force draw-in width draw-in height
smooth shearingzone
deflexion
Process parameters affect workpiece quality:
example:
draw-in height die clearance sheet thickness
blank holder forcecounter punchforce
Workpiece quality can be influenced by process parameters:example:
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Fineblanking – obtainable precision
Definition of degree of difficulty in fineblanking
s
l o t a , s t i c k b / m m
sheet thickness s / mm
e d g e r a d i u s r
i , r a / m m
sheet thickness s / mm
degree of difficulty
S1 – easy
S2 – medium
S3 – difficultedge angle a
Fi bl ki i f t h i
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Fineblanking – comparison of techniques
Comparison of sheared surface in shearing and fineblanking
shearing
fineblanking
In fineblanking, the smooth sheared zone can take a share of 100%
Fi bl ki li ti
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Fineblanking – application
Application examples
fineblanking
shearing
In fineblanking, the sheared surface can be used as a functional surface
Fineblanking Field of application
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Fineblanking – Field of application
Application examples in automotive industry
valve plate
gear shifting gate door lock window lift
synchronising disc
belt pretensioner
ABS-pulse generator
cooling systemseat belt componentsseat adjustment
brakes
gear
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Calculation of blanking parts5
Fineblanking4
Shearing3
Requirements on blanking parts2
Introduction1
Outline
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Calculation of blanking process
• Analytical calculation method
• FEA of (fine)blanking processes
Principals and drawbacks
Advantage over analytical calculation by means of examples
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Calculation of blanking process - cutting force
S S S k lsF ⋅⋅=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
( )∫=g x
S S dx xF W 0
maxS gS F xcW ⋅⋅=
cutting energy
x :cutting distanceFS :current cutting force
c :correction factorincluding variables likematerial properties,effective cutting distance,size of die clearance andfriction
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Calculation of fine blanking process - vee ring force
m R R R RhlF ⋅⋅⋅=
4approximation 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 q AF ⋅=
220
mm
N qG =
270
mm
N qG =
Approximation for the counter punch force
Aq :cutting piece surface
qG :specific counter punch force
Value of the specific counter punch force for
small sized, thin workpieces
Value of the specific counter punch force forlarge, thick workpieces
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Calculation of fine blanking process - cutting force
GSt S F F F −=
sl
F
A
F k
S
S
S
S S
⋅
== maxmax
m
S
R
k C =
1
mgS gS RslC slF ⋅⋅⋅=⋅⋅= 1τ
9,06,01
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Simulation fine blanking
Simulation of fine blanking offers the opportunity to include:
This leads to the following results:
• force over punch travel• stress field
• strain rate field• draw-ins• prediction of fracture
• flow stress data• friction properties• thermomechanical coupling
More exact input data can be enclosed:
instead of mgS RslC F ⋅⋅⋅= 1
.const Rm =