Forming - Blanking

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Forming - Blanking
Forming - Blanking
Manufacturing Technology II
Lecture 6
Laboratory for Machine Tools and Production Engineering
Chair of Manufacturing Technology
Prof. Dr.-Ing. Dr.-Ing. E.h. F. Klocke
© WZL / IPT
Seite 1
Content
„ Introduction
Demands on blanking parts
Shearing
Fine blanking
Laser cutting
Water-jet cutting
© WZL / IPT
Seite 2
1
Introduction
Sheet Forming Process
Manufacturing Processes
according to DIN 8580ff
Casting
Forming
TensoCompressive
Forming
Compressive
Forming
„ Open Die
„
„
„
„
„
„
„
Forging
Closed Die
Forging
Cold Extrusion
Rod Extrusion
Rolling
Upsetting
Hobbing
Thread Rolling
Cutting
„
„
„
„
„
„
„
Deep Drawing
Ironing
Spinning
Hydroforming
Wire Drawing
Pipe Drawing
Collar Forming
Tensile
Forming
„
„
„
„
Stretch Forming
Extending
Expanding
Embossing
Joining
Bend Forming
„ With linear
Tool
Movement
„ With
rotating Tool
Movement
Coating
Changing of
Material Properties
Shear
Forming
Severing
„ Translate
„ Twist
„ Intersperse
„ Shearing
„ Fine Blanking
„ Cutting with a
single Blade
„ Cutting with
two approaching
Blades
„ Splitting
„ Tearing
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Seite 3
Introduction
What is blanking?
„ Definition:
Mechanical separation of workpieces without appearance of shapeless material,
therefore without chips … if necessary, including additional forming-operations.
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Seite 4
2
Content
Introduction
„ Demands on blanking parts
Shearing
Fine blanking
Laser cutting
Water-jet cutting
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Seite 5
Demands on blanking parts
Required quality of blanking parts
surface evenness
angular deviation
draw-in
achievable
roughness
rupture zone
smooth sheared zone
cutting burr
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Seite 6
3
Content
Introduction
Demands on blanking parts
„ Shearing
–
–
–
–
–
–
–
Introduction
Characterisation of the process
Achievable accuracy
Forces in shearing
Wear
Tool design
Examples of sheared parts
Fine blanking
Laser cutting
Water-jet cutting
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Seite 7
Shearing - Introduction
Shearing – Introduction
application
IT-classification
costs
output
fine (IT 7)
high
low
rough (IT 11)
low
high
sheared
surface
Shearing
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Seite 8
4
Shearing - Characterisation of the process
Open and closed cut in shearing
open cut
closed cut
tool flank
open flank
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Seite 9
Shearing - Characterisation of the process
Differentiation of blanking and perforating
blanking
piercing
waste
waste
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Seite 10
5
Shearing - Characterisation of the process
Tool design of shearing
punch
u – die clearence
app. 0,05 x sheet thickness
with:
u = ½ · (a – a1)
blank holder
a – dimension of cutting die
U
sheet metal
a1 – punch dimension
α – relief angle
of cutting die
blanking die
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Seite 11
Shearing - Characterisation of the process
Process sequences of shearing
charging of
the punch
1
2
elastic
& plastic
deformation
shearing
& cracking
3
4
break through
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6
Shearing - Characterisation of the process
Stresses in shearing
punch
F
σ
τ
τ
σ
F
cutting
die
„ shearing and tensile stresses cause cracking
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Seite 13
Shearing – Achievable accuracy
Errors on sheared workpieces
draw-in
draw-in height hE
hE
shearing zone
rupture zone
hG
burr height hG
tR
crack depth tR
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Seite 14
7
Shearing – Achievable accuracy
Influence of die clearance on the sheared surfaces
formation of distortion wedge
small
clearance
no formation of distortion wedge
big
clearance
„ By a small die clearance, distortion wedges are generated by squeezing of a the material
between two cracks.
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Seite 15
Shearing – Achievable accuracy
specific die clearance:
die clearance uS / sheet thickness s
Quality of sheared surface depending on specific die clearance
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Seite 16
8
Shearing – Achievable accuracy
Influence of specific die clearance on crack depth
Crack depth
tR
sheet thickness s
blanking
specific die clearance us / %
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Seite 17
Shearing – Achievable accuracy
Relation between burr height and number of cuts
ductile
sheet
brittle
sheet
burr height
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9
Shearing - Forces in shearing
Reduction of cutting force by modification of tools
sloped
cut
plane
cut
h = 0 (plane cut)
Fmax
0,9 Fmax
force F
h = 1/3 s (sloped cut)
s
h
work s(h=0) = work s(h=2s)
=
0,6 Fmax
h = s (sloped cut)
h = 2s
(sloped cut)
0,3 Fmax
Contact between punch and sheet
0
s
2s
3s
total punch stroke
„ Due to workpiece-bending, sloped cut is only suited for piercing.
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Seite 19
Shearing - Forces in shearing
Reduction of cutting force by modification of tools
plane cut
conical die
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sloped cut
grooved die
grooved punch
conical punch
punch offset
Seite 20
10
Shearing - Forces in shearing
Dependence of quality on shearing strength of carbon steel
carbon concentration
tensile strenght
breaking elongation
sheet thickness
die clearance
part diameter
aspect ratio
draw-in
„ Cutting resistance is defined as the cutting force (Fs) referring to the cutting surface (As=
ls*s)
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Seite 21
Shearing – Wear
Wear on the punch
„ fatigue wear and wear on front
face espacially appear for lower
sheet thickness (s < 2 mm)
fatigue wear on front face
wear on front face
„ wear on shaft area is caused by
friction between punch and sheet
in direction of punch movement.
Appears during cutting of thicker
sheets (s ≥ 2 mm)
wear on shaft area
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Seite 22
11
Shearing – wear
Influences on wear
Tool
Machine
material
hardness
surface
guidance
die clearance
stiffness
kinematics
tool wear
Workpiece
Type of process
alloy
stiffness
hardness
dimension
shape
open cut
closed cut
closed cut
open cut
Source: reiner, Müller Weingarten, Feintool
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Seite 23
Shearing – Tool design
Multi-stage blanking tool
4 stage
Multi-stage blanking tool
for shearing of rotor- and
stator-sheets
stator
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rotor
Seite 24
12
Shearing - Examples of sheared parts
Multi-stage cut including assembly of an electronic connector
Gesamtlaufzeit
1:49 min
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Seite 25
Content
Introduction
Demands on blanking parts
Shearing
„ Fine blanking
–
–
–
–
–
–
–
Introduction
Characterisation of the process
Process details and degree of difficulty
Achievable accuracy
Field of application
Tool design
Production examples
Laser cutting
Water-jet cutting
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Seite 26
13
Fine blanking - Introduction
Fine blanking - Introduction
application
IT-classification
costs
output
fine (IT 7)
high
low
rough (IT 11)
low
high
sheared
surface
fine blanking
shearing
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Seite 27
Fine blanking – Characterisation of the process
Animation of fine blanking
clamping
plastic deformation
cutting
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Seite 28
14
Fine blanking – Characterisation of the process
Stresses in fine blanking
blankholder
with vee F
ring
punch
F
σ
σ
σ
σ
τ
τ
σ
σ
σ
σ
σ
σ
σ
σ
F
F
counter
punch
cutting die
superposed compression prevents cracking
© WZL / IPT
Seite 29
Fine blanking – Characterisation of the process
Differences between shearing and fine blanking
shearing
fine blanking
FS – punch force
FS – punch force
FR – vee ring and blank
holder force
FG – counter punch
force
1 – cutting die
(2 – guiding plate)
3 – punch
1 – cutting die
2 – vee ring and
blank holder
3 – punch
4 – counter punch
5%
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die clearance
0,5%
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15
Fine blanking – Details
Geometry of vee rings
vee ring
thin sheets
sheet thickness s
3 – 5 mm
cutting line
outward notch
toothed
inward notch
cutting die
thick sheets
blank holder
with vee ring
sheet thickness s
5 – 15 mm
vee ring
intention:
cutting line
• create compression stresses
• prevent horizontal movement of the
sheet / material flow
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Seite 31
Fine blanking - Details
Dependence of workpiece quality on influencing quantities
Process parameters affect workpiece quality:
example:
counter punch force
draw-in width
draw-in height
smooth shearing
zone
deflexion
Workpiece quality can be influenced by process parameters:
example:
draw-in height
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die clearance
sheet thickness
blank holder force
counter punch
force
Seite 32
16
Fine blanking – obtainable precision
Definition of degree of difficulty in fine blanking
degree of difficulty
S1 – easy
S2 – medium
S3 – difficult
slot a, stick b / mm
edge radius ri , ra / mm
edge angle a
sheet thickness s / mm
sheet thickness s / mm
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Seite 33
Fine blanking – comparison of techniques
Comparison of sheared surface in shearing and fine blanking
shearing
fine blanking
„ In fine blanking, the smooth sheared zone can take a share of 100%
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Seite 34
17
Fine blanking –application
Application examples
fine blanking
shearing
„ In fine blanking, the sheared surface can be used as a functional surface
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Seite 35
Fine blanking – Field of application
Application examples in automotive industry
gear shifting gate
door lock
window lift
synchronising disc
valve plate
belt pretensioner
gear
ABSpulse generator
brakes
seat adjustment
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seat belt components
cooling system
Seite 36
18
Fine blanking – Tool design
Example for a compound press tool
„ In fine blanking, several cuts can be done at the same time.
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Seite 37
Fine blanking – Tool design
Compound press tool – disc brake
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Seite 38
19
Fine blanking – Tool design
Example for a multi-stage tools
fine blanking of a disc using multi-stage tool
fine blanking of a clutch disc
Feed
direction
stage 1
stage 2
stage 1: fine blanking
stage 2: burr stamping
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Seite 39
Fine blanking – Tool design
follow-on composite tool
3 stages in a
Follow-on composite tool
forming –
thread forming –
fine blanking
connecting strap of a car door
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Seite 40
20
Fine blanking – Production examples
Production of a clutch disc
Gesamtlaufzeit
2:13 min
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Seite 41
Fine blanking – Production examples
Planet carrier: Starting point
combined fine blanking / forming
„ A combination of fine blanking and forming realises the production of complex parts
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Seite 42
21
Fine blanking – Production examples
Example planet carrier: Approach
alternative A
- inappropriate contur for forming
- requires machining
alternative B
- No mashining required
example „planet carrier“
„ properly for manufacturing through Redesign
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Seite 43
Fine blanking – Production examples
Planet carrier: Implementation in an 8-stage follow-on composite tool
1
pre-blanking,
pin stop hole
3
5
7
bending tabs 45°
chamfering of hole
fine blanking
of slots and holes
step coining
piercing Ø39 H9
shape coining of tabs
2
bend tab 90°
4
burr stamping
at slots
6
final cut
8
„ Development of forming and blanking sequence
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22
Fine blanking – Production examples
Planet carrier: Follow-on composite tool in modular design
bottom tool
upper tool
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Seite 45
Fine blanking – Production examples
Planet carrier: Follow-on composite tool in modular design
stages / module
1
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2
3
4
5
6
7
8
Seite 46
23
Content
Introdution
Demands on blanking parts
Shearing
Fine blanking
„ Laser cutting
Water-jet cutting
© WZL / IPT
Seite 47
Laser cutting – Characterisation of the process
Principle of laser cutting
power distribution
across laserlaser-profile
„ Cutting by local melting and exhausting of material
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Seite 48
24
Laser cutting – process variables
Cutting speed for several materials
structural steel (O2 0,5 – 4 bar)
CrNi - steel
(O2 0,5 – 4 bar)
Al. - alloy
(O2 10 – 18 bar)
CO2-laser, PL max = 2,6 kW
m
min
12
feed speed vf /
8
4
0
4
8
12
sheet thickness s / mm
16
20
„ Top feed speed depends on material and sheet thickness
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Seite 49
Laser cutting – process variables
Comparison of cutting speeds
20
feed speed vf /
m
min
shearing
laser cutting (1500 W)
water-jet cutting
15
10
5
0
4
8
12
16
20
24
sheet thickness structural steel s / mm
„ Top feed speed depends on material and sheet thickness
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Quelle: Trumpf
Seite 50
25
Laser cutting – Process comparison
Comparision shearing - nibbling - laser beam cutting
special process:
rotational cutting
nibbling
laser cut
30 sec
40 sec
17 sec
B
4 sec
-
16 sec
C
3 sec
15 sec
12 sec
shearing
(rotational)
contour
A
speed
St37
465mm x 5400mm x 2mm
flexibility
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Seite 51
Laser cutting – process variables
Comparison of machinable sheet thicknesses
structural steel
high-grade steel
aluminium
shearing
laser-jet
cutting
(1500 W)
laser-jet
cutting
(2600 W)
water-jet
cutting
0
20
40
60
sheet thickness / mm
80
Quelle: Trumpf
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Seite 52
26
Laser cutting – Field of application
Examples of series production
electronic connector (low lot sizes)
synchronising disc
climbing clamp
stator sheet for special engines
Quelle: tecnologix
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Seite 53
Content
Introdution
Demands on blanking parts
Shearing
Fine blanking
Laser cutting
„ Water-jet cutting
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Seite 54
27
Water-jet cutting – Characterisation of the process
System design
principle
water supply
abrasive
medium
guard
mixing pipe
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Seite 55
Water-jet cutting
Properties of the jet groove
Verrundung
rounding offder
at the jet entry
St rahleint rit t skant e
Konizit ät der
beveled
hole
Schnit
t f uge
Abplat
zungen
chipping
at theamexit
St rahlaust rit t
scoring,
erosion
and cracks on the
Rief
en, Ausw
aschungen,
surface
Risse
auf Schnit t f lächen
Quellenangabe: XYZ
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Seite 56
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Water-jet cutting
cutted surfaces and gaps
feed speed
1
2
vf
= 20 mm/min
Rz,1
= 25 µm
Rz,2
= 30 µm
vf
= 200 mm/min
Rz,1
= 25 µm
Rz,2
= 140 µm
gap
surface
1
2
material
sheet thickness
: AlMgSiO.5
: 25 mm
abrasive medium
mass flow
pressure
: Granat 80 Mesh
: 400 g/min
: 300 MPa
„ The surface quality is heavily dependent on the feed speed
© WZL / IPT
Seite 57
Water-jet cutting – process parameters
Characteristic of the surface
α
bG
b0
bSO
bSu
: angle of shoulder
: burr width
: width of „jet influenced zone“
: notch width on workpiece top
: notch width on workpiece bottom
© WZL / IPT
hG
R0
u
M
s
: burr height
: edge radius
: rectangular and inclination tolerance
: measuring range of u
: sheet thickness
Seite 58
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Water-jet cutting – influencing parameters
Influences on notch width
2,5
3
notch width bSU / mm
notch width bSO / mm
3,5
2,5
2
1,5
1
0,5
0
2
1,5
1
0,5
4
8
10 12
2
6
treatment distance aD / mm
pressure
nozzle diameter
lenght of focussing pipe
feed speed
abrasive medium
mass flow
material
sheet thickness
: 300 MPa
: 0,3 mm
: 50 mm
: 50 mm / min
: Granat 80 Mesh
: 250 g / min
: AlMgSi0.5
: 5 mm
© WZL / IPT
0
4
8
10 12
2
6
treatment distance aD / mm
focussing pipe diameter
d = 1,8 mm
d = 1,5 mm
d = 1,2 mm
d = 0,8 mm
Seite 59
Water-jet cutting – Dependences
Dependence of surface quality on particle size
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Water-jet cutting – Performance characteristic
Performance characteristics of different materials
80
depth of notch hK / mm
depth of notch hK / mm
80
60
40
20
40
20
0
0
0 150
250
200
pressure / MPa
nozzle diameter
lenght of focussing pipe
abrasive medium
mass flow
© WZL / IPT
60
300
: 0,3 mm
: 50 mm
: Granat 80 Mesh
: 250 g / min
0 150
250
200
feed speed / mm/min
300
material
: AlMgSi0.5
: TiAl6V4
: 1.4375
Seite 61
31

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