S Und S Essen 2009

3-DIMENSIONAL FRICTION STIR WELDING USING
A KUKA HIGH PAYLOAD ROBOT

Details and contact

Otto Kellenberger, M.Eng. – KUKA Roboter GmbH

© KUKA Roboter GmbH, KTM | 25.08.2009 | Seite 1 www.kuka.com

Introduction

Process description plunging in welling welding retracting

D

pin friction heat
shoulder is generated

2 mm

HAZ TMAZ Nugget


Introduction - Relevant machine types for FSW

Different machine concepts suitable for FSW

Special FSW CNC
machines milling machines

source: ESAB source: Heller

Parallelkinematic Articulated arm
Systems robots
(Tripods,
Hexapods)


Introduction - Relevant machine types for FSW

Comparison
FSW milling parallel- articulated
machine machine kinematics arm robot

control

stiffness

space requirement

working area

3D-capability

k.o.
welding depth
criterium
invest Not anymore)
advantageous balanced less advantageous

Articulated arm robots represent a flexible tool, which are suited for FSW
on thin profiles (0,3 mm to 8 mm Al alloy, 2xxx, 5xxx, 6xxx, 7xxx).


Introduction

welding of fuselage of the Eclipse 500 Business Jet

Further applications

automotive

railway manufacturing structural component of
shipbuilding the Panoz Esperante
(HSC Gotland Ferry) Shinkansen (source: Friction Stir Link)


Introduction

3-DIMENSIONAL FRICTION STIR WELDING USING
A MODIFIED HIGH PAYLOAD ROBOT

Advantages of the process
• well suited especially for Al-alloys source: Airbus

• high seam quality
• low welding distortion
• no filler metal needed
• intermetallic joints possible

tension
• high process effectivity
FSW joint
• … base material

elongation


Introduction - process notes

Advantages of the process Disadvantages

• well suited especially for Al-alloys • high process forces (depth limitation)
• high seam qualities achievable • well disigned clamping technique required
• high welding depths up to 50mm and more • corrosion behaviour of some welded
• low welding distortion structures (2xxx, 7xxx series)

• no filler metal needed • License required from TWI
(patented: 1991)
• intermetallic joints possible
• no fumes, dust or spatter
• no specially trained staff required


Capability of a high payload articulated arm robot

The „RoboFSW“ consortium for evaluation

application evaluation & supply of KR500 & experimentals,
system integration optimization simulation & evaluation



Actual FSW system

Robot
• KUKA KR500 MT
• modified to realize higher process forces

Welding head
• Electrical/hydraulically driven
• rotation speed up to 5000 rpm

Process forces
• force sensor between flange and welding head
• process force controlled without any additional axes

EADS Laboratory



Force controlled welding mode without additional axes
Fx

6.000 6 Fy

Fz

4.000 4 axial tool
position

distance [mm]
force [N]

2.000 2

0 0

-2.000 -2

-4.000 -4
0 10 20 30 40 50 60 70 80 90 100 110 120 130
time [s]

plunge in welding phase
phase



Recent welding sample (without seam tracking system)

material: Al6156-T6
thickness: 3.4 mm
joint geometry: butt joint
welding position: horizontal (-Z)
welding direction: -X (to the robot base)
rot. speed: 1800 rpm
welding speed: 240 mm/min



Results
yield strength: 190 N/mm2 (bm: 310 N/mm2)
tensile strength: 270 N/mm2 (bm: 350 N/mm2)
elongation: 4 % (bm: 8 %)
fracture: HAZ
bending test: 180 °
cross section: overview
hardness: 75HV0.5 (bm: 130HV0.5)
faults: not detected

140
120
hardness HV 0.5

100
80
60
40
20
0

hardness 180°- bending test cross section: root



HAZ Nugget HAZ
160

140

Linear butt joint 120

100

HV 1
80
AW-6056-T6, 5mm
butt joint 60

40
specimen 1
process force: 9 kN 20 specimen 2
welding speed: 600 mm/min specimen 3
0
-25 -20 -15 -10 -5 0 5 10 15 20
position [mm]



specimen ‘+1.2‘ specimen ‘0‘
AW-6056-T6, 5 mm
butt joint
threaded cone shaped tool pin
Ø3.5 mm to Ø5 mm
Intentional lateral tool
displacement: joint surface
350
-1.5 mm to +1.5 mm
process force: 9 kN 300
250
UTS of 290 MPa with tool
tension [MPa]

200 specimen '-1.2'
displacements of ±1 mm specimen '-0.9'
specimen '-0.6'
150
specimen '-0.3'
specimen '0'
100
specimen +'0.3'
specimen '+0,6'
50
specimen '+0.9'
specimen '+1.2'
0
0,0 1,0 2,0 3,0 4,0 5,0
elongation [%]



AW-6061-T6, 1.8 mm, bead-on-plate, convex-concave
joint line; 3D capability

120

100

80
hardness [HV 1]

60

40
hardness +X /C
20 hardness -X / F
hardness +Y / M

0
0 10 20 30 40
position [mm]

high process robustness in
different welding directions



AW-6061-T6, 1.8 mm
bead-on-plate
convex-concave joint line

angular distortion < 1.5°

3 welding directions:
• radial from the robot base
• radial to the robot base
• tangential


Capability of a high payload articulated
arm robot compared with CNC Machines (Heller and ESAB)

Quelle: Heller

Without Quality difference between the machines:

- modified milling mashine
Mz
z
- KUKA articulated arm
Fx Fy
y
- esab FSW labor mashine
Fz

Picture: EADS


Results - capability of KUKA robot

Engine currents at different loads
(most loaded engine, medium range)

30

max. 25
Most loaded engine current [A]

continuous
current
20

15

10
direction "+X"
direction "+Y"
5
direction "-Z"

0
0 2000 4000 6000 8000 10000 12000 14000
Applied force [N]

process forces of up to 10 kN can be achieved in every basic end-
effector orientation.


Results - capability of the robot welds

Casting Material
FSW welded
AlSi10Mg(Fe)


Evaluation of a high payload articulated arm robot

Options: compensation of the tool deviation – seam tracking

Mz

Fx Fy
y

Fz
z

process forces lead to tool deviations optically controlled lateral tool positioning


Summary

1. Different machine concepts are suitable for FSW. The
optimal use of each concept is defined by the
requirements of the welding job (e.g. welding depth,
material).

2. High playload articulated arm robots are suited for
welding depths up to 5 mm (and more) because of their
limited engine and structure stresses.

force
3. The actual FSW system is able to provide process time

forces of up to 10 kN in any basic end-effector direction. Fx(t)

Welding in a force controlled mode is possible.
Fy(t)

Fz(t),
Mz(t)

4. The high process forces lead to deviations of the tool
from the programmed path.


Summary – processing system (for 800 N and more)

force
time

Fx(t)

Fy(t)

Fz(t),
Mz(t)


KUKA Reference Installation


S Und S Essen 2009

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S Und S Essen 2009