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14.
Mechanisation
and Welding Fixture
14. Mechanisation and Welding Fixtures 197
2005
As the production costs of the metal-working industry are nowadays mainly determined by
the costs of labour, many
factories are compelled to
rationalise their manufac-
turing methods by partially
and fully mechanised pro-
duction processes. In the
field of welding engineering
where a consistently good
quality with a maximum
productivity is a must,
automation aspects are
conse-quently taken into
account.
The levels of mechanisation in welding are
stipulated in DIN 1910, part 1. Distinctions are
made with regard to the type of torch control
and to filler addition and to the type of process
sequence, as, e.g., the transport of parts to
the welding point. Figure 14.1 explains the
four levels of mechanisation.
Figure 14.2. shows manual welding, in this
case: manual electrode welding. The control
of the electrode and/or the arc is carried out
manually. The filler metal (the consumable
electrode) is also fed manually to the welding
point.
Designationexamples
gas-shielded arc weldingTIG GMAW
movement/ working cycles
manual welding
m
partiallymechanised
weldingt
fully mechanisedwelding
v
automaticwelding
a
mechanically
mechanicallymechanically mechanically
mechanicallymechanically
manually manually
manually
manually
manually
manually
torch-/workpiece
control
workpiecehandling
filler wirefeeding
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Figure 14.1
© ISF 2002br-er14-02e.cdr
Manual Welding(Manual Electrode Welding)
Figure 14.2
14. Mechanisation and Welding Fixtures 198
2005
In partially mechanised
welding, e.g. gas-shielded
metal-arc welding, the arc
manipulation is carried out
manually, the filler metal
addition, however, is exe-
cuted mechanically by
means of a wire feed mo-
tor, Figure 14.3.
In fully mechanised weld-
ing, Figure 14.4, an auto-
matic equipment
mechanism carries out the welding advance and thus the torch control. Wire feeding is re-
alised by means of wire feed units. The workpieces must be positioned manually in accor-
dance with the direction of the moving machine support.
In automatic welding, be-
sides the process se-
quences described above,
the work-pieces are me-
chanically positioned at
the welding point and,
after welding, auto-
matically trans-ported to
the next working station.
Figure14. 5 shows an ex-
ample of automatic welding
(assembly line in the car
industry).
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Partially Mechanised Welding(Gas-Shielded Metal-Arc Welding)
Figure 14.3
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Fully Mechanised Welding(Gas-Shielded Metal-Arc Welding)
Figure 14.4
14. Mechanisation and Welding Fixtures 199
2005
Apart from the actual weld-
ing device, that is, the
welding power source, the
filler metal feeding unit and
the simple torch control
units, there is a variety of
auxiliary devices available
which facilitate or make the
welding process at all pos-
sible. Figure 14.6 shows a
survey of the most impor-
tant assisting devices.
Before welding, the parts
are normally aligned and
then tack-welded. Fig-
ure 14.7 depicts a simple
tack-welding jig for pipe
clamping. The lower part of
the device has the shape
of a prism. This allows to
clamp pipes with different
diameters.
Devices, however, may be
significantly more complex.
Figure 14.8 shows an example of an assembly equipment used in car body manufacturing.
This type of device allows to fix complex parts at several points. Thus a defined position of
any weld seam is reproducible.
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Automatic Welding (Assembly Line)
Figure 14.5
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assembly line
welding robot
machine carrier
linear travelling mechanism
track-mounted welding robots
spindle / sliding head turntable
turn-/ tilt table
dollies
assembly devices
Figure 14.6
14. Mechanisation and Welding Fixtures 200
2005
In apparatus engineering
and tank construction it is
often necessary to rotate
the components, e.g.,
when welding circumferen-
tial seams. The equipment
should be as versatile as
possible and suit several
tank diameters. Figure 14.9
shows three types of turn-
ing rolls which fulfil the
demands. Figure bottom:
the rollers are adjustable;
Figure middle: the rollers
automatically adapt to the
tank diameter; Figure top:
the roller spacing may be
varied by a scissor-like ar-
rangement.
In general, dollies are mo-
tor-driven. This provides
also an effortless move-
ment of heavy compo-
nents, Figure 14.10.
A work piece positioner, e.g. a turn-tilt-table, is part of the standard equipment of a robot
working station. Figure 14.11 shows a diagrammatic representation of a turn-tilt-table. Rota-
tions around the tilting axis of approx. 135° are possible while the turn-table can be turned by
365°. Those types of turn-tables are designed for working parts with weights of just a few
kilograms right up to several hundred tons.
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Simple Tack Welding Jig forWelding Circumferential Welds
Figure 14.7
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1 portal with 2 industrial robots IR 400, equipped with tool change system2 resting transformer welding tongs3 depot of welding tongs4 clamping tool5 copper back-up bar for car roof welding6 transformer welding tongs for car roof welding7 driverless transport system8 component support frame9 swivelled support for component support frames10 resting transformer welding tongs for car boot
Figure 14.8
14. Mechanisation and Welding Fixtures 201
2005
A turn-tilt-table with hydrau-
lic adjustment of the tilting
and vertical motion as well
as chucking grooves for the
part fixture is depicted in
Figure 14.12.
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Turning Rolls
set of rollers 1 set of rollers 2
Figure 14.9
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Turning Rolls
Figure 14.10
Figure 14.11
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support
tilting axis
table support
gear segmenttable top
rotational axis
14. Mechanisation and Welding Fixtures 202
2005
Turn-Tilt-Tables
© ISF 2002br-er14-13e.cdr
single-column turn-tilt-table orbital turn-tilt-table
table top table top
rotational axisrotational axis
tilting axis tilting axis
support
table support table support
support
Figure 14.13
In robot technology the
types of turn-tilt-tables - as
shown in Figure 14.13 - are
gaining importance. Posi-
tioners with orbital de-
sign have a decisive
advantage because the
component, when turning
around the tilting axis, re-
mains approx. equally dis-
tant to the welding robot.
Other types of workpiece
positioners are shown in
Figure 14.14 – the double
column turn-tilt-table and
the spindle and sliding
holder turn-tilt-table.
Those types of positioners
are used for special com-
ponent geometries and
allow welding of any seam
in the flat and in the hori-
zontal position.
In the field of welding, spe-
cial units are designed for
special tasks. Figure 14.16 shows a pipe-flange-welding machine. This machine allows the
welding of flanges to a pipe. The weld head has to be guided to follow the seam contour.
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Turn-Tilt-Table With Hydraulic Adjustment
Figure 14.12
14. Mechanisation and Welding Fixtures 203
2005
br-er14-16e.cdr
Figure 14.16
Figure 14.15 Spindle / Sliding Holder Turntable
© ISF 2002br-er14-15e.cdr
bed way
spindle holder
table tops
sliding holder
Double-Column Turn-Tilt-Table
© ISF 2002br-er14-14e.cdr
table support
rotational axis
table top
tilting axis
support
Figure 14.14
14. Mechanisation and Welding Fixtures 204
2005
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Figure 14.17
Plain plates or rounded
tanks are clamped by
means of longitudinal jigs
for the welding of a longi-
tudinal seam, Figure 14.17.
The design and the grip-
ping power are very de-
pendent of the thickness of
the plates to be welded.
A simple example of a
special welding machine is
the tractor travelling car-
riage for submerged-arc
welding, Figure 14.18. This device is de-
signed for the application on-site and pro-
vides, besides the supply of the filler metal,
also the welding speed as well as the feeding
and suction of the welding flux.
For the guidance of a welding head and/or
welding device, machine supports may be
used. Figure 14.19 shows different types of
machine supports for welding and cutting.
Apart from the translatory and rotary principal
axes they are often also equipped with addi-
tional axes to allow precise positioning.
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Tractor for Submerged-Arc Welding
Figure 14.18
14. Mechanisation and Welding Fixtures 205
2005
To increase levels of
mechanisation of welding
processes robots are fre-
quently applied. Robots are
handling devices which are
equipped with more than
three user-programmable
axes. Figure 14.20 de-
scribes kinematic chains
which can be realised by
different combinations of
translatory and rotary axes.
The most common design
of a track-mounted weld-
ing robot is shown in Fig-
ure 14.21. The robot
depicted here is a hinged-
arm robot with six axes. The
axes are divided into three
principal and three addi-
tional axes or hand axes.
The wire feed unit and the
spool carriers for the wire
electrodes are often fixed on
the robot. This allows a
compact welding design.
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boom
pillar
travelling mechanism
a b c
d e
main piloting system case cross pilotingsystem case
auxiliary piloting system case
auxiliary piloting system case
Figure 14.19
Kinematic Chains
© ISF 2002br-er14-20e.cdr
designation
arrangement
kinematicschedule
operatingspace
cartesianrobot
cylindercoordinated
robot
sphericalcoordinated
robot
horizontalknuckle arm
robot
verticalknuckle arm
robot
x
y
zz
z
C
C
CC
B
BR R D
A
Figure 14.20
14. Mechanisation and Welding Fixtures 206
2005
Varying lever lengths permit the design of robots with different operating ranges. Fig-
ure 14.22 shows the operating range of a robot. In the unrestricted operating range the
component may be reached with the torch in
any position. The restricted operating range
allows the torch to reach the component only
certain positions. In the case of a suspended
arrangement the robot fixing device is short-
ened thus allowing a compact design.
For the completion of a robot welding station
workpiece positioners are necessary. Fig-
ure 14.23 shows positioner devices where
also several axes may be combined. These
axes may either turn to certain defined posi-
tions or be guided by the robot control and
moved synchronically with the internal axes.
The complexity and versatility of the axis posi-
tions increases with the number of axes which
participate in the movement.
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Figure 14.22
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Robot Motions
Figure 14.21
14. Mechanisation and Welding Fixtures 207
2005
Movement by means of a
linear travelling mecha-
nism increases the operat-
ing range of the robot,
Figure 14.24. This may be
done in ease of stationary
as well as suspended ar-
rangement, where there is
a possibility to move to
fixed end positions or to
stay in a synchronised mo-
tion with the other move-
ment axes.
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Figure 14.24
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Figure 14.23