14. mechanisation and welding fixturesdantn/wt/wt1-c14.pdf · 14. mechanisation and welding...

2003

14.

Mechanisation

and Welding Fixtures

14. Mechanisation and Welding Fixtures 188

As the production costs of the metal-working industry are nowadays mainly deter-

mined by the costs of labour, many factories are compelled to rationalise their manu-

facturing methods

by partially and

fully mechanised

production proc-

esses. In the field

of welding engi-

neering where a

consistently good

quality with a maxi-

mum productivity is

a must, automation

aspects are conse-

quently taken into

account.

The levels of mechanisation in weld-

ing 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 se-

quence, as, e.g., the transport of parts

to the welding point. Figure 14.1 ex-

plains the four levels of mechanisation.

Figure 14.2. shows manual welding,

in this case: manual electrode wel-

ding. The control of the electrode

and/or the arc is carried out manu-ally.

The filler metal (the consumable elec-

trode) is also fed manually to the weld-

ing point.

© ISF 2002br-er14-02e.cdr

Manual Welding(Manual Electrode Welding)

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

controlworkpiecehandling

filler wirefeeding

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Figure 14.1

Figure 14.2


In partially

mechanised weld-

ing, e.g. gas-

shielded metal-arc

welding, the arc

manipulation is car-

ried out manually,

the filler metal ad-

dition, however, is

executed mechani-

cally by means of a

wire feed motor,

Figure 14.3.

In fully mechanised welding, Figure 14.4, an automatic equipment mechanism car-

ries out the weld-

ing advance and

thus the torch con-

trol. Wire feeding

is realised by

means of wire feed

units. The work-

pieces must be

positioned manu-

ally in accordance

with the direction of

the moving ma-

chine support.

In automatic welding, besides the process sequences described above, the work-

pieces are mechanically positioned at the welding point and, after welding, auto-

matically trans-ported to the next working station. Figure14. 5 shows an example 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


Apart from the ac-

tual welding de-

vice, 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 proc-

ess at all possible.

Figure 14.6 shows

a survey of the

most important

assisting devices.

Before welding,

the parts are nor-

mally aligned and

then tack-welded.

Figure 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 exam-

ple 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


In apparatus engi-

neering and tank

construction it is of-

ten necessary to

rotate the compo-

nents, e.g., when

welding circumferen-

tial seams. The

equipment should be

as versatile as pos-

sible and suit sev-

eral tank diameters.

Figure 14.9 shows

three types of turn-

ing rolls which fulfil

the demands. Figure

top: the rollers are

adjustable; Figure

middle: the rollers

automatically adapt

to the tank diameter;

Figure bottom: the

roller spacing may

be varied by a scis-

sor-like arrange-

ment.

In general, dollies are motor-driven. This provides also an effortless movement of

heavy components, Figure 14.10.

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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 17.8


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. Rotations

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 work-

ing parts with

weights of just a

few kilograms right

up to several hun-

dred tons.

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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 axistable support

gear segmenttable top

rotational axis


A turn-tilt table with

hydraulic adjustment

of the tilting and ver-

tical motion as well

as chucking grooves

for the part fixture is

depicted in Fig-

ure 14.12.

In robot technology the types of turn-tilt-tables - as shown in Figure 14.13 - are gain-

ing importance. Positioners with orbital design have a decisive advantage be-

cause the component, when turning around the tilting axis, remains approx. equally

distant to the welding robot.

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Turn-Tilt-Table With Hydraulic Adjustment

Figure 14.12

Turn-Tilt-Tables


single-column turn-tilt-table orbital turn-tilt-table

table top table top

rotational axis rotational axis

tilting axis tilting axissupport

table support table support

support

Figure 14.13


Other types of workpiece positioners are shown in Figure 14.14 – the double col-

umn turn-tilt-table and the spindle and sliding holder turn-tilt-table. Those types

of positioners are used for special component geometries and allow welding of any

seam in the flat and in the horizontal position.

In the field of welding, special 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.

Double-Column Turn-Tilt-Table


table support

rotational axis

table toptilting axis

support

Figure 14.14

Figure 14.15

Spindle / Sliding Holder Turntable


bed way

spindle holder

table tops

sliding holder


Plain plates or rounded tanks are clamped by means of longitudinal jigs for the

welding of a longitudinal seam, Figure 14.17. The design and the gripping power are

very dependent of the thickness of the plates to be welded.

A simple example of a special welding machine is the tractor travelling carriage for

submerged-arc welding, Figure 14.18. This device is designed for the application

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Figure 14.16

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Figure 14.17


on-site and provides, besides the sup-

ply 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 sup-

ports 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 additional axes to allow

precise positioning.

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

describes kine-

matic chains which

can be realised by

different combina-

tions of translatory

and rotary axes.

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Tractor for Submerged-Arc Welding

Figure 14.18

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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


The most common design of a track-

mounted welding robot is shown in

Figure 14.21. The robot depicted here

is a hinged-arm robot with six axes.

The axes are divided into three princi-

pal and three additional 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.

Kinematic Chains


designation

arrangement

kinematicschedule

operatingspace

cartesianrobot

cylindercoordinated

robot

sphericalcoordinated

robothorizontal

knuckle armrobot

verticalknuckle arm

robot

x

y

zz

z

C

C

CC

BB

R R DA

Figure 14.20

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Robot Motions

Figure 14.21


Varying lever lengths permit the design of robots with different operating ranges.

Figure 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 compo-

nent only certain

positions. In the

case of a sus-

pended arrange-

ment the robot

fixing device is

shortened thus al-

lowing a compact

design.

For the completion of a robot welding station workpiece positioners are necessary.

Figure 14.23 shows positioner devices where also several axes may be combined.

These axes may either turn to certain defined positions or be guided by the robot

control and moved

synchronically with

the internal axes.

The complexity and

versatility of the

axis positions in-

creases with the

number of axes

which participate in

the movement.

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Figure 14.22

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Figure 14.23


Movement by means of a linear travelling mechanism increases the operating

range of the robot, Figure 14.24. This may be done in ease of stationary as well as

suspended arrangement, where there is a possibility to move to fixed end positions or

to stay in a synchronised motion with the other movement axes.

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Figure 14.24

14. mechanisation and welding fixturesdantn/wt/wt1-c14.pdf · 14. mechanisation and welding...

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