AFRICAN FUSION—MARCH2014
20
Fixture-free robot welding
T
o meet the demands of an ever-more competitive
market, flexibility is required from today’s production
systems.But inaddition, theymust becharacterisedby
high versatility. Versatility is understood to be the capability
of a system’s structure and technology to be adapted very
quickly when boundary conditions change, where there is
a significant number of product variants and/or where the
number of products per batch is low.
Forqualitymanagementof tolerances, thepartsare, inau-
tomatedweldingproduction,mostly fixed in jiggingor fixture
devices that themselves have a highly complex design and
thus account for significant manufacturing costs. Economic
viability isachievedonly formediumandhighmanufacturing
volumes, since switching tomanufacture different products
causes considerable
changeover expendi-
ture. In single unit and
small batchproduction,
therefore,manualweld-
ing is often used for its
high flexibility.
In automatedweld-
ing production, a high
degree of versatility is
only achievable if the
final welding product
is produced without
using jigging or fixture
devices that have been
custom-manufactured
for primary individual
parts. This work imple-
mentsanapproach that
pursues the conversion
of the welder-assistant
principle of manual
production to an auto-
matedwelding solution
that uses cooperating
robot systems. Within
the scope of this ar-
ticle, the methods for
the development of a
versatile welding pro-
duction system and the
procedure regarding
the implementation of
the associated process
sequences for welding
without fixture devices
are illustrated.
The versatility problem
Production systems of today are confrontedwith increased
demands in terms of flexibility and need to react quickly to
changes in economic factors, environmental conditions or
customer requests. The term versatility is seen as the capa-
bility to adapt rapidly to changing boundary conditions that
are beyond those anticipated. Versatility, however, should
not be restricted to individual organisational and technologi-
cal elements of production, but should always target the
design of the overall system. This concerns the value-add
chain on one hand, and internal business processes on the
other [1-2].
TheGermanFederalMinistry of EducationandResearch
(BMBF)-research project, ProAktiW, aims to develop a ver-
satile production system for individual enterprises via the
integration of technology, organisation and information. In
doing so, the holistic design and interaction of individual
elements on the management, planning and process level,
come to the fore (
Figure 1
).
Since versatility is accompanied by higher investment
costs and technical effort, it is important to determine the
necessary degree of versatility and the combination of solu-
tion elements for themost versatile final design of an overall
system. On the process level, the research activities are
concentrated on automated welding production and on the
search for suitable solutions for increasing the versatility.
Objectives of thework
When gas-metal arcwelding is used for manufacturing, two
productionmethods areusually applied. Inautomatedweld-
ing production, welding robots are used that work on single
or several work-pieces at one station. To control the toler-
ances, thepartsare fixed indevices that areoften technically
complex and thus causehighmanufacturing costs. Although
theuseof a robotmakesautomatedweldinghighly flexible in
termsof programconversion for anewcomponent, the fixture
device is, as a rule, set-up specifically for onepart andhas a
lowdegreeof versatility. For this reason, economicproduction
in automatedwelding is only feasible for themanufacture of
medium to largequantities. Theconversionof theautomated
system to manufacture a new product inevitably requires
new fixture devices, which are associatedwith considerable
changeover expenditure (
Figure 2
).
Manual welding is mainly applied in the field or in job-
bing shops and for small-batch production. The assembly of
theparts is carriedout by ahelper usingdefinedprocedures.
Owing to the flexibility and versatility of the operators, little
expenditure is required for changeover processes when a
component has to be changed. On the contrary, complex
devicesareagreatobstacle toversatilityof automatedwelding
manufacturing systems.
Fixture-free GMA-welding
and the application of cooperating robots
This paper, presented at the IIW International Conference in Essen in 2013, presents a
holistic approach to fixture-freewelding to enhance the versatility of automatedwelding
systems for smaller production quantities.
UReisgen, AKampker and KWillms, Aachen, Germany
Figure 2: Classification of the solution approach for
fixture-free welding.
Figure 1: The holistic solution concept in project
ProAktiW.
