216
March 2014
Article
Tracto-Technik GmbH & Co KG
GmbH & Co KG
Classification of bending profiles
for manufacturing complexity
By Christopher Kuhnhen, Christian Mathes, Armin Schmidt, Matthias Hermes, Christian Gerlach, Michael Rohrmann,
Bernd Engel and A Erman Tekkaya, University of Siegen, TU Dortmund University and Tracto-Technik GmbH & Co KG
Present situation
There is a broad range of industrial applications for tubes
and tube design. In particular, automotive lightweight design
requires light structures paired with high stiffnesses. Here,
tubes and profiles with closed cross-sections are especially
suitable. With respect to the material used they display a
high stiffness, eg as required for body design. Furthermore,
with the help of different bending processes, varying lots of
bending components can be produced cost-efficiently. The
current prime example is the start-up sector of electromobility.
Altered auto bodies require flexible production concepts even
for small quantities. That way, new products can efficiently be
placed on the market right from the start. This is a necessary
first step for the establishment of electromobility as a mass
product on the consumer goods market
[1]
.
Despite all the advantages of the use of bending components,
manufacturers of bending machines and their users are
facing steadily growing customer requirements regarding
the geometry of bending components. While technological
restrictions remain, bending radii decrease, 3D geometries
are complex and tolerances regarding surface contours
and connection faces are low
[2, p.28; 3, p.17]
. The number of
parts which need to be discarded due to bending-specific
quality characteristics increases with the complexity of the
Tube and profile bending components are currently
experiencing an increased demand on the market.
Reasons for this are declining product life cycles and
an adapting value-added structure. Both customer-
specific design of mass products and small batch
production are moving into the focus of manufacturing.
The increasing demand for bending components calls
for a fast and production-orientated design. Frequently,
these requirements cannot be met by the design
engineer due to a lack of production-related know-how,
which is a result of the vast amount of different bending
procedures.
Since mid-2011, the University of Siegen, TU Dortmund
University and Tracto-Technik GmbH & Co KG
(Lennestadt) have been working on the development of
a cross-sector standard which can be used by suppliers
of semi-finished goods, users and bending experts
alike and which is intended to considerably simplify the
design of bending components. This article presents
criteria for the assessment of the complexity of the
geometry of tube and profile bending components.
geometry of the bending component. Moreover, with the
existing wide range of different bending processes, material-
specific restrictions can be exploited to a greater or lesser
extent. Knowledge of the processes and their efficiencies is
a determining factor on whether or not a planned product will
bring in profits or losses in subsequent production. Meanwhile,
knowledge of the functioning of a bending process is based
on the level of education and the experience of the machine
operator and the respective machine manufacturer
[4, p.16]
.
For designers of bending components, the present situation
is highly confusing and unsatisfactory with respect to the
pre-selection of a bending process. There are pluralities of
different processes as well as the thereby producible bending
geometries. Common criteria for the assessment of complex
geometries do not exist.
Aim of the project
The BMWi-funded research project “RoPro” of the Chair of
Forming Technology at University of Siegen, the Institute of
Forming Technology and Lightweight Construction (IUL) at TU
Dortmund University and the bending machine manufacturer
Tracto-Technik GmbH & Co KG, based in Lennestadt,
Sauerland, Germany, aims to reduce the difficulties in choosing
component-specific bending processes.
For this, extensive searches of current standards and
guidelines have been carried out. Thereby analyses of
company-internal guidelines were carried out. These and
other results from the project will be anonymously enclosed
to a standardisation application to the Fundamental Technical
Standards Committee of the DIN (German Institute for
Standardization). The aim is to obtain a German or an
international standardisation which establishes standards in
the field of profile and tube bending technology.
As a result of the project, designers of bending components
receive a tool which suggests an effective and economic
bending process based on bending geometry and semi-
finished product. A bending process is considered effective if
it allows for the bending geometry to be manufactured below
specified tolerances. The economic efficiency analysis is
based on individual investment costs of the bending processes,
which are included in the tool.
The core idea of the research project is the development of a
matrix (see figure 1) which helps to identify the most suitable
bending process based on a pre-selection of bending geometry
and semi-finished product (material and cross-section) to be
used. Thus, the creation of interfaces between semi-finished
