design process for cold-formed metal pieces - such as nuts, bolts, screws
and rivets - has largely been one of trial and error. Now, a CRAFT project
has developed a new 3D modelling program specifically for use by SME fastener
manufacturers. The software, which is based on the finite-element method,
allows process designs to be optimised before they are tried out on actual
equipment, saving both time and money. Manufacturers can also use it to
improve existing products. In addition, it can be used by personnel with
no specialist training in finite-element techniques, making it ideal for
rapid introduction into existing work procedures.
fastener industry plays a crucial role in supplying many other industries
with the nuts, bolts, screws and rivets that, quite literally, hold everything
together. These items are manufactured by a process known as cold forming,
where the metal is pressed into the desired shape using high pressure
and specially designed tools. Until now, designing new tools has largely
been a matter of trial and error, even though some tool designers have
over 20 years' experience in the industry. Clearly, this is an expensive
and time-consuming process.
a third dimension
impetus for the CRAFT
project came from the German SME, Nutap-Schuhl,
which manufactures nuts. Tool designers at Nutap-Schuhl were using
a two-dimensional design program and they were aware of its limitations.
However, all attempts to find an easy-to-use 3D program had failed.
problem encountered was that all the existing programs had been
developed for general purpose use and were difficult to master.
In addition, for cold-forming applications it is necessary for the
tool surfaces and process conditions to be accurately described
as part of the pre-processing system. Usually the tool surface is
described using a mesh of triangular elements generated by general-purpose
CAD (computer-aided design) systems, but Nutap-Schuhl had discovered
the models created in this way were rarely accurate enough for the
simulation it was trying to achieve.
a European consortium
Nutap-Schuhl contacted the German research organisation, CPM,
for assistance in developing a CRAFT project proposal. CPM used
its contacts to help Nutap-Schuhl set up the consortium of European
SMEs that would enable the development work to take place, with
all, five other SMEs participated in the project, including a second
German company, Ernst
Rosenbach, which specialises in screws, and, from Italy, both
Oslat, a major supplier of components to FIAT, and Meci Italia,
another screw manufacturer. Two UK SMEs joined: CSW
Coldform, a bolt and screw manufacturer, and Henrob
- a specialist rivet producer that was involved in the production
of the first aluminium car by Audi.
associated companies also joined the group. Johnson Precision Tooling
from the UK provides specialist equipment to the fastener industry,
Metallurgische Verfahrenstechnik of Germany specialises in tool
coatings, and so provided valuable technical input regarding tool
Gerhard Arfmann of CPM, who co-ordinated the project, says: "Following
the initial request, we set about investigating potential 3D software.
When we came across a program that had been developed at the UK's
of Birmingham, we knew we had found the basis for what we needed.
The CRAFT project's main aims were therefore to develop pre- and
post-processing modules to add to this existing software."
new software modules, which run on a PC under the Linux operating
system, have brought various different benefits to the SMEs. As
originally intended, the pre-processing simulation allows the companies
to optimise designs on the computer. This not only means less time
spent in physical testing, with associated savings in manpower and
machinery time, but it means less waste material too. In addition,
the software is simple enough for staff to use without an expert
background in numerical modelling.
efficiency of the optimisation process has also allowed the SMEs
to extend their product range. Where before it would have been too
expensive to consider testing an idea on a speculative basis, the
software provides a cost-effective method of trying out some rather
more adventurous concepts.
a profitable dialogue
feature is the post-processing aspect. Companies can now look at
the production of existing products and check that they are being
manufactured efficiently and to the highest possible standards.
This is good news for customers who may find they are being offered
a better quality product, good news for the companies who may be
able to cut their costs, and good news for the environment if less
waste is produced.
the software allows SMEs to demonstrate production concepts to customers,
and enter into dialogue with them at an early stage of design. In
the past, only large companies have been able to offer such a service.
The result is that SMEs can now work in partnership with the companies
they supply, influencing the design of products for the benefit
of all concerned.
CRAFT project finished in 1998, and the SMEs are now using the software.
They have, however, also been exploring ways to make the results
available on a wider scale. To this end, a user group is being set
up that will be open to all SME fastener manufacturers, on a subscription
basis. The subscription will give the SMEs the right to use the
software and also the opportunity have their say in the form of
any future development work, for example adapting the modules for
other specific applications.
date a number of companies from both the UK and Germany have expressed
an interest in the group.