Topic of the Month October 2008

A newly developed laser soldering technique helps to optimize the fixing of carbide tips on a saw blade – and the process is also faster than conventional induction soldering.
Photo: Laser Zentrum Hannover e.V.

The various jointing processes have always played a central role in every industrial application because they bring together what belongs together – in a defined, functional and safe manner!

However, new developments – especially in the field of bonding and soldering technologies – are currently driving a real wave of innovations, which makes it possible to implement completely new design and construction concepts in a wide range of application areas. The key topics of the wire and Tube exhibitions, at their interfaces to constructive applications, also benefit from these innovations that can bring economic and technical optimization to manufacturing and assembly processes and significantly improve the product characteristics.

Clever: Bonding and loosening on command

Enormous adhesive strengths and intelligent adhesive characteristics are provided by a recently presented material development by the German technology group Evonik Industries AG in Essen. MagSilica®, an adhesive additive made of nanoscale particles, provides adhesives with a completely new set of properties. By integrating the additive into an adhesive matrix, it is e.g. possible to dramatically shorten the curing time. This phase, which used to take 5 to 30 minutes, can now be reduced to a time window of 30 to 60 seconds. This is made possible by the so-called inductive curing process, which is supported by alternating electrical fields and results in low-stress bonded joints. Recent research has also shown that the adhesive strength could be increased by up to 300 per cent in some applications. This feature offers several advantages for users – first, it permits mechanically extremely stable joints, and second, the size bonding surface can be significantly reduced –, which in turn drives progress, e.g. in the miniaturization of components and parts. Another feature of MagSilica®-modified adhesive is that the so produced joints can easily be separated again. This process is similar to the initiation of the actual bonding process but with different parameters. Especially in the context of the practical cases of repair and recycling in piping installations, this product feature is a key advantage over conventional bonding techniques.

Economical & effective: Laser welding

Carbide tips are the central function element of circular saw blades that are used a million times in nearly any industry for the reliable cutting of a wide range of semi-finished products, such as pipes and sections. Up to now, the tips are usually induction-soldered to the steel blade. The application of high temperatures to the saw blade frequently resulted in intolerable variations of the tool geometry, i.e. the blade became warped. This usually required a time-consuming and expensive straightening process. Scientists and engineers at the Laser Zentrum Hannover e.V. carried out a research project about this subject, with the objective of substituting the existing jointing process with a laser-assisted soldering method. The results of the investigations show that laser soldering causes a very limited local application of heat in the jointing zone, significantly reducing the thermal stress of the tip support material. This process innovation eliminates the need of subsequent straightening of the saw blade. In addition, the process has a positive effect on the overall manufacturing costs of saw blades because laser welding permits time savings of up to 33 per cent compared with induction soldering.

Bionics: Adhesion without adhesive

Geckos can swiftly move on the ceiling, flies run safely over smooth glass panes, and beetles and spiders can easily climb vertical walls. It is the domain of bionic research to explain how nature provides these creatures with such capabilities, how these exciting adhesion mechanisms work and how they can be utilized for technical applications. Dr. Stanislav Gorb and his team from the Max-Planck-Institut für Metallforschung in Stuttgart have been researching these processes for years. The scientists have recently discovered the adhesion mechanism of the foot of a specific beetle species by using a scanning electron microscope and, using a special polymer mix, transferred it to a non-biological material system. Tests on the synthetic counterpart demonstrated surprising properties, also and especially in view of industrial exploitation: In addition to sufficient adhesive strengths, the material has a fully reversible behavior, withstands many application cycles and does not contaminate the contacted surfaces. These findings are interesting e.g. for the development of adhesion, gripping and moving tools for a new generation of climbing robots that are designed to examine and monitor shafts, supply lines and the inner and outer condition of pipe systems. This is carried out within the context of the BMBF project “InspiRat – Bionically inspired climbing robot for the external inspection of linear structures” under the direction of the biomechatronics expert Prof. Dr. Hartmut Witte of TU Ilmenau.

Dr.-Ing. Christoph Konetschny
Materials Consultant and Nano Expert

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