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sts.components.contact.mr.placeholder Sebastian Webel
Mr. Sebastian Webel

Editor-in-Chief

Tel: +49 (89) 636-32221

Fax: +49 89 636-35292

Werner-von-Siemens-Straße 1
80333 Munich


sts.components.contact.mr.placeholder Arthur F. Pease
Mr. Arthur F. Pease

Executive Editor English Edition

Tel: +49 (89) 636-48824

Fax: +49 89 636-35292

Otto-Hahn-Ring 6
81739 Munich
Germany

Pictures of the Future
The Magazine for Research and Innovation
 

Materials Science and Processing

The Fine Art of Tailoring Materials

Siemens researchers subject generator bars to a potential difference of over 70,000 volts in order to test their capacity. Spectacular discharges occur during the process.

The electronics industry requires plastics with precisely defined properties. Siemens is developing technologies that make it possible to combine materials in such a way as to meet increasingly specific demands.

Each of us is in contact with plastics every day. In toothbrushes, ballpoint pens, smartphones — there’s no getting away from plastic, or, as the experts put it, synthetic polymers. Many of these everyday plastics have straightforward properties such as light weight, flexibility or hardness. Plastics for use in industry, especially in electrical engineering, require much more specialized properties. These range from transparency and magnetic qualities to the ability to withstand temperature extremes, and the ability to conduct – or minimize conduction of – heat or electricity.

In view of this, Siemens Corporate Technology (CT) is developing innovative recipes for plastics with new properties. For example, plastics with defined and reproducible electrical conductivity are crucial for boosting the efficiency of rotating electrical machines such as generators. The optimization of such machines is very important because it saves energy.

New materials can be mixed using powder-dosing robots.

Making Generators More Compact

Siemens researchers have developed what are known as field-controlling systems such as overhang corona shielding and outer corona protection. They rely on new types of materials to achieve more efficient control of the electric field. These materials consist of specially doped tin oxide or silicon carbide and are embedded in a polymer matrix composed of resin, various additives, hardeners, catalysts, and solvents. The composition determines the electrical conductivity and the field-controlling effect of the new composite material. Thanks to this new development, the length of the overhang corona shielding can be reduced by one third, and the service life of the external corona protection increased by a factor of four. In concrete terms, this means that a large generator can be made more compact yet still deliver the same power output, which saves copper and insulating materials.

The compounding process — the process of combining various materials — offers even more possibilities. The electrical properties and the workability of a molding compound can be specifically determined, depending on the material, size, shape, and number of particles mixed into the polymer matrix. In this way, researchers at Siemens are able to develop materials with defined properties, for example, for the insulation of motors or transformers. An increase in the power density — i.e. smaller designs or higher power in the same construction volume — and reduced costs are possible.

At Siemens' high-voltage laboratory in Erlangen, generator bars are subjected to extremely high voltages to determine the strength of insulation.

Before the new materials can go into production, they are subjected to extensive testing at Siemens’ high-voltage laboratory in Erlangen. Transformers step up the voltage to 70,000 volts and pass the current through coated generator bars. This determines how long the bars can withstand extreme loads, which provides insight into their service life under normal operating conditions.

Connecting Different Materials

Not only are CT researchers interested in the composition of individual materials and their properties., but also in how such materials are joined together. Thanks to a process known as  spark plasma sintering, they have solved the problem of pressing various powders into high-strength, non-porous components. Here, a 3,000 ampere, four-volt electric current passes through a powder blank, causing very high temperatures. The result is that the boundary layers — the interfaces between particles — heat up rapidly, reducing processing time compared with other processes. The resulting product is almost as solid as if it were a homogeneous material.

Siemens researchers experiment with the spark plasma sintering process for pressing and welding them together.

Layer by Layer

High temperatures also play a key role in additive manufacturing methods — also known as 3D printing —for metal components. This technology could revolutionize the processes used for industrial mechanical engineering. For example, a laser can be used to heat a nickel-alloy powder to its melting point in order to fuse the fine particles together to create a three-dimensional structure layer by layer

The benefit here is that complex workpieces, which to date could not be manufactured at all, or only from multiple individual parts and with great effort, can now be produced directly from 3D CAD volume models. The intricate cooling channels in the interior of turbine blades, for instance, optimize blade cooling. Indeed, Siemens has for the first time tested gas turbine blades in a gas turbine at full power that were produced completely by means of additive manufacturing. Another application of additive manufacturing is in repairing gas turbine burner tips. As a result, associated maintenance processes now take one tenth of the previous time and their costs have been reduced by around 30 percent. Individual spare parts can be manufactured faster, decentrally, and more economically by means of 3D printing.

Extremely high temperatures — and searing light — are generated where a laser beam hits a powder bed.

3D printing makes it clear just how tightly material and manufacturing processes can be interlinked. High-quality materials with complex properties are thus always the starting point for individual components. However, product properties such as stiffness and geometry first arise in the 3D printing process. Highly developed simulation processes based on physical models enable manufacturing processes to be tested and optimized in the virtual world, where errors can be eliminated before printing starts. In this way materials, component design, and process parameters can be optimally matched with one another, even before production facilities are started. Only then can high-quality powder materials also be used to create dimensionally-accurate components that are free from distortion, with minimal internal stresses and customized  properties.

Ulrich Kreutzer