PI 015-14 2014-03-11

Pioneering work for castings of the future

When manufacturing prototypes and short runs, 3D printing technology lets foundries make up molds and cores without tooling.

The 3D printer paves the road to industry leadership. The Bosch Rexroth foundry in Lohr am Main is putting its faith in innovative processes when making cores for castings.

In the field of hydraulics, the more complex demands being voiced by customers require new functions in castings. To respond to these expectations with the greatest possible flexibility and economy, the foundry operated by Bosch Rexroth AG in Lohr am Main, Germany, is turning toward innovative 3D printing to make up its casting cores.

In the interest of overcoming the technological barriers associated with the traditional core shooting process, where sand is forced into a mold at high pressure, the foundry in Lohr is now using two 3D printers for short production runs and rapid prototyping. They make it possible to implement complex geometries and shapes while resulting in both shorter development periods and lower costs. Thus short runs and spare parts can be produced at greater efficiency and lower costs. In this way, Bosch Rexroth is responding both quickly and flexibly to customer wishes. It should be noted that the numbers of variations in products are increasing steadily, while the number of items produced for each variation is declining. When manufacturing prototypes and short runs, 3D printing technology – or additive manufacturing – lets foundries make up molds and cores without tooling. The result is that every geometry and all the changes in the geometry can be manufactured immediately, using a data file.

The 3D printer is free of the technological limitations of core shooting, since printing is possible in every direction. In addition, even before the start of volume production, additive cores can be used to optimize sequences in the casting process, for trial assembly of the core, and for analyses of the play in the core. This lets customers test new cast components efficiently. Moreover, the geometry can easily be adjusted during prototype development or for new products, without having to prepare a new tool for every modification.

Two processes, for differing strengths

Two printing techniques, using furan resin and phenol resin, are in use. 3D printing using phenol resin is a new process. Here the foundry and the supplier of the machine had to carry out basic research to make the process consistent in everyday use. Thus both partners were doing pioneering work in the field of additive printing. If delicate shapes, such as small channels, have to be cast, then these can be realized with the 800 N/cm² achieved in the phenol resin process. The less expensive furan resin procedure (250 N/cm2) is suitable for coarser geometries.

Printing in layers

In both 3D procedures, data describing the shape to be created are transferred, via the software, directly to the printer. Any desired number of components of different shapes can be programmed and produced simultaneously, just as long as they all fit in the printing chamber. Printing is carried out in layers 0.28 millimeters thick. In the solid areas of the core, the printing head deposits a binder on sand which has been mixed with the activator – the curing agent. The printer requires 30 seconds per layer. The shape then grows layer by layer.

Economical, precise, safe, and energy efficient: drive and control technology from Bosch Rexroth moves machines and systems of any size. The company bundles global application experience in the market segments of Mobile Applications, Machinery Applications and Engineering, Factory Automation, and Renewable Energies to develop innovative components as well as tailored system solutions and services. Bosch Rexroth offers its customers hydraulics, electric drives and controls, gear technology, and linear motion and assembly technology all from one source. With locations in over 80 countries, roughly 36,700 associates generated sales revenue of approximately 5.7 billion euros in 2013.

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The Bosch Group is a leading global supplier of technology and services. According to preliminary figures, its roughly 281,000 associates generated sales of 46.4 billion euros in 2013 (Note: due to a change in the legal rules governing consolidation, the 2013 figures can only be compared to a limited extent with the 2012 figures). Its operations are divided into four business sectors: Automotive Technology, Industrial Technology, Consumer Goods, and Energy and Building Technology. The Bosch Group comprises Robert Bosch GmbH and its more than 360 subsidiaries and regional companies in some 50 countries. If its sales and service partners are included, then Bosch is represented in roughly 150 countries. This worldwide development, manufacturing, and sales network is the foundation for further growth. In 2013, Bosch applied for some 5,000 patents worldwide. The Bosch Group’s products and services are designed to fascinate, and to improve the quality of life by providing solutions which are both innovative and beneficial. In this way, the company offers technology worldwide that is “Invented for life.”

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Jana Benzinger
Maria-Theresien-Straße 23
97816 Lohr am Main
Phone: +49 9352 18-1589