Application-optimised solutions for rapid prototyping

Citation

(2002), "Application-optimised solutions for rapid prototyping", Assembly Automation, Vol. 22 No. 2. https://doi.org/10.1108/aa.2002.03322baf.003

Application-optimised solutions for rapid prototyping

Keywords: Rapid prototyping, Materials, Tooling

Laser-sintering saves time and money for prototyping during product development. In recent times, however, this technique is more and more used for the economical production of small series for plastic and metal parts, which are also used as final products. The technical innovations which are expanding the use of laser-sinter-technologies into every phase of the product life cycle possible and, importantly, making this more profitable. include on the one hand new and more productive systems and on the other hand improved materials, which lead to better part quality and shorter processing times.

The new material DirectSteel 20

The steel-based powder DirectSteel 20 is a further development of the proven metal powders for Direct Metal Laser-Sintering (DMLS), which are optimised for the particular applications. DirectSteel 20 makes layer thicknesses of only 20 micrometer possible and by this an optimal detail resolution. The surface quality of the resulting parts is sufficient for use in injection moulding in many cases without polishing, after only a short and simple micro-shot- peening. The shot-peened surface is similar to the textured surfaces which are manufactured conventionally by eroding and etching. frequently used for plastic injection moulded parts. Wherever a polished surface is demanded for technical or aesthetic reasons, this can be achieved without any problem. In comparison with former powders, the significantly improved surface quality leads to considerably shorter finishing times. The high density, together with the compressing effect of micro-shot-peening, makes it possible to polish even up to a mirror-like finish.

Also the mechanical properties have been improved, e.g. the tensile strength of 600 N/mm² lies significantly higher than for typical aluminium alloys used for tooling. This allows the use also in heavy-duty applications. For example, in a die-casting project more than 500 aluminium parts were manufactured in one tool from DirectSteel 20. And, the new material has already been proved in several projects for building metallic prototypes. an application called DirectPart®, which is becoming more and more significant.

With the new DirectSteel 20, four bronze- and steel-based materials are now available with different particle sizes, optimised for particular applications.

From CAD to high-quality injection moulded part within three days

The project of the English Rapid Manufacturing Consortium under the direction of Prof. Philip Dickens with the Swedish automobile group Volvo Car Corporation dealt with the manufacturing of a core and a cavity for the injection moulding of an adapter for a car. The inserts were about 60 mm in diameter and 22 mm high with internal 90° angles. which could not be produced by milling but would normally require EDM. In this case, the inserts were built from the new, extremely fine material DirectSteel 20 in a fully automatic process on an EOSINT M 250 Xtended system. With the help of a coordinate measuring machine six measurements were taken on each tool insert, which showed an average deviation of only 0.032 mm and a maximum deviation of merely 0.068 mm.

Plate 3

In this way high-quality injection moulded parts were available within only three after completion of the 3D CAD data (Plate 3).

Surface finishing of DMLS parts

In tool manufacture the touching-up and polishing of the tool inserts is an important part of the process chain and accordingly of the DirectTool® process too. EOS has built up know-how in this field and presented the different methods and devices for the optimised finishing of DMIS parts in a workshop at this year's International User Meeting. It was shown that micro shot- peening of the parts does not only lead quickly and simply to significantly-improved surfaces but also represents an important preliminary step for creating of a smooth, non-porous surface by grinding and polishing. It was demonstrated how to achieve nearly any surface quality using ultrasonic devices and diamond pastes, for example.