Hybrid Manufacturing

Hybrid Production

Additive manufacturing respectively 3D-Printing of metallic material can be considered as a primary shaping process. In contradiction to other primary shaping processes like casting, additive manufacturing doesn’t require molding tools. This makes this process very interesting for economic lot size 1 production. Furthermore, additive manufacturing has additional advantages with respect to subtractive manufacturing like milling. Hence it is considered for industrial part production already with high potential of further growth.

Hybrid manufacturing in in the context of metallic 3D-printing means the integrative combination of additive and subtractive manufacturing processes, both with respect to information technology and manufacturing systems. The technical approach shall complement the advantages of both processes and at the same time compensate particular disadvantages at both sides.

Typical representatives of additive manufacturing processes are powder bed processes like Selective Laser Melting (SLM) or build-up welding based processes like Direct Energy Deposition (DED). At powder bed based processes, metallic powder will be applied at plane layers and melted with a mirror controlled Laser beam at each position of the layer where material has to be added. At the DED process the material feed is performed either by powder or by wire using a multi-axes driven application head that brings the material to the application area where it will be melted with a heat energy source. This could be performed either by Laser beam or by an electric arc.

Advantage of those additive manufacturing processes is a considerably extended freedom of geometrical shaping. This would allow that part shaping better complies with the functional part requirements. One example is multi-functional integration in one part, which saves assembly efforts. Especially at aerospace, additive manufacturing processes allow the realization of light weight concepts that follows bionic principals.

Although the mentioned processes are capable of performing near-net-shape part geometry, it is not possible to meet quality and accuracy requirements for functional surfaces or fittings. Hence, a subsequent processing with more precise subtractive processes like milling are necessary. Furthermore, additive manufacturing could require additional support structures in order to support overhangs, to transfer heat or to avoid heat indicated distortions. Those support structures have to be removed after the 3D-printing process which could be performed with a milling process.

Meanwhile hybrid manufacturing systems exists already. They are capable of combined performing of additive and subtractive processes in one setup without additional part handling, which reduces material usage and processing time.

Planning of those hybrid manufacturing processes leads to extended requirements for process planning and NC-programming. For optimization of path planning for a DED process, it has to be taken into account that collision critical interference contours only appears during the additive process and has to be considered for subsequent moves of the application head.

Unfortunately, it is not sufficient for NC-programming of DED process to invert corresponding milling tool paths. Usually, it is not relevant for the milling process, that the cutter is passing an already milled area again. At additive process, the same would scrap the part.

Beside this, further requirements exists with respect to data integration along the value chain of hybrid manufacturing. In the area of data preparation for additive manufacturing the STL-format is still widely used, although it produces breaks in the information chain. This is due to the fact that a lot of information that is generated through the design process and represented in a 3D-CAD model get lost. One reason is the approximated geometry representation that based on triangular facets which lead to reduction of geometrical accuracy, which is not qualified for the generation of accurate cutting tool paths, e.g. for removal of support structures. Due to extended capabilities of modern additive manufacturing process in terms of accuracy, the disadvantage comes more and more in focus, since the increase of geometrical accuracy on a facet model leads to unproportioned increase of data amount without substantial increase of information content. Hence, an optimized data integration approach has to make use of the exact geometry data representation of a 3D-Cad model directly. Today’s 3D-CAD Systems are not only able to represent geometry with high accuracy, they would also allow the representation of manufacturing relevant topology features like holes, ribs, pockets, etc. but also the representation of manufacturing relevant technology information like tolerances and surface quality information. An integrated data management of those information is a prerequisite for an optimized planning of complex hybrid manufacturing processes.

In order to address those requirements CENIT is participating at two research projects in the area of hybrid manufacturing. With the EC funded project Bionic Aircraft a holistic view of the whole lifecycle of additive produced light weight parts in the aerospace industry from design down to recycling is investigated. At the German government funded research project PR0F1T, CENIT is investigating the data integration along the value chain of hybrid manufacturing processes which bases on exact 3D-CAD data. The heterogeneous tool chain used in hybrid manufacturing process for structure analysis, topology optimization, design and manufacturing data preparation, both for additive and subtractive processes as well as for quality data management, leads to extended requirements for data integration which are not sufficiently resolved today.

The gained knowledge from this research activities will be considered for future developments in the frame of the digital factory solution FASTSUITE Edition 2 as well as for the extension of consulting capabilities in the promising area of hybrid manufacturing.

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