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Diode lasers the future of additive manufacturing

Greg Blackman reports from Photonex in Coventry, UK on diode laser technology for additive manufacturing

The future direction of Fraunhofer Institute for Laser Technology’s (ILT) additive manufacturing research will rely much more on diode lasers, Christian Hinke at Fraunhofer ILT commented during Photonex, a UK photonics event that took place in Coventry from 14 to 15 October.

Hinke, speaking during a high power diode lasers and systems conference at the show, said that innovative and scalable selective laser melting (SLM) machines can be built with diode lasers. Most commercial SLM machines from the likes of EOS and Concept Laser are based on fibre lasers.

Fraunhofer ILT presented a processing head for selective laser melting at Euromold last year containing a number of diode lasers arranged in a line – the system Hinke showed at Photonex had five laser spots although he said this could be extended.

Hinke noted that the cost of SLM is still prohibitively expensive. He said that the laser source could help reduce both the capital cost of the machine and the time and cost of building the part.

Fraunhofer designed an SLM system with Concept Laser costing €1.5 million which was used to produce a prototype V8 engine block for an automotive client. Despite the expense, the SLM machine cut the time to manufacture the prototype from months to weeks.

However, with a multi-scanner SLM system based on diode lasers, the cost of the machine and the processing can be lowered dramatically. Hinke said that SLM only needs 200W of laser power and a beam quality of 10mm*mrad, both of which can be achieved with today’s diode laser technology.

Hinke gave the example of the 3D printing tool MakerBot as a low cost 3D printing system. He said that the vision of the future for additive manufacturing would be to combine the mechanics of a system like MakerBot, which costs around $2,000, with inexpensive laser diodes to make a machine costing around $5,000.

Fraunhofer ILT is part of an industrial project to develop low-priced high-brilliance diode sources to increase the build-up rate of selective laser melting. It has also, in collaboration with Fraunhofer Institute for Production Technology IPT, opened an additive manufacturing centre in Aachen for companies to gain knowledge and experience with the technology.

Additive manufactuing has now advanced to the point where it is moving from a rapid prototyping tool to a rapid manufacturing tool, noted Hinke, such that functional prototypes can be made that have the same performance as serial production parts. BMW makes more than 70,000 parts per year using additive manufacturing for prototype cars, according to Hinke. General Electric has roadmaps to increase the use of additive manufacturing for some of its aerospace parts.

There is also a greater degree of activity surrounding diode lasers for industrial processing, which always used to struggle in this area because of poor beam quality. Trumpf has recently opened a subsidiary in Berlin for advanced engineering of diode lasers, while companies like JDSU and Amada have released kilowatt direct diode systems for materials processing.

As with additive manufacturing, ultrashort pulsed (USP) lasers are also now becoming much more attractive for industrial machining, especially since the cost of the laser is coming down – Frank Gäbler, director of marketing at laser provider Coherent, commented that there has been an 80 per cent reduction in the dollars per watt of USP lasers since 2007. Gäbler spoke during the ‘laser processes in ultra precision manufacturing’ set of talks during Photonex.

He said that there will continue to be a cost reduction in USP lasers. He put a low power picosecond system at around $100,000, while femtosecond systems cost around $200,000.

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