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Multi-laser AM systems discussed at Laser World of Photonics

Matthew Dale reports from an additive manufacturing application panel at Laser World of Photonics, where high-end, multi-laser systems along with low-cost machines were both discussed

Additive manufacturing system providers are exploring new approaches to increase productivity and scale to larger parts, according to recent work presented at Laser World of Photonics in Munich at the end of June. During an AM application panel, systems with moveable build chambers and those that incorporate multiple lasers were introduced.

Doubling the number of lasers in a standard AM system increases build rates by up to 90 per cent. (Credit: Trumpf)

For SMEs and universities that cannot afford to invest in such advanced AM technology, an alternative affordable selective laser melting (SLM) system for a fraction of the price of standard commercial systems was also presented.

Tiago Faro, CTO of Adira Metalforming Solutions, explained to panel attendees how the requirements of the industry have led the company to design a new SLM concept that enables the fabrication of exceptionally large parts through a modular process known as tiled laser melting (TLM).

‘We have developed a concept SLM machine comprising a moveable build chamber in which the necessary local atmospheric process conditions can be maintained while moving,’ Faro said. ‘With it we can fabricate parts much larger than those possible by conventional systems by first locally assembling part segments on individual tiles, and then joining these together to form a complete structure. This brings a lot of scalability to the additive manufacturing process.’

Adira’s first concept machine, Version One, which was presented last year at Euroblech in Hanover, features a working envelope of 1 x 1 x 0.2 metres and comprises a 1kW single-mode fibre laser. Currently intended mainly for R&D purposes, the machine operates with a scanning speed of up to 9m/s and achieves a minimum layer thickness of 25µm.

‘We see a trend towards larger and larger machines and therefore see this concept playing a role in the future additive manufacturing market,’ commented Faro, who showed that with the new system the company was able to fabricate a 316L stainless steel conceptual cooling structure 0.9 metres in length from six separate tiles, bonding the modular parts together using a special type of stitching. Additionally, he explained that with a process called dynamic tiling the machine is able to move the tiles both vertically and horizontally, allowing it to bring the tiles to the position of the processing field when building a pyramid, for example.

(Credit: Fraunhofer ILT)

The company is now faced with a series of challenges that come with the concept, such as overlapping the scan pattern and the large amounts of powder being used to fabricate larger parts. ‘We are looking to further develop the powder recirculation system, improve the traceability and handling procedures, and extend the material portfolio; Inconel is the next alloy to come,’ Faro said.

Looking to the future the company intends to develop industrial TLM systems that, unlike many current systems that tend to be closed off in terms of digital and physical operations, can be fully integrated into modern production environments. Adira also intends for the concept to become automated and compliant with Industry 4.0.

Faro commented: ‘We see it as a potential solution for the moulding, automotive and aeronautic industries and are aiming to start selling the machine next year.’

Meanwhile, in the short term, Adira is considering increasing the number of laser sources in its concept machine to reduce build times, a feature particularly important when constructing large parts that take longer to produce.

This use of multiple lasers to increase productivity is a relatively new concept across the metal AM industry that presents a number of challenges to system manufacturers, in particular ensuring the lasers are operating continuously to maximise build efficiencies. The subject of multi-laser systems and their optimisation was the focus of a presentation by Trumpf’s Dr Damien Buchbinder, head of AM product management.

According to the company, switching from one laser to two lasers could increase build rates by up to 90 per cent, and adding a third could increase them by an additional 80 per cent. However, while introducing a fourth laser could improve productivity even further, using this many lasers can have a negative effect on the cost-benefit of the whole system. ‘For a four-laser system a company would have to be producing thousands of parts a year continuously while constantly maintaining a high fill level for it to be of any benefit,’ explained Buchbinder. ‘If this can’t be guaranteed then the part costs will be higher than a two- or three-laser system.’

In addition to considering how the number of lasers will affect build rates, Trumpf has also taken into account factors such as beam shape, energy distribution, laser power, beam accuracy, layer thickness and build area to identify at least 25 separate exposure strategies based on physical and economic influences that have the potential to increase AM productivity.

‘At Formnext last year we presented a system with 100 per cent overlap between three lasers over the entire substrate, no matter its geometries,’ said Buchbinder. ‘This means that every laser can always touch every part and can work 100 per cent of the time.’

Trumpf's dual 200W laser TruPrint 1000 laser metal fusion system. (Credit: Trumpf)

At this year's Laser World of Photonics the company was showcasing its dual 200W laser TruPrint 1000 laser metal fusion system optimised for the large-scale manufacturing requirements of the dental industry. The machine is able to print dental bridgework and caps at speeds 80 per cent faster than a single laser system.

The TruPrint 1000 dual laser system is optimised for the large-scale manufacturing requirements of the dental industry. (Credit: Trumpf)

Affordable additive

An important factor for the uptake of metal AM is its adoption not only by larger corporations, but also SMEs looking to introduce the technology into their production chain. For many of these smaller firms, however, the financial risks of hiring 3D printing specialists or purchasing a modern AM system are too high for them to invest in, as industrial systems often cost between £100,000 and $1 million, according to Dawid Ziebura, project engineer at Fraunhofer ILT.

The Aachen Center of 3D Printing has designed an introductory AM system that costs only a fraction of the price of standard metal 3D printers. (Credit: Fraunhofer ILT)

While the larger corporations can benefit from the increasing build envelope and multi-laser efficiency of advanced AM systems, these benefits are not necessarily as important for SMEs. It is therefore important for there to be an affordable metal 3D printing solution that provides SMEs with a way to enter this growing market at an introductory level.

As part of its work for The Aachen Center of 3D Printing, a collaborative group formed alongside the Aachen University of Applied Sciences to be an access point of 3D printing for SMEs, the Fraunhofer ILT has helped design an introductory AM system that costs only a fraction of the price of standard metal 3D printers. ‘The goal is to realise a basic SLM system for less than €100,000 retail price in order to make the SLM process affordable for a wider range of users,’ it was stated in the abstract of Ziebura’s presentation. The centre achieved this by first identifying the most expensive parts of additive systems – namely the laser scanner, optics, mechanical and electronic parts – and replacing them with less costly alternatives. ‘It was [therefore] necessary to develop and find a cheap laser source, a new optical concept, a new process concept, new electronics and new software, and the system had to be easy to use,’ Ziebura explained.

The centre’s first prototype featuring these less-expensive components was presented at Laser World of Photonics at Fraunhofer ILT’s booth. ‘It's a diode-based laser SLM concept without a scanner that instead uses an x and y plotter, costing around 10 per cent of the conventional component costs,’ explained Ziebura. ‘We are also using open source software at no cost, along with standard electronics and mechanical parts, again at 10 per cent of conventional costs. The system uses a 140W diode laser with a focus of 250µm and a build volume of 80mm in diameter.’

For its first results with the system for stainless steel the group was able to reach a density of 99.7 per cent, a minimum resolution of 0.5mm and tensile strengths equal to those produced by conventional SLM systems. With it the group intends SMEs and universities to be able to introduce additive manufacturing to their employees and students, allowing them to experiment with different parameters and materials, and build cheap metal prototypes. Once established in their production chains SMEs could then make the choice in the future to move on to the more advanced AM systems.

In the future, the centre intends to improve the process parameters of its affordable AM system to decrease build times. ‘We want to develop a machine with stronger motors as well to achieve better acceleration and faster build times,’ said Ziebura. ‘We also want to make more materials such as tool steel and aluminium possible to process with the system.’

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