FEATURE
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All adding up

Matthew Dale asks what measures are needed to bring metal 3D printing into mainstream production

The global additive manufacturing sector is forecast to reach $30.19 billion by 2022, at a compound annual growth rate of 28.5 per cent between 2016 and 2022, according to a recent report from Markets and Markets. It has also been estimated by Siemens that additive manufacturing will become 50 per cent less expensive, and 400 per cent faster, over the next five years.

These are promising figures for metal 3D printing; however, certain barriers still exist that need to be overcome in order for this modern technique to reach its full potential and revolutionise modern manufacturing, as it is expected to do. Speaking to Laser Systems Europe, Andy Martin, supply chain manager for additive manufacturing at GE Aviation, noted that factors such as low productivity, the steep learning curves faced by new users, and the limited availability of powder materials are holding back 3D printing from becoming a mainstream industrial process. Martin spoke on a 3D printing panel discussion at SPIE Photonics West in San Francisco at the end of January.

GE recently acquired stakes in Arcam and Concept Laser to bolster its additive manufacturing capabilities.

Agreeing with Martin, David Wimpenny, chief technologist at the Manufacturing Technology Centre (MTC) in the UK, also named throughput as one of the big obstacles stopping widespread adoption of additive technologies. ‘The main barrier preventing the uptake of additive manufacturing is the relatively low productivity of the machine,’ he said. ‘The machine might cost anything upwards of €500,000 and it’s only melting 150g of material an hour.’

The MTC is one of the partners of European 3D printing project Amaze, which began in 2013 and involves 26 leading companies and institutions all with the aim of bringing additive manufacturing into the mainstream.

Higher-power production

Various approaches are currently being taken by machine suppliers to improve the throughput of additive techniques. According to Wimpenny, machine designers have been able to increase the rate of production by a factor of ten using optimised part manufacturing strategies. 

‘In improving the machinery, typically higher power lasers are now being used,’ Wimpenny said. ‘The early additive manufacturing machines used lasers of around 200W; now they are moving towards 1kW fibre lasers and modifying the power distribution, sometimes moving from Gaussian to top hat distributions to make the lasers more efficient.

‘We know from talking to laser providers, that additive manufacturing is now making a serious impact on the production volumes of lasers,’ he continued. ‘It’s now becoming a little more industrialised and that’s helping to drive up the quality of fibre lasers and also drive down the cost.’

Daniel Lichtenstein, head of sales and market development for additive manufacturing at Trumpf, confirmed that lasers now offer higher quality uptime and brilliance than when 3D printing was first being investigated, adding that ‘what is ultimately important for this technology is that the lasers get cheaper’.

Trumpf is currently developing new types of lasers and optics, which will enable new machine designs, that give higher productivity at reduced cost, according to Lichtenstein. ‘The laser technology is really the enabler of completely new additive machine concepts,’ he said.

At Euromold last year in Munich, Fraunhofer ILT presented a processing head for selective laser melting, containing a number of diode lasers. It was noted by the institute that the cost of selective laser melting is still prohibitively expensive, and that laser diodes could help reduce both the capital cost of the machine and the time and cost of building a part.

The high-power fibre lasers often used in additive manufacturing have been declining in price steadily year on year, according to MTC’s Wimpenny. ‘They are reducing in cost and that’s starting to make these processes much more effective.’ Wimpenny explained that the increasing number of suppliers of fibre lasers over the past 10 years has led to a more competitive supply base, resulting in their cost being driven down. The lower price-per-Watt now available is enabling alternative approaches to be taken in order to increase machine throughput. 

Multi-laser manufacturing

A relatively new concept being explored by machine designers is increasing the number of lasers involved in additive processes. ‘By scaling the laser power along with the number of lasers, this significantly drives up productivity while driving down cost,’ Lichtenstein of Trumpf commented. Using more than one laser enables a component to be worked on from multiple angles simultaneously, saving on the time needed to move a single laser around a product mid-process.

‘Putting higher powered lasers and multiple lasers on machines is altering the build strategies so that they draw the components more efficiently,’ said MTC’s Wimpenny. ‘It may seem like a subtle effect, perhaps saving one second a layer, but applying this over thousands of layers adds up to improve the productivity of the machine.’

According to Martin of GE Aviation, machine and software obstacles have to be overcome to use multiple lasers effectively. ‘Adding multiple lasers will certainly improve machine productivity if the user can keep them all coordinated,’ he commented. ‘If you switch from one to four lasers you can build close to 400 per cent faster if all four lasers are working constantly.’ Being able to achieve this synergy with multiple lasers therefore presents new coordination challenges, especially if the lasers overlap on the part being processed. 

In Frankfurt last year, Trumpf demonstrated its new TruPrint 5000 additive system at Formnext 2016. The machine has three 500W lasers working simultaneously without being limited to predefined areas, leading to faster build times. Automated smart exposure strategies are used in the machine to determine the ideal laser paths so that each laser is always operating effectively. ‘We have a 100 per cent overlap of the multiple lasers we are using,’ commented Lichtenstein.

A C-sump aircraft component made by GE

Manufacturers of additive systems are still experimenting with the maximum number of lasers that could be used in a system simultaneously without compromising productivity. ‘The jury is still out on what stage of adding more lasers becomes slightly ineffective,’ said MTC’s Wimpenny. ‘I’ve heard of 16-laser machines being mooted by developers.’

According to Martin, system developers are now looking to combine multiple laser types in a single system. ‘There’s a current shift at the moment towards 3D scanners, and lasers combined with 3D scanners,’ he explained. Wimpenny of MTC has also noticed a similar trend. ‘[System developers] are moving towards multiple lasers… where fine, lower power lasers will scan the surface of a component to get the resolution, and then a higher power laser with a broader beam will melt the core of the component. That allows the build process to be accelerated, and it’s been very effective at reducing the build time,’ he commented.

‘It [faster build times] fits in better with normal working practice, as it’s not normal to leave a machine running for multiple days,’ Wimpenny added. ‘Shorter cycle times also reduce the risk of failure significantly.’

Scrap savings

Although the low throughput of additive manufacturing has previously proved a disadvantage for its users, it has ultimately made engineers more creative about how they use the technology. ‘One of the things it’s forced people to do is that before they even start thinking about making the part… they design it from the absolute root foundation around how it is intended to perform,’ explained Wimpenny. ‘It has forced people to go away from the conventional shape of products.’

Parts made by additive manufacturing often share a frame-like structure that can achieve the strength and stability of conventionally manufactured parts while dramatically reducing the amount of material. ‘By doing this it is often possible to reduce the weight of the object by more than 50 per cent,’ confirmed Wimpenny. ‘This is a huge benefit in areas that are weight-sensitive, such as aerospace and space sectors. In addition, this also halves the price of manufacturing the component.’

GE Aviation has recently taken full advantage of these benefits in designing a new engine that will be tested later this year. ‘We have launched our Advanced Turboprop (ATP) Engine, and really thought about that engine from a design-for-additive perspective from the beginning,’ explained Martin. Designing the engine around additive manufacturing has allowed GE’s designers to apply the technique very broadly throughout the engine. ‘About 30-40 per cent of that engine is additively manufactured,’ Martin continued. ‘What’s really remarkable is that we have been able to use additive manufacturing to lower the weight of the engine, improve the fuel consumption of the engine and also massively consolidate parts.’ Through improved designs that could only be fabricated using additive manufacturing, GE Aviation has consolidated 850 engine parts down to a total of 12. ‘That engine will now have more design-for-additive content that any engine in the aviation industry on the commercial side,’ Martin said.

A collaborative effort

As part of the European Amaze project, four pilot-scale integrated additive manufacturing factories are being built, two of which – one at AvioAero in Italy, the other at Irepa in France – will focus on laser powder bed processing and direct energy deposition.

According to Dr Antonio Candel-Ruiz from the industry management of laser metal deposition at Trumpf, a partner of Amaze, the project is taking real industrial examples of products that companies have difficulty producing conventionally, and demonstrates how they can be made using additive techniques. ‘With the production of these real parts by additive manufacturing we want to show that additive manufacturing opens up new possibilities, for both the geometrical and material properties point of view, for real industrial business cases,’ said Candel-Ruiz.

The Amaze project will also establish the world’s first comprehensive design, process and material database for high-quality additive production. Ensuring optimal material use, will minimise the component defects, and establishing a material database will help new users choose the correct materials.

According to Martin of GE Aviation, expanding the range of metals that can be used will also be important in increasing its uptake. ‘The palette of metals today is expanding, which will help with the adoption of 3D printing,’ he said. ‘But I would ask, “are the chemical formulations of the metals optimal for laser powder bed?” Lots of users are working on problems like this… in search of strength, crack resistance or other material properties.’

Within Amaze, protocols for testing materials when they come in from suppliers are being developed, as using poor quality material can lead to defects in the additively manufactured components. ‘As this is a new process, it’s sensitive to things which are not measured very well conventionally,’ said Wimpenny of MTC. ‘An example of that is the flow of powder, which directly affects the quality of components.’ Conventional testing for powder flow involves timing the rate that it passes through a funnel. ‘This is simply not sufficiently accurate or informative enough for complex processes like additive manufacturing,’ commented Wimpenny. ‘So, new methods of testing the powder have had to be developed.’

Martin points to improved machine design as one area that will help increase adoption of the technology. This will come from input from long-term users of additive manufacturing such as GE that have invested time and resources in experimenting with process parameters.

Candel-Ruiz believes that awareness of additive manufacturing is equally important in encouraging its widespread adoption. ‘It’s not only a question of equipment or technology, this technology has to be known,’ he said. ‘Young engineers at university must learn what’s possible with additive manufacturing if we want these technologies to be used in production in the coming years.’ 

Laser Additive Manufacturing Workshop

Taking place from 21 to 22 February in Houston, Texas, the Laser Additive Manufacturing workshop will have presentations covering structure design, materials, and applications of AM. There will be keynote presentations from Greg Morris at GE Aviation, Wayne King from Lawrence Livermore National Laboratory, and Marc Esformes at Stryker, who will speak about AM for medical implants. Furthermore, the latest laser technology for metal 3D printing will be on display

Here are some highlights:

Coherent will be showing its direct-diode laser series, the HighLight D-series, along with its Meta laser CO2 system for cutting and engraving. The HighLight D-series delivers both high power and a range of output beam shapes, making it the ideal source for laser heat treating, cladding, and welding applications.

The newest member of this series, the HighLight 10000D, offers up to 10kW of direct-diode power at 975nm. Free space beam delivery preserves the inherent brightness of the diode laser source and enables the use of an optical system with a 275mm working distance. In laser cladding, the laser provides a deposition rate of up to 20 lbs/hour of material.

www.coherent.com

The BeamSquared system being shown by Ophir-Spiricon is a compact, fully automated tool for measuring laser beam quality (M2). The system is based on the company’s Ultracal baseline correction algorithm that helped establish the ISO 11146-3 standard for beam measurement accuracy.

BeamSquared delivers accuracy, robustness, and reliability for continuous-use applications in manufacturing, science, and R&D. The system measures the propagation characteristics of CW and pulsed lasers, from UV and NIR to telecom wavelengths in automated mode in less than one minute. Manual mode is available for CO2 lasers and wavelengths greater than NIR, including terahertz.

Measurements include waist diameters, full angle divergence, waist locations, Rayleigh lengths, M2 or K and BPP factors, astigmatism, and asymmetry.

www.ophiropt.com

Plasmo, a provider of quality assurance for additive manufacturing, will be displaying its Fastprocessobserver, a photodiode-based measurement system. The device detects the light generated when the metal is melted, and this takes place laterally and coaxially. The measured values, in conjunction with further machine and process parameters, form the basis for monitoring the welding process. Evaluation of the data is carried out by means of specially developed algorithms in real-time.

www.plasmo.eu/en

RPM Innovations will be exhibiting the RPMI 557 laser system, a metal additive manufacturing machine that incorporates laser deposition technology. The rapid solidification of the melt pool it offers provides excellent material properties and precise placement, allowing it to freeform parts directly from CAD models, repair metal components typically considered non-repairable by conventional techniques, or strategically add features to forgings or castings.

The RPMI 557 system has five axes and is atmosphere controlled, with a work area of 5ft (1,524mm) in X and Y, and 7ft (2,133mm) in Z. It also includes a tilt and rotate table.

www.rpm-innovations.com

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