FEATURE
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All adding up

With the Laser Additive Manufacturing (LAM) workshop in Houston, Texas approaching, Tom Eddershaw looks at where 3D printing is finding uses in manufacture

Laser additive manufacturing technology is advancing to larger components, multiple lasers and more robust process monitoring and control, according to Jim Sears, chair of this year’s Laser Additive Manufacturing (LAM) workshop, which is being held in Houston, Texas on 12 and 13 March. Although the event will be conveniently sited for the oil and gas industry, Sears stressed that it is not just for the big names in the industry – indeed most of the integrators of additive manufacturing (AM) technology are small companies.

But despite Sears’ optimism, some big players have expressed doubts about LAM. For example, Trumpf has ceased its production of certain types of AM machines, and Dr Peter Leibinger, vice chairman of the company and president of its laser technology and electronics division, recently told the Photonics West Show Daily magazine that 3D printing is a ‘bubble that is going to burst’. Nonetheless, Trumpf will be represented at the LAM event, showing its products for laser metal deposition (see LAM show preview panel).

Parts made using AM are still very expensive, as are the machines that make them, so the process has not found its way into the mass production industry. But its true niche may not be in mass production at all. For high-end, complex-part geometries, AM can normally build parts much faster than traditional processes with less waste, which reduces sourcing costs.

AM is ideal for rapid manufacture of low-production volumes of specialised and customised parts such as final parts, prototypes or tools for early production processes. ‘For the right component, it can be faster and cheaper to produce parts with AM,’ explained Kevin Lambourne. Lambourne is the founder and managing director of a UK-based company called Graphite Additive Manufacturing. The company manufactures parts for high-end applications, such as Formula 1 cars and the Bloodhound SSC – the 1,000mph world land-speed record car.

Lambourne previously worked for Red Bull Racing as head of Rapid Prototyping. He said: ‘I’ve done studies on AM carbon fibre materials verses traditional carbon fibre components. Composite tooling itself may only be a few hundred pounds, but complicated parts could take several days to just design the tool. Then you need another day or so of composite lay-up and assembly; and this is where the costs and the time build up.’ Lambourne continued: ‘If the CAD user could just hit a button after designing a component, and submit directly to an AM machine, you can have a final part in your hands sooner than it would have taken to design the tool for traditional manufacture. It’s difficult to put a value to that kind of saving.’

Lambourne explained that motor sport teams run wind tunnels more or less all day every day, testing large numbers of parts. This constant testing and refinement of designs creates a continual demand for one-off, quickly produced bodywork parts. Graphite uses the stereo lithography (SL, more commonly known as SLA for Stereo Lithography Apparatus) method to produce these parts. Before AM, this was done with carbon fibre, but to design the part, make a tool, do the carbon lay-up and then assemble the parts, could take around two weeks.

Lambourne continued: ‘Now as soon as the part has been designed, it can be sent to an SLA machine and either the next day, or the day after, they have the part. They can then just sand and paint it, then test it in the tunnel. This is obviously a much faster cycle of development. All the teams are working in this way now, and we support them.’ Aerospace also works in a similar way – albeit not at quite the same pace.

Graphite also manufactures carbon fibre reinforced parts using the selective laser sintering (SLS) process. The parts are commonly used as on-car components for the finished vehicle that takes part in the race. ‘It’s not really a prototype anymore; it’s a production piece. They may only need a few to take to a race and a few spares, or they may build dozens of parts. SLS produces a lightweight, tough material that’s temperature resistant,’ said Lambourne. ‘The beauty is that they can produce quite complicated designs, which would take weeks to manufacture traditionally, quite easily and quite quickly. Within hours, literally within hours, they could have parts to take to the race track.’ That is not to say that all the parts for the teams are manufactured in this way. For strong and structural pieces, such as the wings, wishbones, and most of the bodywork, carbon fibre is still the preferred material.

Sozon Tsopanos is principal project leader at TWI – formerly The Welding Institute – in the UK and was involved in the Intelligent Manufacture from Powder by Advanced Laser Assimilation (IMPALA) project, which ran for four years from 2008. He described the relevance of AM techniques to the medical industry: ‘The patient can have personalised implants, which increases the chance of an operation’s success. You can’t really put a price on that. It also speeds up recovery time. It’s hard to say something is more expensive, when it gives you these other benefits. It should be taken on a case-by-case basis, and sometimes the advantages are more important than the cost.’

The IMPALA project was a collaboration of research institutes from more than 10 countries, which aimed to improve and demonstrate the abilities of metal powder AM. While part of the project was involved in manufacturing small parts for the medical industry, such as hearing implants case actuators, it was also used to demonstrate to other industries what could be done with the technology. Most notably, one outcome of the project was a 700mm metal leading edge for an aerospace turbine blade. For weight reduction the blades are made of composites, but for protection against foreign object impacts, such as bird strikes, the front end must be made of metal. Traditionally these were made by machining titanium, but AM was found to reduce waste and production times.

Another application of AM that offers benefits to many industries is the improvement in repair quality of tools and parts. By using a Direct Metal Deposition (DMD) technique, DM3D Technologies (Michigan, USA) can repair a part to the same standard as when it was built. The metal-on-metal capabilities of DMD allow the material that fills a hole or breakage to be ‘remanufactured’. By using the laser and powder spraying head on a robotic arm, the deposits can be made on areas that are hard to reach. The company’s metal-on-metal capabilities also allow a stronger and faster cladding process on tools and parts. This means that improved heat resistance and tougher surfaces can be applied to most metal pieces.

So-called ‘3D printing machines’ for processing plastics have come down in price so far that people can have them installed at home. This is helping to spread an understanding of what 3D printing can do and what it is best applied to. However, the metal processing machines are still very expensive and, as James Saxon, technical sales engineer at Laser Components, pointed out, they are still not as mainstream as people had hoped.

Laser Components provides machine vision lasers for inspection equipment. Saxon stated that the company is seeing a lot of interest from hobbyists building 3D printers at home. Saxon believes that the technology is still picking up momentum and that the hobbyists are helping to drive it.

Tsopanos’s view is that some of the increased interest can be put down to something as simple as a name. The core process has gone through two name changes to this point, but all three names are still in use today.

In the media, the label currently most associated with the technology is ‘3D printing’. It has caught the public’s attention perhaps because it seems to be related to the well known concept of printing, whereas the industry still prefers to refer to it as ‘additive manufacturing’.

Lambourne recalled that, when first used, the process was named ‘rapid prototyping’. He explained that at the start: ‘Most of the parts were one-offs; they weren’t functional and they weren’t accurate. But as other technologies were invented and materials started getting better, people began using them for production parts. A large part of the market still created prototypes, but functional manufacturing was beginning to come into play.’

Lambourne continued: ‘As they began to explore new markets and applications, such as in the aerospace and automotive industries, the perception changed of the technology and the phrase ‘additive manufacturing’ was born.

Whether it is called rapid prototyping, additive manufacturing or 3D printing, it still involves taking a Computer-Aided Design (CAD) model, slicing it into thin sheets and then using a machine to manufacture each layer one on top of the other. Over the years, different methods have been implemented to carry out the process with ever more interesting materials.

Roger Parsons, CEO of DM3D, said: ‘While many in the community enjoy the buzzwords like 3D printing or additive manufacturing, it is all part of a continuous improvement process.

New materials, new powder feed systems – there are many ways to improve this technology. However, education and awareness for the market is the key, and trying to understand what we do is important. We are always talking to customers telling them what DMD technology can do and what we can’t do. Understanding how the capabilities of DMD relate to specific applications will help drive the growth of this emerging market.’

Lambourne stated: ‘It’s exciting where people are adopting it, using it more and more in different areas, and we are here to help advise them on which is the best material for their application. We can even help with the design process to ensure that the best result is achieved.’

If AM is to have a secure future beyond the hype of the popular press, Parsons explained that as with any technology: ‘We have to deliver the parts and components at a price point that is not cost prohibitive.’

Tsopanos summarised: ‘We hear every day that there are new grants from the government for 3D printing. I think this shows the industry is accepting [the technology] and becoming more and more interested. Also, there seems to be more conferences, more companies, and therefore more research and development.’

Building layer by layer

All additive manufacturing processes use a similar method: A CAD system creates a 3D model of the part, which is dissected into thin slices and each slice drawn one at a time by a laser onto a layer of material.

Three common processes are used: stereo lithography (SL, more commonly known as SLA for stereo lithography apparatus); selective laser sintering (SLS); and direct material deposition (DMD).

SLA uses a laser, a build platform, a re-coater blade, and a vat of resin. The first layer of resin is laser cured straight onto the platform, and then each time a layer is completed the platform is lowered into the vat. The surface tension of the resin struggles to flow over the top of the part, so a re-coater blade is required, which will wet the top of the part with more resin, creating the next layer to be cured.

The main components for SLS are a laser, a part bed, feeder cartridges and a roller. Once each layer is fused by the laser, the part bed lowers and a feeder cartridge introduces a new powder layer. This is then smoothed on top of the previous layer by the roller and laser fused.

DMD sprays a powder onto a point, which is then melted by a laser. A bead of melted metal is kept and fed by more sprayed powder as the laser traces the layered design, gradually building up the part. The bed is kept stationary but the laser rises, completing each layer by moving either on an x-y gantry or by using a robotic arm.

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