ADDITIVE MANUFACTURING <
Additive advantages A
Solutions
Report Simon Lott
lthough the technology has been around for the best part of 20 years, additive layer manufacture has had a
difficult coming of age.
The production of components of potentially vast complexity out of a widening variety of powdered metals is an exciting prospect, but in practice it has typically been the preserve of rapid prototyping, being too expensive and difficult to certify for many commercial applications, with the additional health and safety challenges presented by the handling of fine grained and sometimes volatile powders.
But growing pains like these are set to ease as the industry gets to grips with the process. The purchase of the fledgling MTT by a company as well established as Renishaw sends a clear message that this is an important technology that in time will become a familiar sight across the industry. Already the deal has meant a significant cash injection and access to a large sales and service network that can credibly support customers worldwide. In the longer-term, the development of new capabilities will be aided by a new pool of expertise to draw on as Renishaw’s Additive Manufacturing Products Division develops.
The time is now
The move may have seemed a surprise to some at the time. Renishaw is of course well known as an innovator in the field of process control, but as head of communications Chris Pockett explains, this is an opportunity to use that experience to bring the technology forward. “If you look at what we sell, it is actually manufacturing capability and giving people the ability to manufacture much more efficiently. It’s all about speed, making the best of investment and minimal wastage. We understand the technology and it fits in with where we see efficient manufacturing going. In fact, we’re keen to get away from the term ‘rapid prototyping’ because that suggests it’s purely part of a design process. We are looking at embedding this as part of a production environment.”
Renishaw has actually had a ‘rapid manufacturing’ capability for the last six years, making use of various techniques for a variety of plastics, resins and metals and this is simply a logical extension to that resource. Now with the machine technology in-house, the coming months and years will concentrate on process control, in particular integration and development of new laser technologies and handling of larger amounts of material in the bed. With greater laser powers offering, among other things, faster build speeds,
38 Production Engineering Solutions • January 2012 Figure 1
current developments include a new 1kW machine and a larger system with greater working area. In the longer-term Renishaw hopes to integrate subtractive and additive manufacture seamlessly into the manufacturing process so, for example, finishing operations can be applied in one set-up. Aside from control, developing machines for a wider market will also enable substantial economies of scale by moving away from a hand built process, while at the same time market forces will see the cost of materials come down.
Early adopters
As things stand there are only a handful of companies providing additive manufacturing technology currently in the marketplace, with German company EOS occupying about 50% of worldwide sales. With its new backing and additional expertise, Renishaw hopes to turn the former MTT into a serious worldwide competitor. Marketing manager for its Additive Manufacturing Products Division, Robin Weston, is keen to stress that the competition should help the whole field of additive manufacture, as the key to future success is first and foremost, acceptance and confidence in the concept. “There has actually been a certain resistance to additive methods from mainstream manufacturing because there are so few suppliers
with the capability to offer the service and support as well as the R&D. The acquisition adds credibility to any emerging technologies and aerospace OEMs in particular are not satisfied by a single supplier.”
So what can Renishaw now offer?
With MTT having chosen to focus on machinery for the production of metallic components back in 2008, the main product offering consists of the SLM125 and SLM250 selective laser melting machines, designating bed areas of 125mm x 125mm x 125mm and 250mm x 250mm x 300mm respectively, both featuring build rates of 5-20cm³ and layer thicknesses of 20-100µm. They have been designed especially for the industrial environment, offering a high purity argon gas or nitrogen atmosphere, secure material changeover minimising user contact and simple touchscreen controls.
Applications so far have come first of all from dental and orthopaedic companies where low batches and high complexity suit the tailored products required for individual clients, but also from the aerospace and motorsport sectors where the pressure to produce lightweight components is high. And while Renishaw doesn’t anticipate additive manufacture replacing more straightforward machining tasks, growing interest from a whole variety of sectors is providing the impetus to provide more practical and affordable systems.
Conceptual change
“What you need to look for are the right ingredients for the process,” Mr Weston continues.
“Parts with a low mass of material and hidden features,
Having acquired additive manufacturing machine producer MTT Technologies last April, Renishaw is now positioning itself as a serious competitor in the market. But just how can the technology break into the mainstream?
essentially those that could not be cast or machined relatively easily, are generally considered most appropriate. Parts that have been produced by additive manufacture however include components such as fuel delivery systems and valves or anything with galleries and reasonably intricate internal features in applications where weight is important. “You need to think about how the process works. One of the approaches to design a valve for example is to start with all the hollow forms and features inside. With conventional technology you require intricate toolpaths to remove as much material as possible. With additive machining you design the internal geometry then you skin it in as little material as the component demands to take the forces and loads that will be applied.” Further acceptance into the wider industry will rely heavily on design advantages such as this. For example, lattice structures such as those in Fig.1 are rarely seen as they are far too difficult to machine conventionally, but could be hugely beneficial for weight critical components that would otherwise have a solid interior while giving away very little in terms of strength and integrity. It’s this sort of thing that designers and software developers will have to get their heads around to make the most of the machinery available to them. Mr Weston expands: “This is actually the biggest challenge we will face – bringing designers and production engineers together who often occupy separate worlds. For any given part we would talk to the designer about critical features, any surfaces on that object we need to keep free of support structures and then position the part in a way that it is built in the most optimal orientation, taking into account the features you want to preserve. “As for customers, at the moment we’re looking for organisations that are progressive or have a strong need to reduce the material they use, but we have to educate people on the design rules as much as possible and get people to apply their intellectual experience.” Much like the arrival of CNC machining, the cultural change will be as important as the technological one, but with the level of development going into process control and understanding the design opportunities, additive layer manufacturing looks set to be a valuable addition to the portfolio of any company producing complex metal components.
> RENISHAW
www.renishaw.com
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