Additive manufacturing (AM) is joining materials to make objects from 3D model data, usually layer upon layer, instead of subtractive manufacturing. It gives engineers far more freedom to produce components with complex shapes, more than what is possible using subtractive methods. Its attributes give it the potential to impact more significantly on technology, manufacturing, and retail for the industry than almost any other technology to date.
Motorsport is a constant improvement exercise within rapid timeframes, and this advanced disruptive manufacturing technology is crucial in implementing new improvements. ‘With AM, freedoms are simply realized in hitherto un-manufacturable geometries,’ highlights Michael Fuller, CEO and Founder of Conflux, a company specializing in AM heat exchangers. ‘The sweet spot for AM lies where designers want to create a component with only the required structures for its application, optimizing its size and weight. For example, designing hollow tubes and I-beams inside constructions can help create a stiff internal structure with minimal weight.’
The application’s load case determines where material needs to be present. Often the centre of a structure doesn’t require any material, as the outside of the part carries the stress. ‘The part’s application dictates the technology, material, and any post-processing requirements to ensure it is fit for purpose,’ says Samuel Persaud, Head of Projects at Graphite AM. Fuller adds, ‘Design for AM allows far greater freedom than traditional manufacturing. Limitations of imagination and creativity are common and, as with any industrialized manufacturing technology, training in design for AM is a critical factor for the successful rollout of the technology.’
Subtractive manufacturing and surface finishing can produce tolerances of as little as 0.2 microns and a Ra 0.2, respectively. This level of refinement is only possible with AM with severe post-processing of the part. Even then, it’s unlikely to be that precise. ‘AM surface finish typically falls within +/- .125mm in the x, y or z direction,’ notes Michael Littrell, CEO of CIDEAS. ‘It’s not uncommon to build a part, measure it and scale areas of the part file to dial in tighter tolerances against the AM part.’
Kevin Lambourne, Managing Director of Graphite AM, says, ‘The tolerance and accuracy is technology and material specific. Ultra-high-resolution AM machines can build to tolerances of 25 microns, but these machines are limited in materials and are only suitable for small components. So, there are still plenty of components that must be manufactured using more traditional methods.’ Fuller added, ‘Surface roughness aside, the microstructure across bulk geometries (>0.5mm) can be consistent, and this is achievable and measurable. In the case of thin walls and microfluidic channels, surface roughness can be the same as the geometric features themselves.
Nathan Rawlings, UK Manager at EOS, surmises that there are now so many types of AM that there is likely a solution for most applications. ‘The market can appear confusing to someone with no previous experience, and it depends on what you try to achieve,’ says Rawlings. ‘Some technologies are ideal for wind tunnel testing components, but you wouldn’t make a functional part with that technology.
There are four key technologies which are the most used and most established – SLA (stereolithography), which is curing a moulding resin in a vat with UV light; SLS (selective laser sintering), which is sintering polymer powders into 3D shapes, DMLS (direct metal laser sintering) which is melting metal powders in into a 3D shape using high power lasers and FDM (fusion deposition modelling) which is a printing method but in a structural way.
By units sold, FDM is the most popular technology worldwide due to its low cost and ease of use. Due to speed, build volume and repeatability, SLS is becoming increasingly popular because of their potential for low to medium-volume production applications. DLMS and FDM technologies are often used for the most demanding motorsport applications; however, Tim Chapman, Head of AM at McLaren Racing, emphasizes, ‘Stereolithography technology and the materials have evolved so much recently that it is changing the way we use it. We do not just manufacture prototypes with this technology anymore; we now produce many full-scale components and full-size tooling. Wind tunnel testing is still the gold standard when assessing how every surface works together, either as an assembly or as a complete car. Our [Stratasys] Neo series of AM machines have helped us dramatically reduce the lead times of our aerodynamic wind tunnel and other components.’
