Built to succeed - additive manufacturing for sports equipment

Materials World magazine
4 Jun 2011
"Question mark" image courtesy of Chris Baker

Sporting accomplishments are not only down to athlete conditioning. Extensive progress has been made in the development of equipment manufacturing methods. Martin Parley talks to Dr Ruth Goodridge, Research Associate at Loughborough University, UK, about the potential in creating customised products through additive manufacturing.

What is your background?

I have a Medical Science degree (Biomaterials) from the University of Birmingham and a PhD in Bioengineering from the University of Leeds. After completing the PhD, I was awarded a Japan Society for the Promotion of Science Fellowship to investigate new materials for laser sintering at the Nara Advanced Institute of Science and Technology in Japan, before moving to the Additive Manufacturing Research Group at Loughborough University, where I focus on materials for medical and sporting applications.

What is additive manufacturing and what processes are employed?

Additive Manufacturing (AM) refers collectively to a set of technologies used to produce end-use parts directly from 3D computer aided design (CAD) models, usually by building them in layers. These additive processes contradict more traditional manufacturing techniques that use either subtractive methods, such as machining from a bulk material, or formative processes including injection-moulding, die-casting and forging, which use a tool to produce the part.

Common techniques include 3D printing, laser sintering and stereolithography. There are a number of technologies available, the main differences relate to the form of the starting material, for example, powder or liquid, and the method used to consolidate it, such as laser-based or advanced printing. One of the most common techniques is laser sintering, which uses a laser to selectively fuse powder particles together to form the required part.

What are the advantages of AM over conventional manufacturing processes?

The principal advantage is the ability to manufacture parts with significantly more complex geometries than traditional processes, without the need for production tooling. As tooling is not required, the design constraints normally associated with the subtractive and formative methods of manufacture are significantly reduced. Geometries that are difficult or impossible to fabricate via conventional techniques can be produced as effortlessly and at similar costs to producing simple shapes.

As there is no tooling cost, the cost per part is no longer dependent upon the production volume, allowing low volume production and even completely customised products. Parts can be modified or products can be switched even during a build, reducing lead-times significantly. The same part can be manufactured at multiple locations, reducing distribution costs and risks associated with a single supplier.

How is it used in the area of sports equipment development and manufacture?

It is now commonplace for additive techniques to be used for rapid proto-typing in the sports industry. However, at Loughborough University the aim is to develop this technology so it can be used to manufacture enduse parts. To achieve this, we are working with a number of large sporting good brands and sporting bodies to exploit AM and improve performance, comfort and athlete safety.

What are the benefits and limitations of these techniques for sports equipment?

One of the main benefits to the sports industry is the ability to customise products to the specific requirements of each individual sportsperson. Due to the economies of scale associated with conventional manufacturing, there is a limited range of equipment available for the mass market and personalised equipment for elite athletes carries a significant cost. AM-produced sports equipment will make it more cost effective to tailor items to an individual and sport. The ability to produce functionally graded structures/materials within a single part through variation in geometry or process parameters, including laser power, is also a distinct benefit of AM.

The limited range of materials, particularly polymers, that can be processed using AM techniques is, however, one of the main bottlenecks to the technology at present. Materials for AM do not meet the demands of the majority of sporting applications, particularly in terms of their ability to withstand impact and cyclic forces. For this reason, developing new materials for sports AM is a large part of our research. The exploitation of AM in sports technology is in its infancy and with increasing interest and investment from major sporting goods manufacturers I think we will see significant advances in the next few years, provided that material choice, part properties, repeatability, process speed and material/equipment costs are all addressed.

What is the SCUTA project?

The Tailored Injury Prevention & Performance Improvement for Protective Sports Garments (SCUTA) project is looking to exploit the design freedom of AM, coupled with 3D scanning equipment, to generate custom-fitting protective sportswear. It aims to produce high performance/impact resistant apparel that is tailored to both the individual and to the particular impact conditions that the sportsperson is exposed to.

What developments has this produced?

Research has focused on three main elements – the design of energy absorbing structures by AM, the generation of a methodology to conform these structures to an individual’s body, and furthering understanding of the processing of materials by AM relevant to sports applications, such as elastomers. Functionally graded structures have been designed, incorporating part properties normally specified by the physical properties of the material into the structure to be processed using laser sintering.

What other sports-related AM research projects are currently underway at Loughborough?

Another Engineering and Physical Sciences Research Council and Innovative Manufacturing and Construction Research Centre funded project is investigating the potential to manufacture personalised sports footwear using AM technologies. The work has shown the power generation benefits of personalised sprint spikes for elite athletes. However, the ultimate goal is to provide personalised footwear for the general public.

Much of the work at Loughborough University is to develop new materials for laser sintering in collaboration with industrial partners, including Burton Snowboards, which has a particular interest in elastomeric materials for functional prototype snowboard bindings.

Further information

Dr Ruth Goodridge, Additive Manufacturing Research Group, School of Mechanical and Manufacturing Engineering, Wolfson Building, Loughborough University, Loughborough, LE11 3TU, UK Tel: +44 (0)1509 227567. Email: R.D.Goodridge@lboro.ac.uk