Every runner’s foot strike pattern, degree of pronation (amount a foot rolls inward with each stride) as well as the propulsion and braking forces are unique. New Balance Athletic Shoe Inc in Boston, Massachusetts, believes that personalising a runner’s shoes, specifically the spike plate on the underside of the shoe that provides traction, can help athletes become faster on the track.
Founded in 1908, New Balance continuously explores advanced methods of product design and production. Recently it started 3D printing custom spike plates using plastic laser-sintering technology from EOS to suit the biomechanics and personal characteristics of elite athletes.
Using a proprietary process to collect race simulation data from Team New Balance runners, the company’s sports research laboratory applies advanced algorithms to translate the information into an optimised design that can be additively manufactured from plastic powder in an EOSINT P 395 system.
Sean Murphy, senior manager of innovation and engineering at New Balance, said, “There are so many great things that came out of this process, compared with the methods we used in the past to develop and manufacture products.
“We record a runner’s data, generate multiple plates we feel will meet his or her needs and provide several pairs of track spikes simultaneously for them to try.
“It’s great to have them identify and respond to each different variation that we produce.”
Long before the spike plates are additively manufactured, or even designed, New Balance’s sports research lab collects each runner’s biomechanical data using a force plate, in-shoe sensors and a motion capture system worn by the runner.
The latter helps determine the relationship of the foot to the force plate, generating a three dimensional vector recreation of the foot strike. The in-shoe sensors show discrete pressure information over the course of the runner’s foot strike and how the foot interacts with the shoe. When a particular part of the foot exhibits high pressure values, it generally indicates that the associated 3D vector is important to that area of the shoe at that specific moment.
Murphy continued, “We establish a relationship between these high pressures and the corresponding forces to help us create a map of forces relevant to each area of the foot.
“A simple example is in the toe area. Generally, when you see high pressure there, it corresponds to a force that is pushing toward the heel to create a propulsive force forward.
“We use parametric modelling software to process this data and distribute the position of the spike plate traction elements, calculate the orientation and adjust the size of the elements, and incorporate specific runner preferences into the design.”
The designer is then responsible for performing the CAD cleanup necessary to create the final product, including finishing model surfaces and making adjustments to the spike plate. Once the final geometry has been verified, the CAD files are converted to .stl files and uploaded to the EOSINT P 395 system for layer-by-layer manufacturing.
Track shoe spike plates have three general characteristics that can vary depending on the length of the race the athlete is competing in and their preferences. The fit, stiffness, and design of the plate all influence the comfort and performance of the runner.
Conventionally, each spike plate style requires several injection moulds of various sizes, all costing thousands of dollars. These moulds will run thousands of plates before being retired or replaced, often annually, by a mould for a new model. With the EOS solution, the laser-sintered batch produces around four unique plate pairs and take five to six hours to manufacture.
Katherine Petrecca, business manager of New Balance, commented, “By laser sintering our customised spike plates we can manufacture on demand, fluidly adjust our process to accommodate different sizes and widths, and update designs without the continuing capital investment required by injection molding.
“Incorporating the laser-sintered spike plate also allows us to achieve a five per cent weight reduction compared to traditionally manufactured versions. For a competitive runner, the smallest change in weight can make a significant difference.”
The development and production of the custom 3D printed spike plates is not the only aspect that separates the shoes from their off-the-shelf counterparts. While traditional track spikes are commonly made of thermoplastic polyurethane and polyether block amide, New Balance worked with high performance materials manufacturer Advanced Laser Materials, Texas, to develop a proprietary blend of nylon powder. It results in optimal tensile and flex moduli while minimising build time.
Post production includes standard processing techniques such as bead blasting, after which the plates are processed through a proprietary system for aesthetic finishing and colouration.
With all the time and energy put into the research and development process, there is still one important question: do customised spike plates make a difference in the performance of the runners who wear them? Kim Conley, a member of Team New Balance and a US Olympic runner, thinks so.
After initially visiting New Balance for the simulation testing, Conley first wore her bespoke spike plates for competition at the Mt SAC Relays, held at Mt San Antonio College in Walnut, California. She has continued to wear them, especially at important races such as the World Championships.
Conley said, “My shoes are critical to my performance. They are the most important piece of equipment I have.
“As a professional runner, you obviously want the most effective and comfortable spike plates for competition. For me, they are the ones New Balance designed, based on the curve running data their development team collected.
“They provide better traction and less pressure on the outside of my foot, which allows me to focus on my race plan and not worry about my equipment.”
Conley has run personal record times in both the 3000 metres (8:44.11) and 5,000 metres (15:08.61) wearing her laser-sintered spike plates.
But what does all this mean for the amateur or recreational runner? While athlete-specific spike plates are currently only available for Team New Balance athletes, Petrecca suggests that this will eventually change.
She explained, “Design-driven additive manufacturing really holds the promise of more on-demand production and more individually customised designs. The spike plates are the first step we have taken with our athletes.
“As the material options expand, as our own proficiency with the technology increases and as capacity for additive manufacturing grows, we believe we will be able to bring 3D printed products, in some format, to the everyday consumer.”