Additive Appliances
It’s September 2013 and a feltcovered rubber ball is being zipped back and forth across a tennis court by what is now considered to be the two most successful men to ever play the sport.
Inside the USTA Billie Jean King National Tennis Center, Rafael Nadal crashes a 100+mph serve down to Novak Djokovic’s lefthand side, only for the Serb to return with a double backhand. Fifty-two more shots are knocked back and forth, with only the occasional sliced dropshot breaking the succession of grunts and thuds as the pair compete in one of the sport’s most famous rallies.
Those grunts stem from two fierce competitors harnessing every bit of their strength to overcome the other, but the thud emanates from a tiny piece of silicone rubber clipped onto the lower central strings of the rackets.
Djokovic, Nadal, and an estimated 75% of the 90 million tennis players worldwide rely on these bits of silicone rubber to reduce the shock upon impact and tune the sound into a thud rather than an irritating ping.
In Italy, a company leveraging additive manufacturing technology to enhance consumer and sporting goods has seen the tennis racket dampener as an opportunity. For where there is a part that absorbs shock, there is often a role for additive to play. Additive Appliances thus developed a patent-pending lattice structure, which is said to work in much the same way as a tuned mass damper does in large buildings. Designed to mimic the vibration of the structure it is embedded in while ‘accommodating the movement to dampen the vibration,’ the dampener is said to intercept vibrations that can cause inflammatory issues, while also allowing players to ‘feel the hit’ as they strike a ball.
“What we do is we have a set of lattice structure that we can simulate pretty seamlessly,” said Tommaso Beccuti, CEO of Additive Appliances. “We simulate the behaviour of this lattice structure, and we target the natural frequency of each racket system.”
Targeting the natural frequency of each racket system with tailored dampener products was something that tennis racket manufacturer Head1 outlined as important during a study undertaken in 2009. Doing that with injection moulding, however, was always going to prove difficult. But with 3D printing, Additive Appliances is confident it can tweak the design of its dampeners to suit each brand and model of racket, and do so in an economically viable way, to supplement its already available ‘universal product’.
Across both the universal and brandspecific tennis racket dampeners, Additive Appliances is deploying its lattice IP to ‘scatter the vibration’ through the myriad beams and nodes that the lattice is made up of. By channelling the forces through these paths, the energy is dissipated. According to the literature that Beccuti has studied, there is a belief that lattices proffer superior dampening properties to the conventionally shaped products. This has chimed with Additive Appliances, who has endeavoured to dive deep into the design space to generate solutions for a range of consumer and sporting goods, among them the tennis racket dampener.
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Additive Appliances
“We focus mainly on lattice structures. All our other applications that we have done are related to the so-called metamaterial – you act not on the microscale of objects, you don’t take the problem from a specialty chemistry standpoint, but you rather work on the mesoscale, so talking about microns, millimetres, and you change the shape of the object so that he can actually achieve certain properties. That can be thermal properties, mechanical properties, like in this case, but also electromagnetic properties. It’s very interesting. To me, it is one of the most exciting areas of 3D printing, alongside bioprinting. In terms of simple approaches to mechanics, I think metamaterial has a huge potential.”
Additive Appliances’ tennis racket dampener is additively manufactured using HP’s Multi Jet Fusion technology, with the build volume of the 5200 platform said to be capable of processing thousands of parts at once. The parts, printed in BASF’s Ultrasint TPU material, measure between around 15 to 20 millimetres, and weigh less than 1 gram – up to 70% lighter than the minimal mass requirement of a traditional dampener.
For the design of the components, Additive Appliances has leant on a set of internally developed equations that are transformed into CAD designs through implicit modelling software, such as Altair’s Sulis platform, with the equations being validated using advanced simulation techniques like Optimad Engineering’s proprietary software, before extensive in-house testing is performed with vibrometers and sound spectrum analysers. Post-print, chemical smoothing can help to enhance the aesthetics of the part but has no impact on the mechanical properties and so it can be quicker and cheaper to forego this step.
So far, the 3D printed dampener has come through in-house tests at Additive Appliances with flying colours, with third-party testing now underway. Ranked professional players, such as Federico Gaio – who typically prefer not to use a dampener – have also provided positive feedback. And, Beccuti told TCT, Additive Appliances is in the process of spinning out the product into its own company, with a number of investors helping to set up a business called Athleticae to give a further push to the tennis racket dampener, before other applications are explored.
In terms of the tennis racket dampener, it is expected sales of its universal product will continue via an e-commerce platform, while a reseller network is to be developed. Requests for licensing will always be listened to, but Becutti’s preference would be – in a perfect world – that there is no exclusivity. He concedes that the 3D printed tennis racket dampener is slightly more expensive than a conventionally made one, but there is confidence that a superior performance will ensure value for money. Buoyed by a couple of other recent high volume consumer applications, Becutti is thinking big.
“The real target is millions of pieces,” Becutti said. “Let me be ambitious here. I think the technology is ready for that. We [as an industry] have other use cases. The mascara brush from Dior, I think, is the most famous one and it’s again a small component. Now we have the very positive example of Apple producing the Apple Watch in binder jetting. [The technology
is] maturing and it’s an exciting moment. We’re finally pushing the boundaries of manufacturing and getting at least a little bit closer to traditional manufacturing.”
Additive Appliances
