BLAZING TRAILS, ONE OLLIE AT A TIME

Text: Thomas Masuch; Photos: Philipp Manger / Thomas Masuch

In Project T.O.S.T., Philipp Manger is using titanium skateboard trucks as an example of how to achieve extremely lightweight designs. The principle of combining a bionic design with an internal lattice structure should be relatively easy to transfer to other applications.

Though he isn’t a pro athlete, Philipp Manger probably rides one of the most expensive skateboards in the world. The trucks alone – that is, the parts that connect the wheels to the deck – cost several thousand euros. The fact that they were 3D-printed from titanium hasn’t made Manger much faster on the board, but it has given him plenty of additive insights – and a number of contacts in the industry.

»In the beginning, it was just an idea that popped into my head,« the 31-year-old recalls. »It wasn’t long before it became the biggest project I’d ever put together, though.« Manger is an avid skater himself, having been an active member of the longboard scene for nearly 10 years. With these boards, it’s not about pulling off tricks; it’s about speed. It’s not uncommon for riders to hurtle down mountains and passes at 90 km/h or more, which puts quite a lot of stress on their boards – especially the trucks.

You can apply the concept to any area where you’re trying to achieve lightweight constructions by reducing material usage.

Attending an Airbus engineer’s presentation on additive manufacturing led Manger to take a closer look at the possibilities afforded by metal laser sintering. Ultimately, he came up with the idea to 3D-print his skateboard’s most essential components. In doing so, Manger – a design engineer by training – already had 15 years of CAD experience to rely on.

»hybrid topology«

This endeavor eventually evolved into the research project T.O.S.T. (Topology Optimized Skateboard Trucks), in which Manger has cooperated with Fraunhofer IWU (Dresden) as part of his final work on precision mechanics at the University of Applied Sciences Jena. Here, skateboard trucks have served as a basis for pursuing advancements in how additive components are designed and engineered.

»I was looking to explore and compare different approaches to optimizing additive manufacturing,« Manger explains. In addition to topology optimization, he began focusing on lattice structures for the interior of components. The trucks he eventually produced featured a »hybrid topology« that combined both methods.

To determine the necessary degree of stability, Manger conducted a number of stress tests. He used a data logger of his own design to take measurements during test rides, including on the impact caused by potholes and the forces at play when a rider slides at an angle to slow down. Experimental analyses were also performed at Fraunhofer IWU to measure the rigidity of the trucks typically available in shops.

Since he didn’t have direct access to the resources Project T.O.S.T. would require, Manger had to seek out support from partners. This was how he connected with Fraunhofer IWU, Autodesk – which has provided him with two software applications, NetFabb and Fusion 360 – and eventually, Concept Laser. Working with as few different software tools as possible was another focus of the project, as Manger was intent on »evaluating the lattice structures with a reasonable amount of processing power«.

PUSHING THE PARAMETERS TO THE LIMIT

The titanium trucks were 3D-printed by a Concept Laser M2 Cusing machine at Fraunhofer IWU's facilities in Dresden, with each truck requiring around 40 hours of production time. Manger chose a rather expensive alloy (TiAl6V4) for this purpose due to its specific rigidity and resistance to corrosion. Once printed, the trucks were subjected to vacuum heat treatment to minimize tension and increase the ductility of the metal.

During this undertaking, Manger has tried to push the parameters to the limit. The optimized lattices at the core of his trucks now have a diameter of between .2 and .5mm, and most of the outer shell is less than .8mm thick. »That's how you pull off the significant weight reductions that make extremely lightweight designs possible,« Manger happily points out.

While these expensive trucks will likely never make it to series production, the principle of combining a bionic design with an internal lattice structure should be relatively easy to transfer to other applications. »You can apply the concept to any area where you’re trying to achieve lightweight constructions by reducing material usage,« Manger explains. Among other accolades, his project's accomplishments garnered a nomination to the final round of the 2017 TCT Awards.

Meanwhile, Manger had more good news to report from formnext 2017: His skateboards were featured at the booths of the four partners involved in his project. Each exhibitor had laid out a fairly significant sum to acquire one of these prized decks from Fraunhofer IWU.

Video: