Team TUfast Uses Metal 3D Printing to Improve Cooling Geometry of Its Unique Race Car Housing By 20%

3D printing is often called to the track these days to help student formula teams in augmenting their race cars. This season, the Formula Student racing team from TU Munich (TUM) worked with GKN Additive to step up their game and improve their electric race car’s performance.

Every year, student teams competing in the the Formula SAE and Formula Student competitions are ranked on the acceleration, cost and manufacturing analysis, design, electrical efficiency, and endurance of their cars. Through their research, the students are also helping to shape the future of electric vehicles. Team TUfast (which is the best name ever) was founded as a student initiative in 2002, and currently has over 70 members divided across multiple areas.

Most small power-dense motors located in a car’s wheel hub operate at high temperatures, which damages not only the motor but the team’s score. This year, TUfast improved the cooling geometry of their car’s unique housing in the wheel hub by nearly 20% by using metal 3D printing to make it small enough to fit.

“The result is significantly improved heat transfer compared to last year´s concept while having an even temperature distribution over the surface and further weight reduction of the whole wheel hub drive-package,” Susanne Trautmann, the Global Marketing Manager for GKN Sinter Metals Engineering GmbH, told 3DPrint.com.

Team member Marco Tönjes, who is responsible for the team’s electric motor and its components, explained in a GKN Sinter Metals blog post that TUfast decided to work with the additive side of GKN Powder Metallurgy because the company is well-known in the market for its expertise.

“They helped us to further optimize the housing: we originally wanted to implement the adapter for the cooling connections as an integral part with the housing,” Tönjes said. “However, GKN’s engineers had a different approach. They suggested that we should separate the housing and connection adapter, as this significantly reduces the support structure required for production. The adapter, which is also laser-sintered by the additive business of GKN Powder Metallurgy, is now screwed to the housing with two screws.”

By using as little material as possible, the weight of parts can be reduced, along with production times and material waste. Metal 3D printing allowed TUfast to reduce the overall weight of the wheel package by roughly 0.6 kg.

In previous years, the team used a simple turned part for their electric motor; last year, this didn’t go so well. But now, their “cooling is fundamentally different,” which is why they decided to use 3D printing to manufacture it.

“To enhance our cooling performance, we designed a new concept with an integrated structure. The structure consists of an inner cooling channel with a special optimized pin structure. The cooling channel is directly integrated in the housing, in which the stator is casted,” Tönjes said.

“The manufacturing of this structure with its – despite the inlet and outlet – closed jacket structure, is not realizable with conventional methods. Additive manufacturing, or more precisely, laser sintering, is the only process that makes it possible to manufacture this component.”

Tönjes explained that many other teams purchase their motors, while Team TUfast would rather build their own.

“The electric motor typically is not part of the chassis, but here it is because it has a wheel hub drive. And since it has a wheel hub drive, it has many interfaces to the chassis,” Tönjes said.

“The all-wheel drive wheel hub of this year’s vehicle combines the different drive components, and its functions are integrated in a compact and lightweight-optimized design for the lowest amount of space. Next to the topology optimized upright, the gearbox and the braking system is the electric motor. The laser sintered aluminum body with the new integrated cooling structure is the centerpiece of the powertrain.

“The housing, developed in cooperation with the additive business of GKN Powder Metallurgy, was designed by us.”

The results of TUfast’s new 3D printed housing speak for themselves. In addition to increasing the efficiency and heat conduction of the cooling system by nearly 20%, the peak loads are also cooled down quickly.

“The difference between our previous and latest structure is that the new cooling geometry leads to an increased heat conduction by 2% with the same mass flow. The decreased pressure drop across entire cooling system of the Four-Wheel-Driven Electric car leads to a 31% percent higher total mass flow,” Tönjes explained.

When asked if TUfast would be using more 3D printed components in next season’s vehicle, Tönjes responded with an emphatic “Absolutely!”

“Compared to the normal automotive sector, metal 3D printing is particularly versatile in racing,” Tönjes said. “Especially for small quantities, it is a fascinating technology. You can do everything without needing a mold or a tool.

“The geometries that can be realized are significantly different from conventional production processes. That is what makes 3D printing so interesting for us as engineers: we can implement more innovative ideas.”

Team TUfast’s electric race car, complete with 3D printed housing, will compete in its first race next month in Silverstone at Formula Student UK, followed up by two more races in Hockenheim and Barcelona later this summer.

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[Source: GKN Sinter Metals / Images: TUfast Racing Team]