In racing cars, tight engine tolerances mean each component has to be manufactured with pinpoint precision. There is no room for error if you want the best performance. For example, the geometry and dimensional tolerances of engine bearings are an area of intense study. It can take millions of manhours to get those right.
For students at Leeds University taking part in Formula Student, the need for high-quality mechanical components is obvious. As Europe's most established educational engineering competition, taking first place is a huge boon. Not only does it give those engineers bragging rights, but it also enables them to explore real engineering challenges.
AutoDesk, who build 3D printing software, approached Leeds University hoping to help. AutoDesk support Formula Student teams around the world with a full version of their software (Fusion 360), so they can have access to local simulation, 3D design, design acceleration, and more.
The applications for AutoDesk Fusion 360 are immense. In this particular case, the students used it for the design and simulation of the plenum assembly. The intake plenum is a part of a vehicle’s intake manifold, which transfers the fuel-air mixture to the cylinders.
Traditionally, intake plenums are made from cast aluminium. This creates a durable and strong part, but also a heavy one. With the Formula Student team keen to save weight in any area possible, they decided the intake plenum would be a good candidate for 3D printing. But how would they create a part that's as strong as aluminium, but lighter?
Printing with the Markforged X7
The Markforged X7 is a beast of a 3D printer. It is Markforged's top-end model, with a dual nozzle print system that supports continuous carbon fibre and Kevlar reinforcement.
Parts printed with continuous strands of a composite outperform aluminium, yet they are 40% lighter. This performance potential appealed massively to the Leeds University engineering team because it would enable them to replace a wide variety of aluminium parts with lighter ones.
In simulation, the team had designed a plenum but they needed a functional material to make it. For this, they chose Onyx. Onyx is a proprietary material to Markforged. It's part nylon, part chopped carbon fibre. Out of the box, it's immensely strong and tough. The plenum was 3D printed in Onyx because of its high strength and heat resistant properties.
Our role in this project was to 3D print the model itself. We were asked to help with 3D printing the design using an iterative process (basically, we printed a series of models) and we continued to support the project until the final part was made.
The intake plenum was printed true to design. Onyx exhibits excellent dimensional stability so all design iterations were printed without failure. Onyx is about twice as strong as ABS and has a heat deflection temperature of 145C. It can also be further reinforced with carbon fibre, Kevlar, fibreglass, or HSHT fibreglass to create even stronger parts.
Once printed, a company called Additive Manufacturing Technologies Ltd carried out a surface modification and sealing process through the use of its automated post-processing solution, the PostPro3D. This was the finishing touch to give the intake plenum an oil and grease resistant finish, so it would cope with the rigours of racing hard and fast.
In tests, the plenum performed just as well as the aluminium original. It was also 40% lighter. The plenum showed no performance issues and passed a choke test. The team were also able to make the plenum larger than the aluminium model. This increase in internal volume meant an increase in the amount of air to the engine, improving performance.
The cost of the materials came to £504. The intake plenum was printed in five parts and took 247-hours to manufacture.
3D printer: Markforged X7
Part: Intake plenum, 5-piece assembly