Automotive Applications Embracing Metal Additive Manufacturing

By on November 13, 2018 in DESIGN/MODELING/SIMULATION

Selective laser melting is set to revolutionize the market.

Metal Additive Manufacturing, more commonly referred to as 3-D printing, grabs headlines in the aerospace, defense and medical sectors, but also continues to gain ground in the automotive industry for its ability to lightweight components, reduce assemblies and integrate performance features inconceivable through traditional machining methods.

The term additive manufacturing encompasses a wide variety of technologies that grow parts layer by layer. However, selective laser melting utilizes a high-power laser in a micro-welding process to fully melt layers of metal powder. This process allows for real metal components built with selective laser melting to have mechanical properties that exceed cast parts in terms of density and strength. Parameters, such as laser power and scanning speed, play a crucial role. However, 99.5-percent dense parts are achievable right off the machine, prior to post-processing.

After heat treatment, components surpass metal injection molded parts in terms of porosity. Innovative automotive companies like Bugatti, Audi and BMW, to name a few, have already incorporated selective laser melting into manufacturing supply chains and have begun producing end-use parts for vehicles on the road today.

As it gains more acceptance, selective laser melting is set to revolutionize the automotive market—transitioning from its start with rapid prototyping to high-performance racing cars and increasingly in production vehicles, the benefits of design freedom and maximized functionality are increasing the demand for this disruptive technology. From engine and transmission components to chassis parts and even tire mold segments, selective laser melting reduces time to market, eliminates the need for tooling and opens new possibilities for performance enhancements.

Lightweight components that have gone through topological optimization not only benefit fuel economy, but can also lower inventory and handling costs in the supply chain. On top of weight savings, additive manufacturing allows for the integration of performance-enhancing features, such as internal cooling channels, while also offering the ability to reduce development times and part counts.

LIGHTWEIGHTING THROUGH BIONIC DESIGNS

As a global automotive supplier, the Hirschvogel Automotive Group develops and produces high-strength parts for the automotive industry, and their branch Hirschvogel Tech Solutions combines three service components—part development, additive manufacturing and materials/ failure. To fully exploit the maximum benefits from additive manufacturing, the company specializes in “bionic designs,” which leverage methods and structures developed by nature over millions of years, taking into account functional requirements, and applies them to various areas of engineering and technology.

This “bionic” approach was recently adopted on a steering knuckle, leading to a weight savings of 40 percent in the neck area compared to a conventional forged part. All the necessary performance requirements demanded of the part were fulfilled, including different load cases and stiffness, taking into consideration the given assembly space. This reduction of unsprung weight offers a direct and noticeable improvement in chassis dynamics and ride feel.

To do this, specially developed methods and adapted CAx systems (computer-aided technologies) were applied to produce a fully optimized design that combined lightweighting and a high load-bearing capacity without the limitations imposed by traditional manufacturing methods. With a forged part, features such as hollow spaces, free undercuts and interrupted walls are generally not easy to achieve. Therefore, the design process was carried out with additive manufacturing in mind, allowing the steering knuckle to be manufactured without the many additional internal support structures that would otherwise be required in printing a part that was designed traditionally.

Initially, a number of design variations were developed and assessed before selecting the one best able to fulfill the given boundary conditions. After being built in AlSi10Mg on an SLM®500 selective laser melting system, tests were carried out on tensile and notched bar specimens built in the same process that showed the part successfully matched the forecast values. In addition to significant weight savings, the additively manufactured part also benefited from reduced internal stress and increased stiffness in two directions.

As the understanding of design for additive manufacturing grows, an increasing number of parts will be created more economically with selective laser melting than die casting.

INCREASING PERFORMANCE BY OPTIMIZING DESIGNS

Organizations at the highest levels of motorsports are adopting metal 3-D printing techniques to design and test faster iterations of end-use parts, as well as produce shortrun production or customized components in a variety of exotic metal alloys. Utilizing their knowledge of racing applications, MIMO Technik offers aftermarket upgrades to high-performance vehicles to increase output by specifically engineering components that exploit the benefits offered through selective laser melting.

Taking advantage of the unique design capabilities of metal additive manufacturing, MIMO Technik produces exhaust manifolds that are not only a reduced assembly, but also offer superior flow characteristics over a traditionally manufactured part. 3-D printed out of Inconel 625 metal powder into a solid part for the Porsche 911 turbo, the design decreases turbo lag and provides a more responsive feel from the larger turbos. The high heat-resistance of Inconel 625 allows the manifold to be designed thinner, which also saves weight compared to the traditional stainless or cast-steel equivalent.

The high heat-resistance of Inconel 625 allows the manifold to be designed thinner, which also saves weight compared to the traditional stainless or cast steel equivalent.

MIMO Technik, however, recognizes that components must be designed with additive manufacturing in mind, exploiting the benefits of the disruptive technology in order to be economically feasible. Their production of TiAL turbo intercoolers displays this balancing act. While the intercooler itself performs as needed and is efficiently produced today, the end tanks had the potential to be further improved for increased performance.

MIMO Technik designed intercooler end tanks with the goal of improving the spread of flow across the heat exchanger. Printed out of AlSi10Mg, the tanks were computational fluid dynamics (CFD) tested for optimum flow and could be iterated quickly. The tanks were then welded to the traditionally mass manufactured, and thus cheaper, intercooler. Additionally, through optimized design, the additively manufactured tanks not only provided greater cooling capacity, but were also lighter than their OEM counterparts.

MOVING FORWARD

While metal additive manufacturing will not replace traditional manufacturing techniques, especially in the lowmargin, capital-intensive automotive segment, it opens up new opportunities for innovation and performance that are worth taking advantage of. Currently still limited to rapid prototyping and small-volume parts in the automotive industry, the aerospace sector is paving the path toward acceptance of this disruptive technology. The freedom of design offered by selective laser melting reduces assembly requirements, weight and time to market and will continue to be integrated into supply chains to increase profitability and innovation of end-use components.

 

ABOUT THE AUTHOR
Kyle Adams is an application specialist with SLM Solutions North America. A lifelong car enthusiast, he’s applied his automotive background to his career, spending four years reverse engineering transmissions and driveline components before joining SLM. He is currently responsible for operating the company’s Technology Center, pushing the limits of what is capable with the four metal powder bed fusion machines in the lab while consulting customers on the feasibility and optimization of their selective laser melting projects.

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