Emerging Technologies in Transportation Casebook/3D Printing/Direct effects

Local Motors' Olli autonomous shuttle, made with 3D printed materials

As of this writing, 3D printing is already being used in the production processes of several sectors of transportation.

Automotive Industry

Working Shelby Cobra replica, made with 3D printed parts from the Big Area Additive Manufacturing (BAAM) machine

Vehicle development is one area where 3D printing is commonly employed. Manufacturers have used the technology to quickly create scale models of its vehicles and working prototypes of parts like air vents which can then be tested to ensure they function correctly and are comfortable to use. Producing these prototypes with 3D printing requires less expense and time than traditional assembly, which streamlines the overall design process. Spare parts for trucks are also being created using SLS printing, which allows for on-demand production and reduces the need for manufacturing and storing spare parts in bulk. Vehicles with FDM printed bodies have also been produced, although it has so far been restricted to concept and limited production vehicles. The material used in these vehicles is a plastic composite, reinforced with carbon fiber. Local Motors’ Strati car and Olli shuttle are two examples, as well as a working replica of a Shelby Cobra created by Oak Ridge National Laboratory.

Aviation

Aircraft parts often have high costs and highly specialized designs, making them ideal candidates for 3D printing production. 3D printing aircraft-grade parts is expensive but is less expensive than some current production methods. Importantly, 3D printing has the potential to reduce the weight of parts. Less weight means less fuel is needed to operate aircraft, which can mean large cost savings as fuel is very expensive. If parts are redesigned with 3D printing rather than traditional manufacturing in mind, dramatic reductions in the number of parts can be achieved. Many simple parts can be consolidated into one complex part that would be infeasible to produce with traditional techniques such as machining. The reduction in parts also means less wear and tear for mechanical components such as engines, and the ability to make more complex structures can allow for more efficient designs.

Some 3D printed parts have been developed but are not currently used in commercial aircraft, such as Airbus’ design for a partition between the galley and passenger cabin intended for future use in the Airbus A320. The 3D printed design uses a lattice structure that gives it high strength for its weight, and a 45% overall reduction in weight. One turboprop engine developed by GE has over 30% 3D printed parts, and is expected to be installed on its planes in the near future. Redesigning the engine for 3D printing resulted in a 10% decrease in weight, a 20% decrease in fuel use, and allowed engineers to combined 855 parts into only 12 parts. Other 3D printed metal parts are already installed in aircraft, including engine components. GE manufactures components such as engine door brackets using 3D printing, and CFM International 3D prints metal fuel nozzles for the Airbus A320neo’s engine that increase overall fuel efficiency. There are several challenges, such as metal print area limits and imperfections such as voids that require post-processing, that prevent adoption of 3D printing technology on a larger scale. 

Transportation Infrastructure

A bicycle bridge with a 3D printed concrete deck in Gemert, Netherlands

So far, there have not been any bridges or roads for motorized vehicles built using 3D printing. However, no fewer than five pedestrian and cyclist bridges have been created with the technology for public use in Spain, the Netherlands and China. The bridges are made from various materials, including more unusual ones like plastic and concrete composite and fiberglass-reinforced plastic as well the common construction materials of concrete and steel. The longest, created by the Tsinghua University School of Architecture in Shanghai, China, is made of concrete and is over 26 meters (85 feet) long. Several techniques can be used to 3D print the large pieces required for bridge construction, including 6-axis industrial robots, and large area gantry and crane 3D printers. Concrete shapes can be built in a process similar to FDM printing, and steel can be welded together layer by layer with the use of an industrial robot arm. There are some challenges involved in 3D printing concrete, as it cures or hardens more slowly than materials such as plastic.

Typically, bridge components have straight lines for easy manufacturing and constructability. However, 3D printing allows curved shapes to be built right into components and many of these bridge decks have been constructed with internal support patterns that add strength but would ordinarily be difficult and costly to produce. For example, the MX3D steel bridge in Amsterdam is entirely composed of curved shapes ideal for withstanding stresses, and the Gemert bicycle bridge has a unique, loop-like reinforcement structure within the concrete bridge deck. Designs created using generative algorithms, which run through many possibilities to find one with ideal strength and material usage and often yield rounded or web-like shapes, are much easier to construct using 3D printing. These algorithms were used in the design of the world’s first 3D printed bridge open to the public in Madrid, Spain, as well the MX3D bridge. Although the printing system used to create these bridges can be costly, the production of the bridge itself can be faster and more cost-effective. Tsinghua University’s bridge in Shanghai cost two-thirds of what a conventional concrete bridge would cost as it did not require as much manual labor and required no formwork, or molds, for the concrete.

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