Military puts 3D through its paces

Technology uses metal powder to create replacement parts and even larger aircraft components

In early January, a Chinese navy battleship encountered a problem while trying to anchor in harbor - a drive gear tooth on the mooring fractured, preventing the vessel from dropping its anchor.

The maintenance crew walked into a 3D printing workstation at the stern. After some time, they came out with a brand new tooth - a replica of the damaged part - and successfully repaired the drive gear.

Such 3D printing workstations - equipped with computers storing 3D data models, casting devices and different kinds of metal powder - have been given permission to operate and become part of equipment support for China's armed forces, according to a report in PLA Daily, the official newspaper of the People's Liberation Army.

As metal 3D printing technologies develop further, they are gaining wider use in the Chinese military.

Metal 3D printing uses technology similar to the standard 3D printing process. But instead of plastic, it uses metal powder.

Through a high-power laser, fine layers of metallic powder are melted and fused together, each one then stacked on top of another until the desired shape is replicated from a computer blueprint.

"The biggest advantage of 3D printing is that it does not need any machining or molding. You can print any components you need out of the graphical data in your computer, which saves time and increases efficiency significantly," Li Daguang, a professor at the National University of Defense Technology, told Beijing Daily.

The 3D printers currently being used by the army can produce metal parts at the speed of 80 to 100 grams per minute. However, they are not yet capable of printing high-precision parts such as bores.

Global efforts are underway to use 3D printing at larger military installations.

In July, media reports revealed that the US army was developing techniques to use 3D printing to make warheads and rockets in a bid to save money and improve security measures.

China, equipped with the technology to print large titanium alloy parts, seems to be more eager to apply the 3D process to aviation. Industry sources say the technology has found its way into the design of advanced fighter jets J15, J16, J20 and J31.

Although expensive, titanium alloys are ideal for use in the aviation industry due to their high tensile strength and lightness.

A Xinhua report in December said Chinese scientists had produced a 3D printing machine that astronauts will be able to use while on space missions.

"There are no technical difficulties when it comes to printing smaller parts from titanium alloy, but we made the technological breakthrough first in printing high-quality large parts to be used on aircraft," says Wang Minhua, a professor at the Beijing University of Aeronautics and Astronautics.

Wang's team developed a set of methods and equipment to print 5-square-meter titanium alloy parts.

In January 2013, the technology received the State Technological Invention Award, the highest honor bestowed by China for scientific achievements.

Lu Bingheng, a scientist specializing in machinery manufacturing and automation, and a member of the Chinese Academy of Engineering, says efforts to apply 3D printing technology to aircraft started in the United States in the 1980s.

"Due to lack of public records on the current usage of 3D printing in US jets, it is hard to say whether our titanium alloy technology is the best in the world," says Lu.

"But it is safe to say that we are developing at the same pace as the developed countries in applying 3D printing to the aviation industry."

Aside from the fighter jets, Chinese engineers have also used 3D printing technology to design C919, China's first domestically developed large commercial aircraft, particularly for components like the airframe, landing gear and some parts of the engine including the turbine blades and turbine disks.

C919, which is expected to compete with the Boeing 737 and Airbus A320, will take its first test flight by the end of the year. But Lu says it will need further research to prove its safety as a civil aircraft.

Li from the National University of Defense Technology predicts three main applications of 3D printing for military use in the future: Printing replicas of damaged components or parts, emergency supplies and weapons for urgent use.

"The production efficiency of 3D printed components is three times that of the conventional manufacturing method.

"As a result, a 3D printer can be used for producing emergency supplies, which will help relieve the stress of logistics support," he says.

chengyingqi@chinadaily.com.cn