New breakthroughs in 3D printing technology

Posted by Johnson Brown on August 4th, 2021

Traditional 3D printing often has to design the structure first, then select the material, determine the processing process, and finally print the forming. However, due to the complex coupling law of multiple factors such as material, structure and process, it is difficult to realize the high performance or even multiple functions of metal components if the components of 3D printing need repeated trial and error for accurate forming.

Professor Gu Dongdong's team from the College of Materials Science and Technology of Nanjing University of Aeronautics and Astronautics and the Laboratory of Laser Additive Manufacturing Engineering of High-performance Metal Components in Jiangsu Province, China, in conjunction with German, American and British scholars, established a new 3D printing mode that can synchronously design and print a variety of materials and multiclass structures inside complex overall metal components and realize the high-performance and multifunction of components.

Laser additive manufacturing, or 3D printing technology, is a strategic key core technology developed by the current world's scientific and technological competitive power, which can meet the major needs of modern industry for the short-cycle, high-precision, and high-performance manufacturing of difficult to process metal components.

"Conventional 3D printing follows a 'tandem route', i.e., structural design–material selection–processing process–to achieve performance. This route requires repeated trial and error, cycles, and high costs." Gu Dongdong, the first author and corresponding author of the paper, said that based on the challenge, he and the research team proposed a new 3D printing model, the parallel model of "material-structure-performance integrated additive manufacturing".

Popularly speaking, when designing and printing the product structure, this mode considers which material and structure are more suitable in different parts of the part, reconfirms the processing route, and finally prints it out to ensure the high performance and multifunction of the product.

"People increasingly hope that metal parts can meet multiple needs at the same time. Even one part can be printed with different materials and different structures in different positions to achieve different functions. For example, some parts can be heat-resistant, and some parts can be bearing force, and this 3D printing mode can be realized." Gu Dongdong said.

How to prove that this manufacturing method is more reasonable? The research team repeatedly verified the feasibility of 3D printing of the metal overall structure of the "parallel mode" with the "development trend of integration and multifunctionality of the next generation space detector lander system".

High-performance metal components are the cornerstone of modern industries such as aviation, aerospace, transportation, and energy, and the service performance of high-end equipment largely depends on the high performance of components. However, these components are mostly used in extremely harsh environments, which pose a serious challenge to the material selection, manufacturing process, performance, and function of the components.

"In the paper, we set a goal to try to make the lander of the detector insulated, heat resistant, shock absorbing, impact resistant, and space radiation resistant." Gu Dongdong said that in the study of the special structure of some insects, animals and plants in nature, they have attracted their attention. They learn the natural optimized structure in nature, emphasize biological enlightenment, biomimetic design, and use it in the design of "bottom" components of space lander systems.

The three biological structures that entered the research team's field of view were the layered composite structure of the squamate snail shell, the blister configuration of the water spider, and the porous honeycomb. "Scale-footed snails live near hot springs on the seafloor, snail shell is a layered composite structure, the shell is very hard, the outer layer of our 'bottom' component is designed into scale-footed snail shell structure, so that the lander can be firmly like armor and can be insulated and heat-proof; the water spider builds a residence underwater, and its blister-shaped residence is composed of spider silk connected water grass, which can withstand the impact of water flow at different flow rates and different directions for a long time and has excellent toughness and impact resistance. Based on this, we designed shock absorption structures inside the 'bottom', in which the 'spider silk' is criss-cross and can make the lander shock absorption and impact resistance; we attached a layer of high-temperature structural material similar to porous honeycombs to the surface of the 'bottom', which can prevent burns when the lander rubs with the atmosphere." Gu Dongdong introduced.

While designing the structure, the research team also selected composites with fused ceramics, carbon nanotubes, and aluminum alloys based on aerospace needs. “Aluminum alloys are very light, so they are widely used in aerospace, but the melting point is only more than 600 degrees, which cannot withstand such a high temperature when landing, so we added titanium diboride ceramics with a melting point close to 3000 degrees. For another example, carbon nanomaterials have many magical mechanical properties and physicochemical functions, so we have designed carbon nanotube-enhanced metal-based composites to cope with the need for multifunctionality of 3D printed parts.”

Gu Dongdong said that the biggest difficulty in research is to print appropriate materials to the appropriate position. "At present, the 3D printing of single materials has been relatively mature, but there are still great challenges in the printing of multiple materials, which is also a research hotspot. For example, for each printing layer, it is necessary to design different structures, print different materials, and debug the laser parameters and scanning mode. From the microscopic tissue regulation of 3D printing materials at the atomic scale to printing into visible and touchable finished parts, problems such as deformation and cracking during printing should also be considered.” Therefore, during the experimental verification, they repeatedly performed laser 3D printing experiments with a variety of materials and multiple types of structures, and carried out functional verification such as heat conduction experiments and impact resistance experiments.

Eventually, the team revealed the scientific connotation, forming mechanism and realization approach of 3D printing of multi-material components from three complexity levels: multi-phase layout inside alloys and composites, two-dimensional and three-dimensional gradient multi-material layout, and spatial layout of materials and devices.

At the same time, they realize the "unique structure printing to create unique functions", reveal the essence of 3D printing of topological optimized structure, lattice structure, and biomimetic structure, which are printing the optimized designed materials and pores, the least materials, and the naturally optimized structure to the most appropriate position in the component, respectively, and propose the innovative design of three typical structures: layered composite structure based on scale snail shell, blister configuration of water spider, and porous honeycomb, and the principle, method, challenge, and countermeasures of using 3D printing to realize multifunctionalization such as lightweight, bearing, shock absorption, heat insulation, and heat prevention.