“Just as it is already possible to manufacture a wide range of polymer-based (plastic) objects using 3D printing or additive manufacturing (AD), it will soon be possible to make metal parts using that technique in combination with some machining processes.
That innovative manufacturing technology, which plans to replace, at least partially, traditional processes of casting, forging and machining, has attracted the attention of different research groups around the world.
In Brazil, the main institutions working with additive manufacturing in the state of São Paulo gathered together through the project funded by FAPESP, to align efforts to further study, develop and apply the new technology.
Some of the challenges involved in developing the technology in Brazil were mentioned by Reginaldo Teixeira Coelho, a professor in the São Carlos School of Engineering at the University of São Paulo (EESC-USP), in a talk presented at FAPESP Week Belgium, held in the cities of Brussels, Liège and Leuven October 8-10, 2018.
“In the near future, some mechanical, automotive and aircraft parts and components, as well as human prostheses, will be manufactured using this new technology. If Brazil does not at least learn how to use the process, it will fall behind,” Coelho stated.
The technology is based on two 3D printing processes for metals known as Powder Bed Fusion (PBF) and Direct Energy Deposition (DED).
The first process consists of using a laser beam to melt and fuse sequential layers of a metal powder bed. The second involves using both laser beams and metal powders injected into a pool of melted metal on the surface of a part.
The researcher explained that as the metal powder melts, the material is deposited in layers and it cools and solidifies until giving rise to the metal part, based on a digital model. “The process is well-developed for polymers, but it still represents a significant challenge for metals,” Coelho said.
According to the researcher, one of the challenges in making the technique feasible is adjusting the laser energy necessary for melting the materials. While polymers melt at temperatures between 100ºC and 250ºC, the melt temperature of most metals is above 1,000ºC, which requires very high energy. “The challenge is managing to obtain an ideal concentration of energy that allows the equipment to achieve that melt temperature for metals,” he said.
Coelho said that another challenge is the surface finish of metal parts obtained through AD, since they may not meet some of the high-performance applications. To do this, AD needs to be combined with processes such as high speed machining and grinding (HSM/G) in the post-processing of parts.
Through the FAPESP-funded project, the researchers, together with a machine and tool manufacturing company from inland São Paulo – Romi – developed a machine capable of performing these hybrid processes. Now, they plan to develop a second-generation machine, also in partnership with the São Paulo machine manufacturer. “Romi has now become the fifth company in the world to have this hybrid process solution,” Coelho said.
In order to ensure the standard of quality of the metal powder used as raw material in these processes, a group of researchers from the Federal University of São Carlos (UFSCar) and the São Paulo Institute for Technological Research (IPT) plan to develop a technology to make it.
The project also involves the participation of researchers from the Institute of Advanced Studies (IEAv), the Renato Archer Center for Information Technology and the University of Campinas (Unicamp).
“We plan to use the knowledge acquired through the project to develop a model for injection molding of thermoplastics in addition to turbine blades and gates for sugarcane bagasse power generation,” added Coelho.”