New generation of 3D printing requires almost no post-processing

In collaboration with three Danish companies, researchers from DTU have now proved that metal 3D prints can be produced with almost no post-processing.

Photo: Lisbeth Lassen, DTU Mechanical Engineering.

Photo: Lisbeth Lassen, DTU Mechanical Engineering.

3D printing in metal requires some finishing, because the finished prints have very rough surfaces, which is why the industry primarily uses 3D printing for prototypes and the production of very small series. However, a group of Danish researchers and companies have now developed a new, cost-effective method that produces smooth surfaces and which do not require extensive post-processing.

“Early in the year, we and a couple of companies thought out a process which can give 3D-printed metal elements smooth surfaces, making them almost ready for immediate use. We have now successfully completed the first experiments with the process. In other words, we have demonstrated that our idea holds water and can be realized in practice,” says David Bue Pedersen, researcher at DTU Mechanical Engineering.

The new process is a chain where the first step will be to produce a 3D print which is a thin shell of the final product to be produced. This could be the shell for a ball-like structure. This 3D print is made using a technology that is based on photopolymerization—a process employing ultraviolet light and which offers extremely high quality as regards geometry and surface finish.

Metal powder is then dissolved in a liquid (slurry), which has a paste-like texture, in the 3D-printed shell. The blank must now dry, and then the shell can be removed. The last step is baking the so-called green blank which consists of the metal powder paste in an oven. In this way, the individual metal particles become sticky and glue together with the neighbouring particles. This ensures both strength in the metal as well as a very fine surface.

“The next step is to identify and control process parameters, so we can control the new process chain and apply the method to all types of 3D-printed components, whether they are round, square, or have an entirely different shape. And performed in the material you want to use,” explains David Bue Pedersen.

“The process chain control must then be documentation of a new production method which in future will be available, so it can be used by all engineers and does not require expert knowledge.”

Roll-out to companies
By means of the documentation, it can be ensured that the components, for example, are sufficiently strong and that the process is financially profitable. When this is in place, the new method can function as a new, integrated production platform which can be implemented in companies.

“It’s still too early to say when we will have finished the entire control process and the documentation of the process chain. It’s so comprehensive and also vital to ensure that the process subsequently can be used in companies that my best guess is that it will stretch over the next couple of years,” says David Bue Pedersen.

However, as documentation is produced, the partial results will be made available, so that they can be used by companies. The work is part of the project 3DIMS which is supported by Innovation Fund Denmark with DKK 13 million.

In the first step of the process, a shell structure is 3D-printed by means of photopolymerization. The liquid plastic material in the vat is exposed to focused ultraviolet light and subsequently hardens in the desired shape which forms the basis of the metal blank. 

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