www.3ders.org

Sep 30, 2016 | By Alec

No manufacturing technology is perfect, but today’s industrial grade 3D printing conventions are faced with several significant drawbacks. Even when relying on those metal or ceramic powder 3D printers used for aerospace applications, 3D printed parts can exhibit miniscule sharp edges and small levels of porosity, consisting of very tiny defects and gaps. While you can’t even see them, researchers from the Carnegie Mellon University previously found that these small flaws can decrease the 3D printed object’s density and resistance to fatigue.

It’s one of the reasons why industrial 3D printing isn’t being adopted at a very large scale just yet. But researchers from the German Bundesanstalt für Materialforschung und -prüfung (BAM) institute have come up with a revolutionary ceramic powder 3D printing technique that overcomes these problems entirely.

BAM is part of the BMWi, the German Federal Ministry for Economic Affairs and Energy (not to be confused with car brand BMW). As a departmental research institute, they are mostly focused on material engineering and testing, and providing advice on how to protect people, the environment and material goods. German construction, engineering and other industries regularly rely on BAM’s research and validation procedures, and they are one of the institutes behind the German reputation for high engineering standards.

Through this focus BAM is no stranger to 3D printing, though they have outdone themselves with this latest project. Using a custom 3D powder printing technique, they can now 3D print ceramic structures with a higher stability than ever thought possible through this manufacturing technique. Pores and edges are non-existent, reducing a likelihood of fractures and increasing the density of the parts. At the same time, the method is fast, simple, inexpensive and doesn’t use hazardous materials – perfect for a very wide range of manufacturing industries.

At the same time, this method makes ceramic 3D printing far more viable for industrial users. For ceramic production in particular suffers from the high temperatures that are necessary to blend the material into uniform component, while (unlike resins, polymers and metals) they can not be cross-linked. Professor Dr. Jens Günster, who headed ceramic 3D printing efforts at BAM, has now overcome these limitations by relying on so-called pre-ceramic polymers, which are converted into ceramics during 3D printing. Unlike regular ceramics, these can be cross-linked, plastically deformed, melted or dissolved with a variety of solvents. Ceramic 3D printing, in short, has become more potent than ever.

This breakthrough is especially remarkable because it remains inexpensive. “We use a commercial, very inexpensive powder which is used in industrial processes and in the production of cosmetics. We apply it layer by layer and glue it locally with a solvent when the desired structure is completed,” professor Günster revealed. The solvent is 3D printed in layers in a fashion reminiscent of ink-jet printing, with the polymer being fired in oxygen-free environments at temperatures above 1200 degrees Celsius. The result: a ceramic made from vitreous silicon oxycarbide (SiOC).

To make it work the German engineers had to rely on a completely new ploy. They were faced with the problem that the 3D printed polymer would begin to melt at 60 degrees Celsius, making firing impossible. To overcome the problem, they added a ‘cross-linking’ agent to the dissolved powder, which ensures that structure is maintained during firing.

Through this method, they were able to further build on the 3D printing process – which has since grown into a dual print head setup, with a solvent/cross-linking agent being extruded from one and a pure solvent from the other. “We use these two liquids to print the structure’s skeleton and the covering in one process. The skeleton retains its structure during firing since it contains the cross-linking agent. The covering applied without the cross-linking agent melts. It merges with the skeleton and even enters its lattice structure due to an interaction of viscosity, surface tension and gravity. As a result, we obtain a ceramic whose surface is smooth and has no pores or sharp edges. The structure has been optimized through self-assembly and withstands pressure,” the professor argued.

During development, the BAM research group collaborated with German powder-based 3D printing pioneers Voxeljet AG. While no commercialization plans have since been released, this technology breakthrough could obviously provide a huge boost to ceramic and powder-based industrial 3D printing efforts. More will doubtlessly follow.

 

 

Posted in 3D Printing Technology

 

 

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