Experts at the Steinbeis Transfer Center for High-Tech Ceramics have succeeded in producing ceramic components using 3D printing, a special rapid prototyping method. Based on computer-aided designs and 3D object scans, the team manufactured ceramic models and components from a variety of ceramic raw materials. As aluminum oxide (Al2O3) led to the best results, the project team then investigated the possibilities of 3D ceramic printing with this material in more detail. The project was sponsored by the German Federal Ministry of Education and Research.
As expected, the printed components were highly porous due to their layered structure and the agglomeration of the individual granules. This meant only very low strengths were possible. As a result of the procedure, the properties of the components depended on their orientation in the printing chamber. The strength was lowest (ó0= 5 MPa) along the z-axis (the direction in which the layer structure was built up), at a medium level (ó0=10 MPa) along the x-axis (the direction in which the printer moved), and highest (ó0=20 MPa) along the y-axis (the direction in which the print head moved). As the adhesive constituents could not be applied via the print head, they were mixed into the ceramic powder as dry powder. The main constituent of the printer liquid was water.
3D-printed ceramic objects have a variety of technical applications, such as filtration and bone replacement. The technique also allows component designs which would be impossible using traditional ceramic methods. Ceramics produced using the new method can also be used as more wear resistant composite materials after infiltration with metal melts.
Scanning electron microscope images of the material revealed a homogenous microstructure with crystals that had grown together well with pores of 1–5 μm. The Steinbeis team used regression and maximum likelihood methods to determine the average strength ó0 and the Weibull modulus. This revealed that using commercially available raw materials resulted in relatively low green densities and strengths.
The Steinbeis study confirmed the findings of other research groups who have studied this and similar methods. Even complex powder preparations in which the granules had thin adhesive coatings were unable to produce higher green densities and strengths. The ideal raw materials for the 3D printing process are currently not commercially available – they still need to be produced with special equipment in dedicated laboratories. Adding the adhesive in powder form is also not ideal – it would be better to deliver the adhesive via the printer ink. So using different types of printers, such as piezoceramic drop-on-demand printers, could allow for a wider range of inks.
In future research, the Steinbeis team aims to develop 3D printing methods capable of producing higher green densities and strengths – plus homogeneous strength, regardless of the ceramic’s orientation in the chamber. For 3D printing methods to be successfully used to produce ceramic prototypes in high performance industries, components need to match the quality of those manufactured using traditional methods. This Steinbeis study is a major step forward in reaching these goals using new methods and equipment. Other key goals include being able to control important process parameters, and no longer being limited to a single printing technology.
Prof. Dr. Manfred Schumacher
Steinbeis Transfer Center for High-Tech Ceramics Vallendar