Components can be built up from one or more solid or liquid materials. The process is computer-controlled, and the build-up takes place via physical or chemical hardening and melting processes. In the past, lithography processes such as SLS (selective laser sintering) or DLP (digital light processing) were used in the ceramics industry and initially led a niche existence. The reasons for the initially low use of this new technology were the unwillingness of companies to use additive processes for components, a lack of know-how, and the acquisition costs for corresponding equipment of usually well over €100,000, combined with high material costs. The long production times of the components also imply high unit costs. Depending on the manufacturing process, there were and still are limitations in the size of the components, and in the SLS process, the suspensions are system-specific. The issue with some of the 3D printing processes used for technical ceramics is the challenging development of the debinding oven curve, which can take up to five days, and the design changes to implement the customer's components.
Ceramic 3D printing on the rise
Despite all the challenges, additive manufacturing is a technology of the future, including for the ceramics industry. Some companies in this sector have already invested in 3D printing equipment and are using the innovative manufacturing process. Although initial test runs are occasionally associated with cost-intensive learning curves, it is often worthwhile in the long term to enter additive manufacturing. In Bavaria, too, there are more and more companies that are successfully using 3D printing and research institutions that are contributing to the further development of the technology through their work.
The LCM process (Lithography-based Ceramic Manufacturing) is an additive manufacturing process for building 3D objects from technical ceramics. In the stereolithography process, a green body or green compact is built up layer by layer using a liquid suspension of fine-grained ceramic powder and a UV light-sensitive monomer and cured via irradiation. This is followed by a multi-stage thermal treatment at firing temperatures of up to 1,600 °C. During thermal debinding, the polymers used as binders are removed. Only in the final sintering process does the component acquire the properties typical of ceramics. Ceramic suspensions have not yet been universally applicable. Raw material manufacturing companies have addressed this issue in recent years and are working on developing ceramic suspensions for lithography to make them universally applicable.
There are currently two major machine suppliers for technical ceramic 3D printing on the market: Lithoz and 3DCERAM. Lithoz developed LCM technology based on photocrosslinkable polymers. 3DCERAM implements the laser-based stereolithography process for technical ceramics on the same physical basis.
Ceramic innovations from Bavaria and Slovakia
The Upper Franconian Alumina Systems GmbH, which is a partner in the Cluster New Materials of Bayern Innovativ , owns the largest commercially available 3D printer from 3DCERAM to date. The printer has a build area of 600 mm x 600 mm, enabling the production of 3D-printed components in large dimensions. It is now possible to manufacture special parts in small or series production. The company claims to be the undisputed market leader in 3D printing of technical ceramics through innovation and customer proximity. Via the purchase of special IPs, a proprietary 3D printing process has now been brought to industrial maturity in 2020, the "laser-induced slip casting (LIS)". This process comes with significantly lower material costs, as the preparation of the ceramic suspension is much simpler, and therefore comes with significantly lower costs than any other printer available on the market. Build times are orders of magnitude less and part geometry in terms of wall thickness and part size are comparable to isostatic or dry pressed parts. However, the speed and cost advantage comes at the expense of precision, which is not quite in the range of lithography processes. But this is still the subject of current further developments on the prototype machine recently supplied by the cooperation partner.
In late 2020, researchers at the Slovak University of Technology succeeded in developing a new material for ceramic 3D printing. This should make 3D printing with ceramics more affordable for private use. The ceramic material can be additively processed with commercially available FFF 3D printers, even in the low-cost range.
Fused Filament Fabrication (FFF)/Fused Deposition Modeling (FDM) technology is a simple way to manufacture components. What is needed is a print bed on which the object is printed, a spool of filament that provides the print material, and a print head, also called an extruder. The filament is unwound and melted by an extruder. The material is then deposited layer by layer on the printing plate.
The material consists of a PVA-based binder and ceramic powder. It can be extruded from standard 0.4-mm dies. Additional system adjustments and expensive special ovens for post-processing are not necessary. This has made the material interesting for hobby users as well. FFF systems are also inexpensive. Ceramics can also be mixed with polymers such as ABS (acrylonitrile butadiene styrene) and PLA (polylactide) to form novel filaments.
Companies are very interested in manufacturing systems that combine standards of industrial production, such as reliability and high-quality components, with the cost-cutting approach of a modular design. In the project "Economic Additive Manufacturing through Modular Machine Concepts for Small Series Production in SMEs" (AddPro-KMU) of the Technical University of Nuremberg , suitable machine concepts were compiled and implemented. In this, on the one hand, standardized assemblies (drive unit, operating units, print heads, etc.) were used to achieve universal applicability of key components in various machine concepts. On the other hand, the modularity allows the system to be expanded in stages, depending on requirements. In this way, an industrial-level system can be implemented for a relatively low purchase price, the functions of which can be extended by additional modules. Nuremberg University of Technology is a partner in the Cluster Neue Werkstoffe (CNW). A successful modification of this low-cost modular machine allows the FFF technology to be implemented at low cost. The start-up Keramik Innovation Berthold from Erlangen, also partner in the New Materials Cluster , was involved in the implementation of this modification by providing filaments and supporting bachelor theses.
Additive Manufacturing: The Current Market Situation
Over the past three years, global sales of additive manufacturing-related equipment, materials and services have grown by an average of more than 33% per year. A key driver of this growth has been the expiration of early patents related to devices and processes. This has resulted in the creation of many start-ups. The ceramics industry can also benefit from this development, as the opportunities for ceramic 3D printing will increase.
