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Toolless Manufacturing of Complex Structures

Periodic Reporting for period 2 - ToMax (Toolless Manufacturing of Complex Structures)

Reporting period: 2016-07-01 to 2017-12-31

Using light for 3D-structuring parts offers significant benefits compared to competing additive manufacturing technologies (AMT): Lithography based AMT are capable of printing parts with at least one order of magnitude better feature resolution, surface quality and precision. ToMax made heavy use of this benefit, while also aiming at developing integrated lithography-based additive manufacturing systems with improved throughput and reliability. The focus of the project was to unite industrial know-how in the field of software development, photopolymers and ceramics, high-performance light-sources, system integration, life cycle analysis, industrial exploitation and rewarding end-user cases.
The consortium provided 3D-printers with excellent feature resolution and outstanding materials and energy efficiency. The project was industrially driven, with 8 out of 10 partner being SMEs or industry. During the second project period, the consortium successfully achieved a number of major milestones:
(1) A new class of high-performance 3D-printers with excellent feature resolution (20micrometer) and increased build volume has been set up. The system is based on dedicated laser optics, which have been specifically designed and manufactured for ToMax by one of the partners.
(2) The system has been modified in a way that allows processing of high-viscosity materials. These improved capabilities enable the use of highly filled photopolymers. ToMax was therefore able to print silicon nitride parts with world-record mechanical properties in terms of strength. These successful developments where instrumental for introducing 3D-printable silicon nitride ceramics to the market.
(3) By utilizing state-of the art light sources (Phaser) and developing dedicated optics, ToMax-partners succeeded in providing world’s most powerful light engine (based on digital light projection - DLP) for lithography-based AMT.
(4) To further increase the impact of these technological and scientific developments, the ToMax team put significant efforts towards streamlining the exploitation and dissemination of the obtained results. As result of these activities, a recently established spin-off of one of the academic partners has already signed a licensing agreement.
The performed work in the first and second project period was covering the following topics:
(1) Developing advanced high-performance light engines, which facilitate the implementation of hybrid exposure approaches (raster approach using DLP and scanning approach using diode lasers). A dedicated DLP light engine with an optical output of 8W@450nm was developed and integrated into a hybrid system. The hybrid light engine was successfully used as key component for an AM system with large build volume, high throughput and excellent feature resolution.
(3) Key requirement for meeting the end-user requirements are innovative material solutions. The developed AM system allow the processing of materials which are significantly more viscous than in state of the art AM systems. Using ToMax technology, the material spectrum can therefore enhanced significantly, leading to final materials with improved mechanical qualities. Of specific interest in the first project period where silicon nitride materials. The consortium could show that these materials can be processed and the resulting parts exhibit excellent strength (>700MPa) and density values (3.25g/cm³).
(4) Due to the input of all partners, the consortium was able to set up the worldwide first Life Cycle Assessment (LCA) of lithography-based AMT covering the whole process chain from materials production, resin preparation, structuring and post-processing. This will allow an in-depth analysis of the ecological impact of AM technologies in manufacturing.
(5) From the beginning of the project, the consortium was aiming towards a clear roadmap for exploitation of the obtained results. Due to this stringent exploitation strategy, a first licensing agreement could be signed. Furthermore, the developed silicon nitride material as well as software for support generation have moved into a product development stage at the involved ToMax partners.
The following key achievements illustrating the progress beyond state of the art need to be mentioned:
(1) Software with novel ways of interacting with the computer-aided designs of the geometries to be printed and with new aspects linked to the preparation of additive manufacturing processes by photopolymerization has been developed.
(2) Processes for controlling not just the inner structure of additive manufactured parts, but also the surface properties of computer-aided designs have been developed, validated and compared with state-of-the-art software for texturing designs.
(3) In WP3, improved debinding and sintering protocols for post-processing of printed alumina parts enabled the the realization of relative densities of 99.7 % without using any sorts of sintering aids. This constitutes a significant improvement compared to the previously feasible 99.4 % for lithographic AM as well as other AM approaches in general (relative densities <99 %).
For silicon nitride-based materials the results of ToMax constitute the first report of AM-produced parts with equivalent material properties to conventionally fabricated counterparts.
(4) The light engine developed in WP4 has a very high optical output power (> 8W, more than 600 W/m² irradiance in the image plane) due to the laser array illumination system and careful design matching of all components, which is significantly higher than comparable systems on the market, thus reducing the cycle time of the 3D-printing process.
(5) In WP5, a high throughput L-AMT system, designed from scratch, with high- feature-resolution and large building volume (144x90x100 mm³) has been developed. The upscaling of such a system, with respect to previous construction from the TUW, was achieved. This screening was important for obtaining a TLR6-state within ToMax.
(6) The highlight beyond the state of the art is a combination of two exposure units, which separately are intended for L-AMT; a DLP Light Engine (LE) (projecting bitmaps for layer generation) and a laser-scanner system (exposing vector-based structures for layer generation) where constructed and tested separately. A simultaneous acceleration of the exposure step and good surface qualities should be achieved by combining both systems.
(7) Applications in energy engineering, which benefit from the use of complex geometries and structures for improved heat dissipation, heat transfer, promotion of turbulence and integration of structural and thermal functionalities, have been conceived, designed, implemented and tested for validation purposes.
(8) Applications in chemical and biomedical engineering, in which the use of ad hoc defined porous or lattice structures and microtextured surfaces may improve the reactions involved or lead to biomimetic and biomechanical performances have been successfully investigated.
(9) A complete study regarding the impact of different support geometries on the environmental impacts and cost has been performed. The study shows that the use of improved supports developed during ToMax, depending on part geometry, lead to support material savings with values typically ranging from a 40% to almost an 80%. Related cost reductions typically reach values from 10% to 40%.
3D-printed impeller made of siliconnitride