Fraunhofer Institute for Production Technology IPTResearch project "3DHeat"
Double tool life in glass molding
High-precision glass optics are found in many components such as smartphones, medical technology systems, vehicle sensor technology, and defense applications. Users demand the tightest tolerances and outstanding surface quality. At the same time, European optics manufacturing is struggling with massive cost pressure from Asian competition.
From an ecological perspective as well as due to economic efficiency and short cycle times, non-isothermal glass molding is particularly suitable for the production of such optical glass components in large quantities. Efficient processes and durable forming tools are crucial for economic efficiency. This is currently only possible to a limited extent: in non-isothermal glass molding, the tools often last for less than 1000 forming cycles. With cycle times of around 30 seconds, this corresponds to a service life of only a few hours. One of the main reasons for this is local temperature deviations, which cause glass breakage or adhesions to the tool surface.
In the research project “3DHeat – Hybrid Additive Manufacturing of Molding Tools for Glass Molding,” we are developing molding tools with contour-accurate, rapidly controllable temperature regulation. We precisely control the thermal input, thereby reducing wear. The goal is to double the service life.
Additive manufacturing and coating of molding tools
The aim of the research project is the development of processes for the additive manufacturing of long-lasting molding tools. Various methods are used for this: The tool body, made of inexpensive steel, is created in a powder bed using Laser powder bed fusion (LPBF). During construction, the scientists integrate sensors and surface-mounted temperature control elements. These enable local and temporally variable temperature control during glass molding – something that does not work with conventional drilling or external heating or cooling systems.
The top layer of the tool, known as the glass contact zone, is also created using additive manufacturing: Laser metal deposition with wire (LMD-w) is used to apply a high-quality metal material with similar expansion properties to the glass material to the tool body. This minimizes differences in thermal expansion and thus glass breakage.
By specifically structuring the tool surface, the bond between the forming tool and the glass material can be further improved. In the event of wear, the top metal layers can be removed and additively renewed without having to replace the entire tool body.
Research focus
The research project is the first to systematically investigate the interaction of additive, subtractive, and thermal process control for the manufacture of forming tools. To this end, the first phase of the project involves modeling the molding process and the temperature distribution in the molding tool using various simulations. Critical operating points are also identified in the process.
In the next phase of the project, the team will design the necessary processes for manufacturing the tool body in a powder bed and for integrating the temperature control elements and sensors. The process for welding the wire material onto the tool body will also be designed. Subsequently, molding tools will be manufactured in a hybrid process, whereby different glass contact materials will be applied.
In the final project phase, the heating behavior of the additively manufactured molding tool will be validated and the forming process further optimized. For this purpose, glass optics will be produced and analyzed using the molding tools. The analysis of the produced optics and the tool will enable a comparison of the actual heating with the simulation results. In addition, the tool life will be qualitatively examined and evaluated.
Increased tool life, reduced scrap, lower production costs
Additively manufactured molding tools increase tool life, reduce scrap through improved temperature control, and lower production costs.
Extending tool life is particularly important, as molding tool costs account for a large portion of manufacturing costs. In addition to series production, this approach also enables prototype construction for process design through the integration of a wide variety of sensor technology.
Small and medium-sized companies in the glass industry in particular benefit from more durable tools, more stable processes, and higher product quality. However, the solutions developed can also be transferred to other industries with high thermal and tribological requirements, such as the steel processing industry.
Project committee
- LIGHTWAY GmbH, Niederzissen
- Coherent Lasersystems GmbH & Co. KG, Göttingen
- LaVa-X GmbH, Herzogenrath
- Hüttentechnische Vereinigung der Deutschen Glasindustrie (HVG) e.V., Offenbach am Main
- Vitrum Technologies GmbH, Alsdorf
- Sato Maschinenbau GmbH & Co.KG, Mönchengladbach
Funding
The research project “3DHeat – Hybrid Additive Manufacturing of Forming Tools for Glass Forming” is funded by the Federal Ministry for Economic Affairs and Energy on the basis of a resolution of the German Bundestag as part of the program for the promotion of industrial joint research (IGF).
Funding code: 01IF23813N
Project management agency: German Aerospace Center (DLR)
