These days, 3D printing can be done with a great many different and extraordinary materials. DEMCON already has experience in this area with the development of a multi-metal printer and printer for premium quality plastics. 3D printing of glass is a new challenge because it becomes a treacly liquid when melted and – in the case of thin-walled products – very brittle after solidifying. Philips Lighting Winschoten (now taken over by the German company QSIL) approached DEMCON with a 3D glass printer they had built themselves, a functional model for ‘manual’ process research. QSIL is a leading manufacturer of quartz and special glass. QSIL asked DEMCON to develop a 2.0 version for systematic process research and the automatic printing of demonstrators.
The printer consists of a printhead in which glass is melted and a platform that makes an x-y-z movement beneath the flow of glass to create the required product. Crucial to the final result is managing the temperature of not only the melting glass in the printhead (1,600 -1,700 ºC) but also the printing platform and ambient atmosphere (low oxygen to prevent corrosion). If the end product cools down too quickly, tension can build up within it. For this reason the platform and atmosphere are set at maximum 700 ºC.
DEMCON fitted the printhead and platform in a furnace, designed a robust construction and automated the motion and temperature regulation. Key areas of attention were the mechanical stability of the setup, the printing accuracy and operator safety. A precondition was the interfacing with existing facilities at QSIL including the HF unit for heating the glass using an induction current in the printhead. An xyz stage was placed outside the furnace and connected to the platform through a heat conduit. DEMCON linked the controls to a so-called slicer, which converts the CAD model into a printable file.
The system is equipped with heaters and coolers that ensure balanced temperature regulation; a pyrometer measures the temperature of the printhead. The nitrogen which is continually blown into the furnace is pre-heated to prevent temperature fluctuations. Due to the high process temperatures, thermal expansion was an important design aspect. Simulations served to underpin the design choices in terms of hardware (materials) and software (possible compensations).
DEMCON took care of the entire process from specification, concept and design to assembly, test and installation at the customer’s premises. Experience used from other 3D printer projects included the thermal management, the low-oxygen environment and the operating software. The higher temperatures in the glass printer demanded advanced control and safety strategies. As such the QSIL commission called upon typical DEMCON competences such as mechatronics, thermodynamics, materials science and production.