High-precision optics by application-optimized compression induced solidification (CIS)

• Applicant: Professor Dr.-Ing. Dietmar Drummer
• Subject Area: Plastics Engineering
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 290812922

The processing technique Compression Induced Solidification (CIS), which was developed at the Institute of Polymer Technology, facilitates obviating problems with standard plastic processing like sink marks, residual stresses and warpage, which arise while the polymer melt undergoes a two phase cooling. The CIS process is possible because the glass transition temperature range of amorphous plastics is pressure dependent and shifts to higher temperatures with increasing pressure. Thus, the plastic can first be solidified at higher temperatures by applying pressure within the cavity, regardless of thickness, and then cooled as a solid. The DFG funded projects "Grundlegende Betrachtungen zum Einfluss hoher Drücke auf den Phasenübergang bei der Kunststoffverarbeitung" and "Übertragung der Grundlagen auf die Spritzgießvariante Druckverfestigung" have expounded upon the fundamental understanding of amorphous thermoplastic materials and shown the great potential behind CIS by producing precise and homogeneous parts. With the fabrication of experimental mold CIS was able to be integrated into automated injection molding processes. Yet, despite this progress the current cycle time is too long to be able to employ CIS for industrial purposes in its current state. Additionally, the mold technology behind the trial mold remains too complicated and expensive for further industrial applications. The purpose of the transfer project "High precision optics by application-optimized, compression induced solidification" is, therefore, to reduce CIS cycle time with innovative approaches. Additionally, the mold and process control concepts will be improved upon and simplified to further facilitate the implementation of CIS into existing processing frameworks. Numerous points meriting scientific research arise from the aim to reduce CIS cycle time. Firstly, the compression speeds effect on the components volume and physical aging remains insufficiently described. This is particular important for components employed at higher temperatures. Another important point is the varying melt temperatures effect on the component properties in the cavity during compression. This effect is directly related to the pressure dependent viscosity of polymer melts, which is to be analyzed with the novel scientific equipment 'Gegendruckviskosimeter'. Furthermore, the exact impression of microstructures is also very promising for thick walled components, because of the high cavity pressures as determined by the process itself. With the production of a specimen 'disc' the aforementioned points can be scientifically and empirically researched. A component 'lens' practically demonstrates the capability of economically producing high precision plastic optics with the innovative method of CIS.

• DFG Programme: Research Grants (Transfer Project)
• Application Partner: Covestro AG; HB-THERM AG; KraussMaffei Technologies GmbH; Viaoptic GmbH