Material qualification for medical 3D printing

The Plastic Freeforming process, patented by Arburg, is an additive manufacturing process which combines a melting unit familiar from injection moulding with a novel discharge unit, which deposits plastic melt in the form of droplets onto a component. Further additive manufacturing processes deposits a continues polymer flow through the die, where the material can be used as granules for a screw based or a filament-based system. Both processes therefore belong to the additive manufacturing category and is ideal for producing personalised plastic implants without the need for mechanical processing. However, the machine principles result in different long dwell times, which negatively affects the mechanical properties. Furthermore, it is anticipated that the thermal degradation resulting from this process will produce decomposition products that pose a particular risk in medical applications, such as cranial implants. The extent of thermal material degradation in this process has not yet been investigated. Another issue is that the size and spacing of the positioned plastic must be precisely defined in order to achieve reliable and reproducible mechanical properties. This is determined during material qualification. However, since the current methods of material qualification are based on subjective operator assessment, there is currently no reproducible method. That is why the Kunststofftechnik Paderborn at the Paderborn University, the Institute of Polymer Processing at the Montanuniversität, the Graz University of Technology with its Institute of Engineering and Business Informatics, and the Medical University of Graz with its Department of Neurosurgery have joined forces to define three main objectives for this project. The first objective is to develop a model-based software tool that combines the analysis of thermal damage in the process with the calculation of the dwell time in order to predict the formation of decomposition products in the final component. The second objective is to develop a reproducible software-supported method for material qualification to ensure consistent mechanical properties, regardless of the machine or operator involved. The third objective is to combine the results of the first two objectives in a software suite that can be integrated into existing manufacturing execution systems (MES). Once the project is complete, this integrated software suite should enable materials for the medical sector to be quickly and reliably qualified and evaluated, allowing freeform plastic technology, as well as the continues deposition to be used in medical applications such as the production of patient-specific implants.