Friedrich-Alexander-Universität Erlangen-Nürnberg

Process-related Aging Behaviour of Polymers for Powder Based Manufacturing Technologies

Process-related Aging Behaviour of Polymers for Powder Based Manufacturing Technologies

As a result of the process-related high temperatures that exist within the build chamber during processing, the microstructure of the initial powder material will degrade, if the material is processed by additive manufacturing methods such as selective laser sintering. The powder’s long residence time at temperatures just below melting range will lead to physical and chemical aging. This may lead, for instance, to changes in the melting and crystallization behaviour of the material, and in the melt’s flow behaviour.

Figure 1: Melting and crystallization behaviour, as well as flow behaviour of materials of different degrees of aging

These degradation processes make reproducible manufacturing impossible, resulting in variations in component properties.

Figure 2: Laser-sintered PA12 components with different degrees of surface reproduction accuracies

The non-sintered share of the polymer powder, called part cake, must be added up to 50 % of virgin powder. Because the reproducibility of powder-based additive manufacturing methods and the properties of laser-sintered components are due to improve, the process-induced effects exerted on the employed materials need to be scrutinized thoroughly and understood perfectly. Only if scientists entirely understand the processes going on, they will be able to influence these factors in a well-aimed way, and improve the performance and reproducibility of additive layer manufacturing methods for the purpose of serial production of customized products.

 

The sub-project subject to the application is due to systematically investigate the time- and temperature-related processes going on in regard to microstructure, during the selective laser sintering of polymer powders. Model tests will be carried out for the purpose of profound considerations on process-related degradation behaviour. In the framework of these examinations, the effects of various process conditions will be investigated too, e.g. processing in an inert gas atmosphere or in a vacuum, material pre-treatment, on the exclusion of fixed oxygen and water on or inside the material, as well as on stabilizers introduced into the powder, regarding their impacts on physical and chemical material aging. The findings from processing tests will be correlated to the model tests, and will serve for derivation of an aging equivalent. Characteristic values of material aging, as well as the input energy, are thus due to serve as a basis for the calculation of the powder’s condition.  While the share of added virgin material is invariable today, processors will thus be able to adjust this share to the actual condition of the material. In addition, this will safeguard defined material properties such as melting and crystallization behaviour, or the melt’s flow behaviour. The final stage will look into the matter of well-aimed powder treatment and property setting by examining various regeneration strategies as to their effects on the features of material and component.

Publications

  1. Kühnlein, F.; Drummer, D.; Rietzel, D.: Degradation Behavior and Material Properties of PA12-Plastic Powders Processed by Powder Based Additive Manufacturing Technologies. In: International Conference on Additive Technologies 2010 (Nova Gorica, Slovenia, 22.-24.09.2010) - Tagungsband.
  2. Drummer, D; Kühnlein, F.; Rietzel, D.; Hülder, G.: Untersuchung der Materialalterung bei pulverbasierten Schichtbauverfahren. RTejournal - Forum für Rapid Technologie 7 (2010). URL: www.rtejournal.de/ausgabe7/2601/ [2010-07-26].

Mission

SAOT provides an interdisciplinary research and education program of excellence within a broad international network of distinguished experts to promote innovation and leadership in the areas

Optical Metrology
Optical Material Processing
Optics in Medicine
Optics in Communication and Information Technology
Optical Materials and Systems
and Computational Optics.