Theory on the Continuation of Melting Processes as basic Requirement for Robust Processing Conditions in Laser Sintering of Polymers
Additive manufacturing techniques win more and more importance as a series production technique for small and medium batch series. Compared to conventional production techniques, e.g. laser sintering offers the achievement of significantly greater flexibility in design and at the same time a good cost-effectiveness for small batches. Therefore, new innovative solutions become possible. Despite the manifold potentials, several unsolved problems still exist and prevent the unrestricted use of laser sintering as production technique until today. One problem is the lacking reproducibility of part properties which is caused by various insufficient understood effects. One of these is the decisive process step in laser sintering: the melting of the powder caused by the laser energy input. The temperature-time profiles emerging form the laser-powder interaction significantly determine the generation of the parts. However, these processes are hardly analysed yet.
The following thesis picks up on these problems in order to generate new solutions or solution approaches for these topics by establishing a profound understanding of the process. Fundamental correlations between process influencing factors, noise factors and relevant part properties are determined by using a systematic approach. Based on these established correlations and correlation models, an optimization of the processing conditions as well as an identification of robust parameter ranges becomes possible. For the first time the influences of different noise factors on the part properties are analysed in detail. At the same time, the influences on dimensional and form accuracy of laser sintered parts are studied fundamentally for the first time.
In a second step, the laser-powder interaction is characterised in detail by using high-speed thermal imaging. Therefore, the decisive temperature profiles during the melting of the powder are initially measured depending on the energy input using a verified experimental setup. Fundamental correlations between process parameters and measured melt temperatures can be established on the basis of these measurements. In addition to that, a significant correlation between the measured temperature profile and the part quality can be confirmed in this context.
Furthermore, the ascertained fundamental knowledge is summarized to a new process theory named “Theory on the Continuation of Melting Processes in Laser Sintering”. The fulfilment of this theory is the basic requirement for establishing robust processing conditions. Furthermore, the established results prove that further developments of the machine equipment are urgently necessary in order to improve reproducibility to a degree adequate for series production.Lesen Sie die deutsche Zusammenfassung auf Kunststoffe.de
laser sintering, polyamide 12, polymers, process correlations, optimization of parameters, robust processing conditions, thermal imaging, melt temperatures, influence of noise factors, comparison of maschines
Institute / chair: Fakultät für Ingenieurwissenschaften Abteilung Maschinenbau und Verfahrenstechnik der Universität Duisburg-Essen
Technical consultant for expert services: Prof. Dr.-Ing. Gerd Witt (Betreuer), Prof. Dr.-Ing. Dietmar Drummer
Publication year: 2015
Provider: Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK) / Kunststoffe.de
About the PhD Dissertation Data Base
In cooperation with the Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK), we provide free access to current dissertations in the field of plastics technology.