Friedrich-Alexander-Universität Erlangen-Nürnberg

Incremental In-line Test Technique for Additive Production

Incremental In-line Test Technique for Additive Production

Additive manufacturing techniques such as the selective laser beam melting (SLM) of plastics enable the toolless production of complex customized components. Variations occurring during the process of component generation in layers can lead to intolerable quality defects concerning shape and rigidity. Such flaws can be detected today only after production, in retained samples and test specimens produced along with the actual charge in an elaborate process, which moreover reduces efficiencies. To avoid this downside, it is essential to monitor qualities during production, and control the process on this basis.


This project will investigate incremental in-line measurement after each applied layer, to solve this issue. By controlling process parameters and by thus enabling automatic correction of component defects resulting from process variations, this technique is due to reduce waste, costs and times required for provision significantly. Being a robust and optical-laminar probing technique of measuring and testing, fringe pattern projection appears predestined for incremental testing of internal and external component structures. The integration of optical measurement and process control into additive manufacturing units have not been investigated so far, and neither have strategies designed for incremental component measurement.


This sub-project is aimed at the qualification of measuring and testing technique, as well as strategies suited to provide for incremental in-line inspection in additive manufacturing. For this purpose, relevant basic research will be conducted, and a prototype of a fringe pattern projection measuring system be integrated into an SLM unit, in the first stage. To enable this, scientists will analyse the SLM process with regard to aspects of testing technology, and define the requirements posed to measuring and testing technology. Sensor concepts will be worked out, and the methods of integrating them into SLM units be basically investigated. It will then be possible to set up test strategies for powder bed inspection and for incremental component testing, as well as deduce from this the general strategies of test parameter definition. The results obtained from experimental verification of the measuring and testing prototype will be transferable to other additive manufacturing methods and testing techniques.


The understanding obtained in the first stage of the investigations, concerning process monitoring tailored to the respective process, will serve as a basis for the subsequent stages of research. These stages will be aimed at working out the basic scientific knowledge for the dynamic and fully automatic process control by active correction of quality defects.


  1. Kühnlein, F.; Rietzel, D.; Drummer, D.: Feasibility Study of Additive Manufacturing of Thermally Conductive PA12 Powders by Selective Mask Sintering. In: 68th Annual Technical Conference of the Society of Plastics Engineers 2010, ANTEC 2010 (Orlando, USA, 16.-20.05.2010) - Tagungsband, S. 2295-2300.
  2. Drummer, D.; Rietzel, D.; Kühnlein, F.: Selektives Lasersintern von teilkristallinen Thermoplasten. In: RTejournal - Forum für Rapid Technologie 6 2009.
    URL: [20.09.2010].


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.