Test MethodStructure-property correlations of laser sintered nylon 12 for dynamic dye testing of plastic parts

Industrial practice requires simple, fast and reliable verification of the mechanical properties of the parts within the process of quality assurance. Therefore, it is necessary to investigate the correlations between structural parameters that can be analysed non-destructively, such as density, and mechanical properties. Using the example of PA12, it was possible to show a linear relation between density, that is porosity, and tensile strength as well as impact strength for notched specimens. Furthermore, a linear correlation was found between elongation at break and notched impact strength as a function of the degree of crystallinity. The relevance of enclosed defects is significant for the maximum load of laser sintered parts. The structure-related imperfections that are invisible from outside can now be detected with a newly developed process, the dynamic dye test of laser sintered parts. It benefits from the correlation between colour saturation, porosity and mechanical properties. Therefore, it is possible to detect failures caused by the layer-based fabrication directly on the part. Consequently, the reliability of the laser sintering process is ensured.