Experimental study on the variance of mechanical properties of polyamide 6 during multi-layer sintering process in selective laser sintering

During the selective laser sintering layer-by-layer manufacturing process, many factors such as the ambient temperature and the densification effect will influence the mechanical properties of sintered specimens. In the experimental study, the porosity ratio, crystallinity, and tensile strength of sintered specimens with different ambient temperatures and layers were analyzed. The results indicated that when the ambient temperature rose from 25 to 180 degrees C, the average porosity ratio decreased from 60% at 25 degrees C to 39.7-38.7% at 140-180 degrees C; the relative crystallinity and tensile strength reached a maximum value of 34% and 10MPa at 140 degrees C with the same number of sintered layers. According to the measurement of sintered specimens with different layers, the porosity ratio rapidly reduced by 21% from 3 to 10 layers, and the tensile strength improved by 22.5MPa. When the number of sintered layers reached 10, the change of the porosity ratio and tensile strength were relatively slow, and it would almost disappear as the number of layers exceeded 14. The results showed that the densification process and energy accumulation effect were beneficial to reduce the porosity ratio of specimens, thereby improving its tensile strength in the early period of laser sintering.