effects of scan direction and orientation on mechanical properties of laser sintered polyamide-12

in order to understand the impact of layer-wise scanning direction in the selective laser sintering process, test coupons were manufactured for mechanical testing from duraform™ polyamide powder. the effects of laser energy density, varying between 0.003 and 0.024 j/mm 2 were examined in test specimens rotated 90º through the z axis. sls machines do not always facilitate ‘cross-hatching’ of layers and therefore orientation has a major influence on part quality. when employed, the cross-hatching technique scans successive layers perpendicularly to the previous. studying how parts perform with scan lines in a common direction, will assist in the understanding of how sls parts behave in practice. results showed that physical density, tensile strength and elongation rose with energy density up to 0.012 j/mm². this initial rise was due to a continued improvement in particle fusion with increasing energy density. above 0.012 j/mm², these properties started to decline at different rates depending on their orientation (scan direction) on the part bed. specimen’s oriented perpendicularly to the x axis exhibited a greater elongation at the expense of tensile strength, when compared to parallel specimens.