A Process Control and Interlayer Heating Approach to Reuse Polyamide 12 Powders and Create Parts With Improved Mechanical Properties in Selective Laser Sintering

Capable of building high-quality, complex parts directly from digital models, selective laser sintering (SLS) additive manufacture (AM) is a core method of agile manufacturing. Polyamide 12 is the most commonly and successfully used polymer powders to date in SLS due to the conforming thermal behaviors of this thermoplastic polymer. State of the art technology produces a substantial amount of un-sintered powders after the manufacturing process. Failure to recycle and reuse these aged powders not only leads to economic losses but also is environmentally unfriendly. This is particularly problematic for powders close to the heat-affected zones that go through severe thermal degradations during the laser sintering processes. Limited procedures exist for systematically reusing such extremely aged powders. This work proposes a new process control method to maximize reusability of aged and extremely aged polyamide 12 powders. Building on a previously untapped interlayer heating, preprocessing, and mixing of powder materials, we show how reclaimed polyamide 12 powders can be consistently reprinted into functional samples, with mechanical properties even superior to current industrial norms. In particular, the proposed method can yield printed samples with 18.04 percent higher tensile strength and 55.29 percwent larger elongation at break using as much as 30 percent of extremely aged powders compared to the benchmark sample.

Journal article