A New Processing Method for Laser Sintering Polymer Powders at Low Bed Temperatures

Most current laser sintering (LS) machines for polymer powders operate with a maximum bed temperature of 200 °C, limiting the use of higher melting polymers like polyethylene terephthalate (PET), which melts at ~250 °C. Using bed temperatures of ≤200 °C leads to severe part-distortion due to curl and warpage during the sintering process. The paper presents a processing method for LS at low bed temperatures, using an in situ printed anchor film to conquer curl and warpage. With the use of the anchor film, PET parts were successfully printed without machine stoppage at bed temperatures as low as 150 °C, which is about 80 °C lower than the bed temperature for a regular process for PET without the anchor film. The anchor film acts as a frictional restraint, effectively preventing the curling and warping during printing that typically result from crystallization-induced shrinkage at low bed temperatures. Whereas previous studies have employed 13 mm thick anchoring sheets bolted to the machine to prevent curl and warpage at low bed temperatures, our method uses a flexible in situ printed ~70 μm thick film to which the built part naturally adheres. The in situ printed film is easily detachable from the part after the build. The standard LS material, polyamide 12 (PA12), was also printed with lowered bed temperaturewhere the benefit would be reduced thermal degradation of the powder and decreased energy consumption during the sintering process.