Different features of polymer powders influence the process of laser sintering (LS) and the properties of LS-parts to a great extent. This study investigates important aspects of the “powder/process/part”-property relationships by comparing two polyamide 12 (PA12) powders commercially available for LS, with pronounced powder characteristic differences (Duraform^® PA and Orgasol^® Invent Smooth). Due to the fact that the primary influence factor on polymer behaviour, the chemical structure of the polymer chain, is identical in this case, the impacts resulting from powder distribution, particle shape, thermal behaviour, and crystalline and molecular structure, can be studied in detail. It was shown that although both systems are PA12, completely different processing conditions must be applied to accomplish high-resolution parts. The reason for this was discovered by the different thermal behaviour based on the powder production and the resulting crystalline structure. Moreover, the parts built from Orgasol^® Invent Smooth unveil mechanical properties with pronounced anisotropy, caused from the high melt viscosity and termination of polymer chains. Further differences are seen in relation to the powder characteristics and other significant correlations could be revealed. For example, the study demonstrated how the particle morphology and shape impact the surface roughness of the parts.

This work describes the production of a spherical polybutylene terephthalate (PBT) powder and its processing with selective laser sintering (SLS). The powder was produced via melt emulsification, a continuous extrusion-based process. PBT was melt blended with polyethylene glycol (PEG), creating an emulsion of spherical PBT droplets in a PEG matrix. Powder could be extracted after dissolving the PEG matrix phase in water. The extrusion settings were adjusted to optimize the size and yield of PBT particles. After classification, 79 vol. % of particles fell within a range of 10–100 µm. Owing to its spherical shape, the powder exhibited excellent flowability and packing properties. After powder production, the width of the thermal processing (sintering) window was reduced by 7.6 °C. Processing of the powder on a laser sintering machine was only possible with difficulties. The parts exhibited mechanical properties inferior to injection-molded specimens. The main reason lied in the PBT being prone to thermal degradation and hydrolysis during the powder production process. Melt emulsification in general is a process well suited to produce a large variety of SLS powders with exceptional flowability.

Powder bed fusion of polymers is becoming increasingly adopted by a variety of industries to tailor the strength, weight and functionality of end-use products. To meet the high standards of the modern manufacturing industry, parts built with powder bed fusion require consistent properties and to be free of defects, which is intrinsically connected to the quality of the powder bed prior to melting. The hypothesis of this work is that the roughness of the top surface of an unmelted powder bed can serve as a proxy for the powder bed density, which is known to correlate with final part density. In this study, a laser line scan profilometer is integrated onto the recoater arm of a custom powder test bench, which is able to automatically create layers of powder. A diverse group of polymers was investigated including polyamide 12 (PA12), polyamide 11 (PA11), polypropylene (PP), and a thermoplastic elastomer (TPU) under different recoating speed in order to increase the variance of the dataset. Data analytics were employed to compare roughness to measured powder bed density and a statically significant correlation was established between them.

An appropriate thermal behavior of polymer powders is essential for successful application in Selective Laser Sintering (SLS) process. A narrow and not sufficient “Sintering-Window” is a primary hurdle for a lot of semi-crystalline Polymers in this connection. Thermo-analytical (DSC) measurements are used to understand the behavior of polymers during SLS-process and to reveal the difference between proper and less proper thermal properties. Commercial PA12-SLS powders are investigated in this sense and compared to a non-commercial one. Thus, the contribution summarizes some very basic polymer properties essential for successful SLS application and explains consequently at the same time why just very few polymers are applicable to SLS today.

Laser-based additive manufacturing (LAM) in all its variations is now being established as a technique for manufacturing components from various material types and alloys