Impact of Part Positioning along Chamber Z-Axis and Processing Parameters in Selective Laser Sintering on Polyamide Properties

Abstract

Featured Application: The application of the research results includes help in determining the influencing processing parameters when making products by selective laser sintering. It is known from previous research that energy density has the greatest influence, and, according to many equations given by other authors, the most important factor in energy density is the hatch distance (distance between the paths of the laser beam). Furthermore, due to the SLS technology working principle, to optimize printing costs, a complete working chamber should be used for printing as much as possible. Therefore, this study provides an insight into whether the same mechanical properties and dimensional stability are achieved if 3D-printed parts are processed with different processing parameters at different heights of the working chamber with respect to the z axis. Additive manufacturing procedures are being increasingly developed, from prototyping to finished functional products. However, their rapid development also brings along the testing of properties with different manufacturing parameters. In selective laser sintering, the most influential manufacturing parameter is the energy density, which also consists, among other things, of the hatch distance. For better usage of the entire chamber and a reduction in the overall price of the finished product, in practice, the manufacturing of products at different heights (levels) of the working chamber with different orientations is inevitable. The study examines how hatch distance and product orientation impact the tensile strength and dimensional stability of polyamide products across two levels within the chamber. Upon analysis, it was observed that manufacturing products at different levels within the working chamber does not influence their dimensions. Achieving precise product dimensions comparable to those in the CAD model is possible. Furthermore, the same factors (orientation and hatch distance) and their combinations affect the length, thickness, and width of the product. Although all test specimens were tested, a tensile strength analysis of variance (ANOVA) of test specimens produced at the lower level of the chamber with a combination of hatch distance (ranging from 0.23 to 0.6 mm) and orientation (ranging from 0° to 60°) was not feasible in the design of the experiment. Despite this limitation, it was noted that both chamber levels had the potential to reach a maximum tensile strength of 47 N/mm2. Nevertheless, the average tensile strength of PA12, obtained through combinations of input factors, stood at only 30 N/mm2, which is quite a low value for polyamide made by selective laser sintering.