Processing Parameters for Selective Laser Sintering or Melting of Oxide Ceramics

Abstract

In this chapter, we present a detailed introduction to the factors which influence laser powder bed fusion (LPBF) on oxide ceramics. These factors can be in general divided in three main categories: laser-related factors (wavelength, power, scanning speed, hatch distance, scan pattern, beam diameter, etc.), powder-and material-related factors (flowability, size distribution, shape, powder deposition, thickness of deposited layers, etc.), and other factors (pre-or post-processing, inert gas atmosphere, etc.). The process parameters directly affect the amount of energy delivered to the surface of the thin layer and the energy density absorbed by the powders; therefore, decide the physical and mechanical properties of the built parts, such as relative density, porosity, surface roughness, dimensional accuracy, strength, etc. The parameter-property relation is hence reviewed for the most studied oxide ceramic materials, including families from alumina, silica, and some ceramic mixtures. Among those parameters, reducing temperature gradient which decreases the thermal stresses is one of the key factors to improve the ceramic quality. Although realizing crack-free ceramics combined with a smooth surface is still a major challenge, through optimizing the parameters, it is possible for LPBF processed ceramic parts to achieve properties close to those of conventionally produced ceramics.

Preliminary Testing to Determine the Best Process Parameters for Polymer Laser Sintering of a New Polypropylene Polymeric Material

“…(1) A low melt viscosity at low shear stresses Process parameters influence the mechanical properties, density, hardness, porosity, surface roughness, and the dimensional accuracy of the printed parts [5]. Therefore, optimizing the process parameters is crucial in meeting part requirements.…”

“…In addition, the technology does not require the use of binders or support structures, as the powder on the build platform serves this purpose [3]. However, setting the process parameters to obtain the desired properties of polymeric materials is an intricate exercise [4,5]. This has led to a paucity of the available polymers for PLS and slowed the uptake of the technology in manufacturing of polymer components [4,5].…”

“…Process parameters can be classified into laser-related factors, scan-related, and temperature-related parameters [6]. Some of the laser-related factors include wavelength, laser power, hatch distance, vector length, ratio of length to width, point overlapping, beam spatial distribution, continuous or pulsed laser operation, and beam diameter [5]. Some of the scan-related factors include scanning speed, scanning pattern, and scanning angle.…”

“…The laser power, scanning speed, hatch distance, and layer thickness are the most easily adjustable process parameters in PLS. The four parameters determine the amount of laser energy that is transferred to the powder and are related to one another as shown by Equations (1) and (2) [5]. Previous studies have shown that increasing laser energy density increases part density and mechanical properties, but in turn Table 1: A summary of the suitable process parameters for various commercially available polypropylene powders based on best mechanical properties [8].…”

A Review of Methods Used to Reduce the Effects of High Temperature Associated with Polyamide 12 and Polypropylene Laser Sintering

“…Apart from the properties of materials, PLS is subject to process parameters such as building chamber temperature, extraction chamber temperature, power layer thickness, laser power, laser scan speed, hatch distance, and number of scans [20]. These parameters affect printed parts differently.…”