Powder bed penetration depth control in laser sintering and effect on depth of fusion

• Published in: Additive manufacturing Vol. 46; p. 102219
• Main Authors: Yamauchi, Yuki, Kigure, Takashi, Isoda, Kazutaka, Niino, Toshiki
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2021
• Subjects: Absorbance; Depth of fusion; Laser sintering; Near infrared laser; Penetration depth; Powder bed fusion; Depth of fusion; Powder bed fusion; Absorbance; Near infrared laser; Laser sintering; Penetration depth
• ISSN: 2214-8604; 2214-7810
• DOI: 10.1016/j.addma.2021.102219

The relationship between absorptance of a powder bed and various parameters affecting interlayer adhesion in plastic laser sintering is discussed. To control absorptance a near-infrared laser, which is rarely absorbed by most polymeric materials, and a light absorbing additive are employed. Transmittance and reflectance are measured for powders with different amounts of absorbent. Attenuation of light in the powder bed is found to follow the Beer–Lambert law despite scattering in the medium. There was a proportional relationship between absorbance and absorbent content. Thus, the amount of absorbent that gives a desired penetration depth can be determined. Thicknesses of parts obtained by single layer exposure for various penetration depths are measured to evaluate depth of fusion, which directly affects interlayer adhesion in laser sintering. Penetration depth and depth of fusion are positively correlated when energy density is optimized to maximize part density for each penetration depth.