DETERMINATION OF INPUT LASER ENERGY FOR MELTING POWDER LAYERS OF VARIOUS THICKNESSES IN HIGH-SPEED PBF-LB/P USING NEARINFRARED LASER AND ABSORBENT

The rate of production of PBF-LB/P can be increased by increasing the layer thickness. However, this reduces the part resolution in the stacking direction. To obtain both a high rate of production and high part resolution, layer thickness adjustment in accordance with part geometry can be effective. Optimizing the input laser energy with respect to the layer thickness ensures sufficient melting and part strength. According to previous studies, the use of a nearinfrared laser and absorbent can increase penetration depth or depth of fusion. However, the optical properties of the powder bed can vary significantly depending on the layer thickness, and, therefore, the input energy that actually contributes to melting also changes with layer thickness. This study proposes a method for determining the input laser energy for various layer thickness without trial and error by estimating the amount of energy required to melt the powder layer while accounting for the optical properties of the bed.Mechanical Engineerin

Cellular Polyamine Catalogues of the Five Classes of the PhylumProteobacteria: Distributions of Homospermidine within the ClassAlphaproteobacteria, Hydroxyputrescine within the ClassBetaproteobacteria, Norspermidine within the ClassGammaproteobacteria, and Spermine within the ClassesDeltaproteobacteria and Epsilonproteobacteria

Cellular polyamines extracted from reclassified or newly validated 47 alphaproteobacteria, 46 betaproteobacteria, 96 gammaproteobacteria, 12 deltaproteobacteria and 10 epsilonproteobacteria were analyzed by high-performance liquid chromatography. Homospermidine was widely distributed within the class Alphaproteobacteria, however, homospermidine-dominant type, spermidine-dominant type and homospermidine/spermidinedominant type were found and the three triamine profiles were genus-specific. The all genera belonging to the class Betaproteobacteria, ubiquitously contained putrescine and 2- hydroxyputrescine. Triamines were absent in almost betaproteobacteria. Many genera, including psychrophilic species, of the class Gammaproteobacteria, contained putrescine and spermidine as the major polyaminenes. Diaminopropane and norspermidine were selectively distributed in several genera of the class Gammaproteobacteria. Spermidine was the major polyamine in the classes Deltaproteobacteria and Epsilonproteobacteria. Spermine was found in some thermophiles within Betaproteobacteria, Deltaproteobacteria and Epsilonproteobacteria, suggesting that the occurrence of spermine correlate to their thermophily. Additional these polyamine catalogues serve for the classification of the phylum Proteobacteria, as a chemotaxonomic marker

Influence of Process Time and Geometry on Part Quality of Low Temperature Laser Sintering

The authors are developing a novel laser sintering process that prevents parts from warping by anchoring them to a rigid base plate. Since the powder bed temperature of the process is normally lower than in the standard process, the laser is required to supply more energy in the novel process, namely low temperature process. Accordingly, the part quality is more sensitive to laser parameters. Additionally, accumulation and dispersion of energy which is supplied by the laser through layers plays an important role in the consolidation of the powder. Thus, in low temperature process, parameter relating part geometry and time affects the part quality more than in standard high temperature process. In this research, the influence of part size and process time per layer on the density of parts as a primary index of part quality is investigated. Density decreases as the process time per layer increases. With respect to part size, density increases as parts become larger.Mechanical Engineerin

Optimization of penetration depth and powder layer thickness for proper interlayer adhesion in polymer laser sintering

In laser sintering, the melt pool depth relative to the powder layer thickness is the main factor influencing interlayer adhesion strength. The melt pool depth is closely related to the amount of laser energy and its penetration depth. Previous studies have shown that using a near-infrared laser and an additive agent that absorbs its light allows for a wide range of penetration depth control. This research focuses on the optimization of the powder layer thickness and penetration depth to achieve appropriate interlayer adhesion. To determine the optimal amount of laser energy, the relationship between the amount of laser energy and part density for each layer pitch and penetration depth was determined. The relationship between the amount of energy supplied normalized by the penetration depth and part density was consistent regardless of the penetration depth of the powder material. The adhesion strength of specimens prepared using different optimal amounts of energy to maximize part density was evaluated. Based on this evaluation, layer thickness normalized by penetration depth is the dominant factor influencing interlayer adhesion strength.Mechanical Engineerin

Investigation into Laser Sintering of PEEK using Commercially Available Low Powder Bed Temperature Machine

Polyetheretherketone (PEEK) is one of the highest performance plastics in terms of heat and chemical resistance and mechanical strength. Laser sintering of PEEK requires high powder bed temperature above 300℃, and this pushes up machine price and pulls down powder recycle rate which leads to high material cost. The authors are proposing a modified laser sintering process which allows the bed temperature to be set lower than recrystallization temperature, namely low temperature process. In this research, bed temperature of 170 ℃, which is typical for PA12 process, and bed temperature of 200 ℃ which is same as previous study were tested. As a result, parts with a high relative density of more than 95% were obtained at both powder bed temperatures, and parts with a tensile strength of 80 MPa were obtained at a powder bed temperature of 170 °C. This shows that laser sintering of PEEK can be processed with a commercially available laser sintering machine resulting in drastic cost cut in terms of machine and material costs.Mechanical Engineerin

Low Temperature Laser Sintering of PA Powder Using Fiber Laser

Low temperature process is a novel plastic laser sintering process having potential for improving powder recyclability dramatically. Although fiber laser has been rarely used for plastic laser sintering in commercial base, its ability of being focused in a very small spot suits it to improve precision of plastic laser sintering. In this research, low temperature laser sintering using fiber laser was tested. The highest part density of 99% was obtained while standard high temperature process can provide only 81%. Although generation of fume, which is a major problem in low temperature process using CO2 laser, is not suppressed, it did not affect quality of parts. Part density was strongly affected by slice size of parts and improved when the size is reduced.Mechanical Engineerin