Selective Laser Sintering of Quartz Powder

This research describes the feasibility of fusing quartz powder by Selective Laser Sintering (SLS). SLS is a method of rapid prototyping three-dimensional objects from a computer-aided design database. The effects of different processing parameters, including powder size, laser power and scan mte were explored. Single and multiple layer specimens have been made. The resulting structures were evaluated using SEM and the density of the multiple-layer structure was detected by a geometrical mass/volume technique. It was determined that particle size was the dominant variable affecting part quality. Smaller and spherical unifonn particles are preferred. Future work will concentrate on optimizing powder size and shape and higher laser power.Mechanical Engineerin

Effect of In-Plane Voiding on the Fracture Behavior of Laser Sintered Polyamide

The primary contributors to poor mechanical properties in polyamide materials used during Selective Laser Sintering® are qualified. Methods to quantify the decreased mechanical properties, including Scanning Electron Microscopy (SEM) of fracture surfaces, are compared against each other and against mechanical properties of components fabricated using multiple process parameters. Of primary interest are Ultimate Tensile Strength (UTS) and Elongation at Break (EOB) of tensile specimens fabricated under conditions that produce varying degrees of ductile and brittle fracture.Mechanical Engineerin

Multiple material systems for selective beam sintering

A method and apparatus for selectively sintering a layer of powder to produce a part comprising a plurality of sintered layers. The apparatus includes a computer controlling a laser to direct the laser energy onto the powder to produce a sintered mass. The computer either determines or is programmed with the boundaries of the desired cross-sectional regions of the part. For each cross-section, the aim of the laser beam is scanned over a layer of powder and the beam is switched on to sinter only the powder within the boundaries of the cross-section. Powder is applied and successive layers sintered until a completed part is formed. Preferably, the powder comprises a plurality of materials having different dissociation or bonding temperatures. The powder preferably comprises blended or coated materials.Board of Regents, University of Texas Syste

Direct selective laser sintering of metals

A method of fabricating a fully dense, three dimensional object by direct laser sintering is disclosed. In a chamber with a partial pressure atmosphere, a beam of directed energy melts metallic powder in order to form a solid layer cross section. Another layer of powder is deposited and melted, along with a portion of the previous layer. The energy beam typically is in the form of a laser, scanning along a path resembling a parametric curve or another, arbitrary piecewise parametric curve. In another embodiment, the previous layer is not remelted, thus creating an oxide film that acts as a clean stop to prevent unwanted downward growth.Board of Regents, University of Texas Syste

Selective laser sintering with assisted powder handling

A method and apparatus for selectively sintering a layer of powder to produce a part comprising a plurality of sintered layers. The apparatus includes a computer controlling a laser to direct the laser energy onto the powder to produce a sintered mass. The computer either determines or is programmed with the boundaries of the desired cross-sectional regions of the part. For each cross-section, the aim of the laser beam is scanned over a layer of powder and the beam is switched on to sinter only the powder within the boundaries of the cross-section. Powder is applied and successive layers sintered until a completed part is formed. Preferably, the powder is deposited to the target area of the laser and attains high bulk density during sintering.Board of Regents, University of Texas Syste

A Sieve Feed System for the Selective Laser Sintering Process

A sieve feed system has been designed for use with the Selective Laser Sintering process. The sieve feed system uses electrostatic charge to help apply polymer powder to a green powder bed. The sieve feed system was found to help the application of polymer powder as measured by a 10 to 15% increase in final part density. The sieve feed system has many potential applications, including material property design, and material mixing during the sintering process.Mechanical Engineerin

Nickel Applied for Selective Laser Sintering Using a Magnetic Field

Metal powder was applied for the Selective Laser Sintering process using the sieve feed system and a magnetic field. The magnetic field had a negative effect on final part quality as measured by a reduction in final part density. This negative effect is theorized to be due to the shape and orientation ofthe magnetic field. It appears possible to change the field to a benevolent orientation.Mechanical Engineerin

Mechanical Property Correlation and Laser Parameter Development for the Selective Laser Sintering of Carbon Fiber Reinforced Polyetheretherketone

This thesis specifically investigates parameter and set point development for a material novel to the SLS process, Carbon Fiber Reinforced Polyetheretherketone (CFR PEEK).Mechanical Engineerin

Laser-directed fabrication of full-density metal articles using hot isostatic processing

" A method of fabricating a fully-dense three-dimensional metal article is disclosed. According to a first embodiment of the invention, the interior portion of the article is formed by way of selective laser sintering, in a cross-section of a layer of powder. After formation of the layer of powder, the laser is directed to form a gas-impervious skin around the interior portion of the article in that layer. The process is repeated, until the article is completed. The article surrounded by the skin is then subjected to hot isostatic pressing to densify the article; the skin, which serves as the ""can"" for the hot isostatic pressing, may or may not be removed from the article, as desired. According to a second embodiment of the invention, the can is formed first by way of laser generation, and is then filled with the metal powder, prior to hot isostatic pressing. "Board of Regents, University of Texas Syste