Video Microscopy of Selective Laser Sintering

This paper presents the design and implementation of a video microscopy system that enables real time observation and archival of selective laser sintering of polymer and metal materials. The design objectives and selection of system components are discussed in the first section of this paper. Experimental results from preliminary experiments conducted on polycarbonate, wax and nylon powders are also presented.Mechanical Engineerin

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

Densification of Selective Laser Sintered Metal Part by Hot Isostatic Pressing

Metal matrix alloy composite parts were made from powders by Selective Laser Sintering (SLS). In this study, partially dense (60%-80%) metal parts made by SLS were densified to full density (>98%) by hot isostatic pressing (HIPping) without any loss of shape. HIPping was done by vacuum sealing SLS samples in glass capsules. HIPping parameters, such as, temperature, pressure, and time, were studied with respect to density, linear shrinkage, and microstructures. Anisotropy in linear shrinkage was correlated to the SLS processing parameters. Densification resulting from HIPping was correlated to microstructures and theoretical HIP densification maps. A detailed analysis of such maps is presented.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