Description

Selective laser sintering could be used commercially to fabricate metallic objects. Due to the relatively high ratio of surface tension to viscosity of metals compared to polymers (four orders of magnitude), metal powders have a strong propensity to form spherical balls when irradiated. In order to alleviate this problem and to ensure full density throughout the part, careful design of beam scan path, power, and scan spacing is required. These scanning methods maintain continuity of the solid-liquid interface by constantly maintaining a melt pool directly under the beam as it draws each layer and remelt a portion of the previously fabricated underlying layer in order to allow grains of the new layer to nucleate heterogeneously off the remelted layer by epitaxial solidification.

Scientist at The University of Texas at Austin have developed improvements to the selective laser sintering process for materials which lie in a certain range of surface tension, melt viscosity, and which have inclination to form skin layers which inhibit wetting, such as oxides. Specifically, this technology is a method of fabricating a fully dense, three-dimensional object by direct laser sintering.

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 some other, 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.

Market Potential/Applications

Strong business and technology trends drive the rapid prototyping market. The business trends include users' need to reduce time to market and tooling costs, ever-shortening product life cycles, reorganization along cross-functional lines, and globalization. The technology trends include the vast reduction in the cost of computing, the introduction of lower cost 3D CAD applications, and the growth of network communications.

The business trends result in a need for design and manufacturing engineers to seek ways to reduce both the cost and length of the product introduction process. In addition, they result in a need to improve communication with other departments and suppliers, as well as geographically remote teams. The ultimate goal is to introduce more competitive, higher quality products, and to do it much more quickly. Commercialization of this technology would mean that metal prototypes could be produced more quickly and more cost effectively, a very lucrative opportunity.

Contact:

University of Texas,
Austin, USA
Website : www.otc.utexas.edu