The University of Texas System

Other

Joel W Barlow

Harris L Marcus

Joseph Jefferson Beaman, Jr

David L Bourell

Carl Robert Deckard

Richard H Crawford

Richard J Lagow

Goonhee Lee

Neal K Vail

Joseph L Beaman

James R Tobin

Balasubramanian Badrinarayan

A process for making bone implants from calcium phosphate powders is disclosed. This process involves selectively fusing layers of calcium powders that have been coated or mixed with polymer binders. The calcium powder mixture may be formed into layers and the polymer fused with a laser. Complex three-dimensional geometrical shapes can be automatically replicated or modified using this approach.

Artificial bone implants

A mixing and dispensing system for reactively combining organic chemical components to produce a rapidly polymerizing material for use in molding and encapsulating small and usually delicate devices, such as electronic components. The system uses a novel mix head incorporating a high speed rotary mixer having magnetic coupling for mixing and injecting relatively low viscosity polymerizing materials into a mold. The chemical feed to the mix head is from special chemical handling equipment. The design of the system eliminates the need for material control valves and enables relatively low feed line pressures. A novel chemical handling subsystem uses special tubular containers provided by the chemical material manufacturers that mount on specially designed dispensing equipment, and do not require special storage, handling, or mixing by trained personnel. The system has a mold cycle time of typically between 6 and 12 seconds in order to achieve complete polymerization, eliminating the need for curing ovens required in conventional encapsulation methods. The chemicals used in this system are not premixed, but are combined in the mix head just prior to filling a mold. They may be stored almost indefinitely if properly sealed. Because of the relatively low viscosity of the rapidly polymerizing materials, damage to fragile electronic interconnections during encapsulation are greatly reduced. Other advantages of this system is no inherent corrosion problems, lower moisture absorption than epoxy, and lower mold temperatures for reduced thermal stresses.

Mixing and dispensing system for rapidly polymerizing materials

The development of polymer binder compositions that provide novel binders for high temperature inorganic particulates, especially metal and ceramic particulates is described. These materials are especially useful in a laser beam sintering process known as SLS.TM. that forms accurately shaped high strength green objects. The new binders may be thermally removed in post-shaping operations without significant residual ash. The resulting structures contain only metal, ceramic, or metal ceramic materials. The inventive methods developed for producing the new polymeric binder materials are based in part on using emulsion forms of selected polymers at controlled low molecular weights and high melt flow. An important aspect of the process is the semi-batch addition of selected chain transfer agents to the reacting emulsion. This optimizes coating characteristics of the polymer binder and results in high part strengths of the prototype parts produced in the SLS.TM. process.

Binder compositions for laser sintering processes

A mold useful for injection molding, comprising: a porous network of metal and oxidized metal and a cured epoxy resin dispersed in the porous network. The mold can be prepared by a process comprising the sequential steps of (a) forming a mixture of a metal powder and a polymer binder; (b) heating the mixture at a temperature in the range from about 100.degree. C. to about 300.degree. C. to remove a majority of the polymer binder from the mixture; (c) heating the mixture resulting from step (b) at a temperature greater than about 300.degree. C. and less than the melting point of the metal in the presence of oxygen to oxidize at least a portion of the metal to form a self-adhering porous network of metal and oxidized metal; (d) contacting the self-adhering porous network with an epoxy resin to fill at least a portion of the porous network with epoxy resin; and (e) curing the body resulting from step (d) to form the mold. The shape of the mold can be performed by selective laser sintering of the mixture.

Mold useful for injection molding of plastics, and methods of production

Bone implants are made from calcium phosphate powders by selectively fusing layers of calcium powders that have been coated or mixed with polymer binders. The calcium powder mixture may be formed into layers and the polymer fused with a laser. Complex three-dimensional geometrical shapes can be automatically replicated or modified using this approach.

Method for fabricating artificial bone implant green parts

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.

Multiple material systems for selective beam sintering

A method of producing high temperature parts by way of relatively low temperature sintering is disclosed. A powder is produced, for example by spray drying a slurry, in which particles of a high temperature material such as a ceramic are partially coated with a low temperature material such as a polymer. The powder is subjected to selective laser sintering, or another heat-based layerwise additive process, to form a green part where the ceramic particles are bound by the polymer. The green part is permeated with a cementing agent having high temperature properties when cured; the cementing agent binds the exposed ceramic surfaces in the green part. The polymer is then removed, leaving the high temperature part. Additional cementing agent, or another high temperature material, may then be added to the part after removal of the polymer.

Method of producing high-temperature parts by way of low-temperature

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 onto 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.

Growing community of inventors

Austin, TX, United States of America

Joel W Barlow