Dtm Corporation

3d Systems, Inc.

Paul F Forderhase

Kevin P McAlea

Elmer D Dickens, Jr

Angelo J Magistro

Glenn A Taylor

Biing Lin Lee

Hendra Ng

Carl Robert Deckard

Biing-Lin Lee

Frederic W Kunig

Richard B Booth

Jack M Klein

Mark E Ganninger

Angelo Joseph Magistro

Glenn Alfred Taylor

A laser-sinterable powder product has been prepared having unique properties which allow the powder to be sintered in a selective laser sintering machine to form a sintered part which is near-fully dense. For most purposes, the sintered part is indistinguishable from another part having the same dimensions made by isotropically molding the powder. In addition to being freely flowable at a temperature near its softening temperature, a useful powder is disclosed that has a two-tier distribution in which substantially no primary particles have an average diameter greater than 180 &#x3bc;m, provided further that the number average ratio of particles smaller than 53 &#x3bc;m is greater than 80%, the remaining larger particles being in the size range from 53 &#x3bc;m to 180 &#x3bc;m. A powder with slow recrystallization rates, as evidenced by non-overlapping or slightly overlapping endothermic and exothermic peaks in their differential scanning calorimetry characteristics for scan rates of on the order of 10&#xb0; C. to 20&#xb0; C. per minute, will also result in sintered parts that are near-fully dense, with minimal dimensional distortion.

Sinterable semi-crystalline powder and near-fully dense article formed therewith

A laser-sinterable powder product has been prepared having unique properties which allow the powder to be sintered in a selective laser sintering machine to form a sintered part which is near-fully dense. For most purposes, the sintered part is indistinguishable from another part having the same dimensions made by isotropically molding the powder. In addition to being freely flowable at a temperature near its softening temperature, a useful powder is disclosed that has a two-tier distribution in which substantially no primary particles have an average diameter greater than 180 .mu.m, provided further that the number average ratio of particles smaller than 53 .mu.m is greater than 80%, the remaining larger particles being in the size range from 53 .mu.m to 180 .mu.m. A powder with slow recrystallization rates, as evidenced by non-overlapping or slightly overlapping endothermic and exothermic peaks in their differential scanning calorimetry characteristics for scan rates of on the order of 10.degree. C. to 20.degree. C. per minute, will also result in sintered parts that are near-fully dense, with minimal dimensional distortion.

Sinterable semi-crystalline powder and near-fully dense article formed

A powder for use in selective laser sintering, from which prototype articles and masters for molds may be formed, is disclosed. The powder is formed by spray drying a polymer emulsion to yield a distribution of particles of substantially spherical shape. The powder is then air classified to remove excessively small particles from the distribution; the powder may also be screened to remove large particles therefrom, as well. The resulting distribution of particle sizes, by volume, preferably has a mean particle size of between about 20.mu. and about 50.mu., with preferably less than about 5% (by volume) of its particles with a size of less than about 15.mu. and less than about 2% (by volume) of its particles with a size of greater than about 75.mu.. The powder is subjected to selective laser sintering to produce an article of approximately 55% to 75% of theoretical density. The article may be used as a prototype article or part, or as a pattern or master for a mold.

Selective laser sintering of polymer powder of controlled particle size

A composite powder specially adapted for use in selective laser sintering is disclosed. The composite powder includes a polymer powder dry mixed with a reinforcement powder, where the polymer powder has a melting temperature substantially lower than that of the reinforcement powder. In the case where nearfully dense parts are to be formed, the first constituent powder is preferably a semi-crystalline powder, for example nylon 11, of a composition suitable for forming near-fully dense parts when used unblended in selective laser sintering; if porous parts are desired, the polymer powder is an amorphous powder, such as polycarbonate, polystyrene, acrylates, and styrene/acrylate copolymers. The reinforcement powder is preferably microspheres of glass, preferably coated to enhance wetting and adhesion with the polymer powder when selective laser sintering is performed. Besides improving the stiffness and heat resistance of the part produced, the composite powder widens the process window over that provided by unblended powder, provides improved dimensional accuracy in the part produced, and facilitates roughbreakout and smooth finishing of the part produced.

Selective laser sintering with composite plastic material

A laser-sinterable powder product has been prepared having unique properties which allow the powder to be sintered in a selective laser sintering machine to form a sintered part which is near-fully dense. For most purposes, the sintered part is indistinguishable from another part having the same dimensions made by isotropically molding the powder. In addition to being freely flowable at a temperature near its softening temperature, a useful powder is disclosed that has a two-tier distribution in which substantially no primary particles have an average diameter greater than 180 .mu.m, provided further that the number average ratio of particles smaller than 53 .mu.m is greater than 80%, the remaining larger particles being in the size range from 53 .mu.m to 180 .mu.m. A powder with slow recrystallization rates, as evidenced by non-overlapping endothermic and exothermic peaks in their differential scanning calorimetry characteristics for scan rates of on the order of 10.degree. C. to 20.degree. C. per minute, will also result in sintered parts that are near-fully dense, with minimal dimensional distortion.

An apparatus and method for producing parts by fusing selected portions of a layer of powder at a target area, including the systems for delivering the powder to the target area, is disclosed. Multiple powder pistons are included in the apparatus, each of which lift a volume of powder above a surface in an alternating manner relative to one another. Powder delivery begins by the lifting of a volume of powder at a first location on one side of the target area. A counter-rotating roller moves across the lifted powder, distributes it over the target area, and rests beyond a second powder lifting location on the other side of the target area. Portions of the powder layer are then fused at the target area according to a cross-section of the part to be produced, and is followed by lowering a part cylinder at the target area in order to accept the next layer of powder. A second volume of powder is lifted at the second location, and the counter-rotating roller moves across the second location and the target area to deliver the next layer of powder to the target area. The multiple powder piston system reduces the excess powder in the chamber, speeds the delivery of powder, and facilitates the installation of powder during the process.

Growing community of inventors

Austin, TX, United States of America

Paul F Forderhase