The B. F. Goodrich Company

Dtm Corporation

Rjf International Corporation

Flexmag Industries, Inc.

Frederic W Kunig

Eric Martin Weissman

Angelo J Magistro

Raymond C Srail

Thomas R Szczepanski

Richard A Glover

Elmer D Dickens, Jr

Kevin P McAlea

Paul F Forderhase

Glenn A Taylor

Timothy R Hradek

Mark E Ganninger

A process and apparatus for permitting the magnetization of flexible hard magnetic materials in the form of sheets or strips, such as magnetic rubber, wherein opposing arrays formed from alternating magnetic disks and flux conducting elements are use in sets of two with opposing polar moments such as to induce a magnetic flux in the gap between the discs. The width of the magnetic disk and flux conducting elements, respectively, are selected to optimize the magnetic pull strength of the material. At the array ends are flux conducting elements that are about 1/2 (i.e., from about 0.25 to about 0.75, and preferably from about 0.4 to 0.6) of the width of the internal flux conducting elements. A material to be magnetized is passed between the array sets in contrast with both disks and consequently imprinted with magnetic poles. The magnetized properties of the material is enhanced by passing the material through a second set of arrays which are axially offset with respect to the first set of arrays. This enhances the residual induction of the sample, the shape of the Br.sup.2 versus distance curve, and significantly improves the pull strength of the material. A device is provided for the production of the material, and further can be used without modification to imprint non-traversing magnetization by biasing the material to one of the arrays of the second, i.e. exiting, set of arrays.

Magnetized material having enhanced magnetic pull strength and a process

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 process and apparatus for permitting the magnetization of flexible hard magnetic materials in the form of sheets or strips, such as magnetic rubber, wherein opposing arrays formed from alternating magnetic disks and flux conducting elements are use in sets of two with opposing polar moments such as to induce a magnetic flux in the gap between the discs. The width of the magnetic disk and flux conducting elements, respectively, are selected to optimize the magnetic pull strength of the material. At the array ends are flux conducting elements that are about 1/2 (i.e., from about 0.25 to about 0.75, and preferably from about 0.4 to 0.6) of the width of the internal flux conducting elements. A material to be magnetized is passed between the array sets in contrast with both disks and consequently imprinted with magnetic poles. The magnetized properties of the material is enhanced by passing the material through a second set of arrays which are axially offset with respect to the first set of arrays. This enhances the residual induction of the sample, the shape of the Br.sup.2 versus distance curve, and significantly improves the pull strength of the material. A device is provided for the production of the material, and further can be used without modification to imprint nontraversing magnetization by biasing the material to one of the arrays of the second, i.e. exiting, set of arrays.

Magnetized material having enhanced magnetic pull strength and process

This method teaches how to recover and reuse a powder of a thermally degradable material which is used in a selective laser sintering (SLS) process. To recycle such a laser-sinterable powder successfully in a SLS machine it is protected against degradation by cooling the hot bed while layer-upon-layer (layer-wise) of powder is being sintered, seriatim, to form successive slices fused together to form an article of arbitrary shape (part). The process requires maintaining the powder which has more than 80% of the number of particles &lt;53 .mu.m as a quiescent bed which is nevertheless porous enough to permit flowing a cooling gas downwardly through the bed without disrupting its surface. Since each slice is formed at the surface, and the part, as it is formed, is supported in a well-insulated bed, the powder adjacent the slice is at a much higher temperature than powder in the rest of the bed, which, but for the cooling gas, would get overheated. Overheated powder not only degrades but is fused to the surfaces of the hot part forming a 'growth' which makes the part unusable for its intended purpose. The process allows one to recycle the unused powder from the bed to extinction, economically. If the powder, when hot, is also sensitive to oxygen, an inert gas is used as the cooling gas.

Method of recovering recyclable unsintered powder from the part bed of a

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Akron, OH, United States of America

Frederic W Kunig