Kevin P Mcalea

US Patent:

57334978, Mar 31, 1998

Filed:

Sep 13, 1995

Appl. No.:

8/527840

Inventors:

Kevin P. McAlea - Austin TX
Paul F. Forderhase - Austin TX
Mark E. Ganninger - Pflugerville TX
Frederic W. Kunig - Akron OH
Angelo J. Magistro - Brecksville OH

Assignee:

DTM Corporation - Austin TX

International Classification:

B29C 3508
B29C 4102

US Classification:

264497

Abstract:

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.

US Patent:

55278779, Jun 18, 1996

Filed:

Aug 30, 1994

Appl. No.:

8/298076

Inventors:

Elmer D. Dickens - Richfield OH
Biing L. Lee - Broadview Heights OH
Glenn A. Taylor - Twinsburg OH
Angelo J. Magistro - Brecksville OH
Hendra Ng - E. Cleveland OH
Kevin McAlea - Austin TX
Paul F. Forderhase - Austin TX

Assignee:

DTM Corporation - Austin TX

International Classification:

C08G 6914

US Classification:

528323

Abstract:

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.

US Patent:

56484500, Jul 15, 1997

Filed:

Jun 17, 1996

Appl. No.:

8/664356

Inventors:

Elmer Douglas Dickens - Richfield OH
Biing Lin Lee - Broadview Heights OH
Glenn Alfred Taylor - Houston TX
Angelo Joseph Magistro - Brecksville OH
Hendra Ng - E. Cleveland OH
Kevin P. McAlea - Austin TX
Paul F. Forderhase - Austin TX

Assignee:

DTM Corporation - Austin TX

International Classification:

C08G 6914

US Classification:

528323

Abstract:

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.

US Patent:

61369489, Oct 24, 2000

Filed:

Jul 14, 1997

Appl. No.:

8/892583

Inventors:

Elmer Douglas Dickens - Richfield OH
Biing Lin Lee - Broadview Heights OH
Glenn Alfred Taylor - Houston TX
Angelo Joseph Magistro - Brecksville OH
Hendra Ng - E. Cleveland OH
Kevin P. McAlea - Austin TX
Paul F. Forderhase - Austin TX

Assignee:

DTM Corporation - Austin TX

International Classification:

C08G 6914

US Classification:

528323

Abstract:

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.

US Patent:

54088828, Apr 25, 1995

Filed:

Jul 21, 1993

Appl. No.:

8/095638

Inventors:

Barbara J. McKinley - Castleton NY
Dean S. Matsumoto - Niskayuna NY
Robert S. Gilmore - Burnt Hills NY
Kevin P. McAlea - Austin TX

Assignee:

General Electric Company - Schenectady NY

International Classification:

G01N 2918

US Classification:

73597

Abstract:

An ultrasonic measurement device and a method for a non-destructive evaluation of polymer composites having discontinuous fibers distributed therein. The device has one or a plurality of substantially matched pairs of transducers disposed on wedge shaped focuser and a relay, the focuser and relay each have their impedances substantially matched to that of the polymer composite being analyzed. The device is placed on a surface of the composite with the apexes of the focuser and relay in close contact with the surface. A velocity of a substantially longitudinal ultrasonic wave generated by the first transducer and received by the second transducer after its passage through the composite is determined at several angles of orientations about a center point, and the measured velocities of the ultrasonic wave are processed through a computer having software to determine the physical attributes of the composite, such as weight percentage of fibers present in the composite, Young's modulus, shear modulus and Poisson's ratio of the composite.

US Patent:

57490414, May 5, 1998

Filed:

Oct 13, 1995

Appl. No.:

8/542977

Inventors:

Udaykumar Lakshminarayan - Austin TX
Kevin P. McAlea - Austin TX
Richard B. Booth - Pflugerville TX

Assignee:

DTM Corporation - Austin TX

International Classification:

B22F 102
B22F 326

US Classification:

419 2

Abstract:

A method of fabricating articles, such as prototype parts and prototype tooling for injection molding, is disclosed. The method begins with the fabrication of the article in a "green" state by the selective laser sintering, or another additive thermal process, applied to a composite powder, preferably a powder of metal particles coated with a thermoplastic polymer. Both the green article and also an aqueous emulsion of a thermosetting material are then preheated to a temperature below the glass transition temperature of the thermoplastic polymer, and the green article is then infiltrated with the aqueous emulsion. The thermosetting material may be a thermosetting polymer with an appropriate cross-linking agent, or may be a cross-linking agent that will react with the thermoplastic binder polymer. After infiltration, the article is dried, and a rigid skeleton of a thermosetting material is now present within the structure of the article. Further processing may now be performed.

US Patent:

58172068, Oct 6, 1998

Filed:

Feb 7, 1996

Appl. No.:

8/597805

Inventors:

Kevin P. McAlea - Austin TX
Paul F. Forderhase - Austin TX
Richard B. Booth - Pflugerville TX

Assignee:

DTM Corporation - Austin TX

International Classification:

B27N 300
B32B 3100

US Classification:

1562728

Abstract:

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.