Method for producing parts by selective sintering

• US 5,639,070 A
• Filed: 06/07/1995
• Issued: 06/17/1997
• Est. Priority Date: 10/17/1986
• Status: Expired due to Term

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Deckard, Carl R.
• Primary Examiner(s): Fiorilla, Christopher A.
• Application Number:
  US08/484,125
• Time in Patent Office: 741 Days
• Field of Search: 264/497, 264/434, 264/460, 264/461, 264/462
• US Class Current: 264/497
• CPC Class Codes: B05C 19/00 Apparatus specially adapted for applying particulate materials to surfaces
• CPC Class Codes: B05C 19/008 Accessories or implements for use in connection with applying particulate materials to surfaces; not provided elsewhere in B05C19/00
• CPC Class Codes: B22F 10/28 Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
• CPC Class Codes: B22F 10/366 Scanning parameters, e.g. hatch distance or scanning strategy
• CPC Class Codes: B22F 10/60 Treatment of workpieces or articles after build-up
• CPC Class Codes: B22F 12/10 Auxiliary heating means
• CPC Class Codes: B22F 12/41 characterised by the type, e.g. laser or electron beam
• CPC Class Codes: B22F 12/49 Scanners
• CPC Class Codes: B22F 12/57 Metering means
• CPC Class Codes: B22F 12/60 Planarisation devices; Compression devices
• CPC Class Codes: B22F 2003/1052 assisted by energy absorption enhanced by the coating or powder
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 3/004 Filling molds with powder feeding material to presses in general B30B15/302
• CPC Class Codes: B22F 3/105 by using electric current other than for infrared radiant energy, laser radiation or plasma B22F3/11 takes precedence; by ultrasonic bonding B22F3/115 takes precedence
• CPC Class Codes: B22F 3/26 Impregnating making ferrous alloys by impregnation C22C33/0242
• CPC Class Codes: B22F 7/02 of composite layers B22F7/002 takes precedence
• CPC Class Codes: B23K 26/0624 using ultrashort pulses, i.e. pulses of 1ns or less
• CPC Class Codes: B23K 26/08 Devices involving relative movement between laser beam and workpiece
• CPC Class Codes: B23K 26/082 Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head
• CPC Class Codes: B23K 26/34 : Laser welding for purposes other than joining
• CPC Class Codes: B29C 35/045 : using gas or flames
• CPC Class Codes: B29C 41/12 : Spreading-out the material on a substrate , e.g. on the surface of a liquid
• CPC Class Codes: B29C 41/46 : Heating or cooling
• CPC Class Codes: B29C 64/153 : using layers of powder being selectively joined, e.g. by selective laser sintering or melting
• CPC Class Codes: B33Y 10/00 : Processes of additive manufacturing
• CPC Class Codes: B33Y 30/00 : Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B33Y 40/00 : Auxiliary operations or equipment, e.g. for material handling
• CPC Class Codes: C23C 24/08 : by application of heat or pressure and heat C23C24/04 takes precedence
• CPC Class Codes: C23C 24/10 : with intermediate formation of a liquid phase in the layer
• CPC Class Codes: C23C 26/02 : applying molten material to the substrate
• CPC Class Codes: G05B 19/4099 : Surface or curve machining, making 3D objects, e.g. desktop manufacturing
• CPC Class Codes: G05B 19/41 : characterised by interpolation, e.g. the computation of intermediate points between programmed end points to define the path to be followed and the rate of travel along that path G05B19/25, G05B19/31, G05B19/37, G05B19/39, G05B19/40 take precedence
• CPC Class Codes: G05B 2219/49013 : Deposit layers, cured by scanning laser, stereo lithography SLA, prototyping
• CPC Class Codes: G05B 2219/49018 : Laser sintering of powder in layers, selective laser sintering SLS
• CPC Class Codes: Y02P 10/25 : Process efficiency

Abstract

A method and apparatus for selectively sintering a layer of powder to produce a part as 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 dispensing mechanism includes a drum which is moved horizontally across the target area and counter-rotated to smooth and distribute the powder in an even layer across the target area. A downdraft system provides controlled temperature air flow through the target area to moderate powder temperature during sintering.

Claims

1. A method of producing a part from a powder, comprising the steps of:

depositing a first layer of the powder at a target surface;

directing energy at selected locations of said first layer of powder corresponding to a first cross-section of the part to fuse the powder threat, with unfused portions of the first layer of powder remaining in place;

depositing a second layer of powder over both fused and remaining unfused portions of said first layer of powder after said directing step, so that the second layer of powder is supported by fused and remaining unfused portions of said first layer of powder;

after the depositing step, heating the second layer of powder to a temperature below the sintering temperature of the powder, to moderate a temperature difference between the second layer of powder and fused portions of the first layer of powder therebeneath; and

directing energy at selected locations of said second layer of powder corresponding to a second cross-section of the part to fuse the powder threat, and so that fused powder at one of said selected locations of said second layer of powder fuses to fused powder in said first layer.

2. The method of claim 1, wherein said step of directing energy at selected locations of said second layer of powder comprises:

directing a laser beam at selected locations of said second layer of powder to provide, in combination with the heating step, the heat of fusion of the powder.

3. The method of claim 1, wherein said heating step heats the powder at the target surface.

4. The method of claim 3, wherein said heating step comprises:

heating a gas; and

directing the heated gas toward said target surface.

5. The method of claim 4, further comprising:

exhausting directed heated gas from said target surface.

6. The method of claim 5, wherein the exhausting of the directed heated gas is performed from below said target surface.

7. The method of claim 1, wherein said heating step is performed to moderate temperature differences in the sintered and unsintered powder.

8. The method of claim 1, wherein the depositing steps each comprise:

dispensing powder proximate said target surface; and

after said providing step, moving a drum across said target surface;

during said moving step, rotating the drum counter to the direction of movement of said drum across said target surface; and

contacting the powder with the counter-rotating drum as it moves across the target surface so that a layer of powder remains over said target surface after said moving step.

9. The method of claim 1, further comprising:

repeating the steps of depositing, heating, and directing for a plurality of layers following the second layer of powder.