Direct selective laser sintering of metals

• US 6,676,892 B2
• Filed: 06/01/2001
• Issued: 01/13/2004
• Est. Priority Date: 06/01/2000
• 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: Das, Suman, Beaman, Joseph J.
• Primary Examiner(s): Jenkins, Daniel J.
• Application Number:
  US09/873,055
• Publication Number:
  US 20020015654A1
• Time in Patent Office: 956 Days
• Field of Search: 419/7
• US Class Current: 419/7
• CPC Class Codes: B22F 10/28 Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
• CPC Class Codes: B22F 10/32 of the atmosphere, e.g. composition or pressure in a building chamber
• CPC Class Codes: B22F 10/366 Scanning parameters, e.g. hatch distance or scanning strategy
• CPC Class Codes: B22F 10/73 of powder
• 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 2201/20 Use of vacuum
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B23K 35/0244 Powders, particles or spheres; Preforms made therefrom
• 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: G05B 19/4062 Monitoring servoloop, e.g. overload of servomotor, loss of feedback or reference
• 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 of fabricating a fully dense, three dimensional object by direct laser sintering is disclosed. In a chamber with a partial pressure atmosphere, a beam of directed energy melts metallic powder in order to form a solid layer cross section. Another layer of powder is deposited and melted, along with a portion of the previous layer. The energy beam typically is in the form of a laser, scanning along a path resembling a parametric curve or another, arbitrary piecewise parametric curve. In another embodiment, the previous layer is not remelted, thus creating an oxide film that acts as a clean stop to prevent unwanted downward growth.

Claims

1. A method for direct laser sintering of metals, comprising:

depositing a layer of metallic powder onto a target surface in a chamber with a partial pressure atmosphere; and

directing energy at selected locations of the layer corresponding to a cross section of a part, wherein the directed energy melts the layer at the selected locations and the selected locations comprise a continuous vector scan path

wherein the continuous vector scan path comprises an area-filling scan whereby each distinct bounded region of the scan is scanned so that the scan path never intersects itself and the energy is continuously applied until the entire distinct bounded region is scanned.

2. The method of claim 1, wherein the continuous vector scan path further comprises a starting radius and further comprising the step of directing the energy around the starting radius a plurality times before directing the energy over the remaining scan path.

3. The method of claim 2, further comprising the step of directing energy at second selected locations, wherein the second selected locations resemble a plurality of concentric circles.

4. The method of claim 1, further comprising the step of directing energy at second selected locations, wherein the second selected locations resemble a plurality of concentric circles.

6. The method of claim 1, wherein the partial pressure atmosphere is a vacuum on the order of 10⁻

2 to 10<sup>−

7</sup> Torr.

7. The method of claim 1, wherein the partial pressure atmosphere is a vacuum on the order of 10⁻

2 to 10<sup>−

4</sup> Torr.

8. The method of claim 1, wherein the partial pressure atmosphere is a vacuum on the order of 10⁻

3 Torr.

5. A method for direct laser sintering of metals, comprising:

depositing a supporting layer of metallic powder onto a target surface in a chamber;

directing energy at first selected locations of the supporting layer corresponding to a first cross section of a part, wherein the directed energy melts the supporting layer at the first selected locations;

directing energy at second selected locations of the supporting layer, wherein the second selected locations do not correspond to the first cross section and the directed energy melts the supporting layer at the second selected locations;

depositing a second layer of metallic powder on the supporting layer; and

directing energy at third selected locations of the second layer, wherein the third selected locations correspond to the second selected locations and no portion of the supporting layer at the second selected locations is remelted.