Method and apparatus for detecting defects in freeform fabrication

• US 10,144,063 B2
• Filed: 12/05/2012
• Issued: 12/04/2018
• Est. Priority Date: 12/28/2011
• Status: Active Grant

• Current Assignee: Arcam Ab (Danaher Corporation)
• Original Assignee: Arcam Ab (Danaher Corporation)
• Inventors: Ljungblad, Ulric
• Primary Examiner(s): Kessler, Christopher S
• Application Number:
  US14/349,283
• Publication Number:
  US 20140308153A1
• Time in Patent Office: 2,190 Days
• Field of Search: 419 53
• CPC Class Codes: B22F 10/28 Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
• CPC Class Codes: B22F 10/38 to achieve specific product aspects, e.g. surface smoothness, density, porosity or hollow structures
• CPC Class Codes: B22F 10/85 for controlling or regulating additive manufacturing processes
• CPC Class Codes: B22F 12/52 Hoppers
• CPC Class Codes: B22F 12/90 Means for process control, e.g. cameras or sensors
• CPC Class Codes: B22F 3/15 Hot isostatic pressing
• CPC Class Codes: B29C 64/153 using layers of powder being selectively joined, e.g. by selective laser sintering or melting
• CPC Class Codes: B32B 15/01 all layers being exclusively metallic making layered metal workpieces by pressure cladding B23K20/22; making coatings with a metallic material characterised by its composition C23C30/00
• CPC Class Codes: B32B 15/012 one layer being formed of an iron alloy or steel, another layer being formed of aluminium or an aluminium alloy
• CPC Class Codes: B32B 15/013 one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium
• CPC Class Codes: C22C 14/00 Alloys based on titanium
• CPC Class Codes: C22C 19/07 based on cobalt
• CPC Class Codes: C22C 21/00 Alloys based on aluminium
• CPC Class Codes: C22C 38/00 Ferrous alloys, e.g. steel alloys cast-iron alloys C22C37/00
• CPC Class Codes: G01N 21/9515 Objects of complex shape, e.g. examined with use of a surface follower device measuring contours and curvatures G01B11/24
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

A method for detecting defects in three-dimensional articles. Providing a model of said article. Providing a first powder layer on a substrate, directing an energy beam over said substrate causing said first powder layer to fuse in selected locations forming a first cross section of said three-dimensional article, providing a second powder layer on said substrate, directing the energy beam over said substrate causing said second powder layer to fuse in selected locations to form a second cross section of said three-dimensional article. A first and second image of a first and second fusion zone of said first powder layer respectively is captured. Comparing said first and second images with corresponding layers in said model. Detecting a defect in the three-dimensional article if a deviation in said first image with respect to said model is at least partially overlapping a deviation in said second image with respect to said model.

Claims

1. A method for detecting defects when forming a three-dimensional article through successive fusion of parts of a powder bed, which parts corresponds to successive cross sections of the three-dimensional article, said method comprising the steps of:

providing a model of said three dimensional article;

providing a first powder layer on a work table;

directing an energy beam over said work table causing said first powder layer to fuse in selected locations according to said model to form a first cross section of said three-dimensional article;

providing a second powder layer on said work table;

directing the energy beam over said work table causing said second powder layer to fuse in selected locations according to said model to form a second cross section of said three-dimensional article, wherein said second layer is bonded to said first layer;

capturing at least one first heat image of at least a first fusion zone of said first powder layer after having fused selected portions of said first powder layer;

capturing at least one second heat image of at least a second fusion zone of said second powder layer after having fused selected portions of said second powder layer, wherein said second fusion zone is at least partly overlapping said first fusion zone;

comparing said first and second heat images with corresponding layers in said model;

determining a first deviation in said first image with respect to said model, wherein the first deviation comprises at least one of cavities or irregularities in the first fused layer that are large enough for the camera to capture;

determining a second deviation in said second image with respect to said model, wherein the second deviation comprises at least one of cavities or irregularities in the second fused layer that are large enough for the camera to capture;

responsive only to detecting at least a partial overlap of said first deviation and said second deviation, identifying a defect in the three-dimensional article; and

repairing the identified defect by either;

re-melting the defect and a predetermined area surrounding said defect to smooth out the defect surface and healing the defect in a process of fusing a third powder layer, wherein the re-melting of the defect and the predetermined area surrounding said defect in the process of fusing the third powder layer is by at least one of increasing the power of the energy beam or increasing the time said energy beam is present at the defect position and the predetermined area surrounding said defect, or

re-fusing the identified defect and a predetermined area around said defect via at least one of increasing or decreasing the power of the energy beam or decreasing or increasing the time said energy beam is present.

2. The method according to claim 1, wherein said model, to which said images are compared to, is a CAD-model.

3. The method according to claim 1, wherein said energy beam is an electron beam.

4. The method according to claim 1, wherein said powder is metallic powder.

5. The method according to claim 1, wherein said image is captured by an IR-camera.

6. The method according to claim 1, wherein said model comprises simulated reference images corresponding to building layers of said three-dimensional article.