Method and apparatus for detecting electron beam source filament wear

• US 10,529,070 B2
• Filed: 10/08/2018
• Issued: 01/07/2020
• Est. Priority Date: 11/10/2017
• Status: Active Grant

• Current Assignee: Arcam Ab (Danaher Corporation)
• Original Assignee: Arcam Ab (Danaher Corporation)
• Inventors: Hellestam, Calle, Fager, Mattias
• Primary Examiner(s): Gaworecki, Mark R
• Application Number:
  US16/154,374
• Publication Number:
  US 20190147578A1
• Time in Patent Office: 456 Days
• 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 10/36 of energy beam parameters
• CPC Class Codes: B22F 12/44 characterised by the configuration of the radiation means
• CPC Class Codes: B22F 12/45 Two or more
• CPC Class Codes: B22F 12/49 Scanners
• CPC Class Codes: B22F 12/52 Hoppers
• CPC Class Codes: B22F 12/55 Two or more means for feeding material
• CPC Class Codes: B22F 12/90 Means for process control, e.g. cameras or sensors
• CPC Class Codes: B29C 64/153 using layers of powder being selectively joined, e.g. by selective laser sintering or melting
• CPC Class Codes: B29C 64/393 for controlling or regulating additive manufacturing processes
• 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: G06T 7/001 using an image reference approach
• CPC Class Codes: H01J 2237/065 Source emittance characteristics
• CPC Class Codes: H01J 2237/30433 System calibration for microscopes H01J2237/2826
• CPC Class Codes: H01J 2237/3128 Melting
• CPC Class Codes: H01J 3/028 Replacing parts of the gun; Relative adjustment H01J3/021 - H01J3/025 take precedence
• CPC Class Codes: H01J 37/222 Image processing arrangements associated with the tube image data processing or generation, in general G06T
• CPC Class Codes: H01J 37/304 Controlling tubes by information coming from the objects or from the beam, e.g. correction signals
• CPC Class Codes: Y02P 10/25 : Process efficiency

Abstract

A method for detecting electron beam filament wear in an electron beam source, the method comprising the steps of: enlarging a beam spot emanating from the electron beam source on a work table to a predetermined minimum size, capturing an image of the beam spot on the work table by a camera, comparing the captured image of the beam spot with a reference image, and detecting filament wear if the captured image is deviating more than a predetermined value from the reference image.

Claims

1. A method for detecting electron beam filament wear in an electron beam source, the method comprising the steps of:

fixing the electron beam source in a reference condition,

moving a focus plane of electron beams emanating from the electron beam source a predetermined distance from a target surface for reproducing electron emission of the filament onto the target surface,

capturing an image of the reproduced electron emission of the filament onto the target surface by a camera,

comparing the captured image with a reference image of the reproduced electron emission of the filament onto the target surface, and

detecting filament wear if a luminous flux in the captured image is deviating more than a predetermined value from the reference image.

2. The method according to claim 1, further comprising the steps of:

determining a total area of electron emission less than a predetermined emission value in the captured image within the boundary of the reference image of the reproduced electron emission of the filament onto the target surface, and

detecting filament wear if a luminous flux in the captured image is deviating more than a predetermined value from the reference image and/or if the total area of emission less than the predetermined emission value in the captured image is above a predetermined value.

3. The method according to claim 1, wherein the focus plane is moved the predetermined distance below the target surface.

4. The method according to claim 1, wherein the image of the reproduced electron emission of the filament onto the target surface is captured for a non-deflected electron beam.

5. The method according to claim 1, wherein the focus plane of the electron beams is moved by at least one focusing coil.

6. The method according to claim 1, wherein the predetermined distance the focus plane is moved from the target surface is 1-10 cm.

7. A method for forming a three-dimensional article, the method comprising:

successively depositing individual layers of powder material that are fused together with an electron beam from an electron beam source so as to form the article, and

performing the beam filament wear detecting method according to claim 1.

8. The method according to claim 7, wherein the filament wear detection method is performed when the three-dimensional article is ready.

9. The method according to claim 7, wherein the filament wear detection method is performed before each layer of the three-dimensional article is to be fused.

10. The method according to claim 7, wherein the target surface is:

the powder to be fused, already fused powder, a detecting surface provided on a movable powder distributor, or a detection area outside a manufacturing area.

11. The method according to claim 1, wherein:

the method further comprises a step of receiving and storing, within one or more memory storage areas, a model of a three-dimensional article.

12. An apparatus for detecting electron beam filament wear in an electron beam source, the apparatus comprising:

means for fixing the electron beam source in a reference condition,

means for moving a focus plane of electron beams emanating from the electron beam source a predetermined distance from a target surface for reproducing electron emission of the filament onto the target surface,

a camera for capturing an image of the reproduced electron emission of the filament onto the target surface, and

a processor configured for;

comparing the captured image with a reference image, and

detecting filament wear if a luminous flux in the captured image is deviating more than a predetermined value from the reference image.

13. The apparatus according to claim 12, wherein the processor is further configured for:

determining a total area of electron emission below a predetermined emission value in the captured image within the boundary of the reference image of the reproduced electron emission of the filament onto the target surface, and

detecting filament wear if a luminous flux in the captured image is deviating more than a predetermined value from the reference image and/or if the total area of emission being below the predetermined emission value in the captured image is above a predetermined value.

14. The apparatus according to claim 12, wherein the focus plane is moved the predetermined distance below the target surface.

15. The apparatus according to claim 12, wherein the means for defocusing the spot of the electron beam is at least one focusing lens.

16. The apparatus according to claim 12, wherein a focus coil provides the means for fixing the electron beam source in the reference condition and for moving the focus plane of the electron beams.

17. The apparatus according to claim 12, wherein the means for fixing the electron beam source in the reference condition comprise one of:

a fixed setting of a focus coil such that the focus plane is moved a predetermined distance from the target surface;

a fixed setting of one or more deflection coils;

or

a fixed setting of one or more astigmatism coils.

18. The apparatus according to claim 12, wherein the predetermined distance the focus plane is moved from the target surface is 1-10 cm.

19. A computer program product comprising at least one non-transitory computer-readable storage medium having computer-readable program code portions embodied therein, the computer-readable program code portions comprising one or more executable portions configured for:

fixing the electron beam source in a reference condition,

moving a focus plane of electron beams emanating from the electron beam source a predetermined distance from a target surface for reproducing electron emission of the filament onto the target surface,

capturing an image of the reproduced electron emission of the filament onto the target surface by a camera,

comparing the captured image with a reference image, and

detecting filament wear if a luminous flux in the captured image is deviating more than a predetermined value from the reference image.

20. A computer program product according to claim 19, wherein the one or more executable portions are further configured for:

determining a total area of electron emission below a predetermined emission value in the captured image within the boundary of the reference image of the reproduced electron emission of the filament onto the target surface, and

detecting filament wear if a luminous flux in the captured image is deviating more than a predetermined value from the reference image and/or if the total area of emission below a predetermined emission value in the captured image is above a predetermined value.