Additive manufacturing of three-dimensional articles

Patent metadata

Field	Value
Publication number	US-10525531-B2
Application number	US-201615290635-A
Country	US
Kind code	B2
Filing date	Oct 11, 2016
Priority date	Nov 17, 2015
Publication date	Jan 7, 2020
Grant date	Jan 7, 2020

Abstract

The present invention relates to a method for prolonging lifetime of a triod electron beam source when forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article, the method comprising the steps of: adjusting a cathode heating power at a predetermined value above a threshold heating value, which threshold heating value creates a predetermined X-ray signal emanating from the triod electron beam source, fusing the three-dimensional article with the electron beam source having the cathode heating power at a predetermined value above a threshold heating value.

First claim

The invention claimed is:

1. A method for prolonging lifetime of at least one electron beam source when forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article, the method comprising the steps of:
providing the at least one electron beam source emitting an electron beam for at least one of heating or fusing the powder material, wherein the electron beam source comprises a cathode, an anode, and a grid between the cathode and anode;
setting an electron beam current, a cathode heating power, a grid potential (Ug) and a cathode potential (Uc) to predetermined start values;
reducing the cathode heating power with a predetermined value and decreasing a Uc-Ug potential difference for maintaining the predetermined electron beam current;
detecting an X-ray signals emanating from the electron beam source with at least one X-ray detector;
repeating said reducing and detecting steps until the detected X-ray signal is above a predetermined value; and
increasing the cathode heating power by a predetermined safety value from a threshold heating power value which resulted in x-ray signals, emanating from the electron beam source, above the predetermined value.

2. The method according to claim 1 , wherein said reducing and detecting steps are performed during preheating of the surface prior to applying a new powder layer onto the surface, preheating of a new powder layer, powder distribution, and post heat treatment of an already fused powder layer or during the fusion process.

3. The method according to claim 1 , wherein the start value of the electron beam current is between 20-50 mA.

4. The method according to claim 1 , wherein an updating of the cathode heating power is performed between a fusion process of each layer.

5. The method according to claim 1 , further comprising the step of arranging the X-ray detector in the electron beam source.

6. The method according to claim 1 , wherein the start value of the cathode heating power is about 5 W.

7. The method according to claim 1 , wherein the predetermined value in which the cathode heating power is reduced is in steps of 0.05 W.

8. The method according to claim 1 , wherein the predetermined safety value is between 0.4-0.8 W.

9. The method according to claim 1 , further comprising the step of filtering out any x-ray signal not emanating from the electron beam source.

10. The method according to claim 1 , further comprising the step of arranging the at least one x-ray detector out of sight from x-ray signals emanating from the powder layer.

11. An apparatus for forming a three-dimensional article through successively depositing individual layers of powder material so as to form the article, the apparatus comprising:
at least one electron beam source emitting an electron beam for at least one of heating or fusing the powder material, where the electron beam source comprises a cathode, an anode, and a grid between the cathode and anode;
an X-ray detector for detecting x-rays emanating from the at least one electron beam source; and
at least one control unit, the at least one control unit being configured for:
setting an electron beam current, a cathode heating power, a grid potential (Ug) and a cathode potential (Uc) to predetermined start values,
reducing the cathode heating power with a predetermined value and decreasing a Uc-Ug potential difference for maintaining the predetermined electron beam current,
detecting, via the at least one X-ray detector, X-ray signals emanating from the electron beam source,
repeating the reducing and detecting steps until the detected X-ray signal is above a predetermined value, and
increasing the cathode heating power by a predetermined safety value from a threshold heating power value which resulted in x-ray signals, emanating from the electron beam source, above the predetermined value, so as to establish a usable range of heating powers of a cathode element of the electron beam source.

12. The apparatus of claim 11 , wherein the start value of the electron beam current is between 20-50 mA.

13. The apparatus of claim 11 , wherein the X-ray detector is positioned in the electron beam source.

14. The apparatus of claim 11 , wherein the X-ray detector is positioned out of sight from x-ray signals emanating from the powder layer.

15. The apparatus of claim 11 , wherein at least one of:
the start value of the cathode heating power is about 5 W;
the predetermined safety value is between 0.4-0.8 W; or
the predetermined value in which the cathode heating power is reduced is in steps of 0.05 W.

16. 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 at least one executable portion configured for:
setting an electron beam current, a cathode heating powder, a grid potential (Ug) and a cathode potential (Uc) to predetermined start values;
reducing the cathode heating power with a predetermined value and decreasing a Uc-Ug potential difference for maintaining the predetermined electron beam current;
detecting X-ray signal from the electron beam source with an X-ray detector;
repeating the reducing and detecting step until the detected X-ray signal is above a predetermined value; and
increasing the cathode heating power by a predetermined value from the value which resulted in x-ray signals above the predetermined value and using the electron beam for forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article.

17. The computer program product of claim 16 , wherein the at least one executable portion is further configured for updating the cathode heating power between a fusion process of each layer.

18. The computer program product of claim 16 , wherein the at least one executable portion is further configured for filtering out any x-ray signal not emanating from the electron beam source.

19. A method for prolonging lifetime of a triod electron beam source when forming a three-dimensional article through successively depositing individual layers of powder material that are fused together so as to form the article, the method comprising the steps of:
adjusting a cathode heating power with a control unit at a predetermined value above a threshold heating value, which threshold heating value creates a predetermined X-ray signal emanating from the triod electron beam source; and
fusing the three-dimensional article with the electron beam source having the cathode heating power at a predetermined value above a threshold heating value.

Assignees

• Arcam Ab

Inventors

• Fager Mattias

Classifications

• B22F2998/10

  Processes characterised by the sequence of their steps · CPC title

• H01J2237/065

  Source emittance characteristics · CPC title

• B22F3/1017

  Multiple heating or additional steps (B22F3/101 takes precedence) · CPC title

• B29C64/393

  for controlling or regulating additive manufacturing processes · CPC title

• H01J2237/06308

  Thermionic sources · CPC title