ADDITIVE LAYER MANUFACTURING

• US 20150306665A1
• Filed: 11/06/2013
• Published: 10/29/2015
• Est. Priority Date: 11/09/2012
• Status: Active Grant

• Current Assignee: BAE Systems Plc
• Original Assignee: BAE Systems Plc
• Inventors: Sidhu, Jagjit, Wescott, Andrew David, Potter, Mark Alfred
• Granted Patent: US 9,555,475 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B22F 10/25 Direct deposition of metal particles, e.g. direct metal deposition [DMD] or laser engineered net shaping [LENS]
• CPC Class Codes: B22F 10/32 of the atmosphere, e.g. composition or pressure in a building chamber
• CPC Class Codes: B22F 10/50 Treatment of workpieces or articles during build-up, e.g. treatments applied to fused layers during build-up
• CPC Class Codes: B22F 10/80 Data acquisition or data processing
• CPC Class Codes: B22F 10/85 for controlling or regulating additive manufacturing processes
• CPC Class Codes: B22F 12/20 Cooling means
• CPC Class Codes: B22F 12/30 Platforms or substrates
• CPC Class Codes: B22F 12/41 characterised by the type, e.g. laser or electron beam
• CPC Class Codes: B22F 12/43 pulsed; frequency modulated
• 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 2007/042 characterised by the layer forming method
• CPC Class Codes: B22F 7/04 with one or more layers not made from powder, e.g. made from solid metal
• CPC Class Codes: B23K 26/34 Laser welding for purposes other than joining
• CPC Class Codes: B23K 26/354 by melting
• CPC Class Codes: B23K 9/04 Welding for other purposes than joining, e.g. built-up welding
• CPC Class Codes: B23K 9/0956 using sensing means, e.g. optical
• CPC Class Codes: B29C 64/135 the energy source being concentrated, e.g. scanning lasers or focused light sources
• 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 50/02 : for controlling or regulating additive manufacturing processes
• CPC Class Codes: Y02P 10/25 : Process efficiency

Abstract

Apparatus and a method for forming a metallic component by additive layer manufacturing are provided. The method includes the steps of mounting a work piece (3) to ALM manufacturing apparatus including measuring means in the form of load cells (13, 14) to measure stresses tending to distort the work piece, using a laser heat source (24) to apply heat to a surface (18) of the work piece (3) sufficient to melt it; adding metallic material to the melted surface (18) and moving the heat source (24) relative to the work piece (3) whereby progressively to form a layer (30) of metallic material on it; repeating the above steps as required, whereby progressively to form the component and, while doing so, measuring stresses tending to distort the component with the load cells (13, 14) and, if they are above a predetermined threshold, stress relieving the work piece with means such as a pulsed laser (27) while still mounted to the apparatus to reduce distortion to a predetermined level, and again repeating above steps as required to complete the component. A computer (16) may be included to control the whole process.

Claims

1. A method of forming a metallic component by additive layer manufacturing, the method comprising:

a) mounting a work piece to additive layer manufacturing (ALM) manufacturing apparatus including a stress measuring system adapted at least partly to clamp the work piece to the apparatus and to measure stresses tending to distort the work piece;

b) using a heat source to apply heat to a portion of a surface of the work piece sufficient to melt said portion;

c) adding metallic material to the melted portion and moving the heat source relative to the work piece whereby progressively to form a layer of metallic material on the work piece;

d) repeating b) and c) as required, whereby progressively to form the component;

e) while progressively forming the component, measuring stresses tending to distort the work piece with the stress measuring system and, if such stresses are measured to be above a predetermined threshold, stress relieving the work piece while mounted to the apparatus whereby to reduce distortion to a predetermined level; and

repeating b) to e) as required whereby to form the component.

2. A method as in claim 1 including positioning the stress measuring system in the region of extremities of the work piece and measuring stresses across at least a substantial portion of the work piece.

3. A method as in claim 1 in which measuring stresses tending to distort the work piece and stress relieving the work piece include measuring clamping loads applied to the work piece to clamp it in position on the apparatus before ALM manufacture commences and after forming a predetermined number of layers of added material on the work piece, stress relieving the work piece, measuring the clamping loads again and, if the clamping loads exceed a predetermined said threshold, further stress relieving the work piece.

4. A method as in claim 2 in which measuring stresses tending to distort the work piece and stress relieving the work piece include measuring clamping loads applied to the work piece to clamp it in position on the apparatus before ALM manufacture commences and after forming a predetermined number of layers of added material on the work piece, stress relieving the work piece, measuring the clamping loads again and, if the clamping loads exceed a predetermined said threshold, further stress relieving the work piece.

5. A method as in claim 1 in which stress relieving the layer comprises applying a peening step to the layer.

6. A method as in claim 5 in which the peening step comprises high frequency peening.

7. A method as in claim 6 in which the high frequency peening step comprises applying a pulsed laser to the layer.

8. A method as in claim 6 in which the high frequency peening step comprises applying ultra-sonic impact treatment to the layer.

9. An additive layer manufacturing (ALM) apparatus for forming a metallic component, the apparatus including:

one or more clamps configured to mount a work piece to the apparatus;

a heat source moveable relative to the work piece and configured to apply heat to a portion of a surface of the work piece sufficient to melt said portion;

a material delivery system to add metallic material to the melted portion whereby a layer of metallic material can be progressively formed on the work piece as the heat source moves relative to the work piece;

a stress measuring system forming part of the one or more clamps and configured to measure stresses tending to distort the work piece; and

a stress relieving system configured to relieve stress in the work piece while mounted to the apparatus whereby to reduce distortion of the work piece during forming of the component.

10. Apparatus as in claim 9 in which the stress measuring system is positioned in the region of extremities of the work piece whereby to measure distortion across at least a substantial portion of the work piece.

11. Apparatus as in claim 9 including a cooling system configured to cool the work piece before operation of the stress relieving system.

12. Apparatus as in claim 10 including a cooling system configured to cool the work piece before operation of the stress relieving system.

13. Apparatus as in claim 9 in which the stress relieving system comprises a pulsed laser whereby to apply laser peening to the added layer.

14. Apparatus as in claim 9 in which the stress relieving system is configured to provide ultrasonic impact treatment to the added layer.

15. Apparatus as in claim 9 including a computer programmed to control each of:

the heat source, the delivery system to add metallic material to the melted portion of the surface of the work piece, movement of the heat source relative to the work piece, and the stress relieving system in dependence upon stresses in the work piece measured by the stress measuring system.

16. (canceled)

17. A computer program product containing a computer program instructions that when executed by one or more processors cause a process for forming a metallic component by additive layer manufacturing to be carried out the process comprising:

a) causing a heat source to apply heat to a portion of a surface of a work piece sufficient to melt said portion, the work piece to mounted to an additive layer manufacturing (ALM) manufacturing apparatus including a stress measuring system adapted at least partly to clamp the work piece to the apparatus and to measure stresses tending to distort the work piece;

b) causing metallic material to be added to the melted portion and further causing the heat source to move relative to the work piece whereby progressively to form a layer of metallic material on the work piece;

c) repeating a) and b) as required, whereby progressively to form the component;

d) while progressively forming the component, causing stresses tending to distort the work piece to be measured with the stress measuring system and, if such stresses are measured to be above a predetermined threshold, further causing stress relieving the work piece while mounted to the apparatus whereby to reduce distortion to a predetermined level; and

repeating b) to d) as required whereby to form the component.

21. A computer program product as in claim 17, wherein measuring stresses tending to distort the work piece and stress relieving the work piece include measuring clamping loads applied to the work piece to clamp it in position on the apparatus before ALM manufacture commences and after forming a predetermined number of layers of added material on the work piece, stress relieving the work piece, measuring the clamping loads again and, if the clamping loads exceed a predetermined said threshold, further stress relieving the work piece.

22. A computer program product as in claim 17, wherein the stress measuring system is positioned in the region of extremities of the work piece and stresses are measured across at least a substantial portion of the work piece.

23. A computer program product as in claim 22, wherein measuring stresses tending to distort the work piece and stress relieving the work piece include measuring clamping loads applied to the work piece to clamp it in position on the apparatus before ALM manufacture commences and after forming a predetermined number of layers of added material on the work piece, stress relieving the work piece, measuring the clamping loads again and, if the clamping loads exceed a predetermined said threshold, further stress relieving the work piece.

24. A computer program product as in claim 17, wherein stress relieving the layer comprises applying a peening step to the layer, and wherein the peening step comprises at least one of high frequency peening, applying a pulsed laser to the layer, and applying ultra-sonic impact treatment to the layer.

18. (canceled)

19. (canceled)

20. (canceled)