Height control and deposition measurement for the electron beam free form fabrication (EBF3) process

Patent metadata

Field	Value
Publication number	US-9764415-B2
Application number	US-201313834294-A
Country	US
Kind code	B2
Filing date	Mar 15, 2013
Priority date	Mar 15, 2013
Publication date	Sep 19, 2017
Grant date	Sep 19, 2017

Abstract

A method of controlling a height of an electron beam gun and wire feeder during an electron freeform fabrication process includes utilizing a camera to generate an image of the molten pool of material. The image generated by the camera is utilized to determine a measured height of the electron beam gun relative to the surface of the molten pool. The method further includes ensuring that the measured height is within the range of acceptable heights of the electron beam gun relative to the surface of the molten pool. The present invention also provides for measuring a height of a solid metal deposit formed upon cooling of a molten pool. The height of a single point can be measured, or a plurality of points can be measured to provide 2D or 3D surface height measurements.

First claim

The invention claimed is:

1. A method of controlling a measured actual height of an EBF 3 electron beam gun and wire feeder during deposition of layers of molten matter onto a substrate, the EBF 3 method comprising:
providing a substrate;
providing a wire source through a wire feeder;
positioning an EBF 3 electron beam gun and wire source in the vicinity of the substrate;
positioning a video camera at a fixed position relative to the EBF 3 electron beam gun;
calibrating the video camera by calculating a constant slope correlating pixel location of a first digital image from the video camera to a height of the EBF 3 electron beam gun;
forming a molten pool of material on the substrate by melting the wire source utilizing the EBF 3 electron beam gun, the molten pool having a surface defining a measured actual height relative to the EBF 3 electron beam gun;
depositing layers of molten matter of the wire source melted by the EBF 3 electron beam gun;
utilizing the video camera to generate a second digital image of at least a portion of the molten pool of material;
determining a range of acceptable actual heights of the electron beam gun relative to the surface of the molten pool;
determining a measured actual height of the EBF 3 electron beam gun relative to the surface of the molten pool by calculating a product of: a pixel location of a centroid of the molten pool on the second digital image, and the calculated constant slope;
controlling the height of the EBF 3 electron beam gun based on the measured actual height of the EBF 3 electron beam gun relative to me surface of the molten pool to provide automated control of the EBF 3 method; and
ensuring that the measured height is within the range of acceptable heights of the electron beam gun relative to the surface of the molten pool.

2. The method of claim 1 , wherein the calibrating the video camera further comprises: generating data relating digital images generated by the video camera to a distance of the EBF 3 electron beam gun from the surface of the molten pool.

3. The method of claim 2 , wherein the calibrating the video camera further comprises: providing a position sensor that outputs sensor positions concerning a height of the EBF 3 electron gun relative to the substrate.

4. The method of claim 3 , wherein the calibrating the video camera further comprises:
positioning a target on the substrate within a line of sight of the video camera;
setting the height of the EBF 3 electron beam gun relative to the substrate at a plurality of sensor positions;
utilizing the video camera to generate digital image locations corresponding to each sensor position.

5. The method of claim 4 , further comprising:
determining a relationship between the sensor positions and the image locations such that a measured actual height of the EBF 3 electron gun relative to the substrate can be determined from a digital image location generated by the video camera.

6. The method of claim 4 , further comprising:
forming a database comprising pairs of data, wherein a first number of each pair represents sensor position of the EBF 3 electron beam gun relative to the substrate, and wherein a second number of each pair represents a digital image location generated by the video camera.

7. The method of claim 1 , further comprising:
allowing the molten pool to solidify to form a metal deposit;
causing the EBF 3 electron beam gun to generate a beam of electrons that are incident on the surface of the metal deposit to illuminate a region of the surface of the metal deposit;
causing the electron beam to move to illuminate a plurality of regions of the surface of the metal deposit;
determining the height of the regions utilizing digital images formed by the video camera.

8. A method of measuring a position of a metal surface relative to an EBF 3 electron beam gun; the EBF 3 method comprising:
providing a substrate and an EBF 3 electron beam gun that is movable relative to the substrate;
positioning a video camera at a fixed position relative to the EBF 3 electron beam gun;
utilizing the video camera to generate images;
calibrating the video camera by calculating a constant slope correlating pixel location of a first digital image, from the generated images, to a height of the EBF 3 electron beam gun from the substrate:
forming a metal surface;
utilizing the EBF 3 electron beam gun to illuminate a region of the metal surface;
utilizing the video camera to generate a second digital image of the illuminated region of the metal surface;
utilizing the second digital image of the illuminated region of the metal surface to determine a measured actual position of the metal surface relative to the EBF 3 electron beam gun by calculating a product of: a pixel location of the illuminated region of the metal surface on the second digital image, and the calculated constant slope to provide automated control of the EBF 3 method.

9. The method of claim 8 , wherein:
forming a metal surface includes utilizing the EBF 3 electron beam gun to form a molten pool of metal having a metal surface.

10. the method of claim 9 , wherein:
the images of the metal surface are generated while the metal is in a molten state.

11. The method of claim 9 , further comprising:
solidifying the molten pool of metal; and
wherein the images of the metal surface are generated after the molten metal has solidified.

12. The method of claim 11 , wherein:
the metal defines material properties upon solidification of the molten metal;
the EBF 3 electron beam gun is controlled to generate an electron beam having, sufficient power to illuminate a region of the metal surface of the solidified metal and generate a video camera image of the illuminated region without significantly altering the material properties of the solidified metal.

13. The method of claim 12 , further comprising:
causing the electron beam to illuminate a plurality of adjacent regions of the surface of the metal;
utilizing the camera to generate one or more images of the adjacent regions;
determining a shape of the surface of the metal utilizing the images.

14. The method of claim 13 , further comprising:
determining a three dimensional shape of the surface of the metal by determining three dimensional locations of a plurality of points on the metal surface utilizing the illuminated regions of the images.

Assignees

• Nasa
• Nasa

Inventors

• Seufzer William J
• Hafley Robert A

Classifications

• B23K15/0086

  welding for purposes other than joining, e.g. build-up welding · CPC title

• B23K15/0013 Primary

  Positioning or observing workpieces, e.g. with respect to the impact; Aligning, aiming or focusing electron beams · CPC title