Three-dimensional printing system optimizing contour formation for multiple energy beams

1. A system for manufacturing a three-dimensional (3D) article, the system including a powder dispenser for sequentially dispensing individual layers of powder, a fusing apparatus for generating and scanning a plurality of energy beams including a first beam and a second beam to selectively melt the layers of powder, and a controller, the controller including a processor coupled to a non-volatile memory, the memory storing software instructions, in response to execution by the processor the software instructions cause the controller to:

read a joint alignment uncertainty for at least the first beam with respect to the second beam;

operate the powder dispenser to dispense a layer of powder;

operate the fusing apparatus to selectively fuse the layer of powder including:

operate the first beam to fuse a hatch pattern over an area of the layer of powder; and

operate the second beam to fuse a contour that defines at least part of an outer surface of the 3D article, fusing the contour includes scanning the second beam to circumnavigate the hatch pattern N times, N is an integer at least equal to one and is selected based upon the read joint alignment uncertainty.

2. The system of claim 1 wherein N is increasing with the read joint alignment uncertainty.

3. The system of claim 1 wherein N times a melt width of a single scan is at least equal to the read joint alignment uncertainty.

4. The system of claim 1 wherein the contour has a width along a transverse axis T that is perpendicular to a scan direction S at individual points along the contour, the width along the transverse axis T is greater than a melt width of a single scan but less than a melt width of N times the melt width of a single scan due to overlap between scans.

5. The system of claim 1 wherein the selection of N can take on values up to and including N=3.

6. The system of claim 1 wherein the selection of N can take on values up to an including N=5.

7. The system of claim 1 wherein the plurality of energy beams includes a third beam.

8. A system for manufacturing a three-dimensional (3D) article, the system including a powder dispenser for sequentially dispensing individual layers of powder, a fusing apparatus for generating and scanning a plurality of energy beams including a first beam and a second beam to selectively melt the layers of powder, and a controller, the controller including a processor coupled to a non-volatile memory, the memory storing software instructions, in response to execution by processor the software instructions cause the controller to:

read a joint alignment uncertainty for at least the first beam with respect to the second beam;

operate the powder dispenser to dispense a layer of powder;

operate the fusing apparatus to selectively fuse the layer of powder including:

operate the first beam to fuse a hatch melt pattern over an area of the layer of powder; and

operate at least the second beam to fuse a melted contour that defines at least part of an outer surface of the 3D article, fusing the melted contour includes scanning the second beam to circumnavigate the hatch pattern N times, N is an integer at least equal to one and is selected based on the joint alignment uncertainty and to provide an overall contour width sufficient to prevent one or more defects including a surface defect caused by the hatch melt pattern extending through the melted contour and to the outer surface of the 3D article and a subsurface weakness defect caused by an insufficient coupling of the hatch melt pattern and the melted contour.

9. The system of claim 8 wherein N is increasing with the read joint alignment uncertainty.

10. The system of claim 8 wherein N times a melt width of a single scan is at least equal to the read joint alignment uncertainty.

11. The system of claim 8 wherein the contour has a width along a transverse axis T that is perpendicular to a scan direction S at individual points along the contour, the width along the transverse axis T is greater than a melt width of a single scan but less than a melt width of N times the melt width of a single scan due to overlap between scans.

12. The system of claim 8 wherein the selection of N can take on values up to an including N=3.

13. The system of claim 8 wherein the selection of N can take on values up to an including N=5.

14. The system of claim 8 wherein the plurality of energy beams includes a third beam.

15. A system for manufacturing a three-dimensional (3D) article, the system including a powder dispenser for sequentially dispensing individual layers of powder, a fusing apparatus for generating and scanning a plurality of energy beams including a first beam and a second beam to selectively melt the layers of powder, and a controller, the controller including a processor coupled to a non-volatile memory, the memory storing software instructions, in response to execution by the processor the software instructions cause the controller to:

operate the powder dispenser to dispense a layer of powder;

operate the fusing apparatus to selectively fuse the layer of powder including:

operate the first beam to fuse a hatch melt pattern over an area of the layer of powder; and

operate at least the second beam to fuse a contour that provides a boundary to the hatch pattern and defines at least a part of an outer surface of the 3D article, fusing the contour includes scanning along a scan axis S that follows the contour, fusing the contour includes N overlapping scans to provide a contour width that is greater than a melt width of a single scan along a transverse axis T that is perpendicular to S, the value of N is selected based upon an effect of a joint alignment uncertainty of the first beam and the second beam, the effect being one of a surface defect caused by the hatch melt pattern extending through the melted contour and to the outer surface of the 3D article and a subsurface weakness defect caused by an insufficient coupling of the hatch melt pattern and the melted contour.

16. The system of claim 15 wherein N times a melt width of a single scan is at least equal to the joint alignment uncertainty.

17. The system of claim 15 wherein the selection of N can take on values up to an including N=3.

18. The system of claim 15 wherein the selection of N can take on values up to an including N=5.

19. The system of claim 15 wherein the plurality of energy beams includes a third beam.