Rastered laser melting of a curved surface path with uniform power density distribution

Patent metadata

Field	Value
Publication number	US-9358635-B2
Application number	US-201314133696-A
Country	US
Kind code	B2
Filing date	Dec 19, 2013
Priority date	Dec 19, 2013
Publication date	Jun 7, 2016
Grant date	Jun 7, 2016

Abstract

A method of progressing a melt front ( 55 ) around a curved progression path ( 20 ) via a pattern (LP) of transverse laser scan lines (S 1 -S 8 ) of differing lengths. Multiple area bands (B 1 -B 8 ) conceptually divide a width of the curved path. The multiple transverse scan lines distribute the laser power among the bands with a predetermined uniformity that provides relatively consistent power density across the melt front. The scan lines may extend from a less curved side ( 24 ) of the curved path, through a band (B 4 or B 8 ) of largest area, toward a more curved side ( 22 ) of the path. At least one of the scan lines (S 1 , S 8 ) may cross all bands. Other scan lines are shorter and extend by varying distances into the inner bands (B 1 -B 3 or B 1 -B 7 ), normalizing the power density across the bands.

First claim

The invention claimed is:

1. A method comprising:
scanning a laser beam along a series of scan lines on a material surface;
progressing the scan lines in a curved path, wherein each scan line is oriented within 20 degrees of normal to the curved path;
forming a pattern of a plurality of the scan lines of differing lengths that delivers a power of the beam across a plurality of equal-width area bands equally dividing a width of the curved path;
wherein an area density of the power delivered to each band varies by less than 35% between each two of the bands along a length of the pattern as a result of the pattern;
wherein the energy beam, by following the pattern, creates a melt front progressing on the curved path on the material surface while maintaining said area density of the power along the melt front.

2. The method of claim 1 , wherein a first side of the curved path has greater curvature than a second side, and further comprising forming the scan lines wherein the beam reaches the second side on each scan line of the pattern, and does not reach the first side on some scan lines of the pattern.

3. The method of claim 1 , further comprising forming the scan line pattern wherein a total scan time in the pattern is apportioned among the bands according to an area percentage of each band relative to a total area of the pattern as a result of the differing lengths of the scan lines.

4. The method of claim 1 , wherein a first side of the curved path has greater curvature than a second side, the bands have successively greater respective areas from the first side to the second side, and further comprising forming the scan line pattern wherein more of the scan lines of the pattern traverse ones of the bands with greater respective areas than traverse others of the bands with lesser respective areas.

5. The method of claim 1 , wherein first and second sides of the curved path comprise respective radially inner and outer concentric arcs, the area bands comprise concentric bands of equal radial width between the arcs, and the scan lines of the pattern are aligned to within less than 10 degrees with successively spaced radii of the arcs.

6. The method of claim 5 , wherein the successively spaced radii are evenly spaced at an angular distance that overlaps a scan width of the laser beam by at least 1/10 at radially outer ends of the scan lines.

7. The method of claim 1 , wherein the scan lines progress sequentially in alternating directions, and are connected from end to end by increment lines that move the laser beam from an end of each scan line of the pattern to a beginning of a next scan line of the pattern.

8. The method of claim 7 , wherein every scan line of a sub-pattern of the pattern has a different length transverse to the curved path, and the sub-pattern is repeated to form the pattern.

9. The method of claim 1 wherein the pattern starts and ends in a smallest one of the area bands by area.

10. The method of claim 1 , wherein the plurality of equal-width area bands consists of 4 bands.

11. A method comprising:
directing a laser beam of a predetermined power and beam width along each of a series of scan lines in succession between a more curved side and a less curved side of a curved scan progression path on a material surface at a predetermined scan rate;
wherein each of the scan lines is less than 10 degrees from normal to one or both of the sides of the curved scan progression path, and the scan lines vary in length, forming a scan line pattern of a plurality of scan lines that provides a uniform power density of the laser within a difference of less than 10% between each two bands among a plurality of equal-width area bands equally dividing a width of the curved scan progression path;
wherein the energy beam, by following the pattern, creates a melt front that is elongated transverse to the curved scan progression path and progresses thereon while maintaining said uniform power density along the melt front.

12. The method of claim 11 , further comprising forming the scan lines wherein the beam reaches the less curved side of the progression path on each scan line of the pattern, and does not reach the more curved side on some scan lines of the pattern.

13. The method of claim 11 , further comprising forming the scan line pattern wherein a total scan time in the pattern is apportioned among the bands by an area percentage of each band relative to a total area of the pattern as a result of the varying lengths of the scan lines.

14. The method of claim 11 , wherein the bands have successively greater respective areas from the less curved side to the more curved side, and further comprising forming the scan line pattern wherein more of the scan lines of the pattern traverse ones of the bands with greater respective areas than traverse others of the bands with lesser respective areas.

15. The method of claim 11 , wherein the sides of the progression path comprise concentric arcs, the area bands comprise concentric bands of equal radial width between the arcs, and the scan lines of the pattern are each aligned within less than 5 degrees with successively spaced radii of the arcs.

16. A method comprising:
defining a curved progression path for a melt front on a material surface;
defining a sequence of transverse laser scan lines across the progression path that are each aligned within less than 10 degrees to a radius of curvature of the progression path, wherein the sequence of scan lines progresses along the progression path;
directing an energy beam along each of the scan lines in succession;
wherein at least some of the scan lines have different respective lengths, forming a scan line pattern that provides a surface power density of the energy beam that is uniform within a difference of less than 10% between each two bands in a plurality of equal-width area bands equally dividing a width of the progression path;
wherein the energy beam, by following the pattern, creates the melt front elongated transverse to the curved progression path and progressing thereon while maintaining said uniformity of the surface power density along a length of the melt front.

17. The method of claim 16 , wherein the scan lines progress sequentially in alternating directions, and are connected from end to end by increment lines that move the energy beam from an end of each scan line of the pattern to a beginning of a next scan line of the pattern.

18. The method of claim 16 , wherein every scan line of a scan line sub-pattern has a different length, and the sub-pattern is repeated.

19. The method of claim 16 , wherein the pattern starts and ends in a smallest one of the bands by area.

20. The method of claim 16 , wherein the step of directing an energy beam comprises directing a laser beam.

Assignees

• Bruck Gerald J
• Siemens Energy Inc

Inventors

• Bruck Gerald J

Classifications

• B23K26/354 Primary

  by melting · CPC title

• B23K26/359

  by providing a line or line pattern, e.g. a dotted break initiation line · CPC title

• B23K26/082

  Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head · CPC title

• B23K26/342

  Build-up welding · CPC title

• B23K26/0081 Primary

  Operations & Transport · mapped topic