Ablation cutting of a workpiece by a pulsed laser beam
A method for ablating a workpiece by a pulsed laser beam includes pretreating a workpiece surface of the workpiece by moving the pulsed laser beam over the workpiece surface along a surface path, first consecutive laser pulses of the pulsed laser beam having a first pulse overlap on the workpiece surface in a path direction, and ablating the pretreated workpiece surface by moving the pulsed laser beam over the workpiece surface along the surface path multiple times. The second consecutive laser pulses of the pulsed laser beam have a second pulse overlap on the workpiece surface in the path direction, and the second pulse overlap is less than the first pulse overlap.
1. A method of parting an optically transparent workpiece, the method comprising:
pretreating a workpiece surface of the optically transparent workpiece by moving a first pulsed laser beam at a first constant speed over the workpiece surface along a pretreating surface path with a particular path width, wherein first consecutive laser pulses of the first pulsed laser beam have a first pulse overlap on the workpiece surface in a path direction; and
ablating the pretreated workpiece surface of the optically transparent workpiece by moving a second pulsed laser beam at a second constant speed over the pretreated workpiece surface along the pretreating surface path with the particular path width multiple times, wherein second consecutive laser pulses of the second pulsed laser beam have a second pulse overlap on the workpiece surface in the path direction, and wherein the second pulse overlap is less than the first pulse overlap,
wherein pretreating the workpiece surface comprises moving the first pulsed laser beam over the workpiece surface along a first plurality of surface paths in the path direction, the first plurality of surface paths being offset laterally from each other and overlapping laterally with each other, and
wherein ablating the pretreated workpiece surface comprises moving the second pulsed laser beam over the workpiece surface along a second plurality of surface paths in the path direction, the second plurality of surface paths being offset laterally from each other and overlapping laterally with each other.
2. The method of claim 1 , wherein the first consecutive laser pulses and the second consecutive laser pulses have a same pulse power and a same diameter on the workpiece surface.
3. The method of claim 1 , wherein the first and second pulse overlaps are achieved by changing at least one of a pulse frequency or a feed speed.
4. The method of claim 1 , wherein the first pulse overlap is more than 90%.
5. The method of claim 4 , wherein the first pulse overlap is more than 95%.
6. The method of claim 1 , wherein the second pulse overlap is less than 70%.
7. The method of claim 6 , wherein the second pulse overlap is less than 50%.
8. The method of claim 1 , wherein pretreating a workpiece surface of the optically transparent workpiece comprises:
moving the first pulsed laser beam over the workpiece surface along the surface path no more than twice.
9. The method of claim 1 , wherein the first pulsed laser beam and the second pulsed laser beam are generated with a same laser.
10. The method of claim 1 , wherein pretreating a workpiece surface of the optically transparent workpiece comprises:
reducing transmission of a workpiece region near the workpiece surface.
11. The method of claim 10 , wherein pretreating a workpiece surface of the workpiece comprises:
roughening the workpiece surface by the first pulsed laser beam.
12. The method of claim 1 , wherein ablating the pretreated workpiece surface of the optically transparent workpiece comprises:
repeating the ablating for a plurality of times until the optically transparent workpiece is parted completely along the surface path.
13. The method of claim 1 , further comprising:
parting the optically transparent workpiece completely on the ablated workpiece surface by mechanical ablation.
14. The method of claim 13 , wherein the mechanical ablation includes a scratching process.
15. The method of claim 1 , further comprising:
carrying out the pretreating and ablating on both sides of the optically transparent workpiece along the same surface path.
16. The method of claim 15 , further comprising:
carrying out the pretreating and ablating on a first side of the optically transparent workpiece along the surface path; then
carrying out the pretreating and ablating on a second, reverse side of the optically transparent workpiece along the same surface path.
17. The method of claim 16 , further comprising:
turning the optically transparent workpiece over after carrying out the pretreating and ablating on the first side of the optically transparent workpiece,
wherein a single laser is used for carrying out the pretreating and ablating on the first side and on the second side.
18. The method of claim 1 , wherein the first and second pulse overlaps are achieved by increasing the first constant speed to the second constant speed while keeping a pulse frequency of the second pulsed laser beam to be the same as a pulse frequency of the first pulsed laser beam.
19. The method of claim 1 , wherein the first and second pulse overlaps are achieved by reducing a first pulse frequency of the first pulsed laser beam to a second pulse frequency of the second pulsed laser beam while keeping the second constant speed to be the same as the first constant speed.