Method and device for the removal of material by means of laser pulses

• US 20090294422A1
• Filed: 08/21/2006
• Published: 12/03/2009
• Est. Priority Date: 08/22/2005
• Status: Active Grant

• Current Assignee: Rowiak GmbH
• Original Assignee: Rowiak GmbH
• Inventors: Rathjen, Christian, Lubatschowski, Holger, Ripken, Tammo
• Granted Patent: US 9,162,319 B2
• Time in Patent Office: Days
• US Class Current: 219/121.72
• CPC Class Codes: B23K 26/0624 using ultrashort pulses, i.e. pulses of 1ns or less
• CPC Class Codes: B23K 26/0626 Energy control of the laser beam B23K26/0622 takes precedence
• CPC Class Codes: B23K 26/38 by boring or cutting

Abstract

The invention relates to a method for removing material by means of a laser, wherein a sequence of laser pulses is generated and an area of material to be machined is irradiated with the sequence of laser pulses. Methods of this kind are used to cut a number of different materials. One problem with this method is that thermal or mechanical damage occurs in the surroundings of the area being machined and causes impairment of areas of material that are not being machined. The invention solves this problem by the pulse energy of a single pulse in the sequence of laser pulses being lower than the laser pulse energy required to produce material removal using an isolated laser pulse in the region irradiated with the single laser pulse of the sequence of laser pulses.

Claims

1. A method for removing material by means of a laser, wherein a sequence of laser pulses is generated and an area of material to be machined is irradiated with the sequence of laser pulses,

characterized in that the pulse energy of a single pulse in the sequence of laser pulses is lower than the laser pulse energy required to produce the removal of material by an isolated laser pulse in the area irradiated by the single pulse of the sequence of laser pulses.

2. The method of claim 1,

characterized in that the laser pulse energy is reduced by reducing the laser pulse intensity and/or the laser pulse duration.

3. The method of claim 1,

characterized in that the irradiated area is spatially overlapped by at least two consecutive laser pulses of the sequence of laser pulses.

4. The method of claim 3,

characterized in that the irradiated area is spatially overlapped to 100% by at least two consecutive laser pulses of the sequence of laser pulses, or to an extent ranging between 10% and 100%, preferably to about 70% to 99%, in particular to about 92% to 99%.

5. The method of claim 1,

characterized in that the laser pulse energy, the laser pulse intensity, the dimensions of the focused area, the laser pulse duration of a single laser pulse, the laser pulse repetition rate of the sequence of laser pulses and/or the feed speed between the laser beam and the material to be machined is preset according to the properties of the material.

6. The method of claim 1,

characterized in that the laser pulse repetition rate of the sequence of laser pulses is so high that at least two laser pulses are delivered to the material to be removed within a duration specific to the material to be removed.

7. The method of claim 6,

characterized in that the laser pulse repetition rate is greater than 10 Hz, in particular greater than 50 Hz, and is preferably between 100 Hz and 50 MHz.

8. The method of claim 1,

characterized in that the laser pulse energy, the laser pulse intensity, the dimensions of the focused area, the laser pulse duration of a single laser pulse, the laser pulse repetition rate of the sequence of laser pulses and/or the feed speed between the laser beam and the material to be machined is altered during the machining operation.

9. The method of claim 8,

characterized in that a first laser pulse energy is set for a first laser pulse repetition rate and a second laser pulse energy that is lower than the first laser pulse energy is set for a second laser pulse repetition rate that is higher than the first laser pulse repetition rate.

10. The method of claim 9,

characterized in that

a. the laser pulse repetition rate is automatically set according to the laser pulse energy, or

b. the laser pulse energy is automatically set according to the laser pulse repetition rate,

c. the laser pulse repetition rate is automatically set according to the feed speed, or

d. the laser pulse repetition rate, the laser pulse energy and/or the feed speed are automatically set according to at least one property of the material to be removed.

11. The method of claim 1,

characterized in that, in the starting region for the removal operation, the total energy introduced at one location on the material to be machined is greater than in a region during the further course of the removal operation.

12. The method of claim 1,

characterized in that the laser pulse energy and/or the laser pulse repetition rate is higher and/or the feed speed between the laser beam and the material to be machined is lower in the starting region for the removal operation than in the further course of the removal operation.

13. The method of claim 1,

characterized in that the laser pulse intensity is higher and/or the laser pulse duration of a single laser pulse in the starting region of the removal operation is longer than in a region during the further course of the removal operation.

14. The method of claim 1,

characterized in that the laser pulse duration is less than ten picoseconds, preferably less than one picosecond.

15. The method of claim 1,

characterized in that the laser beam is focused, preferably with an optical system having a numerical aperture that is at least so large that material removal is achieved under the surface of a semi or fully transparent material, without regions of material lying which are above or below the removal region being damaged.

16. The method

characterized in that the removal operation is observed and, if the removal performance declines, the total energy introduced is increased by altering one of the parameters referred to in claim 8.

17. A device for removing material, comprising

a means for generating a sequence of laser pulses

a means for guiding the laser pulses onto a region of material to be removed,

characterized in that the means for generating a sequence of laser pulses is configured in such a way that the pulse energy of a single pulse in the sequence of laser pulses is less than the laser pulse energy required to produce material removal using an isolated laser pulse in the region irradiated with the single laser pulse of the sequence of laser pulses.

18. The device of claim 17,

characterized in that means for generating the sequence of laser pulses is configured to reduce the laser pulse energy by reducing the laser pulse intensity and/or the laser pulse duration.

19. The device of claim 18,

characterized by feeding means for generating a relative movement between the laser beam and the material to be removed, and means for generating a laser pulse repetition rate, which cooperate in such a way that the irradiated region is spatially overlapped by two consecutive laser pulses of the sequence of laser pulses.

20. The device of claim 19,

characterized in that the feeding means and the means for generating a laser pulse repetition rate co-operate in such a way that the irradiated region is spatially overlapped to 100% by two consecutive laser pulses of the sequence of laser pulses, preferably to between 10% and 100% or to a range between 70% to 99%, in particular to between 92% and 99%.

21. The device of claim 17,

characterized by control means for setting the laser pulse energy, the laser pulse intensity, the laser pulse duration of a single laser pulse, the laser pulse repetition rate of the sequence of laser pulses, the dimensions of the focused area of the laser beam at the machining location, for example the diameter of the laser beam at the focus, and/or the feed speed between the laser beam and the material to be machined, according to the properties of the material.

22. The device of claim 21,

characterized in that the control means is configured in such a way that a first laser pulse energy is set for a first laser pulse repetition rate and a second laser pulse energy which is lower than the first laser pulse energy is set for a second laser pulse repetition rate which is higher than the first laser pulse repetition rate.

23. The device of claim 22,

characterized in that the control means is configured in such a way that the laser pulse repetition rate of the sequence of laser pulses is so high that, within a relaxation time of the material to be removed that is significant for the specific material, at least two laser pulses are delivered to the material to be removed.

24. The device of claim 23,

characterized in that the control means is configured in such a way that the laser pulse repetition rate size can be set to greater than 10 Hz, in particular to greater than 50 Hz and preferably to between 100 Hz and 50 MHz.

25. The device

characterized in that the control means is configured to alter at least one of the parameters listed in claim 21 during the machining operation.

26. The device of claim 25,

characterized in that the control means is configured in such a way that

a. the laser pulse repetition rate is automatically set according to the laser pulse energy, or

b. the laser pulse energy is automatically set according to the laser pulse repetition rate,

c. the laser pulse energy and/or the laser pulse repetition rate is automatically set according to the speed of movement, or

d. the laser pulse repetition rate, the laser pulse energy and/or the feed speed are automatically set according to at least one property of the material to be removed.

27. The device further comprising first control means,

characterized in that the control means is configured to control at least one of the parameters listed in claim 21 in such a way that the total energy introduced at one location on the material to be machined in the starting region of the removal operation is greater than in a region during the further course of the removal operation.

28. The device of claim 27,

characterized in that the control means is configured to set the laser pulse energy and/or the laser pulse repetition rate higher and/or the feed speed between the laser beam and the material to be machined lower in the starting region of the removal operation than in the further course of the removal operation.

29. The device of claim 28,

characterized in that the control means is configured to set the laser pulse intensity higher and/or the laser pulse duration of a single laser pulse longer in the starting region of the removal operation than in the further course of the removal operation.

30. The device of claim 29,

characterized in that the means for generating a sequence of laser pulses is configured to produce a laser pulse duration of less than ten picoseconds, preferably less than one picosecond.

31. The device of claim 30,

characterized by focusing means for focusing the laser beam, preferably with an optical system having a numerical aperture that is at least so large that material removal is achieved under the surface of a semi- or fully transparent material without regions of material lying above or below the removal region being damaged.

32. The device of

characterized by an observation device for observing the removal operation, said observation device co-operating with the means for generating a sequence of laser pulses, the means for guiding the laser pulses onto an area of material to be removed and/or with the feeding means in such a way that, if the removal performance declines, the total energy introduced is increased by altering at least one of the parameters referred to in claim 24.