Laser processing machine, laser cutting machine, and method for adjusting a focused laser beam

• US 9,289,852 B2
• Filed: 07/20/2013
• Issued: 03/22/2016
• Est. Priority Date: 01/27/2011
• Status: Active Grant

• Current Assignee: Bystronic Laser AG (Invico Asset Management AG)
• Original Assignee: Bystronic Laser AG (Invico Asset Management AG)
• Inventors: Luedi, Andreas, Cathry, Daniel
• Primary Examiner(s): Heinrich, Samuel M
• Application Number:
  US13/947,060
• Publication Number:
  US 20130334181A1
• Time in Patent Office: 976 Days
• Field of Search: 219/121.62, 219/121.67, 219/121.73, 219/121.81
• US Class Current: 1/1
• CPC Class Codes: B23K 26/04 Automatically aligning, aiming or focusing the laser beam, e.g. using the back-scattered light
• CPC Class Codes: B23K 26/042 Automatically aligning the laser beam
• CPC Class Codes: B23K 26/043 along the beam path, i.e. alignment of laser beam axis relative to laser beam apparatus
• CPC Class Codes: B23K 26/0626 Energy control of the laser beam B23K26/0622 takes precedence
• CPC Class Codes: B23K 26/073 Shaping the laser spot
• CPC Class Codes: B23K 26/1462 Nozzles; Features related to nozzles
• CPC Class Codes: B23K 26/34 Laser welding for purposes other than joining
• CPC Class Codes: B23K 26/38 by boring or cutting

Abstract

Laser processing machines and methods for adjusting focused laser beams. Laser processing heads have nozzle with openings admitting primary laser beam. An orientation device is included, as well as at least one sensor to mutually center primary beam and opening of nozzle. A first beam handling unit is arranged near the nozzle opening and may convert primary beam into a secondary wide-band heat beam, and then may emit this secondary beam towards a sensor; or may reflect/scatter at least a portion of the primary beam towards sensor. The sensor detecting the converted secondary beam is arranged within the laser processing head. In an adjustment process, a primary beam may be converted into a wide-band heat radiation as secondary radiation at the beam handling unit, and emitted and/or diverted into a scattered/reflex beam towards the sensor. Respective position of nozzle opening center and primary beam is calculated from sensor-measured values, and nozzle center and beam center are automatically displaced to mutual center. The axial position of beam focus may be also be measured and set via the nozzle centering procedure.

Claims

1. A laser processing machine comprising:

a laser processing head, said laser processing head having an interior, said interior having an interior wall, said interior wall being disposed about a central axis;

a nozzle associated with said laser processing head, said nozzle having a nozzle opening for a focused laser beam, said nozzle opening having at least one edge;

a beam handling unit disposed near said nozzle opening, said beam handling unit being made of a material converting a focused laser beam at said at least one nozzle opening edge to a wide-band heat beam, said beam handling unit positioned to emit the wide-band heat beam as a secondary electromagnetic radiation beam in a propagation direction back into said interior and away from said nozzle opening and said beam handling unit;

a beam reflector disposed in said laser processing head to reflect the secondary electromagnetic radiation beam; and

,

a plurality of radiation sensors, said plurality of radiation sensors being located to sense electromagnetic radiation through at least one hole in said interior wall, said plurality of radiation sensors each respectively disposed at a respective axial distance from said beam handling unit, said beam reflector being positioned to reflect the secondary electromagnetic radiation beam for sensing by at least one of said plurality of radiation sensors.

2. The laser processing machine as claimed in claim 1, wherein:

said nozzle is a special calibration nozzle releasably connected to said laser processing head, said calibration nozzle replacing a laser processing nozzle at said laser processing head.

3. The laser processing machine as claimed in claim 2, wherein:

said beam handling unit is a conversion ring arranged in said calibration nozzle.

4. The laser processing machine as claimed in claim 3, wherein:

said conversion ring is made of sapphire, and said conversion ring is located on said at least one edge of said nozzle opening.

5. The laser processing machine as claimed in claim 3, wherein:

said conversion ring is made of glass that absorbs CO₂ radiation.

6. A laser processing machine as claimed in claim 3, further comprising:

a reflection coating on said conversion ring.

7. The laser processing machine as claimed in claim 6, wherein:

said reflection coating is a gold coating.

8. A laser processing machine comprising:

a laser processing head, said laser processing head having an interior, said interior having an interior wall, said interior wall being disposed about a central axis;

an external centering accessory disposed outside of said laser processing head interior;

a beam conversion unit disposed on said external centering accessory, said beam conversion unit being made of a material that converts a focused laser beam exiting said laser processing head interior and impinging on said beam conversion unit into a wide-band heat beam, said beam conversion unit positioned to emit the wide-band heat beam as a secondary electromagnetic radiation beam in a propagation direction back into said interior and away from said external centering accessory and said beam conversion unit;

a beam reflector disposed in said laser processing head to reflect the secondary electromagnetic radiation beam; and

,

a plurality of radiation sensors, said plurality of radiation sensors being located to sense electromagnetic radiation through at least one hole in said interior wall, said plurality of radiation sensors each respectively disposed at a respective axial distance from said beam handling unit, said beam reflector being positioned to reflect the secondary electromagnetic radiation beam for sensing by at least one of said plurality of radiation sensors.

9. A laser processing machine as claimed in claim 8, further comprising:

at least one of said plurality of radiation sensors has a glass pane through which must pass electromagnetic radiation passing through said at least one hole in said interior wall, to said at least one of said plurality of radiation sensors from said laser processing head interior; and

,

said glass pane has a coating that exhibits high reflectivity for CO₂ laser radiation.

10. A laser processing machine comprising:

a laser processing head, said laser processing head having an interior, said interior having an interior wall, said interior wall being disposed about a central axis;

a nozzle configured to operatively connect to said laser processing head;

a beam handling unit disposed at said at least one nozzle edge, said beam handling unit being made of a material reflecting a focused laser beam at said at least one nozzle opening edge as a secondary electromagnetic radiation beam in a propagation direction back into said laser processing head interior and away from said nozzle opening and said beam handling unit;

a beam reflector disposed in said laser processing head to reflect the secondary electromagnetic radiation beam; and

,

a radiation detector, said radiation detector being located to directly sense secondary electromagnetic radiation of said secondary electromagnetic radiation beam through at least one hole in said interior wall, said radiation detector being disposed at a respective axial distance from said beam handling unit, said beam reflector being positioned to reflect the secondary electromagnetic radiation beam for sensing by said radiation detector.

11. A laser processing machine as claimed in claim 10, further comprising:

a focusing lens in said laser processing head, said radiation detector being disposed on an opposite of said focusing lens relative to said nozzle.

12. The laser processing machine as claimed in claim 10, wherein:

said radiation detector is a thermopile.

13. The laser processing machine as claimed in claim 10, wherein:

said radiation detector is an infrared detector configured to detect CO₂ radiation.

14. A process for aligning a focused laser beam comprising the steps of:

starting a laser work beam at a previously-recorded center location;

running the laser work beam towards a beam handling unit and a nozzle edge in a first direction;

sensing a secondary electromagnetic radiation beam by a sensor to indicate contact of the laser work beam with the beam handling unit;

saving the beam coordinates after said step of sensing a secondary electromagnetic radiation beam by a sensor to indicate contact of the laser work beam with the beam handling unit;

running the laser work beam at least two more times towards the beam handling unit and the nozzle edge in at least two additional directions to the first direction and saving corresponding beam coordinates;

calculating with the saved beam coordinates a new center location of the laser work beam in a nozzle; and

,

effecting a relative displacement of the nozzle center relative to the center of the laser work beam to mutually align their centers in the new center location calculated.

15. A process for aligning a focused laser beam as claimed in claim 14 further comprising the steps of:

providing the beam handling unit as a conversion ring; and

,

converting at least a portion of the laser work beam into a secondary electromagnetic radiation beam that is a wide-band heat beam emitted in propagation direction towards a beam reflector.

16. The process for aligning a focused laser beam as claimed in claim 15 wherein:

the step of providing the beam handling unit as a conversion ring includes the provision of a sapphire ring.

17. A process for aligning a focused laser beam as claimed in claim 16 further comprising the step of:

providing reflection coating as a gold coating on the sapphire ring.

18. A process for aligning a focused laser beam as claimed in claim 14 further comprising the step of:

reflecting at least a portion of the laser work beam as a secondary electronic radiation beam in propagation direction towards a beam reflector.

19. A process for aligning a focused laser beam as claimed in claim 14 further comprising the step of:

using successive nozzle-to-beam centering measurements to determine the axial position of the focus of the laser work beam.

20. A process for aligning a focused laser beam as claimed in claim 19 further comprising the steps of:

carrying out said step of using successive nozzle-to-beam centering measurements to determine the axial position of the focus of the laser work beam, at various laser powers to measure laser-induced thermal axial focus offset; and

,

correlating the measured laser-induced thermal axial focus offset to quality of the focusing lens, or to quality of the optical elements along the optical path, or to both the quality of the focusing lens and the quality of the optical elements along the optical path.