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EP-4739417-A1 - LASER PROCESSING SYSTEM, AND METHOD

EP4739417A1EP 4739417 A1EP4739417 A1EP 4739417A1EP-4739417-A1

Abstract

The present disclosure concerns a laser processing system with a laser processing machine, especially a laser processing machine equipped to generate the laser radiation with a power of at least 1 kW. The laser processing system further comprises a water-cooling unit (1) operable to cool at least one component of the laser processing machine. The water-cooling unit comprises a cooling water circuit for the cooling water and a protective gas supply for supplying a protective gas to the cooling circuit for bringing the cooling water in the cooling circuit in contact with the protective gas, such as Nitrogen or Argon. This will cause diffusion of oxygen out of the water due to the concentration gradient until an equilibrium with strongly reduced oxygen concentration in the water is reached. Thus, the simple measure of supplying a protective gas to the cooling water circuit causes the cooling water to be less corrosive and, because of the absence of oxygen, to prevent the growth of microorganisms.

Inventors

  • AMSTAD, Beat
  • GFELLER, ROBERT
  • Lüdi, Andreas

Assignees

  • Bystronic Laser AG

Dates

Publication Date
20260513
Application Date
20240813

Claims (15)

  1. 1. A laser processing system (200), comprising a laser processing machine equipped to generate laser radiation for impinging on a workpiece, the laser processing system further comprising a water-cooling unit (201) comprising a closed vessel (1) and a first cooling water line for supplying cooling water from the closed vessel (1) to at least one component of the laser processing machine and for directing the cooling water back to the closed vessel (1), characterized in that the water cooling unit further comprises a heat exchanger (2) and a second cooling water line for supplying cooling water from the closed vessel (1) to the heat exchanger (2) and back to the closed vessel (1), in that the closed vessel (1) has a gas volume (3) above a water volume (4), and in that the water-cooling unit (201) further comprises a protective gas supply (22) to supply a protective gas to the closed vessel (1).
  2. 2. The laser processing system of claim 1, wherein the protective gas supply (22) is a nitrogen supply.
  3. 3. The laser processing system of claim 1 or 2, wherein the protective gas supply (22) is equipped to supply the protective gas to the gas volume (3) and/or to supply the protective gas to the water volume (4) from where the protective gas bubbles up to the gas volume (3).
  4. 4. The laser processing system of any one of the previous claims, wherein the cooling unit (201) further comprises a measurement device for measuring an oxygen content and/or carbon dioxide content of the cooling water and/or of gas in the cooling water circuit.
  5. 5. The laser processing system according to any one of the previous claims being equipped to emit laser having a power of at least 1 kW.
  6. 6. The laser processing system according to any one of the previous claims, being a laser cutting system, wherein the laser processing machine is a laser cutting machine.
  7. 7. The laser processing system according to any one of the previous claims, wherein the water cooling unit (201) further comprises a microbubble resorber arranged along the first cooling water line.
  8. 8. The laser processing system according to any one of the previous claims, equipped to supply the protective gas to the closed vessel so as to subject the closed vessel to an over-pressure compared to ambient.
  9. 9. The laser processing system according to any one of the previous claims, being equipped and programmed to supply the protective gas intermittently.
  10. 10. A method of operating a laser processing system (200) according to any one of the previous claims, the method comprising the step of supplying the protective gas to the closed vessel until the gas volume is filled by the protective gas.
  11. 11. The method according to claim 10, wherein the protective gas is nitrogen gas.
  12. 12. The method according to claim 10 or 11, comprising the further step of measuring the content of oxygen and/or carbon dioxide in the cooling water and/or in gas in the cooling water circuit, and for example comprising the step of supplying fresh protective gas depending on a result of the step of measuring.
  13. 13. The method according to any one of claim 10-12, and comprising the step of supplying fresh protective gas intermittently, in regular intervals and/or depending on an operation mode.
  14. 14. The method according to any one of claims 1013, wherein an oxygen content in the protective gas is at most 200 ppm.
  15. 15. The method according to any one of claims 10-14, and comprising the step of keeping the cooling water in the first cooling water line free of bubbles.

Description

LASER PROCESSING SYSTEM, AND METHOD The invention is in the field of laser processing systems, in particular for laser cutting. Especially, it is in the field of laser processing machines, particularly laser cutting machines, with a laser power of 1 kW or more. Laser processing machines with high laser powers of 1 kW or more, especially laser cutting machines, usually require cooled components. Several components need to be cooled due to absorption of the laser power, especially components which are typically part of a laser processing head, especially of a laser cutting head. An optical aperture or mirror of such laser processing or cutting head that comes into contact with high laser power absorbs some 10W even with low absorption of 1% or less. In the case of optical shutters and optical apertures, which are used in such laser processing or cutting heads to selectively cut off edge parts of the laser beam, the absorbed laser power may well rise to several times 100 W. The absorbed laser power produces waste heat that must be dissipated by cooling the respective component. The laser source itself must also be well cooled. The efficiency of a typical laser source is between 10% and 50%. This means that in order to generate IkW laser beam power, at least 1 kW of waste heat is generated, which must be dissipated by cooling. In addition to the optical components, there are often motors of axes (robot axes, etc.) in processing systems that must be cooled. Cooling is usually done with water. Water has a large heat capacity, can absorb a lot of heat and is available worldwide. Often, a cooling unit is integrated in a laser processing machine or is placed in a vicinity thereof. The cooling unit supplies cooling water to the components to be cooled via a supply line. The cooling water thereby is heated up and returns to the cooling unit, where the cooling water is, for example via an air-water heat exchanger, cooled to its initial temperature. Water cooling has its disadvantages, too. Especially, the cooling water may cause corrosion of the components that come into contact with it. Also, microorganisms may develop in the water, and this may reduce the cooling capacity and clog or even block cooling channels. In order to reduce corrosion and to combat microorganisms, it has been known to add additives and inhibitors to the cooling water. Such chemicals reduce corrosion and the generation of microorganisms. However, they are poisonous, detrimental for the environment and subject to environmental regulations, as well as difficult to obtain and to ship. US 10,505,342 B2 discloses a laser device with microbubble-containing cooling water. The microbubbles are supposed to reduce management tasks by having an anticorrosion function and to increase the laser cavity cooling performance. US 8,141,620 Bl discloses a method for conditioning a cooling loop of a heat exchange system for apparatuses in electronics, automobile, avionics and spacecraft industries, in which the cooling loop is purged from oxygen with an inert gas, especially Nitrogen. The Nitrogen, when circulated in the cooling loop, may, according to US 8,141,620 Bl, go into solution with the coolant in the form of a dissolved gas forming micro-bubbles. The bubbly liquid, according to US 8,141,620 Bl enhances reliability and longevity of the heat exchange system. It is an object of the present invention to provide a laser processing system, in particular a laser processing system with a laser cutting machine, and a method of operating a laser processing system overcoming drawbacks of previous laser processing systems and operating methods. Especially, it is an aim to reduce corrosion and/or combat microorganisms in the cooling water lines of the laser processing system without the need for toxic chemicals and without adding too much complexity. According to an aspect of the present invention, a laser processing system is provided. The laser processing system comprises a laser processing machine being equipped to generate laser radiation that during operation impinges on a workpiece for processing the workpiece, for example for generating a cut in the workpiece. The laser processing machine is especially equipped to generate the laser radiation with a power of at least 1 kW. The laser processing system further comprises a water-cooling unit operable to cool at least one component of the laser processing machine. The water-cooling unit may belong to the laser processing machine or may be a separate unit. In embodiments, the laser processing system may consist of the laser processing machine, i.e., it is possible that all parts of the laser processing system are integrated in the laser processing machine and are for example controlled by the machine control of the laser processing machine. The laser processing machine may in particular be a sheet and/or tube metal laser processing machine. In particular, the laser processing machine may be a laser cutting mach