Laser processing system and method

Abstract

This disclosure relates to a laser processing system comprising a laser processing machine, and more particularly, a laser processing machine equipped to generate a laser beam with an output of at least 1 kW. The laser processing system further comprises a water cooling unit (1) capable of operating to cool at least one component of the laser processing machine. The water cooling unit comprises a water cooling circuit for cooling water and a protective gas supply unit that supplies a protective gas to the cooling circuit so as to bring the cooling water in the cooling circuit into contact with a protective gas such as nitrogen or argon. This causes oxygen to be released from the water by a concentration gradient until an equilibrium is reached in which the oxygen concentration in the water is significantly reduced. Thus, this simple measure of supplying a protective gas to the water cooling circuit makes the cooling water less corrosive and prevents the growth of microorganisms in the absence of oxygen.

Description

Technical Field

[0001] The present invention belongs to the field of laser processing systems, particularly the field of laser cutting. In particular, it belongs to the field of laser processing machines with a laser output of 1 kW or more, and more specifically, the field of laser cutting machines.

Background Art

[0002] Laser processing machines, particularly laser cutting machines, with a high laser output of 1 kW or more generally require cooling of components. Some components need to be cooled due to the absorption of laser output. In particular, components forming the part of the laser processing head, especially the laser cutting head, generally require cooling. In such optical apertures and mirrors of the laser processing or cutting head that are in contact with a high laser output, even with a low absorption of 1% or less, an absorption of about 10 W occurs. In the case of optical shutters and optical apertures used to selectively block the edge portion of the laser beam in such laser processing or cutting heads, the absorbed laser output can easily reach several hundred watts. The waste heat generated by the absorbed laser output needs to be dissipated by cooling each component.

[0003] The laser source itself also needs to be sufficiently cooled. The efficiency of a general laser source is between 10% and 50%. Therefore, to generate a laser beam output of 1 kW, at least 1 kW of waste heat that needs to be dissipated by cooling is generated.

[0004] In addition to optical components, motors of the shafts (such as robot shafts) of the processing system also often need to be cooled.

[0005] Cooling is usually performed with water. Water has a large heat capacity, can absorb a large amount of heat, and is available worldwide. In many cases, a cooling unit is incorporated into the laser processing machine or placed in its vicinity. The cooling unit supplies cooling water to the components to be cooled through a supply line. As a result, the cooling water is heated and returned to the cooling unit, where it is cooled to the initial temperature, for example, through an air / water heat exchanger.

[0006] Water cooling also has its drawbacks. In particular, the cooling water can cause corrosion of the parts it comes into contact with. Also, microorganisms can grow in the water. This can lead to a decrease in cooling capacity, clogging of the cooling pathways, and ultimately blockage.

[0007] Additives and inhibitors are known to be added to coolant to reduce corrosion and eliminate microorganisms. While such chemicals suppress corrosion and microbial growth, they are toxic, harmful to the environment, subject to environmental regulations, and difficult to obtain and transport.

[0008] Patent Document 1 discloses a laser device equipped with cooling water containing microbubbles. Microbubbles are thought to reduce maintenance work and improve laser cavity cooling performance by having corrosion-preventive properties.

[0009] Patent Document 2 discloses a method for regulating the cooling loop of a heat exchange system for equipment in the electronics, automotive, avionics, and spacecraft industries, in which oxygen is purged from the cooling loop using an inert gas, particularly nitrogen. According to Patent Document 2, as nitrogen circulates within the cooling loop, it can dissolve with the coolant in the form of a dissolved gas that forms microbubbles. According to Patent Document 2, this foamy liquid improves the reliability and lifespan of the heat exchange system. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] US 10,505,342B2 [Patent Document 2] US 8,141,620B1 [Overview of the project] [Problems that the invention aims to solve]

[0011] The object of the present invention is to provide a laser processing machine system, particularly a laser processing system equipped with a laser cutting machine, and a method for operating a laser processing system, which overcome the shortcomings of conventional laser processing systems and operating methods. In particular, the object is to reduce corrosion of the cooling water line of the laser processing system and / or eliminate microorganisms without requiring harmful chemicals and without significantly increasing complexity. [Means for solving the problem]

[0012] According to an aspect of the present invention, a laser processing system is provided. The laser processing system comprises a laser processing machine mounted to generate a laser beam that is directed onto a workpiece during operation for processing the workpiece, for example, to make an incision in the workpiece. The laser processing machine is particularly mounted to generate a laser beam with a power of at least 1 kW. The laser processing system further comprises a water cooling unit capable of cooling 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 a laser processing machine, i.e., all parts of the laser processing system may be integrated into the laser processing machine and controlled, for example, by the mechanical control of the laser processing machine.

[0013] A laser processing machine may, in particular, be a sheet and / or tube metal laser processing machine. In particular, a laser processing machine may be a laser cutting machine. More specifically, it may be a flatbed laser cutting machine or a tube laser cutting machine for cutting sheet metal.

[0014] The water-cooling unit includes a cooling water circuit for cooling water. Such a cooling water circuit includes a closed container for cooling water, a first cooling water line for supplying cooling water from the closed container to one or more parts of the laser processing machine and for moving the cooling water back to the closed container, and a second cooling water line for supplying cooling water from the closed container to a heat exchanger so that heat can be dissipated from the cooling water and returned to the closed container. The laser processing system further includes a protective gas supply unit for supplying protective gas to the closed container.

[0015] During operation, the entire volume of the enclosed container to which the protective gas is supplied is divided into a (lower) water portion and an (upper) gas portion, separated by the water surface. By supplying the protective gas to the enclosed container, the partial pressure of oxygen in the gas portion decreases (compared to air), which can lead to the diffusion of oxygen and / or other corrosive substances from the cooling water through the interface between the water portion and the gas portion within the enclosed container, as described above.

[0016] A closed container can be an aquarium.

[0017] Unlike an open bucket, a closed container is sealed to hold gas above the cooling water. However, the inside of the closed container does not need to be airtight. It can even be advantageous for some degree of intentional leakage to occur from the closed container. Due to temperature differences, evaporation, etc., the water level inside the closed container continues to change during operation. Therefore, the system needs to be able to adapt to such changes. Such adaptation can be achieved by a separate expansion container, known from heating systems, or a valve, possibly combined with a filter, or, as mentioned above, by tolerating some residual leakage. Certain leakage has the further advantage that when the protective gas is supplied to the cooling water circuit, no additional measures are needed to release the replaced air. The protective gas also diffuses from the closed container, so there is a disadvantage that the gas needs to be supplied continuously or at least frequently, but this is not serious. For example, nitrogen gas is inexpensive and readily available, and it is clear that releasing it into the atmosphere will have no adverse effect on the environment.

[0018] Therefore, the present invention provides a laser processing system that is installed to bring the cooling water in the cooling circuit into contact with a protective gas such as nitrogen or argon. This causes oxygen to be released from the water by a concentration gradient until an equilibrium is reached in which the oxygen concentration in the water is significantly reduced. The same applies to other corrosive substances such as carbon dioxide, which, when dissolved in the cooling water, make the cooling water acidic. Thus, a simple measure of supplying a protective gas to the cooling water circuit makes the cooling water less corrosive and prevents the growth of microorganisms due to the absence of oxygen.

[0019] Therefore, the present invention proposes to avoid corrosion and microbial growth by removing oxygen and, optionally, other corrosive substances from the cooling water through dissipation. This is more economical and practical than methods that completely seal the cooling circuit to isolate oxygen from the cooling water. Isolating oxygen from the cooling water requires completely closing the cooling water circuit, which is extremely difficult to achieve without irrational effort and requirements, considering that conventional seals, pipes, connections, and threaded fittings are usually not airtight, a tank with air volume (as expansion space) is required, and parts need to be replaced from time to time because the cooling water circuit needs to be opened for this purpose.

[0020] Unlike conventional methods that rely on microbubbles, the present invention proposes utilizing the effect of oxygen diffusion from cooling water when a partial pressure of oxygen in the gas comes into contact with the cooling water at the interface between water and gas (which can be the water surface in a closed container, or the inner surface of macroscopic bubbles in a closed container when gas bubbles up inside the container).

[0021] In particular, microbubbles have been shown to have adverse effects by causing long-term damage not only to pumps but also to some cooling components of laser cutting machines. They can also reduce thermal contact between the cooling water and the components being cooled, leading to decreased efficiency. Therefore, this invention proposes reducing the dissolved oxygen content in the cooling water by utilizing evaporation rather than using microbubbles.

[0022] In each embodiment, the water cooling unit includes a microbubble remover. The microbubble remover is positioned along a first coolant line, and in particular, upstream of the pump in the first coolant line, so that the coolant flows through the microbubble remover before reaching the pump in the first coolant line. The microbubble remover may be positioned so that the water flows through it before it reaches the components to be cooled, for example, before it reaches any components to be cooled (i.e., at the starting point of the first coolant line). Microbubble removers are known from heating systems for removing air contained in microbubbles from heat exchange liquids, etc. They are also sometimes called "microbubble absorbers," "microbubble separators," or "microbubble degassing devices" and are commercially available. The microbubble remover used in embodiments of the present invention may be made of, for example, plastic, aluminum, stainless steel, etc., and may not contain copper that comes into direct contact with the coolant.

[0023] The protective gas can be, for example, nitrogen. Nitrogen gas is inexpensive and readily available and is included in some form in most laser processing systems. For example, nitrogen is a common process gas in laser cutting machines. Other protective gases include argon or other gases (including mixtures) that are essentially oxygen-free, or have a significantly reduced oxygen content compared to air, for example, up to 3%, up to 1%, up to 0.5%, or up to 0.1%. Specific examples include nitrogen or argon (or mixtures thereof) with a maximum oxygen content of 500 ppm (parts per million), and in some cases, less than 100 ppm, less than 20 ppm, or less than 10 ppm. For example, so-called oxygen-free nitrogen contains less than 0.002% (20 ppm) of oxygen. Another characteristic of protective gases is that the carbon dioxide content is also significantly reduced compared to the carbon dioxide content of air (at least half, and especially at least one-tenth). Both the properties of being essentially oxygen-free and essentially carbon dioxide-free are characteristics of inexpensive industrial nitrogen gas.

[0024] A pumping system comprising at least one pump can generate turbulent flow in a closed container and expand the water surface during operation to pump water from the closed container and return it to the closed container, in addition to the stirring effect. As a result, the dissipation of oxygen and / or carbon dioxide from the cooling water is promoted, and the process of reaching equilibrium at a low oxygen / carbon dioxide concentration is accelerated.

[0025] The supply of the protective gas to the closed container can be carried out continuously, at a constant gas flow rate, or intermittently, depending on the tightness of the cooling water circuit, for example, only during laser processing, twice a day or once a day, once a week, etc., or only after opening the cooling water circuit for maintenance. Also, the oxygen content (or other indicators, such as pH value, carbonic acid content) of the gas in the water and / or gas portion is measured constantly or intermittently, and the gas can be supplied only when certain conditions are met, for example, when the measured value exceeds a threshold value.

[0026] The protective gas can be supplied directly to the gas portion of the closed container or can also be supplied to the lower part (i.e., the water portion) of the closed container. The latter can generate additional turbulent flow to promote the dissipation of oxygen from the water.

[0027] The closed container may be a storage container (water tank) dedicated to cooling water.

[0028] In addition to comprising a closed container and a first cooling water line or a plurality of cooling water lines, the water-cooling unit may also comprise at least one pump for pumping water from the closed container to the cooling target part(s) for cooling and then returning it to the closed container. Furthermore, it may optionally comprise a measuring device for measuring the characteristics of the cooling water and / or the gas in the closed container, such as the oxygen content of the cooling water, its pH value, and / or other characteristics of the cooling water, and / or the oxygen content and / or carbon dioxide content of the gas in the closed container.

[0029] Furthermore, the water-cooling unit comprises a cooling section having a heat exchanger and a second cooling water line for cooling the cooling water. Such a heat exchanger may be an air / water heat exchanger that releases heat to the environment by having cooling fins or similar. Alternatively, it may be a water / water heat exchanger that releases heat to secondary cooling water, which may be tap water or water in a secondary cooling circuit, and this heat is recovered for purposes such as heating. Further alternatively, it may belong to an active chiller that removes heat from the cooling water using, for example, the principle of a heat pump. The cooling section may comprise, for example, a cooling section pump distinct from at least one (first) pump that pressurizes the cooling water through the first cooling water line.

[0030] A significant advantage is gained by arranging the second cooling water line to supply cooling water to the heat exchanger and return it to a closed container, thereby creating a separate and independent cycle within the cooling section from the first cooling water line that includes the cooled components. In particular, by selectively selecting the appropriate mixture of cooling water returning directly from the cooling section and cooling water from the closed container, it becomes possible to supply cooling water at different temperatures to different components, such as cooling the laser source to a different temperature than the cooling temperature of the laser cutting head. This can be advantageous, for example, when the temperature of the laser cutting head is above the dew point, and the laser source is cooled to a lower temperature to avoid condensation of ambient moisture on the laser cutting head. In particular, in each embodiment, the cooling temperature of the laser cutting head is approximately 30°C, which is above the dew point in all climate regions for at least most of the year. At the same time, the method with a separate second cooling water line is optimal for the method with a closed container supplied with a protective gas. The closed container has a water portion and a gas portion, and it is possible to balance the cooling water portion without requiring advanced additional means.

[0031] In each embodiment, the system is configured to supply a protective gas to the sealed container under overpressure, i.e., the sealed container is under overpressure (compared to the ambient pressure) during the injection of the protective gas. In particular, the overpressure can be at least 5 millibars or at least 10 millibars, and can be between 5 and 50 millibars, for example between 10 and 30 millibars, for example, about 20 millibars. It has been confirmed that such overpressure during the injection of protective gas contributes significantly to the removal of initial oxygen from the cooling water.

[0032] Overpressure can be achieved and controlled, for example, by appropriately configuring an overpressure valve in a closed container that opens only when a target overpressure is reached. Furthermore / or, the flow to the closed container can be controlled so that overpressure is achieved, but this is an arbitrary example, and is also true in each embodiment where the closed container does not have an overpressure valve and simply has a leak.

[0033] The laser processing machines described herein may be equipped to emit a laser having an output of at least 1 kW, in particular at least 5 kW, or at least 10 kW.

[0034] The present invention relates not only to laser processing systems but also to methods for operating laser processing systems, such as those described and claimed herein. The method includes providing a laser processing system having a laser processing machine and a cooling unit mounted to cool at least one component of the laser processing machine by supplying cooling water. The method includes the steps of transporting cooling water from a closed container to a component(s) to be cooled such that a water portion and a gas portion above the water portion are present in the closed container, and supplying a protective gas to the closed container such that the gas portion is filled with the protective gas (i.e., substantially oxygen-free, i.e., the residual oxygen content in the gas portion is at most about 2% or about 1%, for example, less).

[0035] This method may further include the step of measuring the oxygen and / or carbon dioxide content of the gas in the cooling water and / or gas portion, as described above. Depending on the measurement results, for example, if the oxygen / carbon dioxide content exceeds a threshold, a new protective gas may be supplied. Furthermore / or, the new protective gas may be supplied intermittently, for example, periodically.

[0036] The supply of a new protective gas can be, for example, in a continuous flow, or in addition to / or in response to a measurement, also in response to the operating mode. For example, it is possible to switch off the laser processing system, especially the cooling unit, when it is not operating, and switch on when it is operating. Furthermore / or, the flow rate of the protective gas may be high after the switch is turned on and then decrease for a certain period of time after the machine starts operating. [Brief explanation of the drawing]

[0037] Embodiments of the present invention will be described in detail below with reference to the drawings. In the drawings, the same reference numerals indicate the same or similar components. [Figure 1] This diagram shows a laser processing system comprising a flatbed laser cutting machine and a cooling unit. [Figure 2] This figure shows a cooling unit for a laser processing system equipped with a flatbed laser cutting machine. [Figure 3] This figure shows the measurement results of the oxygen content in the cooling water. [Modes for carrying out the invention]

[0038] Figure 1 shows an example of a laser processing system 200 comprising a laser cutting machine 210 and a cooling unit 201. The laser cutting machine 210 comprises a laser source 204, a transmission fiber 206, a laser cutting head 203, and a laser cutting head movement mechanism. The workpiece 208 is supported by a work table (not shown in Figure 1). The laser cutting head movement mechanism comprises a bridge 202. The laser cutting head 203 is movable in a first horizontal direction relative to the bridge 202. The bridge 202 itself is also movable in a second horizontal direction relative to the work table and the workpiece 208, for example on a pair of rails 212. In operation, the laser cutting head 203 performs cutting by moving relative to the workpiece 208 and ejecting a laser cutting beam 214 downward and substantially perpendicular to the workpiece. The workpiece 208 may be a metal plate to be cut by the laser processing beam ejected from the laser cutting head. At least one component of the laser processing machine is cooled by a cooling unit, which supplies cooling water to the component via a supply line 11. In Figure 1, the laser source 204 and the laser cutting head 203 are shown to be cooled. Within the laser cutting head, components that may be irradiated by the laser, such as the aperture, nozzle, light shutter, and mirror, can be cooled directly by the cooling water. In some cases, the entire laser cutting head may also be cooled, for example, by thermal contact with its casing. Furthermore, at least one other component, such as a motor for moving the bridge and / or a motor for moving the laser cutting head relative to the bridge and work table, can also be cooled. When multiple components are cooled, the cooling water may flow between the components (series arrangement), and / or multiple supply pipes may lead the cooling water to different components or groups of components (parallel arrangement, schematically shown in Figure 1). A return line 12 is also shown in Figure 1.

[0039] In each embodiment, the cooling unit is positioned near the laser source to prevent the cooling line to the laser source and beyond from becoming too long. The length is typically 2 meters or more. Meanwhile, the cooling water circuit to the cutting head, including the return flow, may be at least 20 meters long.

[0040] The cooling water circuit of the cooling unit includes a closed container 1, i.e., a water tank, as shown in Figure 2. A pump 13 located in the supply line 11 pumps cooling water from the closed container 1 to the component 17 for cooling. Figure 2 also shows an optional sensor 18, for example, to measure the oxygen content. In Figure 2, the pump 13 is shown located in the supply line 11 and the optional sensor 18 is shown located in the return line 12. However, this is not a mandatory requirement. The pump 13 may also be located in the return line 12, and / or the optional sensor 18 may be located in the supply line. Figure 2 further shows a possible microbubble remover 19. This is placed so that the cooling water flows before it flows to the component being cooled, and also before it flows through the pump 13, for example. This protects these devices from the adverse effects of microbubbles in the cooling water.

[0041] In each embodiment, not all components to be cooled are located within the same cooling water circuit; rather, each component is provided with a designated pump, and there may be multiple cooling water circuits, each having a first cooling water line as defined herein.

[0042] In each embodiment, the flow of cooling water to the laser source is considerably faster than the flow of cooling water to the laser cutting head, for example, between 10 and 100 times faster. The flow of cooling water to the linear motor (if present) is also slower than the flow to the laser source, but can be faster than the flow to the laser cutting head. Depending on the laser power used and experience and / or experiment, the flow of cooling water to different components may be adapted.

[0043] Figure 2 shows a second circuit comprising a heat exchanger 2, a heat exchanger supply line 25, and a heat exchanger return line 26. The second circuit may also include a pump (not shown) for pressurizing cooling water to the heat exchanger and returning it to the closed container 1. The heat exchanger 2 is structured to allow heat exchange between the cooling water and air for cooling the cooling water. A liquid / liquid heat exchanger or an active cooler may also be used, in which case the heat exchanger would be part of it.

[0044] Furthermore, an additional heat exchanger can be placed, for example, on the return line 12 of the cooling water circuit.

[0045] In each embodiment, the temperature of the cooling water that cools the laser source may differ from the temperature of the cooling water that cools the cooling portions of the laser cutting head and / or other components that come into contact with the outside air. In these embodiments, the temperature of the cooling water supplied to different first cooling water lines may differ, for example, by mixing a target proportion of cooling water from the heat exchanger return line 26 with the cooling water from the closed container 1.

[0046] The enclosed container 1 is filled with cooling water up to the cooling water level 9 to form a water portion 4, and a gas portion 3 is formed above the water level 9. In the illustrated embodiment, a gas supply line 22 for supplying protective gas opens into the gas portion 3. In the illustrated embodiment, the protective gas (e.g., nitrogen) is shown to be supplied from a protective gas container 21, i.e., a gas cylinder, belonging to the laser processing system itself. However, the protective gas may also be taken from the gas piping of a facility that has a central gas storage facility and / or a nitrogen gas production facility, in which the laser processing system is incorporated.

[0047] Figure 2 also schematically shows an optional overpressure valve 41. The overpressure valve may be configured to open when the pressure inside the sealed container 1 exceeds the ambient pressure by a preset pressure difference, for example, several millibars or tens of millibars. This allows any remaining air to be quickly discharged as soon as the sealed container 1 (more precisely, its gas portion 3) is filled with protective gas during initial adjustment. On the other hand, if the protective gas is supplied intermittently rather than continuously, for example at regular intervals or whenever the oxygen content exceeds a threshold, it may be preferable, particularly for efficiency reasons, for the protective gas to remain in the sealed container thereafter.

[0048] The protective gas may be nitrogen. Alternatively, it may be another gas composition with significantly reduced oxygen and / or carbon dioxide content compared to air.

[0049] The effect of supplying protective gas to a closed container is as follows: The protective gas replaces the air in the gas portion above the cooling water. This reduces the partial pressure of oxygen and other gases not contained in the protective gas. As long as these gases are dissolved in the cooling water, they will dissipate from the cooling water at the water-gas interface (particularly the surface defining water level 9) until an equilibrium is reached where the content of these gases in the cooling water is significantly reduced.

[0050] Figure 3 shows the measurement results of the oxygen content in cooling water in ppb (parts per billion) based on time t. The oxygen content in the cooling water is 4 to 5 ppm (parts per million, i.e., equivalent to 4 to 5 mg / l). From the first time point 31, the tank is filled with nitrogen gas (industrial quality, oxygen content less than 500 ppm, and in some cases less than 100 ppm, less than 20 ppm, or less than 10 ppm). The oxygen concentration in the cooling water rapidly decreases for about 2 to 4 hours after reaching a new equilibrium at the first time point 31, with the oxygen content falling well below 100 ppb, approaching the detection limit of the sensor used. The inflow of nitrogen gas into the closed tank continues until the second time point 32. The tank is an example of a closed container that is not completely airtight, and the inflow of nitrogen gas into the tank creates a constant flow of gas from the water container. After the inflow of nitrogen gas into the container stops at the second time point, the oxygen concentration in the tank slowly rises again. This is because the cooling water is constantly moving within the tank, and consequently, the gas continues to move above the cooling water surface. This movement promotes the exchange of gas within the tank with the surrounding air, increasing the oxygen concentration in the gas, and consequently increasing the oxygen concentration in the cooling water. In addition, the cooling water can come into contact with oxygen in other parts of the cooling circuit. When the oxygen concentration in the cooling water is low, the oxygen content tends to increase due to diffusion. There is a 24-hour time difference between the first time point 31 and the second time point 32.

[0051] Furthermore, experiments were conducted with the cooling water circuit turned off to investigate how much the oxygen concentration would rise when there was no water movement due to the cooling water flow. It was confirmed that the increase in oxygen concentration was significantly slower than when the cooling circuit was on. The oxygen concentration rose to approximately 200 ppb after 24 hours, to 400 ppb after 4 days, and the increase was limited to 600 ppb after 10 days. This indicates that, depending on the settings, the flow of protective gas can be easily turned off during long periods of operation interruption, such as weekends, without a significant increase in the oxygen concentration in the cooling water.

[0052] The process dynamics shown in Figure 3 are influenced by the fact that the water pump actively pumps water at a relatively high throughput, which generates turbulence in the water, thereby facilitating the process to reach an equilibrium where the oxygen content in the cooling water becomes very low. In other settings where this process is too slow without additional measures, options would include actively agitating the cooling water or designing a closed vessel to expand the water-gas interface.

[0053] In the embodiment described above, nitrogen gas is supplied directly to the closed container 1, i.e., the gas portion 3 at the top of the water tank. Alternatively, a protective gas can also be supplied to the water portion, causing bubbles to form in the gas portion. This alternative measure also facilitates the process of reaching a new equilibrium because the water is thus agitated and its surface area is increased.

[0054] In each embodiment, unlike the embodiment in which the experiment was conducted, access may be temporarily opened to release the replaced air when supplying protective gas to the closed container. Furthermore, once the tank is filled with protective gas, it is possible to provide an opening for releasing air equipped with a mechanism such as a check valve to ensure that air does not escape back into the tank. For example, in each embodiment, as mentioned above, if there is a small leak at the top of the tank, the simplest option may be to install a device that ensures a constant flow of protective gas into the tank, always causing a slight overpressure in the air area.

Claims

1. A laser processing system (200) comprising a laser processing machine mounted to generate a laser beam to be applied to a workpiece, The water cooling unit (201) further comprises a closed container (1) and a first cooling water line for supplying cooling water from the closed container (1) to at least one component of the laser processing machine and for moving the cooling water back to the closed container (1), The aforementioned water cooling unit is Heat exchanger (2), The system further includes a second cooling water line for supplying cooling water from the closed container (1) to the heat exchanger (2) and returning it to the closed container (1), The sealed container (1) has a gas portion (3) above the water portion (4), The water cooling unit (201) further comprises a protective gas supply unit (22) that supplies protective gas to the closed container (1). A laser processing system (200) characterized by the following features.

2. The laser processing system according to claim 1, wherein the protective gas supply unit (22) is a nitrogen supply unit.

3. The laser processing system according to claim 1 or 2, wherein the protective gas supply unit (22) is installed to supply the protective gas to the gas portion (3) and / or to supply the protective gas to the water portion (4) such that the protective gas bubbles up toward the gas portion (3) above.

4. The laser processing system according to any one of claims 1 to 3, wherein the water cooling unit (201) further comprises a measuring device for measuring the oxygen content and / or carbon dioxide content of the cooling water and / or gas in the cooling water circuit.

5. A laser processing system according to any one of claims 1 to 4, which is mounted to emit a laser with an output of at least 1 kW.

6. A laser cutting system, The aforementioned laser processing machine is a laser cutting machine. A laser processing system according to any one of claims 1 to 5.

7. The laser processing system according to any one of claims 1 to 6, wherein the water cooling unit (201) further comprises a microbubble remover disposed along the first cooling water line.

8. The laser processing system according to any one of claims 1 to 7, wherein the protective gas is supplied to the closed container so as to apply excessive pressure to the outside air to the closed container.

9. A laser processing system according to any one of claims 1 to 8, which is fitted and programmed to intermittently supply the protective gas.

10. A method for operating a laser processing system (200) according to any one of claims 1 to 9, comprising the step of supplying the protective gas to the closed container until the protective gas is filled to the gas portion.

11. The method according to claim 10, wherein the protective gas is nitrogen gas.

12. The method according to claim 10 or 11, further comprising the step of measuring the oxygen and / or carbon dioxide content in the cooling water and / or gas in the cooling water circuit, and, for example, the step of supplying a new protective gas depending on the result of the measuring step.

13. The method according to any one of claims 10 to 12, comprising the step of supplying a new protective gas intermittently, at regular intervals, and / or according to the operating mode.

14. The method according to any one of claims 10 to 13, wherein the oxygen content in the protective gas is a maximum of 200 ppm.

15. The method according to any one of claims 10 to 14, comprising the step of keeping the cooling water in the first cooling water line free from the generation of bubbles.

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