Laser beam irradiation method and laser processing machine

Abstract

Even if the nozzle temperature rises, it does not affect the laser beam power at the processing point, preventing a decrease in processing speed and quality. [Solution] The laser processing machine 1 includes a processing head 3 that irradiates a workpiece W with a laser beam, a temperature sensor 5 that detects the temperature of a nozzle 15 provided at the tip of the processing head 3, and a control unit 17 that adjusts the focal position of the laser beam based on the temperature of the nozzle 15 detected by the temperature sensor 5. The control unit 17 adjusts the focal position of the laser beam so that the temperature of the nozzle 15 is within the temperature range when the temperature of the nozzle 15 is outside a predetermined temperature range.

Description

【Technical Field】 , , , , , 【0004】 , 【0006】 , , , , 【0005】 , , , , , 【0003】 , , , , 【0001】 The present invention relates to a method of irradiating a laser beam and a laser processing machine. 【Background Art】 【0002】 Patent Document 1 describes a processing head of a laser processing machine in which a ceramic layer is provided on the outer peripheral surface of the tip of a nozzle body, and a temperature sensor is embedded in the ceramic layer. When the temperature sensor of the laser processing machine of Patent Document 1 detects a temperature higher than a predetermined temperature, the intensity of the laser beam is adjusted to be weakened. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Patent Laid-Open No. 3-27889 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 However, when the temperature of the nozzle rises and the intensity of the laser beam is adjusted, it affects the power of the laser beam at the processing point, which may cause a decrease in the processing speed and processing quality. 【Means for Solving the Problems】 【0005】 A first aspect of one or more embodiments is a method of irradiating a laser beam that detects the temperature of a nozzle provided at the tip of a processing head that irradiates a workpiece with a laser beam, and when the detected temperature of the nozzle is outside a predetermined temperature range, adjusts the focal position of the laser beam so that the temperature of the nozzle is within the temperature range. 【0006】 A second aspect of one or more embodiments is a laser processing machine comprising: a processing head for irradiating a workpiece with a laser beam; a temperature sensor for detecting the temperature of a nozzle provided at the tip of the processing head; and a control unit for adjusting the focal position of the laser beam based on the temperature of the nozzle detected by the temperature sensor, wherein the control unit adjusts the focal position of the laser beam so that the temperature of the nozzle falls within a predetermined temperature range when the temperature of the nozzle is outside that range. [Effects of the Invention] 【0007】 According to one or more embodiments of the laser beam irradiation method, even if the nozzle temperature rises, it does not affect the power of the laser beam at the processing point, and a decrease in processing speed and processing quality can be prevented. [Brief explanation of the drawing] 【0008】 [Figure 1] Figure 1 shows the configuration of a laser processing machine according to the first embodiment. [Figure 2A] Figure 2A is a flowchart showing the processing procedure for cutting using a laser processing machine according to the first embodiment. [Figure 2B] Figure 2B is a flowchart illustrating the processing procedure of the cutting process using a laser processing machine according to the first embodiment, following Figure 2A. [Figure 3] Figure 3 shows the structure of a processing head equipped with a temperature sensor according to the first modified example. [Figure 4] Figure 4 shows the structure of a processing head equipped with a temperature sensor according to a second modified example. [Figure 5] Figure 5 shows the configuration of a laser processing machine according to the second embodiment. [Figure 6A] Figure 6A is a flowchart showing the processing procedure for cutting using a laser processing machine according to the second embodiment. [Figure 6B] Figure 6B is a flowchart showing the processing procedure of the cutting process using a laser processing machine according to the second embodiment, following Figure 6A. [Figure 6C] Figure 6C is a flowchart showing the processing procedure of the cutting process using a laser processing machine according to the second embodiment, following Figure 6B. [Modes for carrying out the invention] 【0009】 [First Embodiment] [Configuration of a laser processing machine] The laser processing machine and the laser beam irradiation method according to the first embodiment will be described below with reference to the drawings. Figure 1 is a diagram showing the configuration of the laser processing machine. As shown in Figure 1, the laser processing machine 1 comprises a processing head 3, a temperature sensor 5, an NC (Numerical Control) device 7, and a laser oscillator 9. The laser processing machine 1 is a device that emits a laser beam from the laser oscillator 9 and performs laser cutting on a workpiece W. Typically, the workpiece W is sheet metal. 【0010】 The processing head 3 irradiates the workpiece W with a laser beam. Specifically, the processing head 3 is connected to the laser oscillator 9 via a process fiber 10, and irradiates the surface of the workpiece W from above with a laser beam emitted from the laser oscillator 9. The processing head 3 is equipped with a temperature sensor 5, a bend mirror 11, a focusing lens 13, and a nozzle 15. 【0011】 The temperature sensor 5 detects the temperature of the nozzle 15 located at the tip of the machining head 3. Specifically, the temperature sensor 5 is a radiation thermometer positioned at the upper end of the machining head 3, and it detects the temperature of the inner wall surface of the nozzle 15 non-contact from the back of the bend mirror 11. 【0012】 The NC device 7 is a control device that drives the machining head 3 to control the cutting process of the workpiece W, and includes a control unit 17. The NC device 7 adjusts the laser beam according to the machining method and the material of the workpiece W, and performs control to focus the laser beam with the bend mirror 11 and focusing lens 13 and irradiate the upper surface of the workpiece W. 【0013】 The control unit 17 is a controller that adjusts the focal position of the laser beam based on the temperature of the nozzle 15 detected by the temperature sensor 5. In the present embodiment, the focal position of the laser beam is set above the opening of the nozzle 15. However, even when the focal position is set below the opening of the nozzle 15, the control according to the present embodiment can be applied. 【0014】 When the temperature of the nozzle 15 is outside the range of a predetermined temperature region, the control unit 17 adjusts the focal position of the laser beam so that the temperature of the nozzle 15 is within the range of the predetermined temperature region. Specifically, when the temperature of the nozzle 15 is higher than the predetermined temperature region, the control unit 17 lowers the focal position, and when the temperature of the nozzle 15 is lower than the predetermined temperature region, the control unit 17 raises the focal position. 【0015】 The predetermined temperature region is obtained by experiment or simulation as a temperature range in which normal cutting can be performed without occurrence of processing defects or nozzle breakage. The upper limit value of this temperature region is set within the range of 100°C ± 20°C. When it is higher than this upper limit value, there is a high possibility that the laser beam interferes excessively with the nozzle 15, causing burning or melting of the nozzle 15. On the other hand, the lower limit value of the temperature region is set within the range of the outside air temperature ± 10°C. When it is lower than this lower limit value, there is a high possibility that processing defects such as a rough cut surface occur. The outside air temperature may be obtained from a thermometer that measures the air temperature at the location where the laser processing machine 1 is installed. 【0016】 The control unit 17 is constituted by a controller having a memory, a processor such as a CPU (Central Processing Unit), and various interfaces. The memory and the various interfaces are connected to the processor via a bus. By executing a program stored in the memory by the processor, the control unit 17 executes a process of irradiating the workpiece W with a laser beam for cutting. 【0017】 The laser oscillator 9 is a fiber laser oscillator, a YAG laser oscillator, or the like, which oscillates a laser beam and supplies it to the processing head 3. The laser beam supplied from the laser oscillator 9 is transmitted to the processing head 3 by the process fiber 10. The laser beam with divergent light emitted from the emission end of the process fiber 10 is converted into parallel light (collimated light) by a collimating device composed of a single lens or a combination lens (not shown). The parallel laser beam is reflected by the bend mirror 11, the traveling direction is bent by 90 degrees, and is focused by the focusing lens 13 and irradiated onto the workpiece W. However, the configuration of the bend mirror 11 may be omitted according to the configuration of the optical system, or the angle and the number may be different. 【0018】 The laser processing machine 1 is equipped with devices necessary for cutting the workpiece W. Specifically, it includes a nozzle temperature measuring device 21, a processing head driving device 23, an assist gas supply device 25, a lens adjusting device 27, and a following adjusting device 29. 【0019】 The nozzle temperature measuring device 21 acquires the data detected by the temperature sensor 5, calculates the temperature of the inner wall surface of the nozzle 15, and outputs it to the NC device 7. The processing head driving device 23 moves the processing head 3 to the position where the surface of the workpiece W is irradiated with the laser beam according to the processing program. The assist gas supply device 25 supplies an optimal assist gas to the inside of the processing head 3 according to the processing method of the workpiece W, and injects the assist gas coaxially with the laser beam from the tip of the nozzle 15. The following adjusting device 29 detects minute irregularities on the workpiece W in a non-contact manner, and executes control to raise and lower the processing head 3 so as to keep the distance between the nozzle 15 and the workpiece W constant. 【0020】 The lens adjusting device 27 adjusts the focal position of the laser beam by moving the focusing lens 13 up and down according to the control of the control unit 17. However, the lens adjusting device 27 may adjust the focal position of the laser beam by changing the curvature of the bend mirror 11, or may adjust the focal position of the laser beam with a collimating device (not shown). 【0021】 [Cutting process] Next, the cutting process using the laser processing machine 1 according to the first embodiment will be described. Figures 2A and 2B are flowcharts showing the processing procedure for the cutting process. As shown in Figure 2A, in step S101, the control unit 17 moves the processing head 3 to the processing point according to the processing program. 【0022】 In step S103, the control unit 17 sets the optical system, such as mirrors and lenses, for the piercing process, and proceeds to step S105 to start the piercing process. Simultaneously with the start of the piercing process, the control unit 17 starts measuring the temperature of the nozzle 15 using the temperature sensor 5. However, if cutting is to be started from the end of the workpiece W, piercing is not necessary, so in that case, the process starts from step S121, which will be described later. 【0023】 In step S107, the control unit 17 determines whether the temperature rise of the nozzle 15 is less than 100°C / second. For example, the control unit 17 measures the temperature rise of the nozzle 15 to determine whether the laser beam has interfered excessively with the nozzle 15 after the start of piercing, causing the temperature of the nozzle 15 to rise rapidly. If the temperature rise of the nozzle 15 is less than 100°C / second, the process proceeds to step S109. If the temperature rise of the nozzle 15 is 100°C / second or more, an alarm is issued and the process is stopped, ending the cutting process according to this embodiment. 【0024】 In step S109, the control unit 17 determines whether the focal position for piercing is within the appropriate focal range. The appropriate focal range is determined and set by experimentation or simulation to determine the range of focal positions that can meet the required quality. Therefore, if the focal position is within the appropriate focal range, piercing can be performed normally, but if it is outside the appropriate focal range, there is a risk of some kind of processing defect occurring. If the focal position is within the appropriate focal range, the control unit 17 proceeds to step S111, and if the focal position is outside the appropriate focal range, it issues an alarm and stops the processing, ending the cutting process according to this embodiment. 【0025】 In step S111, the control unit 17 determines whether the temperature of the nozzle 15 is 100°C or less. That is, the control unit 17 determines whether the temperature of the nozzle 15 is below the upper limit of the temperature range. The temperature range is the temperature range in which piercing can be performed normally without processing defects or nozzle damage, which has been determined through experimentation or simulation. 【0026】 For example, if the temperature of the nozzle 15 is higher than the upper limit of the temperature range, the laser beam may interfere excessively with the nozzle 15, increasing the likelihood of burning or melting of the nozzle 15. On the other hand, if the temperature of the nozzle 15 is lower than the lower limit of the temperature range, there is a higher possibility of processing defects such as a rough cut surface. 【0027】 The upper limit of the temperature range should be set within the range of 100°C ± 20°C, but here it is set to 100°C as an example. If the temperature of the nozzle 15 is higher than 100°C, the process proceeds to step S113; if the temperature of the nozzle 15 is 100°C or lower, the process proceeds to step S115. 【0028】 In step S113, the control unit 17 lowers the focal position of the piercing by 0.5 mm and returns to step S109. This reduces interference of the laser beam with the inner surface of the nozzle 15, thereby lowering the temperature of the nozzle 15. However, the amount of change in the focal position of the piercing can be changed to a value other than 0.5 mm depending on temperature changes and the device configuration. 【0029】 In step S115, the control unit 17 determines whether the temperature of the nozzle 15 is 0°C or higher. That is, the control unit 17 determines whether the temperature of the nozzle 15 is above the lower limit of the temperature range. The lower limit of the temperature range can be set within the range of 0°C ± 10°C, but here it is set to 0°C as an example. If the temperature of the nozzle 15 is lower than 0°C, the process proceeds to step S117; if the temperature of the nozzle 15 is 0°C or higher, the process proceeds to step S119. 【0030】 In step S117, the control unit 17 raises the focal position of the piercing by 0.5 mm and returns to step S109. This increases the interference of the laser beam with the inner surface of the nozzle 15, thereby increasing the temperature of the nozzle 15. However, the amount of change in the focal position of the piercing can be changed to a value other than 0.5 mm depending on the temperature change and the equipment configuration. 【0031】 In step S119, the control unit 17 determines whether the piercing process is complete or not. If the piercing process is not complete, it returns to step S109. If the piercing process is complete, it terminates the temperature measurement of the nozzle 15 and proceeds to step S121. 【0032】 Moving to Figure 2B, in step S121, the control unit 17 sets the optical system, such as mirrors and lenses, for the cutting process, and then proceeds to step S123 to start the cutting process. Simultaneously with the start of the cutting process, the control unit 17 starts measuring the temperature of the nozzle 15 using the temperature sensor 5. 【0033】 In step S125, the control unit 17 determines whether the temperature rise of the nozzle 15 is less than 100°C / second. For example, the control unit 17 measures the temperature rise of the nozzle 15 to determine whether the laser beam has interfered excessively with the nozzle 15 after the start of the cutting process, causing the temperature of the nozzle 15 to rise rapidly. If the temperature rise of the nozzle 15 is less than 100°C / second, the process proceeds to step S127. If the temperature rise of the nozzle 15 is 100°C / second or more, an alarm is issued and the process is stopped, ending the cutting process according to this embodiment. 【0034】 In step S127, the control unit 17 determines whether the focal position of the cutting process is within the appropriate focal range. The appropriate focal range is determined and set by experiment or simulation to be the range of focal positions that can satisfy the required cutting quality. Therefore, if the focal position is within the appropriate focal range, the cutting process can be performed normally, but if the focal position is outside the appropriate focal range, there is a risk of some kind of processing defect occurring. If the focal position is within the appropriate focal range, the control unit 17 proceeds to step S129, and if the focal position is outside the appropriate focal range, it issues an alarm and stops the processing, terminating the cutting process according to this embodiment. 【0035】 In step S129, the control unit 17 determines whether the temperature of the nozzle 15 is 100°C or less. That is, the control unit 17 determines whether the temperature of the nozzle 15 is below the upper limit of the temperature range. The temperature range is the temperature range in which cutting can be performed normally without processing defects or nozzle damage, which has been determined through experimentation or simulation. 【0036】 For example, if the temperature of the nozzle 15 is higher than the upper limit of the temperature range, the laser beam may interfere excessively with the nozzle 15, increasing the likelihood of burning or melting of the nozzle 15. On the other hand, if the temperature of the nozzle 15 is lower than the lower limit of the temperature range, there is a higher possibility of processing defects such as a rough cut surface. 【0037】 The upper limit of the temperature range should be set within the range of 100°C ± 20°C, but here it is set to 100°C as an example. If the temperature of the nozzle 15 is higher than 100°C, the process proceeds to step S131; if the temperature of the nozzle 15 is 100°C or lower, the process proceeds to step S133. 【0038】 In step S131, the control unit 17 lowers the focal position of the cutting process by 0.1 mm and returns to step S127. This reduces interference of the laser beam with the inner surface of the nozzle 15, thereby lowering the temperature of the nozzle 15. However, the amount of change in the focal position of the cutting process can be changed to a value other than 0.1 mm depending on temperature changes and the device configuration. 【0039】 In step S133, the control unit 17 determines whether the temperature of the nozzle 15 is 30°C or higher. That is, the control unit 17 determines whether the temperature of the nozzle 15 is above the lower limit of the temperature range. 【0040】 The lower limit of the temperature range can be set within ±10°C of the ambient temperature, but here it is set to 30°C as an example. If the temperature of the nozzle 15 is lower than 30°C, the process proceeds to step S135; if the temperature of the nozzle 15 is 30°C or higher, the process proceeds to step S137. 【0041】 In step S135, the control unit 17 raises the focal position of the cutting process by 0.1 mm and returns to step S127. This increases the interference of the laser beam with the inner surface of the nozzle 15, thereby increasing the temperature of the nozzle 15. However, the amount of change in the focal position of the cutting process can be changed to a value other than 0.1 mm depending on the temperature change and the device configuration. 【0042】 In step S137, the control unit 17 determines whether the cutting process is complete or not. If the cutting process is not complete, it returns to step S127. If the cutting process is complete, it terminates the temperature measurement of the nozzle 15 and ends the cutting process according to this embodiment. 【0043】 [Differentiation] In Figure 1, the temperature sensor 5 is positioned at the upper end of the machining head 3, but the temperature sensor 5 can also be positioned at other locations. For example, as shown in the first modified example in Figure 3, the temperature sensor 5 may be positioned near the nozzle 15. Specifically, the temperature sensor 5 is positioned at the tip of the machining head 3 and directly detects the temperature of the nozzle 15 using a contact-type thermometer such as a thermocouple. 【0044】 Alternatively, as shown in the second modified example in Figure 4, the temperature sensor 5 may be placed on the side of the processing head 3. Specifically, the temperature sensor 5 is a radiation thermometer placed on the side of the tip of the processing head 3, and it detects the temperature of the inner wall surface of the nozzle 15 from the side of the processing head 3 without contact. 【0045】 [Effects of the First Embodiment] As described in detail above, in the laser processing machine 1 according to the first embodiment, if the temperature of the nozzle 15 provided at the tip of the processing head 3 is outside a predetermined temperature range, the laser beam's focal position is adjusted so that the temperature of the nozzle 15 is within the temperature range. As a result, even if the temperature of the nozzle 15 rises, the focal position is adjusted rather than the intensity of the laser beam, so the power of the laser beam at the processing point is not affected, and a decrease in processing speed and processing quality can be prevented. 【0046】 Furthermore, the laser processing machine 1 according to the first embodiment lowers the focal position when the temperature of the nozzle 15 is higher than the temperature range, and raises the focal position when the temperature of the nozzle 15 is lower than the temperature range. As a result, when the temperature of the nozzle 15 is high, interference of the laser beam with the inner surface of the nozzle 15 can be reduced, thereby lowering the temperature of the nozzle 15. On the other hand, when the temperature of the nozzle 15 is low, interference of the laser beam with the inner surface of the nozzle 15 can be increased, thereby raising the temperature of the nozzle 15. 【0047】 Furthermore, in the laser processing machine 1 according to the first embodiment, the focal position of the laser beam is set above the opening of the nozzle 15. This allows the laser beam to interfere with the nozzle 15 and irradiate the workpiece W. By appropriately interfering the laser beam with the nozzle 15, the cutting quality can be improved. 【0048】 Furthermore, the laser processing machine 1 according to the first embodiment sets the upper limit of the temperature range to within 100°C ± 20°C. This specifically prevents burning or melting of the nozzle 15. 【0049】 Furthermore, the laser processing machine 1 according to the first embodiment sets the lower limit of the temperature range to within ±10°C of the ambient temperature. This specifically prevents processing defects such as rough cut surfaces from occurring. 【0050】 [Second Embodiment] [Configuration of a laser processing machine] The laser processing machine and the laser beam irradiation method according to the second embodiment will be described below with reference to the drawings. Figure 5 is a diagram showing the configuration of the laser processing machine according to the second embodiment. As shown in Figure 5, the second embodiment differs from the first embodiment in that it further includes a cooling fluid supply device 31. 【0051】 The cooling fluid supply device 31 cools the nozzle 15 by supplying cooling fluid into the processing head 3, circulating it inside the processing head 3, or injecting it from the tip of the nozzle 15. With the cooling fluid supply device 31 in place, the control unit 17 supplies cooling fluid to the nozzle 15, increasing the flow rate of the cooling fluid when the temperature of the nozzle 15 is above the temperature range, and decreasing the flow rate of the cooling fluid when the temperature of the nozzle 15 is below the temperature range. 【0052】 [Cutting process] Next, the cutting process using the laser processing machine 1 according to the second embodiment will be described. Figures 6A to 6C are flowcharts showing the processing steps of the cutting process according to the second embodiment. As shown in Figures 6A to 6C, the cutting process according to the second embodiment differs from the first embodiment in that steps S122, S130, S132, S134, and S136 are added, while the other steps are the same as those of the first embodiment. Therefore, the explanation of steps S101 to S119 will be omitted, and the explanation will begin from step S121. 【0053】 In step S121 shown in Figure 6B, the control unit 17 sets the optical system, such as mirrors and lenses, for the cutting process. In step S122, it starts supplying cooling fluid from the cooling fluid supply device 31 to the nozzle 15, and then proceeds to step S123 to start the cutting process. Simultaneously with the start of the cutting process, the control unit 17 starts measuring the temperature of the nozzle 15 using the temperature sensor 5. 【0054】 In step S125, the control unit 17 determines whether the temperature rise of the nozzle 15 is less than 100°C / second. If the temperature rise of the nozzle 15 is less than 100°C / second, the process proceeds to step S127. If the temperature rise of the nozzle 15 is 100°C / second or more, an alarm is issued and the processing is stopped, ending the cutting process according to this embodiment. 【0055】 In step S127, the control unit 17 determines whether the focal position of the cutting process is within the appropriate focal range. If the focal position is within the appropriate focal range, the process proceeds to step S129. If the focal position is outside the appropriate focal range, an alarm is issued and the process is stopped, ending the cutting process according to this embodiment. 【0056】 Moving to Figure 6C, in step S129, the control unit 17 determines whether the temperature of the nozzle 15 is 100°C or less. That is, the control unit 17 determines whether the temperature of the nozzle 15 is below the upper limit of the temperature range. 【0057】 The upper limit of the temperature range should be set within the range of 100°C ± 20°C, but here it is set to 100°C as an example. If the temperature of the nozzle 15 is higher than 100°C, the process proceeds to step S130; if the temperature of the nozzle 15 is 100°C or lower, the process proceeds to step S133. 【0058】 In step S130, the control unit 17 determines whether the flow rate of the cooling fluid supplied from the cooling fluid supply device 31 is less than the maximum flow rate. If the flow rate of the cooling fluid is at the maximum flow rate, the process proceeds to step S131; otherwise, the process proceeds to step S132. 【0059】 In step S131, the control unit 17 returns to step S127 after lowering the focal position of the cutting process by 0.1 mm, because the flow rate of the cooling fluid has reached its maximum and cannot be increased any further. In other words, the control unit 17 lowers the focal position if the temperature of the nozzle 15 is higher than the temperature range even when the flow rate of the cooling fluid has increased to its maximum. This reduces interference of the laser beam with the inner surface of the nozzle 15, thereby lowering the temperature of the nozzle 15, even when the flow rate of the cooling fluid has reached its maximum. However, the amount of change in the focal position of the cutting process can be changed to a value other than 0.1 mm depending on the temperature change and the device configuration. 【0060】 In step S132, the control unit 17 increases the flow rate of the cooling fluid supplied from the cooling fluid supply device 31 at a rate of 10 cc / min and returns to step S127. That is, if the temperature of the nozzle 15 is higher than the temperature range, the control unit 17 increases the flow rate of the cooling fluid to lower the temperature of the nozzle 15. However, the amount of change in the flow rate of the cooling fluid can be changed to a value other than 10 cc / min depending on the temperature change and the device configuration. 【0061】 In step S133, the control unit 17 determines whether the temperature of the nozzle 15 is 30°C or higher. That is, the control unit 17 determines whether the temperature of the nozzle 15 is above the lower limit of the temperature range. 【0062】 The lower limit of the temperature range should be set to be above the temperature of the cooling fluid and within ±10°C of the ambient temperature, but here it is set to 30°C as an example. If the temperature of the nozzle 15 is lower than 30°C, the process proceeds to step S134, and if the temperature of the nozzle 15 is 30°C or higher, the process proceeds to step S137. 【0063】 In step S134, the control unit 17 determines whether the flow rate of the cooling fluid supplied from the cooling fluid supply device 31 is greater than the minimum flow rate. If the flow rate of the cooling fluid is the minimum flow rate, the process proceeds to step S135; otherwise, the process proceeds to step S136. 【0064】 In step S135, the control unit 17 returns to step S127 after determining that the flow rate of the cooling fluid has decreased to the minimum flow rate and cannot be reduced any further, by raising the focal position of the cutting process by 0.1 mm. In other words, the control unit 17 raises the focal position if the temperature of the nozzle 15 is below the temperature range even when the flow rate of the cooling fluid has decreased to the minimum flow rate. This allows the temperature of the nozzle 15 to be raised by increasing the interference of the laser beam with the inner surface of the nozzle 15, even when the flow rate of the cooling fluid has decreased to the minimum flow rate. However, the amount of change in the focal position of the cutting process can be changed to a value other than 0.1 mm depending on the temperature change and the device configuration. 【0065】 In step S136, the control unit 17 reduces the flow rate of the cooling fluid supplied from the cooling fluid supply device 31 by a rate of 10 cc / min and returns to step S127. That is, if the temperature of the nozzle 15 is lower than the temperature range, the control unit 17 reduces the flow rate of the cooling fluid to raise the temperature of the nozzle 15. However, the amount of change in the flow rate of the cooling fluid can be changed to a value other than 10 cc / min depending on the temperature change and the device configuration. 【0066】 In step S137, the control unit 17 determines whether the cutting process is complete or not. If the cutting process is not complete, it returns to step S127. If the cutting process is complete, it terminates the temperature measurement of the nozzle 15 and the supply of cooling fluid, and the cutting process according to this embodiment is completed. 【0067】 [Effects of the second embodiment] As described in detail above, the laser processing machine 1 according to the second embodiment supplies cooling fluid to the nozzle 15, increases the flow rate of the cooling fluid when the temperature of the nozzle 15 is higher than the temperature range, and decreases the flow rate of the cooling fluid when the temperature of the nozzle 15 is lower than the temperature range. By adjusting the flow rate of the cooling fluid, the temperature of the nozzle 15 can be adjusted to be within the temperature range. 【0068】 Furthermore, in the laser processing machine 1 according to the second embodiment, if the temperature of the nozzle 15 is higher than the temperature range even when the flow rate of the cooling fluid is increased to the maximum flow rate, the focal position is lowered. On the other hand, in the laser processing machine 1 according to the second embodiment, if the temperature of the nozzle 15 is lower than the temperature range even when the flow rate of the cooling fluid is reduced to the minimum flow rate, the focal position is raised. As a result, even if the temperature of the nozzle 15 cannot be adjusted to within the temperature range by adjusting the flow rate of the cooling fluid, the temperature of the nozzle 15 can be adjusted to within the temperature range by adjusting the focal position. 【0069】 Furthermore, in the laser processing machine 1 according to the second embodiment, the lower limit of the temperature range is set to be above the temperature of the cooling fluid and within ±10°C of the ambient temperature. This specifically prevents processing defects such as rough cut surfaces. It also prevents tracing defects caused by condensation on the nozzle 15 due to excessive cooling fluid. 【0070】 As described above, embodiments of the present invention have been presented, but the statements and drawings that constitute part of this disclosure should not be understood as limiting the invention. Various alternative embodiments, examples, and operational techniques will become apparent to those skilled in the art from this disclosure. [Explanation of Symbols] 【0071】 1. Laser processing machine 3 Machining head 5. Temperature sensor 7 NC device 9. Laser Oscillator 10 Process Fibers 11 Bend Mirror 13 Focusing lens 15 nozzles 17 Control Unit 21 Nozzle temperature measuring device 23 Machining head drive device 25 Assist gas supply device 27 Lens adjustment device 29 Copying adjustment device 31 Cooling fluid supply device Double job

Claims

[Claim 1] The temperature of the nozzle located at the tip of the processing head that irradiates the workpiece with a laser beam is detected. If the detected nozzle temperature is outside a predetermined temperature range, the focal position of the laser beam is adjusted so that the nozzle temperature falls within the temperature range. Method of irradiating with a laser beam. [Claim 2] If the temperature of the nozzle is higher than the temperature range, the focal position is lowered. If the temperature of the nozzle is lower than the temperature range, the focal position is raised. The method of irradiating with a laser beam according to claim 1. [Claim 3] A cooling fluid is supplied to the nozzle, If the temperature of the nozzle is higher than the temperature range, the flow rate of the cooling fluid is increased. If the temperature of the nozzle is lower than the temperature range, the flow rate of the cooling fluid is reduced. A method for irradiating with a laser beam according to claim 1 or 2. [Claim 4] If the temperature of the nozzle remains above the temperature range even after the flow rate of the cooling fluid has increased to the maximum flow rate, the focal position is lowered. If the temperature of the nozzle remains below the temperature range even when the flow rate of the cooling fluid is reduced to the minimum flow rate, the focal position is raised. The method of irradiating with a laser beam according to claim 3. [Claim 5] The focal position of the laser beam is set above the opening of the nozzle. A method for irradiating with a laser beam according to claim 1 or 2. [Claim 6] The upper limit of the aforementioned temperature range is set within the range of 100°C ± 20°C. A method for irradiating with a laser beam according to claim 1 or 2. [Claim 7] The lower limit of the aforementioned temperature range is set within the range of ambient temperature ± 10°C. A method for irradiating with a laser beam according to claim 1 or 2. [Claim 8] The lower limit of the temperature range is set to be above the temperature of the cooling fluid and within a range of ±10°C of the ambient temperature. The method of irradiating with a laser beam according to claim 3. [Claim 9] A processing head that irradiates a laser beam onto the workpiece, A temperature sensor is provided at the tip of the processing head to detect the temperature of the nozzle, The system includes a control unit that adjusts the focal position of the laser beam based on the temperature of the nozzle detected by the temperature sensor, The control unit adjusts the focal position of the laser beam so that the nozzle temperature falls within a predetermined temperature range if the nozzle temperature is outside that range. Laser processing machine.

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