Protective glass dirt detection device and protective glass dirt detection method

Abstract

To detect a degree of dirtiness on protective glass properly according to processing conditions of a laser beam machine.SOLUTION: A protective glass dirt detection device detects dirt on protective glass 25 for protecting, from dirt, a collecting lens 19 for collecting and radiating a laser beam LB to a workpiece W, and includes a scattering light detection part 27, an information acquisition part 35, a dirt threshold setting part 37, and a dirt determination part 39. The scattering light detection part 27 detects scattering light SL generated by dirt 51 adhering to the protective glass 25. The information acquisition part 35 acquires information regarding processing conditions of a laser beam machine. The dirt threshold setting part 37 sets a dirt threshold for detecting dirt of the protective glass 25 from a detection value X detected by the scattering light detection part based on the processing conditions of the laser beam machine. The dirt determination part 39 determines a degree of dirtiness of the protective glass 25 based on the detection value X and the dirt threshold.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a device and a method for detecting dirt on a protective glass. [Background technology]

[0002] Generally, a protective glass is provided at the laser output port of a laser processing head in a laser processing machine to protect the focusing lens from spatter (splash), metal fumes, dust, and other contaminants flying from the workpiece during laser processing.

[0003] The protective glass of this laser processing head becomes dirty on its surface, which can reduce the amount of laser light irradiation and adversely affect processing quality. Therefore, the protective glass needs to be cleaned or replaced depending on the state of dirt.

[0004] Patent document 1 describes a protective glass dirt detection device that has a photodetector that detects scattered light around the edge of the protective glass by dirt particles adhering to the surface of the protective glass and light emitted by the protective glass, and when the detection signal from the photodetector reaches a certain level (threshold), it determines that the protective glass is dirty and indicates the need to replace the protective glass. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2001-509889 Summary of the Invention [Problem to be solved by the invention]

[0006] The protective glass dirt detection device of Patent Document 1 detects dirt on the protective glass by utilizing the fact that the amount of scattered light increases in accordance with the amount of dirt on the protective glass surface, and the level of the detection signal from the photodetector increases.

[0007] Here, the intensity of the scattered light from the protective glass relative to the intensity of the incident light of the laser light entering the protective glass is constant even in a clean protective glass. If a foreign object adheres to the protective glass, the intensity of the scattered light also increases. Therefore, when the incident light intensity of the laser light is 2 If the laser output is doubled, the intensity of the scattered light will also double. Conditions such as the output of the laser light, duty ratio, pulse frequency, and beam diameter, which are related to the incident light intensity of the laser light incident on the protective glass, are changed according to the processing conditions, so the amount of scattered light scattered according to the amount of dirt on the protective glass surface will change depending on the processing conditions. For example, if the laser output is doubled due to the processing conditions, the amount of scattered light will also double, and the level of the detection signal of the photodetector will also double. Therefore, if the threshold value for dirt detection is a constant fixed value despite changes in processing conditions, the degree of dirt on the protective glass may not be detected appropriately.

[0008] The present invention provides a protective glass contamination detection device and a protective glass contamination detection method that can appropriately detect the degree of contamination on a protective glass depending on the processing conditions of a laser processing machine. [Means for solving the problem]

[0009] A protective glass contamination detection device according to one aspect of the present invention is a protective glass contamination detection device that detects contamination on a protective glass that protects a condenser lens that condenses laser light and irradiates it on a workpiece in a laser processing machine from contamination, and detects scattered light caused by contamination on the protective glass. Sensor included The device comprises a scattered light detection unit, an information acquisition unit that acquires information regarding the processing conditions of the laser processing machine, a dirt threshold setting unit that sets a dirt threshold for detecting dirt on the protective glass from the detection value of the scattered light detected by the scattered light detection unit based on the processing conditions of the laser processing machine, and a dirt determination unit that determines the degree of dirt on the protective glass based on the detection value and the dirt threshold. The processing conditions of the laser processing machine preferably include any one of an item for adjusting the average output per unit time of the laser light emitted during processing, an item for adjusting the irradiation area of ​​the laser light irradiated onto the protective glass during processing, the laser conditions of the laser light emitted during processing, the sensor characteristics of the scattered light detection unit, and any variable determined by the machine specifications and the sensor specifications of the scattered light detection unit as the machine specifications of the laser processing machine, and any variable determined by the characteristics of the protective glass.

[0010] The dirt threshold setting unit sets a dirt threshold for detecting dirt on the protective glass based on the processing conditions of the laser processing machine. Even if the amount of scattered light that is scattered according to the amount of dirt on the protective glass surface changes depending on the processing conditions, the dirt threshold can be set to be suitable for the processing conditions. Effect of the Invention

[0011] According to one aspect of the present invention, the degree of contamination of the protective glass of a laser processing machine can be appropriately detected according to processing conditions. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a laser processing machine equipped with a dirt detection device according to the present invention. [Diagram 2] FIG. 2 is a schematic diagram of the protective glass 25 provided in the processing head 21 shown in FIG. [Diagram 3] FIG. 3 is a diagram showing how scattered light from an end face of protective glass 25 having dirt 51 attached thereto is detected while laser light is being irradiated. [Figure 4] FIG. 4 is a block diagram for explaining an example of the configuration of a protective glass contamination detection device and an NC device 23 according to an embodiment of the present invention. [Diagram 5] FIG. 5 is a flowchart showing the operation of the protective glass stain detection device according to the present invention. [Figure 6] FIG. 6 is a flowchart showing an example of a method for selecting a calculation formula for the warning threshold value Wpk(N). [Figure 7] FIG. 7 is an explanatory diagram showing an example of a method for selecting a calculation formula for the warning threshold value Wpk(N) based on the relationship between the pulse frequency F and the duty ratio D of the laser light LB. [Figure 8] FIG. 8 is a graph showing the change in the detection value X of the sensor 27 and the warning threshold value Wpk(1) when the duty ratio of the laser light is 30% and the pulse frequency is 10 Hz. [Figure 9]FIG. 9 is a graph showing the change in the detection value X of the sensor 27 and the warning threshold value Wpk(2) when the duty ratio of the laser light is 40% and the pulse frequency is 5000 Hz. [Figure 10] FIG. 10 is a graph showing the change in the detection value X of the sensor 27 and the warning threshold value Wpk(3) when the duty ratio of the laser light is 20% and the pulse frequency is 100 Hz. [Figure 11] FIG. 11 is a graph showing the change in the detection value X of the sensor 27 and the warning threshold value Wpk(4) when the duty ratio of the laser light is 40% and the pulse frequency is 500 Hz. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A protective glass stain detection device and a protective glass stain detection method according to an embodiment will be described below with reference to the drawings. In the description of the drawings, the same parts are given the same reference numerals and the description will be omitted.

[0014] [Laser processing machine configuration] FIG. 1 is a schematic diagram of a laser processing machine equipped with a dirt detection device according to the present invention. As shown in FIG. 1, in this laser processing machine, a laser beam LB generated by a laser oscillator 1 is sent to a laser processing unit 5 via a process fiber 3, and the laser processing unit 5 focuses the laser beam LB to a high energy density and irradiates it on a workpiece (work) W made of various materials to perform processing. The workpiece W is, for example, a mild steel plate. The workpiece W may be, for example, a ferrous sheet metal other than a mild steel plate, such as stainless steel, or may be a sheet metal such as aluminum, aluminum alloy, or copper steel. In this embodiment, the laser processing machine equipped with the dirt detection device according to the present invention is described as a welding machine that welds the workpiece W with the laser beam LB, but the laser processing machine may be a cutting machine that cuts the workpiece W with the laser beam LB. The type of the laser processing machine is not particularly limited.

[0015] The laser oscillator 1 generates and emits laser light LB. As the laser oscillator 1, a laser oscillator that amplifies pumping light emitted from a laser diode to emit laser light of a predetermined wavelength, or a laser oscillator that directly uses laser light emitted from a laser diode is suitable. The laser oscillator 1 is, for example, a solid-state laser oscillator, a fiber laser oscillator, a disk laser oscillator, or a direct diode laser oscillator (DDL oscillator).

[0016] Specific laser wavelengths of laser diode beams, for example, the laser wavelength of a laser beam emitted by a fiber laser oscillator or a disk laser oscillator is typically 1060 nm to 1080 nm, and the laser wavelength of a laser beam emitted by a DDL oscillator is anywhere in the range of 300 nm to 1000 nm.

[0017] The process fiber 3 transmits the laser light LB emitted from the laser oscillator 1 to the laser processing unit 5 .

[0018] The laser processing unit 5 welds the workpiece W by using the laser light LB transmitted by the process fiber 3. The laser processing unit 5 has a processing table 7 on which the workpiece W is placed, a robot 11, and a collimator unit 13. The robot 11 is configured with multiple axes (6 axes), and the collimator unit 13 is configured to be freely movable in the X-axis, Y-axis, and Z-axis directions, and the orientation of the collimator unit 13 is configured to be freely angled.

[0019] The collimator unit 13 irradiates the workpiece W with the laser light LB transmitted by the process fiber 3. The collimator unit 13 has a collimator lens 15 that converts the laser light LB emitted from the process fiber 3 into a substantially parallel beam, and a condenser lens 19 that condenses the laser light LB converted into a substantially parallel beam. The collimator lens 15 and the condenser lens 19 are arranged with their optical axes adjusted in advance. Note that the beam diameter of the laser light LB when irradiating the upper surface of the workpiece W is variable from the beam waist diameter to a beam diameter larger than the beam waist diameter by changing the beam diameter and the focal position using optical system elements.

[0020] The collimator unit 13 has a processing head 21 that emits a laser beam LB to the workpiece W. The collimator unit 13 is fixed to the robot 11, and is configured to be movable in the X-axis, Y-axis, and Z-axis directions, and the orientation of the processing head 21 is configured to be freely angled. Therefore, the processing head 21, i.e., the position where the laser beam LB is irradiated onto the workpiece W, can be moved along the surface of the workpiece W (X-axis and Y-axis directions). Note that instead of a configuration in which the processing head 21 moves along the surface of the workpiece W, a configuration in which the processing head 21 moves the workpiece W while keeping the position of the processing head 21 fixed may be used. In other words, it is sufficient to have a configuration in which the processing head 21 moves relatively to the surface of the workpiece W.

[0021] The laser processing machine is driven and controlled by an NC (Numerical Control) device 23 and a PLC (Programmable Logic Controller) 29, which will be described later.

[0022] FIG. 2 is a schematic diagram of the protective glass 25 provided in the processing head 21 shown in FIG. 1 and 2, the processing head 21 is configured to be able to select a mechanism for supplying a shielding gas to prevent nitridation or oxidation according to the processing content, and a protective glass 25 is provided between the condenser lens 19 and the workpiece W in the processing head 21 to protect the condenser lens 19 from spatter (splash), metal fumes, dust, and other contaminants flying from the workpiece W during laser processing. Furthermore, an air knife mechanism may be configured to prevent spatter (splash), metal fumes, dust, and other contaminants flying from the workpiece W during laser processing from entering the processing head 21.

[0023] This protective glass 25 is configured to be detachably attached to the processing head 21 while being stored in a protective glass folder that stores the protective glass 25, and the protective glass 25 can be easily replaced by removing the protective glass folder from the processing head 21.

[0024] A sensor 27 is provided at an end of the protective glass 25 to receive scattered light SL from the end face of the protective glass 25 when attached to the processing head 21. That is, the sensor 27 detects scattered light SL caused by dirt 51 adhering to the protective glass 25. A detection signal from the sensor 27 is sent to a PLC 29 that sequentially controls the process of determining the level of dirt on the protective glass 25.

[0025] FIG. 3 shows the detection of scattered light SL from an end face of the protective glass 25 having dirt 51 attached thereto while the laser light is being irradiated. vinegar FIG. As shown in Figure 3, laser processing is performed by irradiating laser light LB. Time Furthermore, when dirt 51 adheres to the lower surface 25b of the protective glass 25, the laser light LB from the condenser lens 19 strikes the dirt 35 and generates scattered light SL. injection That is, the sensor 27 detects the position of the protective glass 25 from the edge of the protective glass 25. injectionThe sensor 27 detects the amount of scattered light continuously during the laser processing.

[0026] FIG. 4 is a block diagram for explaining an example of the configuration of a protective glass contamination detection device and an NC device 23 according to an embodiment of the present invention. In the present embodiment, the protective glass detection device includes a sensor 27 and a PLC 29, and the PLC 29 is connected to the NC device 23. The protective glass detection device detects dirt 51 on the protective glass 25 in the laser processing machine, which protects the condenser lens 19, which condenses the laser light LB and irradiates it on the workpiece, from dirt.

[0027] As shown in FIG. 4, the PLC 29 includes an analog I / F circuit 31, an AD converter 33, an information acquisition unit 35, a dirt threshold setting unit 37, and a dirt determination unit 39.

[0028] The analog I / F circuit 31 amplifies the detection signal from the sensor 27 and cuts out high frequency components (noise). The AD converter 33 converts the analog signal from the analog I / F circuit 31 into a digital signal and outputs it as a detection value X.

[0029] The information acquiring unit 35 acquires the detection value X from the AD converter 33. The information acquiring unit 35 acquires information from the NC device 23 as to whether the NC device 23 has started laser processing or not and whether the NC device 23 has finished laser processing or not. The information acquiring unit 35 also acquires information on the processing conditions of the laser processing machine from the NC device 23. The processing conditions of the laser processing machine include an average output Pav per unit time of the laser light LB emitted during processing and an item for adjusting the irradiation area of ​​the laser light LB irradiated to the protective glass 25 during processing. The average output Pav per unit time indicates the output of the laser light LB irradiated to the workpiece W per unit time, which is determined by the laser output of the laser light LB emitted during processing, the pulse frequency, and the duty ratio obtained by dividing the pulse width by the pulse period.

[0030] When only the average output Pav of the laser light LB per unit time changes, the amount of laser energy irradiated to the protective glass 25 and the amount of laser energy irradiated to the workpiece W are in a proportional relationship, whereas the change in the irradiation area of ​​the laser light LB irradiated to the protective glass 25 and the change in the irradiation area of ​​the laser light LB irradiated to the workpiece W are not necessarily in a proportional relationship, as can be understood, for example, when assuming that the beam waist is set above the workpiece W. For this reason, the change in the laser output of the laser light LB and the irradiation area of ​​the laser light LB irradiated to the protective glass 25 should be separately adjusted and used for detecting dirt on the protective glass. Therefore, the adjustment of the irradiation area of ​​the laser light LB irradiated to the protective glass 25 refers to an adjustment of how to handle the irradiation area of ​​the laser light LB irradiated to the protective glass 25, taking into account the difference between the irradiation area of ​​the laser light LB to the workpiece W and the irradiation area of ​​the protective glass 25.

[0031] The processing conditions of the laser processing machine acquired by the information acquisition unit 35 include the laser conditions of the laser light LB emitted during processing. The laser conditions include the laser peak output value P (kW) of the laser light LB, the pulse frequency F, the duty ratio D, and a gain correction value G determined by the beam diameter of the laser light LB. The values ​​of the laser peak output value P, the pulse frequency F, the duty ratio D, and the gain correction value G are not constant, but are changed depending on the laser conditions. The gain correction value G determined by the beam diameter of the laser light LB indicates, as a coefficient, the degree of change in the beam diameter from the case where the beam diameter of the laser light LB when irradiating the upper surface of the workpiece W with the laser light LB is the beam waist diameter to the case where the beam diameter becomes larger than the beam waist diameter due to a change in the beam diameter by the optical system elements or a change in the focal position. The gain correction value G does not necessarily have to be directly related to a physical quantity. Yo This is a low value.

[0032] The irradiation area of ​​the laser light LB irradiated to the protective glass 25 due to the gain correction value G determined by the beam diameter of the laser light LB is understood as follows. In other words, the gain correction value G indicates the degree of change in the beam diameter irradiated to the workpiece W as a coefficient, and the degree of change in the beam diameter may be changed by changing the beam diameter using an optical system element that changes the BPP (beam parameter product), may be changed by changing the beam diameter using an optical system element that changes the beam diameter without changing the BPP, or may be changed by a combination of the above. Such a change in the gain correction value G is not necessarily based on a certain law (such as a law of proportionality) between the irradiation area of ​​the laser light LB irradiated to the workpiece W and the irradiation area of ​​the laser light LB irradiated to the protective glass 25, and may be obtained by adjusting how to handle the irradiation area of ​​the laser light LB irradiated to the protective glass 25 depending on the case.

[0033] The processing conditions of the laser processing machine acquired by the information acquisition unit 35 include the sensor characteristics of the sensor 27. The sensor characteristics of the sensor 27 include the initial voltage V0 (V) of the sensor 27, a sensor rise time tr (msec), a sensor fall time tf (msec), and a variable s determined by the response time of the sensor 27 and the sampling frequency of the detection signal of the sensor 27. The sensor rise time tr (msec) is the time required for the detection signal of the sensor 27 to reach a peak value from the initial voltage V0. The sensor fall time tf is the time required for the detection signal of the sensor 27 to fall from the peak value to the initial voltage V0 (V). The values ​​of the initial voltage V0, the sensor rise time tr, the sensor fall time tf, and the variable s are not constant but change depending on the sensor characteristics. For example, even if the response of a PD (Photo Diode) chip is fast, the sensor 27 has the ability to stably output a signal at a possible response speed that takes into account the inductance of the lead wires of each component such as an operational amplifier, the parasitic capacitance due to feedback resistors, and floating capacitance, etc. Therefore, the sensor rise time tr and the sensor fall time tf take a certain amount of time depending on the specifications and costs.

[0034] Furthermore, the processing conditions of the laser processing machine acquired by the information acquisition unit 35 include information on the machine specifications of the laser processing machine that emits the laser light LB. The information on the machine specifications of the laser processing machine includes an arbitrary variable a determined by the characteristics of the protective glass 25 used, and an arbitrary variable b determined by the machine specifications and the sensor specifications of the sensor 27. a The value of b is not constant, but is changed depending on the machine specifications of the laser processing machine and the sensor specifications of the sensor 27. The arbitrary variable b is a variable that specifies the timing of switching between the calculation formulas Wpk(3) and Wpk(4) for the contamination threshold value, which will be described later.

[0035] The dirt threshold setting unit 37 sets a dirt threshold for detecting dirt 51 on the protective glass 25 from the detection value X of the scattered light SL detected by the sensor 27, based on the processing conditions of the laser processing machine obtained from the NC device 23. The dirt threshold setting unit 37 selects a calculation formula for the dirt threshold for setting the dirt threshold, based on the processing conditions of the laser processing machine, and calculates the dirt threshold based on the selected calculation formula for the dirt threshold. Then, the dirt threshold for determining the level of dirt on the protective glass 25 is set.

[0036] Here, the significance of setting the contamination threshold value based on the processing conditions of the laser processing machine will be described. When detecting dirt 51 on the protective glass 25, for example, if the laser conditions are changed and the pulse frequency F and duty ratio D of the laser light LB change, the average output Pav of the laser light LB also changes. If the average output Pav of the laser light LB changes, the incident light intensity of the laser light LB incident on the protective glass 25 changes, and the amount of scattered light SL scattered according to the amount of dirt 51 also changes. In this case, even if the dirt 51 on the surface of the protective glass 25 is the same, the detection value X of the sensor 27 changes depending on the laser conditions. Therefore, by setting a dirt threshold value for the protective glass 25 based on the laser conditions, the detection of dirt on the protective glass can be corrected to a constant sensitivity, and the degree of dirt on the protective glass 25 can be appropriately detected.

[0037] In addition, for example, when the sensor characteristics of the sensor 27 are changed and the peak value of the output voltage of the sensor 27 changes, or when the machine specifications of the laser processing machine are changed and the characteristics of the protective glass 25 and the nozzle diameter of the processing head 21 change, the detection value X of the sensor 27 changes depending on the sensor characteristics and the machine specifications of the laser processing machine, even if the dirt 51 on the surface of the protective glass 25 is the same. Therefore, by setting the dirt threshold value of the protective glass 25 based on the sensor characteristics of the sensor 27 and the machine specifications of the laser processing machine, the detection of dirt on the protective glass can be corrected to a constant sensitivity, and the degree of dirt on the protective glass can be more appropriately detected. By setting the dirt threshold value based on the processing conditions of the laser processing machine, the degree of dirt on the protective glass can be appropriately detected.

[0038] Specifically, the dirt threshold setting unit 37 selects a calculation formula for the dirt threshold by determining whether or not the processing conditions of the laser processing machine acquired from the NC device 23 satisfy a pre-stored judgment formula. Then, the dirt threshold for detecting dirt 51 on the protective glass 25 is calculated based on the selected calculation formula for the dirt threshold.

[0039] In this embodiment, the dirt threshold setting unit 37 sets a warning threshold Wpk(N) and an alarm threshold Apk(N) as dirt thresholds. The warning threshold Wpk(N) is a dirt threshold for determining dirt that does not cause obvious problems in laser processing but may affect processing quality depending on the type of processing. The alarm threshold Apk(N) is a dirt threshold for determining dirt that may cause problems in laser processing and require replacement of the protective glass 25, and the alarm threshold Apk(N) is calculated by multiplying the warning threshold Wpk(N) by an arbitrary variable c. Details of the method of selecting the calculation formula for the warning threshold Wpk(N) and the method of calculating the warning threshold Wpk(N) will be described later.

[0040] The dirt determination unit 39 determines the degree of dirt on the protective glass 25 based on the detection value X of the sensor 27 and the dirt threshold set by the dirt threshold setting unit 37. Specifically, the dirt determination unit 39 determines whether or not the detection value X exceeds the warning threshold Wpk(N) set by the dirt threshold setting unit 37. When the detection value X exceeds the warning threshold Wpk(N), the dirt determination unit 39 determines whether or not the detection value X exceeds the alarm threshold Apk(N).

[0041] If the detection value X exceeds the warning threshold Wpk(N) and is equal to or lower than the alarm threshold Apk(N), the dirt determination unit 39 determines that the degree of dirt on the protective glass 25 is at a level requiring attention, and transmits a warning determination signal to the NC device 23. If the detection value X exceeds the warning threshold Wpk(N) and exceeds the alarm threshold Apk(N), the dirt determination unit 39 determines that the degree of dirt on the protective glass 25 is at a level requiring replacement of the protective glass 25, and transmits an alarm determination signal to the NC device 23.

[0042] Next, the NC device 23 will be described. The NC device 23 is a control device that controls each part of the laser processing machine. The NC device 23 is composed of a computer, and has a CPU (Central Processing Unit), a ROM (Read-Only Memory), and a RAM (Random-Access Memory). The NC device 23 has a display unit 23a that displays various information, and, in addition to driving and controlling the laser processing machine, displays information related to detection of dirt on the protective glass 25 via the display unit 23a, as described later.

[0043] The NC device 23 realizes various functions by having the CPU read out various programs from the ROM, load them into the RAM, and execute the loaded programs. As shown in Fig. 4, the NC device 23 has functions as a machining condition storage unit 41, a machining program storage unit 43, an information output unit 45, a machining control unit 47, and a display control unit 49.

[0044] The processing condition holding unit 41 holds the processing conditions of the laser processing machine. The processing conditions of the laser processing machine held by the processing condition holding unit 41 include the laser conditions of the laser light LB emitted during processing, the sensor characteristics of the sensor 27, and information on the mechanical specifications of the laser processing machine that emits the laser light LB.

[0045] The information output unit 45 outputs information on whether the NC device 23 has started laser processing or not and whether the NC device 23 has finished laser processing or not to the PLC 29. In addition, the information output unit 45 outputs various information on the processing conditions of the laser processing machine stored in the processing condition storage unit 41 to the PLC 29.

[0046] The machining program storage unit 43 stores the machining program. The operation of the robot 11 is defined by teaching, and the behavior of the machining head 21 is set to create the machining program. Furthermore, the machining program stored in the machining program storage unit 43 may be created by an external device such as CAM (Computer-Aided Manufacturing), and the machining program storage unit 43 may acquire the machining program from the external device. The external device may store the created machining program in a database in a data management server (not shown). In this case, the machining program storage unit 43 acquires the machining program by reading out the machining program stored in the database of the data management server.

[0047] The processing program includes code that defines the operations of the laser processing machine body 50 required to weld the workpiece W sequentially along a plurality of paths to weld the product.

[0048] The processing program contains codes that define a series of operations of the laser processing machine required to weld products, such as setting processing conditions, starting and stopping emission of the laser light LB, moving the processing head 21 for each element, and moving from path to path. When welding a product, the processing head 21 (laser light LB) is moved along a welding processing trajectory corresponding to a specific spot, inner circumference, and outer circumference of the product. In addition, when welding multiple products from the workpiece W, the processing program contains codes for each of the multiple products.

[0049] The processing control unit 47 executes a processing program to control the laser processing machine. Furthermore, when the processing control unit 47 receives an alarm determination signal from the PLC 29, it stops processing by the laser processing machine.

[0050] The display control unit 49 causes the display unit 23a to display information based on the determination result of the degree of dirt on the protective glass 25, based on the determination signal from the PCL 29. The display control unit 49 causes the display unit 23a to display a warning display such as "Caution: dirt" based on the warning determination signal from the PCL 29. Furthermore, the display control unit 49 causes the display unit 23a to display an alarm display such as "Replace protective glass" based on the alarm determination signal from the PCL 29. This allows the operator to instantly and easily determine that replacement of the protective glass 25 is necessary due to dirt on the protective glass during laser processing, and by replacing the protective glass 25, deterioration of processing quality can be prevented in advance.

[0051] [Operation of protective glass dirt detection device] Next, the operation of the protective glass dirt detection device according to the present invention will be described with reference to FIG.

[0052] FIG. 5 is a flowchart showing the operation of the protective glass stain detection device according to the present invention. 5, the information acquiring unit 35 acquires the laser conditions of the laser light LB emitted during processing from the NC device 23. The information acquiring unit 35 acquires, as the laser conditions of the laser light LB, a laser peak output value P of the laser light LB emitted during processing, a pulse frequency F of the laser light LB, a duty ratio D of the laser light LB, and a gain correction value G determined by the beam diameter of the laser light LB.

[0053] Proceeding to step S11, the information acquiring unit 35 acquires information on the sensor characteristics of the sensor 27 from the NC device 23. The information acquiring unit 35 acquires, as the information on the sensor characteristics of the sensor 27, an initial voltage V0 of the sensor 27, a sensor rise time tr, a sensor fall time tf, and a variable s determined by the response time of the sensor 27 and the sampling frequency of the detection signal.

[0054] Proceeding to step S12, the information acquiring unit 35 acquires information on the machine specifications of the laser processing machine that emits the laser light LB from the NC device 23. The information acquiring unit 35 acquires an arbitrary variable a determined by the characteristics of the protective glass 25 and an arbitrary variable b determined by the machine specifications and the sensor specifications of the sensor 27 as the information on the machine specifications of the laser processing machine.

[0055] Proceeding to step S13, the dirt threshold setting unit 37 selects a dirt threshold calculation formula for setting the dirt threshold based on the laser conditions of the laser light LB emitted during processing, the information on the sensor characteristics of the sensor 27, and the information on the machine specifications of the laser processing machine. The dirt threshold setting unit 37 sets a warning threshold Wpk(N) and an alarm threshold Apk(N) as the dirt thresholds.

[0056] (How to select the formula for calculating the contamination threshold) Here, an example of a method for selecting a calculation formula for the dirt threshold value will be described with reference to FIG. 6 and FIG.

[0057] Fig. 6 is a flowchart showing an example of a method for selecting a calculation formula for the warning threshold Wpk(N). Fig. 7 is a diagram showing an example of a method for selecting a calculation formula for the warning threshold Wpk(N) based on the relationship between the pulse frequency F and duty ratio D of the laser light LB. In this embodiment, the dirt threshold setting unit 37 selects the calculation formula for the warning threshold Wpk(N) based on the relationship between the pulse frequency F and duty ratio D of the laser light LB.

[0058] The dirt threshold setting unit 37 selects a calculation formula for the warning threshold Wpk(N) from among four patterns of calculation formulas Wpk(1) to Wpk(4) stored in advance by sequentially determining whether the processing conditions of the laser processing machine satisfy five judgment formulas L0, L1A, L1B, L2, and L3. Details of the calculation formulas Wpk(1) to Wpk(4) for the warning threshold Wpk(N) will be described later.

[0059] First, in step S1301, the dirt threshold setting unit 37 determines whether or not the value of the duty ratio D among the acquired laser conditions satisfies a determination formula L0 shown in the following formula (1).

[0060] [Number 1] D=100 (1)

[0061] If the laser conditions satisfy the judgment formula L0 (YES in step S1301), that is, if the duty ratio D of the laser light LB is 100, the process proceeds to step S1304, where the dirt threshold setting unit 37 selects Wpk(1) as the calculation formula for the warning threshold Wpk(N). On the other hand, if the laser conditions do not satisfy the judgment formula L0, that is, if the duty ratio D of the laser light LB is not 100 (NO in step S1301), the process proceeds to step S1302.

[0062] In step S1302, the dirt threshold setting unit 37 determines whether or not the pulse frequency F of the laser light LB, the duty ratio D of the laser light LB, and the sensor rise time tr of the acquired laser conditions and sensor characteristics of the sensor 27 satisfy the judgment formula L1A shown in the following formula (2).

[0063] [Number 2] F≦D×10 / tr (2)

[0064] If the laser conditions and the sensor characteristics of the sensor 27 satisfy the judgment formula L1A (YES in step S1302), the process proceeds to step S1304, where the dirt threshold setting unit 37 selects Wpk(1) as the calculation formula for the warning threshold Wpk(N). On the other hand, if the laser conditions and the sensor characteristics of the sensor 27 do not satisfy the judgment formula L1A (NO in step S1302), the process proceeds to step S1303.

[0065] In step S1303, the dirt threshold setting unit 37 determines whether or not the pulse frequency F of the laser light LB, the duty ratio D of the laser light LB, the sensor rise time tr, the sensor fall time tf, and the arbitrary variable b among the acquired laser conditions, the sensor characteristics of the sensor 27, and the mechanical specifications of the laser processing machine satisfy the determination formula L1B shown in the following formula (3).

[0066] [Number 3] F≦{10×D(tr+tf)-1000×tr} / {tf×(tr-b)}···(3)

[0067] If the laser conditions, the sensor characteristics of the sensor 27, and the machine specifications of the laser processing machine satisfy the judgment formula L1B (YES in step S1303), the process proceeds to step S1304, where the dirt threshold setting unit 37 selects Wpk(1) as the calculation formula for the warning threshold Wpk(N). On the other hand, if the sensor characteristics of the sensor 27 and the machine specifications of the laser processing machine do not satisfy the judgment formula L1B (NO in step S1303), the process proceeds to step S1305.

[0068] 7, in a range in which the relationship between the pulse frequency F of the laser light LB and the duty ratio D of the laser light LB satisfies the judgment formula L0, L1A, or L1B, the calculation formula for the warning threshold value Wpk(N) is Wpk(1). When the relationship between the pulse frequency F of the laser light LB and the duty ratio D of the laser light LB satisfies the judgment formula L0, L1A, or L1B, the pulse-on time t_on (msec) of the detection value X of the sensor 27 that detects the dirt 51 adhering to the protective glass 25 becomes sufficiently long with respect to the sensor rise time tr.

[0069] In step S1305, the dirt threshold setting unit 37 determines whether or not the pulse frequency F of the laser light LB, the duty ratio D of the laser light LB, and the variable s among the acquired laser conditions and sensor characteristics of the sensor 27 satisfy the judgment formula L2 shown in the following formula (4).

[0070] [Number 4] F ≧ D × 10 / s (4)

[0071] If the laser conditions and the sensor characteristics of the sensor 27 satisfy the judgment formula L2 (YES in step S1305), the process proceeds to step S1306, where the dirt threshold setting unit 37 selects Wpk(2) as the calculation formula for the warning threshold Wpk(N). On the other hand, if the laser conditions and the sensor characteristics of the sensor 27 do not satisfy the judgment formula L2 (NO in step S1305), the process proceeds to step S1307.

[0072] 7, in a range in which the relationship between the pulse frequency F of the laser light LB and the duty ratio D of the laser light LB does not satisfy the judgment formulas L0, L1A, and L1B but satisfies the judgment formula L2, the calculation formula for the warning threshold value Wpk(N) is Wpk(2). Note that, in a case in which the relationship between the pulse frequency F of the laser light LB and the duty ratio D of the laser light LB does not satisfy the judgment formulas L0, L1A, and L1B but satisfies the judgment formula L2, the pulse-on time t_on of the detection value X of the sensor 27 that detects the dirt 51 adhering to the protective glass 25 becomes shorter than the sensor rise time tr.

[0073] In step S1307, the dirt threshold setting unit 37 determines whether or not the pulse frequency F of the laser light LB, the duty ratio D of the laser light LB, and the arbitrary variable b among the acquired laser conditions, the sensor characteristics of the sensor 27, and the mechanical specifications of the laser processing machine satisfy the determination formula L3 shown in the following formula (5).

[0074] [Number 5] F ≧ (1000—D × 10) / b (5)

[0075] If the laser conditions, the sensor characteristics of the sensor 27, and the machine specifications of the laser processing machine satisfy the judgment formula L3 (YES in step S1307), the process proceeds to step S1308, where the dirt threshold setting unit 37 selects Wpk(3) as the calculation formula for the warning threshold Wpk(N). On the other hand, if the sensor characteristics of the sensor 27 and the machine specifications of the laser processing machine do not satisfy the judgment formula L3 (NO in step S1307), the process proceeds to step S1309.

[0076] 7, in a range in which the relationship between the pulse frequency F of the laser light LB and the duty ratio D of the laser light LB does not satisfy the judgment formulas L0, L1A, L1B, and L2, and satisfies the judgment formula L3, the calculation formula for the warning threshold value Wpk(N) is Wpk(3). Note that, when the relationship between the pulse frequency F of the laser light LB and the duty ratio D of the laser light LB does not satisfy the judgment formulas L0, L1A, L1B, and L2, and satisfies the judgment formula L3, the pulse-on time t_on of the detection value X of the sensor 27 that detects the dirt 51 adhering to the protective glass 25 becomes shorter than the sensor rise time tr, and the pulse-off time t_off becomes longer.

[0077] In step S1309, the contamination threshold setting unit 37 selects Wpk(4) as the calculation formula for the warning threshold Wpk(N).

[0078] 7, in a range in which the relationship between the pulse frequency F of the laser light LB and the duty ratio D of the laser light LB does not satisfy any of the judgment formulas L0, L1A, L1B, L2, and L3, the calculation formula for the warning threshold value Wpk(N) is Wpk(4). When the relationship between the pulse frequency F of the laser light LB and the duty ratio D of the laser light LB does not satisfy any of the judgment formulas L0, L1A, L1B, L2, and L3, the pulse-on time t_on of the detection value X of the sensor 27 that detects the dirt 51 adhering to the protective glass 25 is shorter than the sensor rise time tr, and the pulse-off time t_off is also shorter.

[0079] Returning to step S14 in FIG. 5, the contamination threshold setting unit 37 calculates the warning threshold Wpk(N) and the alarm threshold Apk(N) using the calculation formula selected in step S13, and sets them as the contamination threshold.

[0080] A method for calculating the warning threshold value Wpk(N) and the alarm threshold value Apk(N) will be described with reference to Fig. 8 to Fig. 11. Fig. 8 to Fig. 11 are graphs showing changes in the detection value X (sensor output voltage) of the sensor 27 and the warning threshold value Wpk(N). In Fig. 8 to Fig. 11, it is assumed that the average output power Pav of the laser light LB, the beam diameter of the laser light LB, the sensor characteristics and the mechanical specifications of the sensor 27 are the same.

[0081] In this embodiment, the warning threshold value Wpk(N) is calculated based on the common formula shown in the following formula (6). That is, Wpk(1) to Wpk(4) differ only in k(N) of the common formula shown in formula (6).

[0082] [Number 6] Wpk(N)=P×a×k(N)×G+V0 (6)

[0083] Moreover, the alarm threshold Apk(N) is calculated by multiplying Wpk(N) by an arbitrary variable c, as shown in the following formula (7). The arbitrary variable c may be any value greater than 1, and is set to, for example, 1.5.

[0084] [Number 7] Apk(N) = Wpk(N) × c (7)

[0085] Fig. 8 is a graph showing the change in the detection value X (sensor output voltage) of the sensor 27 and the warning threshold value Wpk(1) when the duty ratio of the laser light is 30% and the pulse frequency is 10 Hz. In Fig. 8, Wpk(1) is selected as the calculation formula for the warning threshold value Wpk(N).

[0086] 8, the pulse-on time t_on of the contamination detection value, which is the detection value X of the sensor 27 when detecting the dirt 51 on the protective glass 25, is sufficiently long with respect to the sensor rise time tr. In this case, the maximum voltage value obtained by changing the pulse frequency F and duty ratio D of the laser light LB is calculated as the warning threshold value Wpk(N) by Wpk(1) shown in the following formula (8). Wpk(1) is a calculation formula in which K(1) in the common formula is 1.

[0087] [Number 8] Wpk(1) = P × a × 1 × G + V0 (8)

[0088] Fig. 9 is a graph showing the change in the detection value X (sensor output voltage) of the sensor 27 and the warning threshold value Wpk(2) when the duty ratio of the laser light is 40% and the pulse frequency is 5000 Hz. In Fig. 9, Wpk(2) is selected as the calculation formula for the warning threshold value Wpk(N).

[0089] In Figure 9, the pulse-on time t_on of the detection value during contamination is shorter than the sensor rise time tr, and the detection value during contamination does not rise to the maximum voltage. In this case, the voltage value proportional to the average output is calculated as the warning threshold value Wpk(N) by Wpk(2) shown in the following formula (9). Wpk(2) is a calculation formula in which K(2) in the common formula is D / 100.

[0090] [Number 9] Wpk(2)=P×a×(D / 100)×G+V0...(9)

[0091] Fig. 10 is a graph showing the change in the detection value X (sensor output voltage) of the sensor 27 and the warning threshold value Wpk(3) when the duty ratio of the laser light is 20% and the pulse frequency is 100 Hz. In Fig. 10, Wpk(3) is selected as the calculation formula for the warning threshold value Wpk(N).

[0092] In Figure 10, the pulse-on time t_on of the contamination detection value is shorter than the sensor rise time tr, and the pulse-off time t_off is longer. In this case, the voltage value proportional to the pulse-on time t_on is calculated as the warning threshold value Wpk(N) using Wpk(3) shown in the following formula (10). Wpk(3) is a calculation formula in which K(3) in the common formula becomes t_on / tr.

[0093] [Number 10] Wpk(3)=P×a×(t_on / tr)×G+V0...(10)

[0094] The pulse-on time t_on is calculated by the following equation (11).

[0095] [Number 11] t_on=(D / 100)×(1000 / F)=D×10 / F···(11)

[0096] Fig. 11 is a graph showing the change in the detection value X (sensor output voltage) of the sensor 27 and the warning threshold value Wpk(4) when the duty ratio of the laser light is 40% and the pulse frequency is 500 Hz. In Fig. 11, Wpk(4) is selected as the calculation formula for the warning threshold value Wpk(N).

[0097] In Fig. 11, the pulse-on time t_on of the contamination detection value is shorter than the sensor rise time tr, and the pulse-off time t_off is also shorter. In this case, the voltage value proportional to the pulse-on time t_on and the negative pulse-off time t_off is calculated as the warning threshold value Wpk(N) by Wpk(4) shown in the following formula (12). Wpk(4) is a calculation formula in which K(4) in the common formula becomes t_on / tr-t_off / tf+b / tr.

[0098] [Number 12] Wpk(4)=P×a×(t_on / tr-t_off / tf+b / tr)×G+V0...(12)

[0099] The pulse-off time t_off is calculated by the following equations (13) and (14).

[0100] [Number 13] t_off = T - t_on (13)

[0101] [Number 14] T=1000 / F (14)

[0102] In the above-described method, the dirt threshold setting unit 37 sets the warning threshold Wpk(N) and the alarm threshold Apk(N) as dirt thresholds for detecting dirt 51 on the protective glass 25 from the detection value X of the scattered light SL detected by the sensor 27, based on the processing conditions of the laser processing machine obtained from the NC device 23. This makes it possible to set a dirt threshold suitable for the processing conditions of the laser processing machine, even if the amount of scattered light SL scattered in accordance with the amount of dirt 51 on the surface of the protective glass 25 changes depending on the processing conditions of the laser processing machine.

[0103] Proceeding to step S15, the information acquisition unit 35 acquires information as to whether or not the NC device 23 has started laser processing from the NC device 23. If the NC device 23 has started laser processing (YES in step S15), the process proceeds to step S16. On the other hand, if the NC device 23 has not started laser processing (NO in step S15), the process returns to step S15.

[0104] In step S16, the sensor 27 detects the scattered light SL from the end face of the protective glass 25 attached to the processing head 21 while the laser light LB is being irradiated. The detection signal of the scattered light SL detected by the sensor 27 is amplified by the analog I / F circuit 31, and high-frequency components (noise) are cut off. The detection signal is converted from an analog signal to a digital signal by the AD converter 33 and output to the information acquisition unit 35 as the detection value X of the sensor 27. The information acquisition unit 35 acquires the detection value X from the AD converter 33.

[0105] Proceeding to step S17, the dirt determination unit 39 determines whether or not the detection value X exceeds the warning threshold value Wpk(N) calculated in step S14. If the detection value X exceeds the warning threshold value Wpk(N) (YES in step S17), that is, if the detection value X is greater than the warning threshold value Wpk(N), the process proceeds to step S18. On the other hand, if the detection value X is equal to or less than the warning threshold value Wpk(N) (NO in step S17), the process proceeds to step S21.

[0106] In step S18, the contamination determination unit 39 determines whether the detection value X exceeds the alarm threshold Apk(N) calculated in step S14. If the detection value X exceeds the alarm threshold Apk(N) (YES in step S18), that is, if the detection value X is greater than the alarm threshold Apk(N), the process proceeds to step S20. On the other hand, if the detection value X is equal to or less than the alarm threshold Apk(N) (NO in step S18), the process proceeds to step S19.

[0107] In step S19, the dirt determination unit 39 transmits a warning determination signal to the NC unit 23. In this case, the NC unit 23 displays a warning display on the display unit 23a. Then, the process proceeds to step S21.

[0108] In step S20, the dirt determination unit 39 transmits an alarm determination signal to the NC unit 23. In this case, the NC unit 23 displays an alarm display on the display unit 23a. The NC unit 23 also stops the processing of the laser processing machine. Then, the process proceeds to step S21.

[0109] In step S21, the information acquisition unit 35 acquires information on whether or not the NC device 23 has finished the laser processing from the NC device 23. If the NC device 23 has finished the laser processing (YES in step S21), the protective glass detection device ends the flow of Fig. 5. On the other hand, if the NC device 23 has not finished the laser processing (NO in step S21), the process returns to step S16.

[0110] [Effects] As described above, according to one aspect of the present invention, the following advantageous effects can be obtained.

[0111] In a laser processing machine, a protective glass dirt detection device that detects dirt on a protective glass 25 that protects a condenser lens 19 that condenses laser light LB and irradiates it on a workpiece W from dirt includes a scattered light detection unit (sensor 27), an information acquisition unit 35, a dirt threshold setting unit 37, and a dirt determination unit 39. The scattered light detection unit detects scattered light SL generated by dirt 51 attached to the protective glass 25. The information acquisition unit 35 acquires information on the processing conditions of the laser processing machine. The dirt threshold setting unit 37 sets a dirt threshold for detecting dirt on the protective glass 25 from a detection value X detected by the scattered light detection unit based on the processing conditions of the laser processing machine. The dirt determination unit 39 determines the degree of dirt on the protective glass 25 based on the detection value X and the dirt threshold.

[0112] The dirt threshold setting unit 37 sets a dirt threshold for detecting dirt on the protective glass based on the processing conditions of the laser processing machine. Even if the amount of scattered light SL scattered according to the amount of dirt 51 on the surface of the protective glass 25 changes depending on the processing conditions, a dirt threshold suitable for the processing conditions can be set. This makes it possible to appropriately detect dirt on the protective glass 25 of the laser processing machine according to the processing conditions. This makes it possible to reduce defective products during laser processing.

[0113] The processing conditions of the laser processing machine include an item for adjusting the average output Pav per unit time of the laser light LB emitted during processing. If the average output Pav of the laser light LB emitted during processing changes, the amount of laser energy irradiated to the protective glass 25 changes. By including an item for adjusting the average output Pav of the laser light LB in the processing conditions of the laser processing machine, it is possible to set a dirt threshold suitable for the processing conditions even if the amount of scattered light SL scattered in accordance with the amount of dirt 51 on the surface of the protective glass 25 changes depending on the average output Pav of the laser light LB emitted to the protective glass 25 during processing.

[0114] The processing conditions of the laser processing machine include an item for adjusting the irradiation area of ​​the laser light LB irradiated onto protective glass 25 during processing. When the irradiation area of ​​the laser light LB onto protective glass 25 changes, the amount of laser energy irradiated onto protective glass 25 changes. This makes it possible to set a dirt threshold suitable for the processing conditions, even if the amount of scattered light SL scattered in accordance with the amount of dirt 51 on the surface of protective glass 25 changes depending on the irradiation area of ​​the laser light LB irradiated onto protective glass 25.

[0115] The processing conditions of the laser processing machine acquired by the information acquisition unit 35 include the laser conditions of the laser light LB emitted during processing. The laser conditions of the laser light LB also include a laser peak output value P of the laser light LB emitted during processing, a pulse frequency F of the laser light LB, and a duty ratio D of the laser light LB. The beam diameter of the laser light LB when irradiating the workpiece W with the laser light LB is variable from the beam waist diameter to a beam diameter larger than the beam waist diameter by changing the beam diameter and the focal position by the optical system elements, and the laser conditions of the laser light LB include a gain correction value G indicating the degree of change in the beam diameter from when the beam diameter of the laser light LB is the beam waist diameter to when it becomes a beam diameter larger than the beam waist diameter.

[0116] The dirt threshold setting unit 37 can set a dirt threshold for detecting dirt on the protective glass 25, based on laser conditions such as the laser peak output value P of the laser light LB emitted during processing, the pulse frequency F, the duty ratio D, and the gain correction value G. Even if the amount of scattered light SL scattered in accordance with the amount of dirt 51 on the surface of the protective glass 25 changes depending on the laser conditions during processing, a dirt threshold suitable for the laser conditions can be set.

[0117] The processing conditions of the laser processing machine acquired by information acquisition unit 35 include the sensor characteristics of the scattered light detection unit. In addition, the sensor characteristics of the scattered light detection unit include a sensor rise time tr, which is the time required for the detection signal of the scattered light detection unit to reach a peak value from an initial voltage, a sensor fall time tf, which is the time required for the detection signal to fall from the peak value to the initial voltage, and a sampling frequency of the detection signal.

[0118] The dirt threshold setting unit 37 can set a dirt threshold for detecting dirt on the protective glass 25 based on sensor characteristics such as the sensor rise time tr and sensor fall time tf of the scattered light detection unit and the sampling frequency of the detection signal. Even if the amount of scattered light SL scattered in accordance with the amount of dirt 51 on the surface of the protective glass 25 changes depending on the sensor characteristics of the scattered light detection unit, a dirt threshold suitable for the sensor characteristics can be set.

[0119] The processing conditions of the laser processing machine acquired by the information acquisition unit 35 include the machine specifications of the laser processing machine that emits the laser beam LB. The machine specifications of the laser processing machine that emits the laser beam LB also include an arbitrary variable b determined by the machine specifications and the sensor specifications of the sensor 27, and an arbitrary variable a determined by the characteristics of the protective glass 25. The arbitrary variable b is a variable that specifies the timing of switching between the calculation formulas Wpk(3) and Wpk(4).

[0120] The dirt threshold setting unit 37 can set a dirt threshold for detecting dirt on the protective glass 25 based on the machine specifications of the laser processing machine, such as an arbitrary variable b that is determined by the machine specifications and the sensor specifications of the sensor 27 and that specifies the timing for switching between the calculation formulas Wpk(3) and Wpk(4), and an arbitrary variable a that is determined by the characteristics of the protective glass 25. Even if the amount of scattered light SL that is scattered according to the amount of dirt 51 on the surface of the protective glass 25 changes depending on the machine specifications of the laser processing machine, a dirt threshold suitable for the machine specifications of the laser processing machine can be set. Even if the machine specifications are changed, dirt on the protective glass 25 can be appropriately detected.

[0121] The dirt threshold setting unit 37 selects a dirt threshold calculation formula for setting the dirt threshold based on the processing conditions of the laser processing machine, and calculates the dirt threshold based on the selected dirt threshold calculation formula.

[0122] The dirt threshold setting unit 37 selects a dirt threshold calculation formula for calculating a dirt threshold suitable for the processing conditions based on the processing conditions of the laser processing machine. The dirt threshold is calculated based on the selected dirt threshold calculation formula. This makes it possible to set a dirt threshold suitable for the processing conditions based on the processing conditions of the laser processing machine.

[0123] The present invention is not limited to the above-described embodiment of the invention, and can be embodied in other forms by making appropriate modifications.

[0124] For example, the functions realized by the PLC 29 and the NC device 23 in the above embodiment may be realized by other devices such as a robot controller.

[0125] In the above embodiment, a single sensor 27 is mounted at a position where it receives scattered light SL from the end face of the protective glass 25, but the position of the sensor 27 may be a position other than the side face of the protective glass 25. Also, a plurality of sensors may be mounted, for example, arranged around the circumference of the side face of the protective glass 25. In this case, the plurality of sensors 27 may be a combination of sensors with different sensor characteristics, or the plurality of sensors 27 may be used separately, for example, for warnings and alarms. Also, a fiber may be attached near the protective glass 25, and the scattered light SL may be transmitted by the fiber to a sensor 27 located away from the protective glass 25.

[0126] In addition, the sensor gain of the sensor 27 may be changed externally. For example, when the dirt threshold value calculated based on the processing conditions is outside the measurement range of the sensor 27, the sensor gain of the sensor 27 may be changed externally so that the calculated dirt threshold value is within the measurement range of the sensor 27.

[0127] In addition, the dirt threshold value may be set based on parameters different from the parameters of the processing conditions of the laser processing machine used in the above embodiment. For example, the pulse width of the laser light LB may be used instead of the duty ratio D of the laser light LB. The defocus of the laser processing machine may be used instead of the gain correction value G determined by the beam diameter of the processing head 21.

[0128] The protective glass dirt detection device and protective glass dirt detection method of the above embodiment may be applied when laser processing is performed by a wobbling operation, or when multiple laser beams LB are incident on the protective glass 25. They may also be applied when laser processing is performed by a hybrid laser. They may also be applied when cutting processing is performed by a laser cutting machine. [Explanation of symbols]

[0129] 19 Condenser lens 25 Protective Glass 27 Scattered light detection unit (sensor) 35 Information Acquisition Department 37 Dirt threshold setting section 39 Dirt detection unit

Claims

1. A protective glass dirt detection device for detecting dirt on a protective glass for protecting a condenser lens for condensing a laser beam and irradiating the laser beam on a workpiece in a laser processing machine, comprising: a scattered light detection unit for detecting scattered light caused by dirt adhering to the protective glass; An information acquisition unit that acquires information regarding the processing conditions of the laser processing machine; a dirt threshold setting unit that sets a dirt threshold for detecting dirt on the protective glass from a detection value detected by the scattered light detection unit based on processing conditions of the laser processing machine; and a dirt determination unit that determines a degree of dirt on the protective glass based on the detection value and the dirt threshold value; Equipped with The processing conditions of the laser processing machine include an item for adjusting the average output per unit time of the laser light emitted during processing. Protective glass dirt detection device.

2. A protective glass dirt detection device for detecting dirt on a protective glass for protecting a condenser lens for condensing a laser beam and irradiating the laser beam on a workpiece in a laser processing machine, comprising: a scattered light detection unit for detecting scattered light caused by dirt adhering to the protective glass; An information acquisition unit that acquires information regarding the processing conditions of the laser processing machine; a dirt threshold setting unit that sets a dirt threshold for detecting dirt on the protective glass from a detection value detected by the scattered light detection unit based on processing conditions of the laser processing machine; and a dirt determination unit that determines a degree of dirt on the protective glass based on the detection value and the dirt threshold value; Equipped with The processing conditions of the laser processing machine include an item for adjusting an irradiation area of ​​the laser light irradiated onto the protective glass during processing. Protective glass dirt detection device.

3. A protective glass dirt detection device for detecting dirt on a protective glass for protecting a condenser lens for condensing a laser beam and irradiating the laser beam on a workpiece in a laser processing machine, comprising: a scattered light detection unit for detecting scattered light caused by dirt adhering to the protective glass; An information acquisition unit that acquires information regarding the processing conditions of the laser processing machine; a dirt threshold setting unit that sets a dirt threshold for detecting dirt on the protective glass from a detection value detected by the scattered light detection unit based on processing conditions of the laser processing machine; and a dirt determination unit that determines a degree of dirt on the protective glass based on the detection value and the dirt threshold value; Equipped with The processing conditions of the laser processing machine include laser conditions of the laser light emitted during processing. Protective glass dirt detection device.

4. A protective glass dirt detection device for detecting dirt on a protective glass for protecting a condenser lens for condensing a laser beam and irradiating the laser beam on a workpiece in a laser processing machine, comprising: a scattered light detection unit including a sensor for detecting scattered light caused by dirt adhering to the protective glass; An information acquisition unit that acquires information regarding the processing conditions of the laser processing machine; a dirt threshold setting unit that sets a dirt threshold for detecting dirt on the protective glass from a detection value detected by the scattered light detection unit based on processing conditions of the laser processing machine; and a dirt determination unit that determines a degree of dirt on the protective glass based on the detection value and the dirt threshold value; Equipped with The processing conditions of the laser processing machine include the sensor characteristics of the scattered light detection unit. Protective glass dirt detection device.

5. A protective glass dirt detection device for detecting dirt on a protective glass for protecting a condenser lens for condensing a laser beam and irradiating the laser beam on a workpiece in a laser processing machine, comprising: a scattered light detection unit for detecting scattered light caused by dirt adhering to the protective glass; An information acquisition unit that acquires information regarding the processing conditions of the laser processing machine; a dirt threshold setting unit that sets a dirt threshold for detecting dirt on the protective glass from a detection value detected by the scattered light detection unit based on processing conditions of the laser processing machine; and a dirt determination unit that determines a degree of dirt on the protective glass based on the detection value and the dirt threshold value; Equipped with The dirt threshold setting unit is Selecting a calculation formula for a dirt threshold for setting the dirt threshold based on the processing conditions of the laser processing machine; Calculating the contamination threshold value based on the selected calculation formula for the contamination threshold value Protective glass dirt detection device.

6. The protective glass contamination detection device according to claim 3 , wherein the laser conditions include a laser peak output value of the laser light emitted during processing, a pulse frequency of the laser light, and a duty ratio of the laser light.

7. a beam diameter of the laser beam when irradiating the upper surface of the workpiece with the laser beam is variable from a beam waist diameter to a beam diameter larger than the beam waist diameter by changing the beam diameter or the focal position using an optical system element; The laser condition includes a gain correction value indicating a degree of change in the beam diameter of the laser light from a beam waist diameter to a beam diameter larger than the beam waist diameter. The protective glass contamination detection device according to claim 3 or 6.

8. The protective glass dirt detection device of claim 4, wherein the sensor characteristics include a sensor rise time, which is the time required for the detection signal of the scattered light detection unit to reach a peak value from an initial voltage, a sensor fall time, which is the time required for the detection signal to fall from the peak value to the initial voltage, and a sampling frequency of the detection signal.

9. A protective glass dirt detection device for detecting dirt on a protective glass for protecting a condenser lens for condensing a laser beam and irradiating the laser beam on a workpiece in a laser processing machine, comprising: a scattered light detection unit including a sensor for detecting scattered light caused by dirt adhering to the protective glass; An information acquisition unit that acquires information regarding the processing conditions of the laser processing machine; a dirt threshold setting unit that sets a dirt threshold for detecting dirt on the protective glass from a detection value detected by the scattered light detection unit based on processing conditions of the laser processing machine; and a dirt determination unit that determines a degree of dirt on the protective glass based on the detection value and the dirt threshold value; Equipped with The processing conditions of the laser processing machine include a mechanical specification of the laser processing machine that emits the laser light, The machine specifications include an arbitrary variable determined by the machine specifications and the sensor specifications of the scattered light detection unit, and an arbitrary variable determined by the characteristics of the protective glass. Protective glass dirt detection device.

10. A method for detecting dirt on a protective glass in a laser processing machine, the method comprising the steps of: detecting dirt on the protective glass, the protective glass protecting a condenser lens for condensing a laser beam and irradiating the condenser lens on a workpiece from dirt flying from the workpiece during laser processing; Detecting scattered light caused by dirt adhering to the protective glass by a scattered light detection unit including a sensor; Acquire information regarding the processing conditions of the laser processing machine; setting a dirt threshold value for detecting dirt on the protective glass from the detection value of the detected scattered light based on processing conditions of the laser processing machine; determining a degree of contamination of the protective glass based on the detection value of the scattered light and the contamination threshold value; The processing conditions of the laser processing machine are as follows: An item for adjusting the average output per unit time of the laser light emitted during processing; an item for adjusting an irradiation area of ​​the laser light irradiated onto the protective glass during processing; Laser conditions of the laser light emitted during processing; a sensor characteristic of the scattered light detection unit; an arbitrary variable determined by the machine specification of the laser processing machine that emits the laser light and the sensor specification of the scattered light detection unit, and an arbitrary variable determined by the characteristics of the protective glass; Contains at least one of A method for detecting dirt on protective glass.

11. A method for detecting dirt on a protective glass in a laser processing machine, the method comprising the steps of: detecting dirt on the protective glass, the protective glass protecting a condenser lens for condensing a laser beam and irradiating the condenser lens on a workpiece from dirt flying from the workpiece during laser processing; Detecting scattered light caused by dirt adhering to the protective glass; Acquire information regarding the processing conditions of the laser processing machine; setting a dirt threshold value for detecting dirt on the protective glass from the detection value of the detected scattered light based on processing conditions of the laser processing machine; determining a degree of contamination of the protective glass based on the detection value of the scattered light and the contamination threshold value; Selecting a calculation formula for a dirt threshold for setting the dirt threshold based on the processing conditions of the laser processing machine; Calculating the contamination threshold value based on the selected calculation formula for the contamination threshold value A method for detecting dirt on protective glass.

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