Laser processing machine and laser processing method

Abstract

To suppress amplitude of a processing head caused by an electrostatic capacitance-type sensor.SOLUTION: A laser processing machine comprises: a processing head 10 that irradiates a work-piece W with a laser beam; a Z-axis motor 30 that moves the processing head 10 along a vertical direction that is a normal direction of the work-piece W; an electrostatic capacitance-type sensor 11 that detects a gap Gp between the work-piece W and a tip of the processing head 10; and a control device 50 that performs copy-control by which the processing head 10 is moved in the vertical direction on the basis of control amounts calculated from a detected value by the sensor 11 and control gain. The control device 50 sets the control gain variably in accordance with the command gap so that the control gain becomes larger as the command gap is smaller.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a laser processing machine and a laser processing method.

Background Art

[0002] As a processing machine for performing cutting processing on a workpiece such as sheet metal, a laser processing machine that performs processing using a laser beam is known. The laser processing machine cuts the workpiece by thermal energy by irradiating the workpiece with a laser beam. The laser processing machine controls the movement of the processing head that irradiates the laser beam in the front-rear direction and the left-right direction according to the shape of the part to be cut out from the workpiece. Further, the laser processing machine performs following control to move the processing head in the vertical direction so that the gap between the workpiece and the tip of the processing head maintains a constant value.

[0003] For example, Patent Documents 1 and 2 disclose a method of switching a control gain, which is the movement response characteristic of the processing head when maintaining the gap between the workpiece and the processing head at a constant value.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Since the capacitive sensor is inexpensive, it is used for detecting the gap. When performing following control using a capacitive sensor, there is a problem that the vertical swing (amplitude) of the processing head becomes large depending on the commanded gap. Even the methods disclosed in Patent Documents 1 and 2 do not solve the problem of the amplitude of the processing head caused by the capacitive sensor. [Means for solving the problem]

[0006] A laser processing machine according to one aspect of the present invention includes a processing head that irradiates a workpiece with a laser beam, a drive unit that moves the processing head along the vertical direction perpendicular to the surface of the workpiece, a capacitive sensor that detects the gap between the workpiece and the tip of the processing head, and a control device that performs tracing control to move the processing head in the vertical direction based on a control amount calculated from the sensor's detected value and a control gain so that the gap maintains a command gap, wherein the control device variably sets the control gain according to the command gap such that the control gain increases as the command gap decreases.

[0007] According to one embodiment of the present invention, when the command gap is small, the control gain increases, improving the tracking ability of the processing head to the workpiece and reducing the gap error, i.e., the difference between the command gap and the actual gap. Increasing the control gain increases the amplitude of the processing head, but the effect of the amplitude is small when the command gap is small. On the other hand, when the command gap is large, the control gain decreases, which can suppress the vertical amplitude of the processing head. [Effects of the Invention]

[0008] According to one aspect of the present invention, the amplitude of the processing head caused by a capacitive sensor can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a block diagram showing the main parts of the laser processing machine according to this embodiment. [Figure 2] Figure 2 is a flowchart showing the procedure for setting the gap control gain in the laser processing method according to this embodiment. [Figure 3] Figure 3 shows the relationship between the Z-axis amplitude and the gap control gain. [Figure 4] Figure 4 shows the relationship between capacitance and gap. [Figure 5] Figure 5 shows the relationship between the Z-axis amplitude and the gap. [Modes for carrying out the invention]

[0010] The laser processing machine and laser processing method according to this embodiment will be described below with reference to the drawings. In this specification, the left-right and front-back directions, which are orthogonal to the horizontal direction, and the up-down directions, which are orthogonal to the left-right and front-back directions respectively, are used as definitions of the directions of the laser processing machine. The left-right and front-back directions correspond to the in-plane direction of the workpiece placed on the workpiece support, and the up-down direction corresponds to the direction perpendicular to the plane of the workpiece placed on the workpiece support.

[0011] Figure 1 is a block diagram showing the main parts of the laser processing machine according to this embodiment. The laser processing machine according to this embodiment includes a processing head 10 that irradiates a workpiece W with a laser beam, a Z-axis motor (drive unit) 30 that moves the processing head 10 along the vertical direction perpendicular to the surface of the workpiece W, a capacitive sensor 11 that detects the gap Gp between the workpiece W and the tip of the processing head 10, and a control device 50 that performs tracing control to move the processing head 10 in the vertical direction based on a control amount calculated from the detected value of the sensor 11 and the gap control gain so that the gap Gp maintains the command gap. The control device 50 variably sets the gap control gain according to the command gap such that the gap control gain increases as the command gap decreases.

[0012] The details of the laser processing machine according to this embodiment will be described below. The laser processing machine mainly consists of a processing head 10, a Z-axis motor 30, and a control device 50.

[0013] The processing head 10 irradiates the workpiece W from above with a laser beam to perform laser processing on the workpiece W. The laser beam emitted from the laser oscillator 16 is transmitted to the processing head 10 via a process fiber 15. A nozzle for emitting the laser beam is detachably attached to the tip of the processing head 10. A circular opening is provided at the tip of the nozzle, and the laser beam is irradiated onto the workpiece W from the opening at the tip of the nozzle.

[0014] The workpiece W is transported by a workpiece transport device (not shown) and supported by a workpiece support unit 20.

[0015] The Z-axis motor 30 is a Z-axis drive unit for moving the machining head 10 in the vertical direction, and is, for example, a servo motor. By driving the Z-axis motor 30, the machining head 10 can be moved in the vertical direction, which is perpendicular to the surface of the workpiece W.

[0016] The Z-axis motor 30 is equipped with an encoder 31 that detects the rotational movement of the Z-axis motor 30. The encoder signal indicating the detection result of the encoder 31 is output to the control device 50.

[0017] Furthermore, the laser processing machine is equipped with an X-axis drive unit for moving the processing head 10 in the left-right direction and a Y-axis drive unit for moving the processing head 10 in the front-back direction. By driving the X-axis drive unit and the Y-axis drive unit, the processing head 10 can be moved in the left-right and front-back directions, respectively, parallel to the workpiece W.

[0018] The control device 50 is composed of a computer having a hardware processor such as a CPU (Central Processing Unit), memory, and various interfaces. The memory and various interfaces are connected to the hardware processor via a bus. By having the hardware processor execute the program stored in memory, the various functions of the control device 50 are realized.

[0019] A sensor signal output from a sensor 11 mounted on the processing head 10 is input to the control device 50. The sensor 11 detects the distance between the workpiece W and the tip (nozzle) of the processing head 10, that is, the gap Gp between the workpiece W and the tip of the processing head 10. The sensor 11 is, for example, a capacitance-type sensor that detects the gap Gp by capacitance.

[0020] In the context of this embodiment, the control device 50 calls a processing program from the memory and executes it, controls the operations of each part of the laser processing machine, and performs laser processing on the workpiece W. For example, the control device 50 moves the processing head 10 in the left-right direction and the front-back direction so as to cut out a part having a predetermined shape from the workpiece W.

[0021] When moving the processing head 10 in the left-right direction and the front-back direction along with the laser processing of the workpiece W, the control device 50 performs follow-up control. Follow-up control refers to feedback control for moving the processing head 10 in the vertical direction so that the detected gap Gp maintains a commanded gap that is a command value in terms of control.

[0022] The control device 50 includes a gap detection unit 51, a deviation calculation unit 52, a gain switching unit 53, a controller 54, and a servo amplifier 55.

[0023] The gap detection unit 51 identifies a detection value of the sensor 11, that is, a detected gap Gp detected by the sensor 11, from the sensor signal input from the sensor 11. The identified detected gap is output to the deviation calculation unit 52.

[0024] The deviation calculation unit 52 calculates a deviation obtained by subtracting the detected gap from the commanded gap. The deviation calculation unit 52 can acquire the commanded gap from processing conditions defined in a processing program for laser-processing the workpiece W. The calculated deviation is output to the gain switching unit 53.

[0025] The gain switching unit 53 is equipped with multiple gap control gains, each associated with a command gap that has been pre-divided into multiple numerical ranges. In the example shown in Figure 1, three gap control gains Kg1, Kg2, and Kg3 are shown, and each of the gap control gains Kg1, Kg2, and Kg3 is associated with a command gap that has been divided into three numerical ranges, as will be described later. The gain switching unit 53 switches between the three gap control gains Kg1, Kg2, and Kg3 to variably set the gap control gain according to the command gap, such that the gap control gain increases as the command gap becomes smaller.

[0026] The number of switchable gap control gains does not need to be limited to the three mentioned above; it can be any number. The gain switching unit 53, like the deviation calculation unit 52, can obtain the command gap from the processing conditions specified in the processing program for laser processing the workpiece W.

[0027] The gap control gain is a parameter that determines the ratio of the vertical movement of the machining head 10 to the change in the gap Gp, and corresponds to the movement response characteristics of the machining head 10. The gain switching unit 53 calculates the amount of control to move the machining head 10 vertically based on the set gap control gain and the deviation calculated by the deviation calculation unit 52. The calculated amount of control is output to the controller 54.

[0028] The controller 54 generates a control signal corresponding to the control amount calculated by the gain switching unit 53, and outputs this control signal to the servo amplifier 55.

[0029] The servo amplifier 55 supplies power to the Z-axis motor 30 according to the error between the controlled amount for the Z-axis motor 30 and the actual amount of movement of the Z-axis motor 30, so that the control signal output from the controller 54 matches the encoder signal from the encoder 31.

[0030] Next, the laser processing method according to this embodiment will be described with reference to Figures 1 and 2. Here, Figure 2 is a flowchart showing the procedure for setting the gap control gain in the laser processing method according to this embodiment. The laser processing method according to this embodiment is implemented in the tracing control associated with laser processing of the workpiece W.

[0031] First, as shown in Figure 1, the sensor 11 detects the gap Gp between the workpiece W and the tip of the machining head 10. The gap detection unit 51 identifies the detected gap from the sensor signal output from the sensor 11.

[0032] The deviation calculation unit 52 reads the command gap defined in the machining conditions. The deviation calculation unit 52 calculates the deviation by subtracting the detection gap from the command gap.

[0033] In step S10 of Figure 2, the gain switching unit 53 reads the command gap defined in the machining conditions, similar to the deviation calculation unit 52.

[0034] In step S11, the gain switching unit 53 determines whether the command gap is less than or equal to the first threshold X1. The first threshold X1 is one of the first and second thresholds X1 and X2 used to divide the command gap into three numerical ranges, and is a smaller value than the second threshold X2.

[0035] If the command gap is less than or equal to the first threshold X1, the result is positive in step S11, and the process proceeds to step S12. On the other hand, if the command gap is greater than the first threshold X1, the result is negative in step S11, and the process proceeds to step S13.

[0036] In step S12, the gain switching unit 53 selects the largest gap control gain Kg1 from the three gap control gains Kg1, Kg2, and Kg3.

[0037] In step S13, the gain switching unit 53 determines whether the command gap is greater than the first threshold and less than or equal to the second threshold X2. If the command gap is greater than the first threshold X1 and less than or equal to the second threshold X2, the determination in step S13 is rejected, and the process proceeds to step S14. On the other hand, if the command gap is greater than the second threshold X2, the determination in step S13 is rejected, and the process proceeds to step S15.

[0038] In step S14, the gain switching unit 53 selects the intermediate gap control gain Kg2 from among the three gap control gains Kg1, Kg2, and Kg3.

[0039] In step S15, the gain switching unit 53 selects the smallest gap control gain Kg3 from the three gap control gains Kg1, Kg2, and Kg3.

[0040] As shown again in Figure 1, the gain switching unit 53 calculates the control amount of the machining head 10 based on the set gap control gain and the deviation calculated by the deviation calculation unit 52. Specifically, the control amount is calculated by integrating the gap control gain and the deviation.

[0041] The controller 54 outputs a control signal to the servo amplifier 55 that corresponds to the control amount calculated by the gain switching unit 53.

[0042] The servo amplifier 55 supplies power to the Z-axis motor 30 according to the error between the control signal output from the controller 54 and the encoder signal from the encoder 31, so that they match. As a result, the Z-axis motor 30 is driven, and the machining head 10 is moved upward and downward according to the controlled amount.

[0043] The relationship between the gap Gp and the vertical runout of the machining head 10 (hereinafter referred to as "Z-axis amplitude") will be explained below with reference to Figures 3 to 5. Here, Figure 3 shows the relationship between the Z-axis amplitude and the gap control gain. Figure 4 shows the relationship between capacitance and gap. Figure 5 shows the relationship between the Z-axis amplitude and gap.

[0044] Generally, a larger gap control gain is preferable because it reduces the difference between the command gap and the detection gap. However, as shown in Figure 3, increasing the gap control gain tends to increase the Z-axis amplitude. Therefore, keeping the gap control gain fixed at a large value is not desirable from the standpoint of Z-axis amplitude.

[0045] As shown in Figure 4, the detection characteristics of the capacitive sensor 11 are such that the capacitance decreases as the gap Gp increases, and therefore the resolution of the sensor 11 decreases as the gap Gp increases. For this reason, when tracking control is performed using the capacitive sensor 11, as shown in Figure 5, the Z-axis amplitude tends to increase as the gap Gp increases.

[0046] In this regard, according to the laser processing machine of this embodiment, the control device 50 variably sets the gap control gain according to the command gap such that the gap control gain increases as the command gap becomes smaller.

[0047] As a result, when the command gap is small, the gap control gain increases, improving the tracking ability of the machining head 10 to the workpiece W and reducing the gap error, i.e., the difference between the command gap and the detected gap. Increasing the gap control gain increases the Z-axis amplitude, but this effect is small when the command gap is small. On the other hand, when the command gap is large, the gap control gain is set low, so the Z-axis amplitude can be suppressed. Therefore, the amplitude of the machining head caused by the capacitive sensor can be suppressed.

[0048] In this embodiment, the control device 50 obtains the command gap from the processing conditions for laser processing the workpiece W.

[0049] This configuration allows for the appropriate acquisition of the command gap, which varies depending on the machining method. This enables the gap control gain to be set appropriately.

[0050] In this embodiment, multiple gap control gains Kg1, Kg2, and Kg3 are provided, each associated with a command gap that has been pre-divided into multiple numerical ranges. The control device 50 selects a gap control gain from among the multiple gap control gains Kg1, Kg2, and Kg3 to calculate the control amount, according to the category to which the command gap obtained from the machining conditions belongs.

[0051] This configuration allows for the appropriate determination of the gap control gain according to the command gap.

[0052] Furthermore, in the laser processing method according to this embodiment, the gap Gp between the workpiece W and the processing head 10 that irradiates the workpiece W with a laser beam is detected by a capacitive sensor 11, and the gap control gain is variably set according to the command gap such that the smaller the command gap relative to the gap Gp, the larger the gap control gain is, and the processing head 10 is moved vertically based on a control amount calculated from the value detected by the sensor 11 and the gap control gain so that the gap Gp maintains the command gap.

[0053] According to this method, when the command gap is small, the gap control gain increases, improving the tracking ability of the machining head 10 to the workpiece W and reducing the gap error, i.e., the difference between the command gap and the detected gap. Increasing the gap control gain increases the Z-axis amplitude, but this effect is small when the command gap is small. On the other hand, when the command gap is large, the gap control gain decreases, which suppresses the Z-axis amplitude. Therefore, the amplitude of the machining head caused by the capacitive sensor can be suppressed.

[0054] In this embodiment, the gap control gain may be one that changes depending on the response frequency of the feedback control system.

[0055] 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]

[0056] 10 Machining heads 11 sensors 15 Process Fibers 16. Laser Oscillator 20 Work support section 30 Z-axis motor 31 encoders 50 Control device 51 Gap detection unit 52 Deviation calculation section 53 Gain switching section 54 Controllers 55 Servo Amplifier

Claims

1. A processing head that irradiates a laser beam onto the workpiece, A drive unit that moves the machining head along the vertical direction which is perpendicular to the surface of the workpiece, A capacitive sensor for detecting the gap between the workpiece and the tip of the machining head, The control device includes a control device that performs tracing control to move the machining head vertically based on a control amount calculated from the sensor's detected value and the control gain, such that the gap maintains the command gap, The control device is The control gain is variably set according to the command gap such that the control gain increases as the command gap becomes smaller. Laser processing machine.

2. The control device acquires the command gap from the processing conditions for laser processing the workpiece. The laser processing machine according to claim 1.

3. Multiple control gains are provided that correspond to the command gap, which is divided into multiple numerical ranges in advance. The control device is Based on the command gap obtained from the processing conditions, the control gain for calculating the control amount is selected from among a plurality of control gains according to the corresponding category. The laser processing machine according to claim 2.

4. The gap between the workpiece and the processing head that irradiates the workpiece with a laser beam is detected by a capacitive sensor. The control gain is variably set according to the command gap such that the control gain increases as the command gap decreases. The machining head is moved vertically, perpendicular to the surface of the workpiece, based on a control amount calculated from the sensor's detected value and the control gain, so that the gap maintains the command gap. Laser processing method.

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