JP2008000801A - Laser beam machining apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining apparatus capable of condensing laser beams, performing welding by performing scanning with the laser beams, and enhancing accuracy of the laser beam welding. <P>SOLUTION: The laser beam machining apparatus 1 has a machining head 3 which has a collimation lens 11 and a condensing lens 12 arranged on the optical axis LS of the laser beams, condenses the laser beams on the scheduled welding line SS of a work W by the condensing lens 12, and moves the machining head 3 so as to perform the scanning along the scheduled welding line SS. The laser beam machining apparatus comprises a wedge substrate 13 arranged on the optical axis LS, a rotary mechanism 22 for rotating the wedge substrate 13 around the optical axis LS, an acceleration sensor 23 for detecting acceleration of the machining head 3, and a correction control unit 26c for outputting a correction control signal for rotating the wedge substrate 13 on the basis of the acceleration detected by the acceleration sensor 23 in order to correct the deviation of the optical axis LS caused by displacement of the machining head 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus that focuses a laser and performs welding by scanning the laser.

Conventionally, a laser processing apparatus described in Patent Document 1 below is known as a technique in such a field. In this laser processing apparatus, the laser output from the laser oscillator is transmitted to the processing head through an optical fiber. In the processing head, a collimation lens and a condenser lens are disposed on the optical axis of the laser. The laser processing apparatus performs continuous welding by performing scanning while irradiating an object to be welded with a laser beam condensed by a condenser lens.
JP-A-11-192573

  When performing continuous welding of workpieces, it is necessary to move the machining head at a predetermined speed along the planned joining line. However, if the machining head is moved, the machining head will be shaken to the left and right, and further, the inertial force acting on the machining head will increase the deflection width of the machining head, possibly reducing the accuracy of laser welding. there were.

  Then, an object of this invention is to provide the laser processing apparatus which can improve the precision of laser welding.

  The present invention includes a processing head having a collimation lens and a condensing lens disposed on the optical axis of a laser, and condenses the laser on the planned joining line of the workpiece by the condensing lens, In a laser processing apparatus that moves a processing head so as to scan along, a wedge substrate disposed on the optical axis, a rotation mechanism that rotates the wedge substrate around the optical axis, and detection that detects a displacement value of the processing head Correction control for outputting a correction control signal for rotating the wedge substrate to the rotation mechanism based on the displacement value detected by the detection unit in order to correct the vibration of the optical axis caused by the displacement of the head and the machining head And a section.

  In this laser processing apparatus, a wedge substrate is disposed on the optical axis of the laser, and the wedge substrate is rotated around the optical axis by a rotation mechanism. The optical axis of the laser that passes through the wedge substrate is refracted in accordance with the inclination angle of the wedge substrate, and moves with the rotation of the wedge substrate. When the machining head moving for laser scanning is displaced and the optical axis of the laser is shaken, the correction control unit outputs a correction control signal for rotating the wedge substrate based on the displacement value of the machining head detected by the detection unit. Output to the rotation mechanism. The rotation mechanism rotates the wedge substrate based on the input correction control signal, and corrects the blurring of the optical axis of the laser. According to the laser processing apparatus, the laser optical axis blur can be corrected by rotating the wedge substrate without moving the processing head, so that the laser optical axis blur can be easily corrected and the accuracy of laser welding can be improved. .

  Furthermore, it is preferable that the wedge substrate is disposed between the collimation lens and the condenser lens. If the wedge substrate is disposed on the upstream side of the optical path from the collimation lens, the laser optical axis blur cannot be sufficiently corrected unless the incident angle of the laser with respect to the lens normal is increased. However, when the incident angle is large, the aberration of the lens increases, and it is difficult to obtain a desired beam spot size, which may reduce the welding accuracy. Further, when the wedge substrate is disposed on the downstream side of the optical path with respect to the condensing lens, the working distance becomes small. Therefore, when the wedge substrate is placed between the collimation lens and the condenser lens, it becomes easy to make the beam spot the desired size while correcting the blurring of the optical axis of the laser. It becomes possible to widen the distance. As a result, the accuracy of laser welding can be improved.

  Furthermore, the detection unit is preferably an acceleration sensor that detects acceleration as a displacement value of the machining head. The displacement direction and displacement amount can be obtained from the acceleration detected by the acceleration sensor, and the wedge substrate is rotated so as to cancel the displacement amount, thereby enabling highly accurate correction, and as a result, the accuracy of laser welding. Can be improved.

  It aims at providing the laser processing apparatus which can improve the precision of laser welding.

  Hereinafter, preferred embodiments of a laser processing apparatus according to the present invention will be described in detail with reference to the drawings.

(Laser processing equipment)
As shown in FIG.1 and FIG.2, the laser processing apparatus 1 is a welding apparatus which uses a YAG laser as a heat source for welding. The laser processing apparatus 1 irradiates a laser beam toward a laser plate 2 (a workpiece to be welded) W and a laser oscillation unit 2 that outputs a laser having an oscillation wavelength of 1.06 μm by irradiating the YAG laser rod with light from an excitation lamp. A processing head 3 to be irradiated, an optical fiber 4 that transmits a laser from the laser oscillation unit 3 to the processing head 3, and a gas that is fixed to the processing head 3 and that injects a shielding gas obliquely from above toward the focal position of the laser. And a supply nozzle 6. The processing head 3 is supported by the manipulator 7 and moves along a straight joining line SS at the place where the two plate materials W are abutted.

  A condensing optical system 8 is provided in the case 3 a of the processing head 3. The optical fiber 4 that transmits the laser from the laser oscillation unit 2 to the condensing optical system 8 has a diameter of 0.6 mm, and the laser emitted from the optical fiber 4 diffuses with NA 0.2.

  2 and 3, the condensing optical system 8 includes a collimation lens 11 and a condensing lens 12 disposed on the optical axis LS of the laser, and the collimation lens 11 on the optical axis LS of the laser. A wedge substrate 13 is disposed between the condenser lenses 12. The collimation lens 11 is a plano-convex lens made of BK7 and having a focal length of 50 mm, and is separated from the tip of the optical fiber 4 by about 50 mm. The laser emitted from the tip of the optical fiber 4 is shaped in parallel by the collimation lens 11 and enters the wedge substrate 13.

  The wedge substrate 13 (see FIG. 4) is circular, and the upper surface 13a on the collimation lens 11 side is inclined with respect to the lower surface 13b on the condenser lens 12 side, and the inclination angle θ is about 10 degrees. The laser incident on the upper surface 13 a of the wedge substrate 13 is refracted by an angle α “about 5.1 degrees” while being parallel and enters the condenser lens 12.

  The condenser lens 12 is a convex lens made of BK7 and having a focal length of 50 mm, and is 10 mm away from the lower surface 13 b of the wedge substrate 13. The laser beam transmitted through the condenser lens 12 is condensed at a position about 50 mm away from the condenser lens 12. The focal position of the condensing lens 12 is shifted by about 4.44 mm as compared to the case where the wedge substrate 13 is not disposed. This deviation amount L is closely related to the inclination angle θ of the wedge substrate 13, and the deviation amount L increases as the inclination angle θ increases (see FIG. 10).

  As shown in FIGS. 3 and 4, the wedge substrate 13 is fixed inside a cylindrical member 17, and the cylindrical member 17 is fixed to a bracket 16 via a bearing 14, and the bracket 16 is fixed to the case 3a. . A gear 17a is provided at a lower portion of the cylindrical member 17 that is rotatably supported by the bearing 14. The gear 17 a is connected to the output shaft 19 a of the motor 19 through the speed reduction mechanism 18. The motor 19 is driven and controlled by a motor driver 21 (see FIG. 2), and the cylindrical member 17 and the wedge substrate 13 are rotated at a predetermined rotational angular velocity by driving the motor 19. The cylindrical member 17, the speed reduction mechanism 18, the motor 19, and the motor driver 21 constitute a rotation mechanism 22 for the wedge substrate 13.

  The wedge substrate 13 rotates about the optical axis LS of the incident laser. When the wedge substrate 13 rotates, the refraction direction of the laser optical axis LS changes, the laser optical axis LS moves, and the focal position moves. When the optical axis LS of the laser is shaken as the machining head 3 is shaken, it can be corrected by rotating the wedge substrate 13. As the tilt angle θ of the wedge substrate 13 is increased, the range in which the blurring of the optical axis LS can be corrected increases. However, as the tilt angle θ increases, the aberration of the focal point increases and affects the processing performance. The inclination angle θ of 13 is preferably about “10 °”.

  An acceleration sensor (detection unit) 23 is fixed to the machining head 3 (see FIG. 2). The acceleration sensor 23 is a semiconductor two-axis sensor, and detects a two-dimensional acceleration in the horizontal plane as a displacement value of the machining head 3. When the machining head 3 is moved in order to perform laser scanning, the machining head 3 is slightly shaken to the left and right with the movement. The acceleration sensor 23 detects the acceleration accompanying this blur.

  As shown in FIG. 2, an incremental rotary encoder 24 is fixed to the motor 19. The rotary encoder 24 outputs a two-phase pulse corresponding to the amount of rotation of the wedge substrate 13. The pulses of each phase are output out of phase, the rotation direction is specified from the pulse output timing, the amount of rotation of the wedge substrate is detected from the number of pulses, and the rotation angle of the wedge substrate can be calculated It is like that. Note that the absolute rotation angle of the wedge substrate 13 may be detected by an absolute rotary encoder.

  The laser processing apparatus 1 includes a main control processing unit 29 including a CPU 26, a ROM 27, a RAM 28, and the like connected via a bus. The CPU 26 is connected to the manipulator 7, the laser oscillation unit 2, the motor driver 21, the acceleration sensor 23, and the rotary encoder 24 so that signals can be transmitted and received by wire or wirelessly.

  The CPU 26 controls the operation of the entire laser processing apparatus 1. In particular, the laser oscillation control unit 26 a that controls laser irradiation, the laser scanning control unit 26 b that controls the laser scanning speed, and the processing head 3 are shaken. And a correction control unit 26c that outputs a correction control signal for correcting the blurring of the optical axis LS of the generated laser to the motor driver 21.

  The laser oscillation control unit 26a outputs to the laser oscillation unit 2 an ON / OFF signal regarding the start and stop of laser irradiation and an irradiation intensity setting signal for setting the laser irradiation intensity. The laser scanning control unit 26 b outputs a speed setting signal for setting the laser scanning speed to the manipulator 7.

  The correction control unit 26c attenuates high frequency noise from the acceleration signal output from the acceleration sensor 23 using a low-pass filter, and extracts only a low frequency component of 100 Hz or less. FIG. 6 shows a vibration waveform WA1 obtained from the acceleration signal output from the acceleration sensor 23, and shows a state in which high-frequency noise is superimposed on a predetermined low-frequency component. FIG. 7 shows a vibration waveform WA2 composed of an acceleration signal obtained by extracting only a low frequency component with a low-pass filter. The period of the vibration waveform WA2 is 0.1 sec, and the amplitude d1 is 5 mm.

  Furthermore, the correction control unit 26c performs a moving average process on the acceleration signal composed of the low frequency component, and calculates the average acceleration of the sampling period. Further, the correction control unit 26c calculates the displacement direction from the average acceleration, integrates the average acceleration to calculate the displacement speed, and further integrates the displacement speed to calculate the displacement amount in the sampling period. Then, from the displacement direction and the displacement amount, the rotation direction and rotation angular velocity of the wedge substrate 13 necessary for correcting the blur of the optical axis LS of the laser are obtained. The RAM 28 stores a table in which the rotation angle, the displacement direction, and the displacement amount as the stop position of the wedge substrate 13 are associated with the rotation direction, the rotation angular velocity, and the rotation time of the wedge substrate 13, and the correction control unit 26c is stored in the RAM 28. Then, the rotation angle, displacement direction, and displacement amount of the wedge substrate 13 are set in the table search key, and the corresponding rotation direction, rotation angular velocity, and rotation time are obtained. A correction control signal related to the rotation direction and the rotation angular velocity is input to the motor driver 21. The motor driver 21 rotates the wedge substrate 13 for the time corresponding to the sampling period with the rotation direction and the rotation angular velocity based on the correction control signal.

  The CPU 26 is also connected to a control valve (not shown) that opens and closes the flow path of the shield gas supplied to the gas supply nozzle 6 so as to transmit a signal, and also outputs an open / close signal to the control valve.

(Correction control)
Next, correction control for correcting blurring of the optical axis LS of the laser during laser scanning will be described. As shown in FIG. 8A, in the laser processing apparatus 1 described above, the laser focal position is aligned with the planned joining line SS, and laser scanning is started. Prior to the start of laser scanning, the stop position before rotating the wedge substrate 13 is stored in the RAM 28 as an initial rotation angle. The rotation angle of the wedge substrate 13 stored in the RAM 28 is updated every time the wedge substrate 13 rotates.

  During laser scanning, as shown in FIG. 8B, the machining head 3 is likely to be shaken by vibration, and the blur width is likely to be increased by the inertial force acting on the machining head 3. As shown in FIG. 9A, when this blur is not corrected, the focal position of the laser draws a meandering locus Ft that blurs to the left and right across the planned joining line SS. The meandering locus Ft draws a sine curve, the wavelength d2 is about 10 mm, the period is 0.1 s, and the meandering width d3 is about 5 mm. Furthermore, the laser scanning speed is set to 6 m / min, and the frequency of the meandering locus Ft is 10 Hz.

  As shown in FIG. 5, during the laser scanning, the acceleration of the machining head 3 is monitored by the acceleration sensor 23. When the acceleration is detected (S1), an acceleration signal is output from the acceleration sensor 23 and the main control is performed. The data is input to the processing unit 29 (S2).

  When the acceleration signal is input from the machining head 3, the correction control unit 26c removes the high frequency by the low-pass filter and extracts only the low frequency component (see FIG. 7) (S3). Thereafter, the correction control unit 26c performs a moving average process on the acceleration signal composed of the low frequency component, and calculates an average acceleration within the sampling period “1/1000 sec” (S4). Further, the correction control unit 26c obtains the displacement direction from the average acceleration, calculates the displacement speed by integrating the average acceleration, and integrates the displacement speed to thereby calculate the displacement amount “0.003 mm” within the sampling period. Is calculated (S5).

  Thereafter, the correction control unit 26 c reads the rotation angle stored in the RAM 28 as the stop position of the wedge substrate 13. The correction control unit 26 c refers to the table stored in the RAM 28 together with the displacement direction and the displacement amount obtained in step 5, the rotation direction of the wedge substrate 13, the rotation angular velocity “5π rad / sec”, and the rotation time “ 0.025 sec "is obtained (S6).

  When the correction control unit 26c calculates the rotation angular velocity and rotation time of the wedge substrate 13, the rotation angle as the stop position of the wedge substrate 13 is referred to by the angle of the wedge substrate 13 depending on the rotation angle of the wedge substrate 13. This is because the displacement width of the focal position with respect to the change amount is different. When the relationship between the rotation angle of the wedge substrate 13 and the displacement width of the focal position is graphed, a sine curve is obtained. For example, when the amplitude is “A” and the angle is changed by “15 °” from the initial stop position at the rotation angle “0 °” so that the rotation angle is “15 °”, the displacement of the focal position is changed. Δy1 is “A × (sin (15 °) −sin (0 °)) = 0.259 × A”. On the other hand, when the rotation angle “15 °” is rotated by an angle change amount of “15 °” from the rotation angle “15 °”, the focal position displacement width Δy2 is “A × (sin (30 °) −sin”. (15 °)) = 0.241 × A ”. As described above, when the stop position of the wedge substrate 13 is different, the displacement widths Δy1 and Δy2 are different when the wedge substrate 13 is rotated by the same amount of angular change from each stop position. For this reason, the rotation angular velocity and the rotation time of the wedge substrate 13 are obtained with reference to the rotation angle as the stop position of the wedge substrate 13.

  Thereafter, the correction control unit 26c inputs a correction control signal related to the rotation direction and rotation angular velocity of the wedge substrate 13 obtained in Step 7 to the motor driver 21 of the rotation mechanism 22 (S7). The motor driver 21 of the rotation mechanism 22 drives and controls the motor 19 based on the correction control signal, and rotates the wedge substrate 13 for a predetermined rotation time at a predetermined rotation angular velocity (S8). As a result, as shown in FIG. 9B, the blurring of the laser optical axis LS caused by the shaking of the machining head 3 is corrected, and the meandering of the focal position of the laser is reduced so that it approaches a desired straight line. become.

  Thereafter, the correction control unit 26c updates the rotation angle as the stop position of the wedge substrate 13 stored in the RAM 28 to a new rotation angle of the wedge substrate 13 detected by the rotary encoder 24 (S9). Thus, the rotation angle of the wedge substrate 13 is updated each time the wedge substrate 13 rotates, and the updated new rotation angle is obtained when the rotation angular velocity and the rotation time of the wedge substrate 13 are obtained in step 6 described above. Used. Each of the above processes is repeatedly executed during laser scanning.

  According to the laser processing apparatus 1, since the blur of the optical axis LS of the laser can be corrected by rotating the wedge substrate 13 without moving the processing head 2, the blur of the optical axis LS of the laser can be easily corrected, and laser welding is performed. Accuracy can be improved.

  Further, if the wedge substrate 13 is disposed on the upstream side of the optical path from the collimation lens 11, the blurring of the optical axis LS of the laser cannot be sufficiently corrected unless the incident angle of the laser with respect to the lens normal is increased. However, when the incident angle is large, the aberration of the lens increases, and it is difficult to obtain a desired beam spot size, which may reduce the welding accuracy. Further, when the wedge substrate 13 is disposed downstream of the condenser lens 12 in the optical path, the working distance becomes small. In the laser processing apparatus 1, since the wedge substrate 13 is disposed between the collimation lens 11 and the condenser lens 12, the beam spot can be easily formed to a desired size while correcting the blurring of the optical axis LS of the laser. In addition, the working distance can be widened.

  Further, since the acceleration sensor 23 is used as a detection unit for detecting the displacement value of the machining head 23, the displacement direction and the displacement amount can be obtained, and the wedge substrate 13 is rotated so as to cancel the displacement amount. It is possible to perform correction with high accuracy, and as a result, the accuracy of laser welding can be improved.

  In addition, this invention is not limited to the above embodiment, You may reduce the influence of an aberration using an F (theta) lens as a condensing lens. Further, a plurality of wedge substrates may be provided, and a rotation mechanism that rotates each wedge substrate may be provided.

1 is a perspective view showing an embodiment of a laser processing apparatus according to the present invention. It is a block diagram of the laser processing apparatus shown in FIG. It is sectional drawing which expands and shows the wedge board | substrate and rotation mechanism of the laser processing apparatus shown in FIG. FIG. 4 is an end view taken along IV-IV in FIG. 3. It is a flowchart which shows the operation | movement procedure of the correction control which correct | amends the blurring of the optical axis of a laser. It is a graph which shows the vibration waveform calculated | required from the acceleration signal detected with the acceleration sensor, and is a figure which shows the state before the high frequency component removal by a low-pass filter. It is a graph which shows the vibration waveform calculated | required from the acceleration signal detected with the acceleration sensor, and is a figure which shows the state after high frequency component removal by a low-pass filter. It is a figure which shows the optical axis of the laser which moves with rotation of a wedge board | substrate, (a) is a figure which shows the state before a processing head shakes, (b) is the state which the processing head has blurred. (C) is a figure which shows the state which rotated the wedge board | substrate and correct | amended the blurring of the optical axis of a laser. The meandering locus | trajectory of the focus position which arises with the blurring of the optical axis of a laser is shown, (a) shows the case where correction | amendment is not performed, (b) is a figure which shows the case where correction | amendment is performed. It is a table | surface which shows the relationship between the inclination | tilt angle of a wedge board | substrate, and the deviation | shift amount of the focus position of a laser.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser processing apparatus, 3 ... Processing head, 11 ... Collimation lens, 12 ... Condensing lens, 13 ... Wedge board | substrate, 22 ... Rotation mechanism, 23 ... Acceleration sensor (detection part), W ... Plate material (to-be-welded object), Joined lines SS, LS ... optical axis.

Claims (3)

A processing head having a collimation lens and a condensing lens arranged on the optical axis of the laser is provided. The condensing lens condenses the laser on a planned joining line of an object to be welded, and follows the planned joining line. In the laser processing apparatus for moving the processing head so as to scan,
A wedge substrate disposed on the optical axis;
A rotation mechanism for rotating the wedge substrate around the optical axis;
A detection unit for detecting a displacement value of the machining head;
A correction control signal for rotating the wedge substrate based on the displacement value detected by the detection unit is output to the rotation mechanism in order to correct the blur of the optical axis caused by the displacement of the processing head. A laser processing apparatus comprising: a correction control unit that performs correction.   The laser processing apparatus according to claim 1, wherein the wedge substrate is disposed between the collimation lens and the condenser lens. The laser processing apparatus according to claim 1, wherein the detection unit is an acceleration sensor that detects acceleration as the displacement value of the processing head.

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