JP5201098B2 - Laser cutting apparatus and laser cutting method - Google Patents

Description

  The present invention relates to a laser cutting method and apparatus for thick steel plates and the like. In particular, it is a technique suitable for more flatly cutting the shape of the laser cut surface of a thick steel plate and other metal materials and inorganic materials capable of laser cutting.

  Laser cutting can be automated, especially when the steel sheet to be cut W is thin, in addition to advantages such as narrow cutting width (kerf) and low thermal distortion, so-called dross-free cutting is relatively easy. Since it is realized and does not require post-processing and is advantageous in terms of work efficiency, it is widely used in many industrial fields. Here, dross-free means, for example, when a horizontally placed steel sheet is cut by irradiating a laser beam from above vertically, a molten re-solidified product of the material W to be cut (cut surface) below the section (cut surface) of the cut steel sheet ( (Also referred to as dross or noro). On the other hand, in gas cutting, since dross adheres to the lower part of the cut surface, a care process for manually removing the adhering dross has been essential.

  However, since the laser output of a commercially available laser cutting machine is finite, as the material to be cut W becomes thicker, the melt tends to stay in the lower part of the cut surface, and heat is accumulated, so overcombustion As a result, the degradation of the cross-sectional quality becomes obvious, such as roughening of the cut surface and adhesion of dross. This is because the melt temperature decreases due to insufficient heat input and the viscosity increases, and the cutting groove (kerf) is narrow with respect to the thickness of the material to be cut W, so that the melt removal action by the assist gas flow is reduced. Is considered to be the main factor.

  On the other hand, a carbon dioxide laser is mainly used as a laser used in a commercially available laser cutting apparatus for a thick plate because of economical efficiency of the initial cost. The maximum average output of current commercial machines is 6kW. According to the investigation by the inventors of the present application, good cutting of mild steel is regularly performed using a 6 kW machine at the site of a shearing manufacturer or the like that mass-produces cut plate products obtained by cutting thick plates according to customer orders. The maximum value of the plate thickness that is possible is at most about 19 mm. Although there are carbon dioxide laser devices with an output exceeding 6 kW, it is difficult to maintain a good unimodal mode in the laser beam spatial mode (cross-sectional intensity distribution) due to distortion of the laser oscillator and optical system. As a result, the distortion of the laser beam becomes large, and some peaks are generated at positions off the optical axis, making it unsuitable for cutting. For these reasons, a carbon dioxide laser oscillator generally exceeding 6 kW is not used for laser cutting.

  Although a technique for reducing distortion by using artificial diamond for the output optical system is known, it is expensive and is not suitable for a laser for a laser cutting machine. In order to drastically eliminate the technical blockage as described above, it is considered necessary to make significant technological progress in carbon dioxide laser oscillators, or to significantly reduce the cost of other high-power lasers such as fiber lasers. .

  In order to improve the productivity by technically relieving the plate thickness limitation in laser cutting of these current thick plates in terms other than laser output, the cutting line (on the surface of the material to be cut) The upper limit of the plate thickness that can be cut is expanded by changing the irradiation position of the laser beam in a direction intersecting the cutting line and vibrating it so as to sew a straight line or a curve formed by the cutting portion) Several methods have been proposed. FIG. 4 shows a schematic diagram of an example of the locus of the laser beam on the surface of the material to be cut when the material to be cut is cut while oscillating the laser beam.

  For example, Patent Document 1 discloses a laser cutting method for cutting a material to be cut W while vibrating a laser beam focused on the surface of the material W to be cut. According to this method, a wide melted part is formed by vibrating the focused laser beam, so that the width of the kerf is widened, and the assist gas is sufficiently supplied to the deep part of the kerf so that the thick workpiece W Can be effectively laser-cut. As an example of the vibration pattern of the laser beam, a straight line perpendicular to the cutting line and a semicircle having a chord perpendicular to the cutting line are described.

  In Patent Document 2, as a method of cutting the workpiece W while vibrating the laser beam focused on the surface of the workpiece W, the vibration pattern of the laser beam is simply oscillated and cut in a direction parallel to the cutting line. A laser cutting method is disclosed in which a single vibration in a direction perpendicular to the line and a circular orbit as a combination of the two or a focal position is vibrated in the traveling direction of the laser light.

  However, the present inventors remarkably increase the limit thickness that can be cut when the laser beam is oscillated in a direction parallel to the cutting line and when the focused spot is oscillated in the traveling direction of the laser beam. It was experimentally investigated that it was difficult to obtain an effect.

  In addition, when the laser beam is oscillated in a direction perpendicular to the cutting line, an effect of increasing a significant limit plate thickness is experimentally recognized as compared with the case where the laser beam is not oscillated.

  On the other hand, in Patent Document 3, when the laser processing nozzle moves along the processing line, only the moving direction of the laser processing nozzle or the moving direction and speed (moving speed) are detected. A scanning laser beam vibration device comprising mirror drive control means for vibrating a laser beam at a predetermined angle, a predetermined frequency, and a predetermined amplitude with respect to the processing line based on a detected value of the moving direction or the moving speed. Has been disclosed by the present applicant.

JP-A-60-210384 JP-A-7-236987 JP 2007-21579 A

  In laser cutting of a steel sheet, it is said that the better the cutting surface is, the more dross-free and the smaller the unevenness of the cutting surface of the material to be cut. In most cases, the evaluation of the cut surface unevenness at the site is a sensory evaluation in which a WES1 standard sample is used as a guideline and compared at the visual level, but according to the quantitative evaluation by the roughness measuring instrument independently conducted by the inventors, the upper section If the Rz value is about 50 μm or less, it is consistent with good judgment by visual evaluation.

  In laser cutting by a laser cutting device provided with a scanning laser beam vibration device as described in Patent Document 3, it is possible to cut a material to be cut in various cutting line shapes. However, in the cutting by the apparatus, the cutting speed often greatly changes (acceleration, deceleration) at a cutting start portion, a corner portion where the cutting line sharply changes direction, or the like. The present inventors have found that a cross-sectional defect often referred to as “sag-like” is likely to occur in the steel plate cross section (cut surface) of the acceleration / deceleration section where the cutting speed changes greatly. Among the thick steel plates, in particular, when the thickness of the material to be cut W is relatively thin, such as 12 mm or less, the defect is frequently observed. FIG. 5 shows an example of the defect. It is a circled part. In addition, it is favorable except the part enclosed by the circle of FIG.

  The present invention has been made in view of the above-mentioned problems, and when cutting a thick plate of a material to be cut such as a steel material while oscillating a laser beam, the cutting speed is greatly changed in the middle of cutting, or complicated. An object is to obtain a cut surface having good properties even when cut with a cutting line having a proper shape.

This invention is made | formed in view of this point, and the summary of this invention for solving the said subject is as follows.
The laser cutting device of the present invention vibrates the laser beam when cutting the laser processing nozzle at a nozzle feed speed Vs relative to the material to be cut along the cutting line on the surface of the material to be cut. A laser cutting device for irradiating the laser beam, the laser processing head having a vibration mirror or a vibration lens for irradiating and condensing a laser beam on the workpiece, and the laser processing head moves along the cutting line When doing
Based on the detection value of the moving speed and the moving speed detecting means for detecting the moving direction and speed (moving speed) of the laser processing head, the vibration frequency and amplitude A so as to intersect the cutting line. Vibration drive control means for controlling the vibration mirror or the vibration lens to vibrate the laser beam while adjusting
The vibration drive control means sets the vibration frequency by multiplying the nozzle feed speed Vs by a preset coefficient C, and further, when the nozzle feed speed Vs is substantially constant, a first threshold value Vst. The amplitude A of the vibration of the laser beam monotonously decreases in the range of the feed speed of ₁ or more and less than the _second threshold value Vst2, and the amplitude A of the vibration is a constant value in the range of less than the _first threshold value Vst1. The nozzle feed speed Vs is based on an amplitude pattern in which the amplitude A is zero in the feed speed range equal to or greater than the _second threshold Vst ₂ and the relationship between the feed speed Vs and the amplitude is set in advance. set the amplitude a of the vibrations to, when the nozzle feeding speed Vs is changed from the initial value V ₁ to the target value V ₂ holds the frequency and amplitude of vibration set to the initial value V _1, the feed nozzle Speed Vs is eye Waiting to settle the target value V _2, and setting the frequency and amplitude of the vibration based on the amplitude pattern for the target value V ₂

  Further, the laser cutting device of the present invention has a distance meter for detecting the distance between the tip of the laser cutting nozzle of the laser processing head and the material to be cut, and the vibration drive control means measures the distance meter. Based on the value, the laser beam is vibrated when the distance is equal to or less than a preset value.

In the laser cutting method of the present invention, laser cutting is performed while oscillating a laser beam when a laser processing nozzle is moved at a nozzle feed speed Vs along a cutting line on a surface to be cut. A method of using a laser processing head having a vibration mirror or a vibration lens for condensing and irradiating a laser beam on the material to be cut, when the laser processing head moves along the cutting line,
Based on the moving speed detection step for detecting the moving direction and speed (moving speed) of the laser processing head, and the detected value of the moving speed, the vibration frequency and amplitude A so as to intersect the cutting line. A vibration drive control step for controlling the vibration mirror or the vibration lens to vibrate the laser beam while adjusting
In the vibration drive control step, the frequency of the vibration is set by multiplying the nozzle feed speed Vs by a preset coefficient C, and when the nozzle feed speed Vs is substantially constant, a first threshold value is set. The laser beam vibration amplitude A monotonously decreases in the feed speed range of Vst ₁ or more and less than the _second threshold value Vst ₂ , and the vibration amplitude A is constant in the range of the _first threshold value Vst _{1 or} less. The nozzle feed speed is a value based on an amplitude pattern in which the relationship between the feed speed Vs and the amplitude is preset in which the amplitude A is zero in the feed speed range of the second threshold Vst ₂ or more. set the amplitude a of the vibrations to Vs, when the nozzle feeding speed Vs is changed from the initial value V ₁ to the target value V ₂ holds the frequency and amplitude of vibration set to the initial value V _1, the nozzle Feeding speed Vs is waiting to settle down to the target value V _2, and setting the frequency and amplitude of the vibration based on the amplitude pattern for the target value V _2.

  When moving the laser cutting torch relative to the material to be cut along the cutting line on the surface of the material of the present invention, the laser beam is vibrated while changing the amplitude and frequency as a function of the moving speed. According to the laser cutting device that irradiates, the function of not reacting to the intermediate speed before reaching the high command feed speed from the stationary state of the torch or the constant low speed state in the laser cutting of the thick plate, and the front By suppressing the beam vibration in the processing step, it is possible to improve the cutting ability and perform stable laser cutting without defects.

It is a figure which shows an example of the laser cutting torch part (side sectional drawing) of the laser cutting device concerning embodiment of this invention, and another block structure. It is a figure which shows an example of the pattern of the relationship between the vibration signal input into the drive part in the vibration mirror 4, and the feed speed Vs in order to vibrate a laser beam. It is a perspective view showing the outline of the laser cutting device concerning an embodiment of the invention. It is a figure which shows the example of a locus | trajectory when the motion of a laser beam spot is made into the linear vibration orthogonal to a cutting line. It is a figure which shows an example of a chipped cutting defect. It is a figure which illustrates the acceleration / deceleration part in the square cutting path | route on a steel plate surface. 1 is a plan view of a schematic configuration example of a laser cutting device including a scanning laser beam vibration device in an embodiment of the present invention. It is a figure which shows an example of the mode of the acceleration from a fine process to this cutting process. It is a figure which shows an example of the experimental result which shows the relationship between the vibration frequency of a laser beam, and the depth of the laser stripe in a cut surface. It is a figure which shows the flowchart of the process which detects rapid acceleration / deceleration of a laser cutting torch in order to suppress a chipping-like cutting defect.

  A mode for carrying out the laser cutting apparatus and method of the present invention will be described in detail with reference to the drawings, taking a steel plate as an example of a material to be cut. In addition, in each figure below, the same number is attached | subjected to the part which has the same function, and duplication is avoided.

  The present inventors have used the laser cutting device provided with the scanning laser beam vibration device as described in Patent Document 3 to cause the above-mentioned cut-like cut surface when laser cutting is performed while vibrating the laser beam. I studied in detail. Specifically, in order to explain at which part of the material to be cut the above-mentioned poor defect is likely to occur, an example of a process in the case of cutting a rectangular steel plate will be described with reference to FIG. Here, the quadrangle shown in FIG. 6 corresponds to the cutting line. The laser beam travels on the cutting line while oscillating so as to cross the cutting line. A steel plate of a material to be cut is placed on the paper surface, and the coordinate system is taken with the upper direction on the paper surface as the Y axis positive direction and the right direction as the X axis positive direction. First, the steel plate is pierced, called piercing. Next, a low-speed cutting process (hereinafter referred to as “fine process”) is performed in the + Y direction. Next, a higher-speed cutting process (hereinafter referred to as “main cutting process”) is performed. Hereinafter, similarly, a square-shaped steel plate can be cut out by repeating the fine process → the main cutting process in the + X direction, the −Y direction, and the −X direction. At this time, since the laser processing head or workpiece to be irradiated with the laser beam has a finite mass and has inertia, it is impossible to change the direction rapidly. Therefore, the relative traveling speed (feeding speed) of the laser beam with respect to the material to be cut needs to be greatly decelerated and accelerated before and after the square corner. A section corresponding to a fine process on the surface of the material to be cut (denoted as a fine section) is indicated by a thick line in FIG. A chipped surface defect occurs during acceleration when switching from a fine section (feed speed Vj) to main cutting (feed speed Vk), or at the apex of the corner from main cutting (feed speed Vk). We found that this is a deceleration zone that switches to stop (feed speed 0). Note that a section corresponding to the main cutting step on the surface of the material to be cut is referred to as a main cutting section.

<Embodiment of Laser Cutting Device>
As an embodiment of the laser cutting device of the present invention, an example of a configuration based on a laser beam cutting device having the configuration of a scanning laser beam vibration device similar to that described in Patent Document 3 is shown in FIG. 3 (perspective view). ) And FIG. 7 (schematic plan view). The laser beam cutting apparatus includes a table on which steel plates of the material to be cut W can be loaded and which can move on the rail in the X-axis direction. The laser beam LB is focused and irradiated on the material W to be cut to produce a laser spot. Control in which the laser cutting head 9 having the laser cutting torch 7 and the oscillating mirror 4 that form the shape can move relatively two-dimensionally in the XY-axis direction on the surface of the workpiece W and control the laser cutting in an integrated manner. (NC) device, and a speed detecting means 1, an arithmetic unit 2, a signal generating device 3 and the like shown in FIG. 7 as a retrofit device for vibrating a laser beam. That is, as shown in FIG. 7, an instruction from the operation panel 15 is output to the speed detection unit 1 via the control panel 14, and a signal detected by the speed detection unit 1 is output to the calculation unit 2. In the calculation unit 2, the frequency and amplitude for vibrating the vibrating mirror 4 are calculated by calculation, and the signal is output to the vibrating mirror 4 via the signal generator 3. These devices are installed on a laser cutting machine gantry 16.

  FIG. 1 is a diagram showing a block configuration of a part mainly composed of the configuration of the optical system in the entire laser cutting apparatus of the present embodiment. The apparatus of the present invention collects and irradiates the laser beam LB on the workpiece W to form a laser spot, and cuts the laser spot while vibrating it in a direction perpendicular to the cutting line according to the feed rate. Device. This apparatus includes a laser apparatus 5 that outputs a laser beam LB and a laser cutting torch 7 that emits an assist gas coaxially with the laser beam LB together with the laser beam LB. As described above, based on the information from the torch, the speed detection means 1 for detecting the feed speed of the laser cutting torch 7 to the workpiece W, and the information from the speed detection means 1, the laser focused spot is used as a cutting line. A calculation unit 2 that determines a frequency and amplitude to be oscillated symmetrically in a direction orthogonal to the direction, a signal generator 3 that generates a vibration control signal of the laser beam LB based on an instruction from the calculation unit 2, and a vibration mirror 4 are provided. ing. Further, the laser cutting torch 7 is provided with a condenser lens 8 and an assist gas supply port 72. The laser cutting torch 7 and the condensing lens 8 are provided with a lifting mechanism (not shown). An example in which the vibrating mirror 4 has a drive unit (not shown) that vibrates the mirror will be described below.

(Speed detection means 1)
3 and 7, the speed detection means 1 for detecting a planar (two-dimensional) moving speed (moving direction and speed) of the laser cutting torch 7 with respect to the workpiece W is a numerical control that controls laser cutting. The position (XY coordinates) of the laser cutting torch 7 (in other words, the laser processing head 9) is obtained by taking out a signal from the (NC) apparatus or using an optical sensor such as a commercially available laser distance meter or an electromagnetic sensor such as a rotary encoder. ) And the moving speed is calculated from the change over time. The speed detecting means 1 can be constituted by a digital controller such as a PLC. At this time, the cycle for calculating the moving speed of the laser cutting torch 7 can be set to 50 msec, for example.

(Calculation unit 2)
The calculation unit 2 crosses the cutting line according to preset rules (amplitude and vibration pattern setting information) based on the information on the moving speed (moving direction and speed) input from the speed detecting unit 1. In order to oscillate the laser beam, a frequency f and an amplitude A for electrically oscillating the oscillating mirror 4 that reflects the laser beam are calculated by calculation. First, for the frequency f, for example, the feed speed of the laser cutting torch 7 with respect to the workpiece W, that is, the cutting speed (vector amount) is represented by V (Vx, Vy) (mm / s), and the absolute value of the feed speed V, that is, When the feed speed (scalar amount) is represented by Vs, the frequency f for oscillating the laser beam LB is determined by calculating f = C × Vs (Hz). Here, the coefficient C is a constant, but as a physical meaning, the pitch of the streak that occurs on the cut surface per unit length (mm) and extends in the thickness direction of the steel sheet (the center of the streak adjacent in parallel). Reciprocal of (interval). If C is increased, the interval between the streaks becomes fine, and if C is decreased, it becomes rough. According to the experiment by the present inventors, as shown in FIG. 9 (experimental value of the depth at which the striation reaches when Vs is 5 mm / s and the laser beam intensity is 1.1 kW), the streak reaches a value of about 20 Hz as shown in an example. It was confirmed that there was a depth peak. Therefore, in this case, it is preferable to set C = 4 from the above formula. However, considering an actual drive system, it is considered that a preferable result can be obtained even if C is set to 3 or more and 6 or less.

  Next, the amplitude A (Vp-p) of the vibration signal input to the drive unit in the vibration mirror 4 that reflects and vibrates the laser beam is set to Vs having a predetermined gradient such as A = 2.75-0.15 Vs. Decide as a function. As shown in an example in FIG. 2, the amplitude A is a function of a downward slope that monotonously decreases with respect to the feed speed. This is based on the fact that, from the viewpoint of heat input, in general, the thinner the plate thickness, the faster the feed rate during laser cutting, and the thicker it is necessary to slow down. Here, the relationship (gain) between the amplitude A of the vibration signal and the amplitude A ′ of the laser beam at the irradiated portion of the workpiece W is adjusted and set in advance. For example, 1 Vp-p of the amplitude A of the vibration signal is set as Xmmp-p of the amplitude A ′ of the laser beam.

  Then, from the X component Vx and the Y component Vy of the feed speed V, the angle between the feed direction of the laser cutting torch 7, that is, the tangential direction of the cut line and the coordinate axis is calculated, and the biaxial sine that electrically vibrates the vibrating mirror 4. The amplitude of the wave is corrected so that the vibration obtained by combining the two axes always has a vibration direction orthogonal to the cutting line.

(Signal generator 3)
The signal generator 3 generates a biaxial vibration signal to be sent to the vibration mirror 4 according to the frequency and amplitude set values output from the calculation unit 2. In the case where a piezoelectric element described later is used as an actuator, it is necessary to provide a DC offset because it is necessary to use the midpoint of the expansion / contraction stroke as an operating point. For example, if the full stroke is 10V, a DC offset of 5V is given. And a vibration signal is superimposed on this.

  The vibration signal generated by the signal generator 3 is not limited to a sine wave, and may be a scanning signal of a laser beam that generates various vibration patterns such as a rectangular wave, a triangular wave, or a sawtooth wave. The calculation unit 2 and the signal generator 3 constitute a vibration drive control unit.

(Vibrating mirror 4)
As shown in the configuration example of FIG. 1, the vibrating mirror 4 has a function of deflecting the laser beam LB by increasing the angle of the mirror and two-dimensionally scanning the laser beam spot on the workpiece W. Two-dimensional freedom is required for two-dimensional scanning. Now, let one axis be the X axis and the other be the Y axis. For example, the mirror 52 is supported by a mirror holder 55, and electrically extending and contracting elements 53 and 54 such as a piezo element are attached to a tilting mechanism of the X axis and the Y axis to vibrate biaxially. The tilt angle of the oscillating mirror 4 due to expansion and contraction of the piezo element and the vibration amplitude of the laser beam LB on the workpiece W correspond one-to-one. For example, when Vs = 8.3 mm / s, the amplitude A of the vibration signal input to the drive unit in the vibration mirror 4 is A = 1.5 Vp-p, and the vibration of the laser beam LB on the workpiece W The amplitude corresponds to 80 μm. The mirror 52 may be directly or indirectly water cooled.

  In the above, an embodiment in which the laser beam is oscillated as a means for oscillating the laser beam has been described. However, a oscillating lens that oscillates the lens in a direction perpendicular to the optical axis in a transmission optical system may be used. Good.

A mode in which a steel sheet is cut while being vibrated with a laser beam by the laser cutting apparatus having the above configuration will be described. The material to be cut W will be described below using a steel plate having a thickness of 9 mm as an example. FIG. 2 shows an example of a vibration signal pattern (vibration pattern) input to the drive unit in the vibration mirror 4 in order to explain an example of setting the amplitude of the laser beam LB. That is, the amplitude A of the vibration of the laser beam monotonously decreases in the feed speed range that is greater than or equal to the _first threshold value Vst ₁ and less than the _second threshold value Vst ₂ , and in the range that is less than the _first threshold value Vst ₁ , This is an example of a vibration pattern in which the amplitude A is a constant value and the amplitude A is zero in the feed speed range equal to or higher than the _second threshold value Vst2.

  Specifically, in the case of a laser cutting machine with an output of 6 kW, when the plate thickness is 9 mm, the feed rate is 6 mm / s or more and less than 18.3 mm / s in the example of FIG. Is set as a range for controlling (amplitude control speed range). A feed speed of less than 6 mm / s is regarded as a fine control range that is a feed speed range in a fine process, and is set to give a constant amplitude. Here, an example in which the constant amplitude is zero is shown. Note that no amplitude is given at the feed rate of 18.3 mm / s or higher, that is, no vibration is generated, but this is a relatively high-speed vibration of 4 × 18.3 = 73.2 Hz. This is because the heat conduction responsiveness in the kerf of the cutting material W is lost, and the heat input as viewed from the material W to be cut is equivalent to an elliptical beam that is long in the direction perpendicular to the cutting line. In other words, when the workpiece thickness is 9mm or less and the feed speed is 18.3mm / s or more, the power density (heat input per unit surface area) decreases even if the laser beam is vibrated. Since the performance deteriorates, the laser beam is not vibrated during high-speed feeding.

  2 shows an example of setting the relationship between the triangular amplitude A having a peak on the side where the feed speed is small and the feed speed Vs, the setting of the amplitude control speed range for the feed speed and The range in which the amplitude A is constant is appropriately set, for example, experimentally depending on the intensity of the laser beam, the thickness of the material to be cut such as a steel plate, and the thermal conductivity of the material to be cut. In addition to the above triangle, the relationship between the amplitude and the feed rate may be set by appropriately setting a pattern in which the amplitude monotonously decreases by experiment or heat conduction simulation.

  In this way, when cutting a steel plate or the like by vibration of a laser beam, as illustrated in FIG. 6 above, the occurrence of a poor cut surface defect is that the vibration amplitude is 0 when the plate thickness of the steel plate is 9 mm. It has already been described that this occurs when switching from a fine process section with a feed rate Vs <6 mm / s to a main cut process section with a feed rate Vs (> 18.3 mm / s) where the vibration amplitude is also zero. In this acceleration / deceleration section (fine process section), if the speed detection unit 1 performs speed detection during the acceleration (or deceleration) time zone shown in FIG. 8, the detected speed value is within the amplitude control speed range. Therefore, a relatively large vibration amplitude is generated. As a result, streaks having a relatively large periodicity are generated at the upper portion of the cut surface, and are conspicuous compared with other surfaces, so that it seems that the defect appears to be a chipped defect. Therefore, it is preferable to switch so that the vibration amplitude remains 0 in this acceleration / deceleration section.

  Also, when the thickness of the steel plate is thicker than 9 mm and the feed speed in the main cutting process section is set within the amplitude control speed range, the vibration amplitude is set to 0 in the fine process section in order to avoid an increase in amplitude.

  In the fine process section described above, in order to prevent a cross-sectional defect such as a void, the laser cutting torch 7 is moved relative to the workpiece W in order to set the vibration amplitude to a constant value including zero. This is realized by performing processing for evaluating the feed rate of the laser cutting torch 7 as shown below.

In the calculation unit 2, the feed speed of the laser cutting torch 7 detected by the speed detection unit 1 or the absolute value thereof at the time t _n (n = 1, 2,...) At a fixed time interval Δt according to the following definition ( Here, the evaluation is repeated using the feed speed Vs). Then, a value (nominal feed speed: adoption speed) of the evaluation result of the feed speed is output to the signal generator 3.

(Evaluation criteria / flow)
A. At time t _n, if the difference between the previous feed rate Vs and (t _n-1) and the current feed rate Vs (t _n) has exceeded the modulation dead width Vf (mm / s), this feed The speed Vs (t _n ) is adopted as the nominal feed speed of the laser cutting torch (denoted as the adopted speed), and the adopted speed Vss (t _n ) = Vs (t _n ).
B. If the difference between the previous adoption speed Vss (t _n-1 ) and the current feed speed Vs (t _n ) is less than the modulation dead width Vf, the previous speed is adopted as the adoption speed Vss (t _n ) = Vs (t _n-1 ) = Vss (t _n-1 ).
C. The previous time in definitions A and B is the speed adopted.
D. If the difference between the previous “actual” speed and the current speed is within the range defined by the modulation stability determination width Va, it is determined that they are equal, and the current speed is adopted.
E. When the speed is 0 mm / sec, it is 0 mm / sec regardless of the above.

In the signal generator 3, when Vs changes, a waveform is generated based on the defined function.

(When Vs = 0mm / s, constant voltage DC5V (generates a waveform that keeps on))

  FIG. 10 shows a flowchart of the process executed in the calculation unit 2 as described above to detect a sudden acceleration / deceleration of the laser cutting torch, set a nominal feed speed, and output the signal to the signal generator 3.

  Next, as a specific example of the process of detecting the fine process section from the time change of the feed speed Vs and adjusting the vibration amplitude, Example 1 is shown in Table 1 and Example 2 is shown in Table 2 (modulation dead width). Is set to 10 mm / sec and the modulation stability judgment width is set to 0.2 mm / sec).

時刻t_n−１においては、(9.0-1.2=7.8)の為今回の速度を使用。
時刻t_nにおいては、(18.3-1.2=17.1)の為今回の速度を使用。 (Example 1)

At time t _n−1 , this speed is used because (9.0−1.2 = 7.8).
At time t _n , this speed is used because (18.3-1.2 = 17.1).

時刻t_n−１においては、(9.0-1.2=7.8)の為前回の速度を使用。
時刻t_nにおいては、前回の実際の速度と変調安定判定幅Ｖａ内で同等の場合、その値を使用。 (Example 2)

At time t _n−1 , the previous speed is used because (9.0−1.2 = 7.8).
At time t _n , if the previous actual speed is equivalent to the modulation stability determination width Va, that value is used.

As described above, when the nozzle feeding speed Vs is changed from the initial value V ₁ to the target value V ₂ holds the frequency and amplitude of vibration set to the initial value V _1, the nozzle feeding speed Vs is waiting to settle down to the target value V _2, to set the frequency and amplitude of the vibration based on the amplitude pattern for the target value V _2.

  As described above, in the present invention, by adding a function that does not react to an intermediate speed before reaching a high command feed speed from a stationary state or a constant low speed state of the torch, the cutting ability is improved and defective Both stable laser cutting can be realized.

  If the direction perpendicular to the surface of the workpiece W is the Z axis, the distance between the workpiece W and the laser cutting nozzle 71 may be controlled to be constant at a predetermined value Z1 during laser cutting. You may make it measure the distance of the front-end | tip of the laser cutting nozzle 71, and the to-be-cut material W with the distance meter using a commercially available semiconductor laser etc., for example. A function of controlling the height of the laser cutting nozzle 71 using the measured value of the distance is incorporated in the vibration drive control means, and further, laser processing that operates based on a height control signal output from the vibration drive control means A lift drive unit (not shown) for the laser cutting nozzle 71 may be added in the head 9 or a lift drive unit (not shown) for moving the entire laser processing head 9 up and down may be provided.

  The vibration drive control is performed so that the laser beam is vibrated when the distance (interval) between the tip of the laser cutting nozzle 71 of the laser processing head and the material W to be cut is equal to or less than a predetermined set value, for example, 20 mm or less. By performing vibration control by means, workability and operability are improved.

  By the way, when cutting a coated steel sheet, a process of burning the coating with the torch raised and defocusing the beam is added as a pretreatment for cutting. In this case, the distance Z2 between the material to be cut W and the cutting nozzle is the above-mentioned cutting speed. Bigger than the case. By using this, only when Z is equal to or less than a predetermined value, the control of beam vibration can be applied to realize a coating burn-out process without unevenness. For example, when Z1 = 2 mm and Z2 = 50 mm, control should be performed with Z ≦ 10 mm.

  In the embodiment of the laser cutting apparatus of the present invention described above, the speed detection unit 1, the calculation unit 2, and the signal generation unit 3 control, for example, a position sensor such as an optical sensor or a rotary encoder, and laser cutting. It can be configured using a programmable logic controller (PLC) or a personal computer equipped with an I / O unit with a numerical control (NC) device that performs the above and an actuator such as a piezo element that drives a vibrating mirror.

  In the above, an example in which the material to be cut is a steel plate has been described in detail. However, the laser cutting apparatus of the present invention is flat even when cutting other metal materials and inorganic material thick plates that can be laser cut. It is useful for obtaining a cut surface having a good shape.

  The laser cutting device of the present invention was installed in a commercially available carbon dioxide laser-equipped cutting machine with an output of 6 kW to attempt laser cutting of mild steel. The condenser lens is made of ZnSe, and the focal length is 222.25 mm. The diameter of the laser beam incident on the condenser lens is about 35 mm, and the spot size at the focal point is about 0.4 mm. The material W to be cut was a mild steel sheet with a black skin.

  This embodiment will be described with reference to FIG. A laser beam LB (not shown) is output from the laser device 5, reflected in the transverse direction by the optical path bending mirror 11A, folded by the optical path length stabilizing device 11B, and directed to the workpiece W by the vibrating mirror 4 (in FIG. 3). -Z direction). The vibrating mirror 4 can be moved in the transverse direction (Y direction in FIG. 3). The laser cutting torch 7 is connected to the vibrating mirror 4 and can be expanded and contracted in the Z direction. These components are mounted on a carriage 12 that moves on the rail 13 in the longitudinal direction (X direction in FIG. 3). The vibrating mirror 4 independently vibrates the laser beam LB along two orthogonal axes. Further, the speed detection device 1 for detecting the feed speed of the laser cutting torch 7 with respect to the workpiece W is installed inside the NC device 10 although not shown. A calculation unit 2 for processing information from the speed detection device 1 is mounted on the carriage 12. A signal generator 3 that generates a vibration signal to be sent to the vibration mirror 4 in accordance with the frequency and amplitude specified by the calculation unit 2 is installed on a carriage 12.

  The logic described in the embodiment is mounted on the arithmetic unit.

  As a result of applying the apparatus of the present invention described above, in the laser cutting of a thick plate, by appropriately controlling the frequency and amplitude corresponding to the feed rate, a plate thickness of 32 mm using a carbon dioxide laser cutting machine with an output of 6 kW. It was confirmed that it was possible to laser cut with mild cross-section quality stably in mass production of up to mild steel.

  INDUSTRIAL APPLICABILITY The present invention can be used, for example, in a laser cutting technique that performs cutting such as welding or cutting using a metal or ceramic as an object to be cut.

DESCRIPTION OF SYMBOLS 1 Speed detection means 2 Calculation part 3 Signal generator 4 Vibration mirror (a drive apparatus is included)
DESCRIPTION OF SYMBOLS 5 Laser apparatus 7 Laser cutting torch 8 Condensing lens 9 Laser processing head 10 NC apparatus of laser cutting machine main body 11A Optical path bending mirror 11B Optical path length equalization apparatus 12 Car 13 Rail 14 Control panel 15 Operation panel 16 Laser cutting machine gantry 52 Mirror 53, 54 Piezo element 55 Mirror holder 71 Laser cutting nozzle 72 Assist gas supply port LB Laser beam W Material to be cut

Claims (3)

A laser cutting device that irradiates while oscillating a laser beam when a laser processing nozzle is moved at a nozzle feed speed Vs relative to the material to be cut along the cutting line on the surface of the material to be cut. There,
A laser processing head having a vibration mirror or a vibration lens for condensing and irradiating a laser beam on the material to be cut;
A moving speed detecting means for detecting a moving speed composed of a moving direction and a speed of the laser processing head when the laser processing head moves along the cutting line;
Based on the detection value of the moving speed, the vibration drive that controls the vibration mirror or the vibration lens to vibrate the laser beam while adjusting the vibration frequency and the amplitude A so as to intersect the cutting line. Control means,
The vibration drive control means sets the vibration frequency by multiplying the nozzle feed speed Vs by a preset coefficient C, and
When the nozzle feed speed Vs is substantially constant, the vibration amplitude A of the laser beam monotonously decreases in the feed speed range of the first threshold value Vst ₁ or more and less than the _second threshold value Vst ₂ . in threshold Vst ₁ below the range, the amplitude a is a constant value of vibration, in the second threshold value Vst ₂ or more feed rate in the range amplitude a is zero, the feed speed Vs and the amplitude Based on the amplitude pattern in which the relationship is set in advance, the vibration amplitude A with respect to the nozzle feed speed Vs is set,
When the nozzle feeding speed Vs is changed from the initial value V ₁ to the target value V ₂ holds the frequency and amplitude of vibration set to the initial value V _1, the nozzle feeding speed Vs is the target value V ₂ wait for the settling, the laser cutting device and setting the frequency and amplitude of the vibration based on the amplitude pattern for the target value V _2. A distance meter for detecting the distance between the tip of the laser cutting nozzle of the laser processing head and the material to be cut;
2. The laser cutting according to claim 1, wherein the vibration drive control unit vibrates the laser beam when the distance is equal to or less than a preset value based on a measurement value of the distance meter. apparatus. A laser cutting method of irradiating while oscillating a laser beam when a laser processing nozzle is moved relatively along a cutting line on a surface to be cut at a nozzle feed speed Vs for cutting.
Using a laser processing head having a vibration mirror or a vibration lens for condensing and irradiating a laser beam on the material to be cut,
A moving speed detecting step of detecting a moving speed composed of a moving direction and a speed of the laser processing head when the laser processing head moves along the cutting line;
Based on the detection value of the moving speed, the vibration drive that controls the vibration mirror or the vibration lens to vibrate the laser beam while adjusting the vibration frequency and the amplitude A so as to intersect the cutting line. A control process,
In the vibration drive control step, the nozzle feed speed Vs is multiplied by a preset coefficient C to set the vibration frequency,
When the nozzle feed speed Vs is substantially constant, the vibration amplitude A of the laser beam monotonously decreases in the feed speed range of the first threshold value Vst ₁ or more and less than the _second threshold value Vst ₂ . in threshold Vst ₁ below the range, the amplitude a is a constant value of vibration, in the second threshold value Vst ₂ or more feed rate in the range amplitude a is zero, the feed speed Vs and the amplitude Based on the amplitude pattern in which the relationship is set in advance, the vibration amplitude A with respect to the nozzle feed speed Vs is set,
When the nozzle feeding speed Vs is changed from the initial value V ₁ to the target value V ₂ holds the frequency and amplitude of vibration set to the initial value V _1, the nozzle feeding speed Vs is the target value V ₂ wait for the settling, laser cutting method characterized by setting the frequency and amplitude of the vibration based on the amplitude pattern for the target value V _2.

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