JP2012250263A - Method and apparatus for laser cutting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for laser cutting by which, when a route on a thick steel plate subject to laser cutting includes a small-diameter arc portion, a delay in cutting progress of the lower surface of a work to the upper surface thereof is reduced in the small-diameter arc portion so that the generation of rough surface can be prevented on a laser cutting face immediately after the laser cutting turns the small-diameter arc portion.SOLUTION: When cutting a thick steel plate by laser, the joint position between a straight portion or a curved portion and a small-diameter arc portion is set to an A position when viewed in the advancing direction of laser cutting, the joint position between the small-diameter arc portion and the following straight portion or curved portion is set to a B position after passing the A position, and the position located a predetermined distance away from the B position in the advancing direction of laser cutting is set to a C position. When compared with laser output and laser cutting speed of laser cutting to the A position, the laser output from the A position to the C position is kept the same and the laser cutting speed is controlled to be low for laser cutting processing, and the laser cutting after the C position is conducted in the same processing condition as the laser cutting to the A position.

Description

  The present invention relates to a laser cutting method and apparatus for performing laser cutting of a thick steel plate of, for example, about 8 mm to 32 mm, and more specifically, for example, a small-diameter arc portion having a radius of about 0.8 mm to 1.2 mm, The present invention relates to a laser cutting processing method and apparatus for cutting an arc portion having a radius not less than the radius of the small-diameter arc portion and not more than about ½ of the plate thickness.

  When performing laser cutting of a plate-shaped workpiece, when cutting the workpiece into a straight line or cutting into a curved line such as an arc with a relatively large radius of curvature, the laser output of the laser oscillator is high. In addition, the laser cutting process is efficiently performed by controlling the processing speed of the laser cutting at a high speed. When the straight cutting line or the curved cutting line is connected to a small-diameter small-diameter arc part or when an edge part that bends sharply is formed, burning due to excessive heat input is performed. In order to prevent this, the output of the laser oscillator is controlled to a small output and the speed of the laser cutting process is controlled to be low (see, for example, Patent Documents 1 and 2).

JP-A-6-63778 JP-A-7-195186

  Patent Document 1 discloses a case where laser cutting of a steel sheet as a workpiece is performed, and the laser beam frequency is controlled as a pulse cutting mode in order to prevent a burning phenomenon during laser cutting of a corner portion or an acute angle portion. It is described to do. In addition, since the thickness of the workpiece | work made into cutting object is not described in patent document 1, it is a case of the workpiece | work (thin board) of the general thickness whose thickness is about several mm.

  In Patent Document 2, when laser cutting of a corner portion of a workpiece is performed, as shown in FIG. 1 of Patent Document 2, the processing speed of laser cutting is controlled at a low speed and the laser output is controlled at a low output. It is described to do.

Furthermore, [0028], [0029], and [0030] of Patent Document 2 describe the following. That is, when approaching the corner portion with a laser power of 3000 W, a duty of 50%, and an assist gas pressure of 0.4 kgf / cm ² when performing a 90 ° edge machining on a workpiece having a workpiece material of SS400 and a workpiece thickness of 16 mm, In the conventional laser cutting processing method in which the laser power, the frequency, the duty, the assist gas pressure are gradually decreased, the laser oscillation is stopped at the corner portion, and the laser cutting processing is started again after a dwell time of 3 seconds. As shown in FIG. 7, the cut surface immediately after the corner was chipped.

  However, when the laser power is changed to 1000 W, the frequency is set to 10 Hz, the duty is changed to 15% at the corner, and the condition is gradually returned to the previous condition after the dwell time of 3 seconds, chipping occurs as shown in FIG. This is a good cross section. In addition, since the radius in the case of performing 90 ° edge processing is not described in Patent Document 2, it is assumed that the workpiece has a thickness of 16 mm, for example, a small diameter of about 1 mm. It is not what you have.

  And since the method of patent document 2 is provided with the dwell time of 3 second, there exists a problem in aiming at the efficiency improvement of a laser cutting process.

  By the way, the steel plate as the workpiece is SS material, oxygen is used as the assist gas, and the corner portion of the thick plate of 8 mm to 32 mm is laser-cut and the small-diameter arc portion having a radius of about 0.8 mm to 1.2 mm is laser-cut. In the same manner as in the case shown in FIG. 7 of Patent Document 2, a dent or burning may occur on the lower side of the cut surface immediately after passing through the corner portion. In addition, when using Chisso gas as the assist gas and performing laser cutting processing on the same small-diameter arc portion of a thick steel plate corner as a workpiece, plasma is generated in the lower part immediately after passing the corner, There may be a rough surface due to a cut surface corresponding to the plasma generation position.

  It should be noted that the lower cut surface immediately after passing the corner portion becomes rough, although it is extremely likely to occur in the case of the radius, although there is a difference in the degree of the rough surface, the thickness of the thick plate is about It may also occur in the case of a radius of 1/2.

  The present invention has been made in view of the above-described problems, and a small-diameter arc portion having a radius of 0.8 mm to 1.2 mm in a minimal range during laser cutting of a thick steel plate workpiece using nitrogen gas as an assist gas. And / or a laser cutting method for cutting a small-diameter arc portion having a radius in a small range that is larger than the radius of the minimum range and smaller than a radius of ½ of the plate thickness, and is a traveling direction in the laser cutting direction The connection position between the straight part or the curved part and the small-diameter arc part is A position, and the connection position between the small-diameter arc part and the next straight part or the curved part through the A position is B position, In addition, when the position at a predetermined distance in the laser cutting processing direction from the B position is the C position, the C output from the A position to the C with respect to the laser output and the laser cutting processing speed during the laser cutting processing up to the A position. Review up to position -Laser cutting is performed by controlling the laser cutting speed to a low speed while maintaining the same output, and the laser cutting after the C position is performed under the same processing conditions as the laser cutting up to the A position. Thus, laser cutting is performed.

  Further, when laser cutting of a workpiece of a thick steel plate using nitrogen gas as an assist gas, a small-diameter arc portion having a radius of 0.8 mm to 1.2 mm and / or a plate thickness larger than the radius of the minimum range is used. A laser cutting method for cutting a small-diameter arc portion having a radius in a small range smaller than a radius of 1/2, wherein the straight-line portion or the curved portion and the small-diameter arc portion as viewed in the traveling direction of the laser-cutting direction Is the A position, the connection position between the small-diameter arc portion and the next straight line portion or the curved portion passing through the A position is the B position, and a predetermined distance in the direction of laser cutting processing from the B position. When the position of C is the C position, the laser cutting processing speed from the A position to the C position is maintained at the same speed with respect to the laser output and the laser cutting processing speed at the time of laser cutting to the A position. laser Laser cutting is performed by controlling the output to a high output, and the laser cutting after the C position is performed under the same processing conditions as the laser cutting up to the A position. It is.

  In addition, when laser cutting a workpiece of a thick steel plate using oxygen as an assist gas, a small-diameter arc portion having a radius of 0.8 mm to 1.2 mm and / or a plate thickness larger than the radius of the minimum range is used. A laser cutting method for cutting a small-diameter arc portion having a radius in a small range smaller than a radius of 1/2, wherein the straight-line portion or the curved portion and the small-diameter arc portion between the small-diameter arc portion when viewed in the advancing direction of laser cutting processing The connection position is A position, the connection position between the small-diameter circular arc part and the next straight line part or curved part passing through the A position is B position, and a predetermined distance from the B position in the advancing direction of laser cutting processing When the position is the C position, the laser output from the A position to the B position is maintained at the same output with respect to the laser output and the laser cutting speed at the time of laser cutting to the A position. Slow speed The laser cutting process is performed under the control of the laser cutting process, and the laser cutting process speed up to the A position and the laser cutting process speed up to the B position are maintained while maintaining the same laser output from the B position to the C position. The laser cutting is performed under the control of the medium speed, and the laser cutting after the C position is performed under the same processing conditions as the laser cutting up to the A position. is there.

  In addition, when laser cutting a workpiece of a thick steel plate using oxygen as an assist gas, a small-diameter arc portion having a radius of 0.8 mm to 1.2 mm and / or a plate thickness larger than the radius of the minimum range is used. A laser cutting method for cutting a small-diameter arc portion having a radius in a small range smaller than a radius of 1/2, wherein the straight-line portion or the curved portion and the small-diameter arc portion between the small-diameter arc portion when viewed in the advancing direction of laser cutting processing The connection position is A, the position where the small-diameter circular arc part and the next straight line part or curved part pass through the A position is the B position, and a position at a predetermined distance from the B position in the direction of laser cutting processing Is set to the C position, the laser output while maintaining the laser cutting speed from the A position to the B position at the same speed with respect to the laser output and laser cutting speed at the time of laser cutting to the A position. To high output Laser cutting is performed under control, and a medium output between the laser output up to the A position and the laser output up to the B position while maintaining the laser cutting processing speed from the B position to the C position at the same speed. The laser cutting is performed by controlling the laser output, and the laser cutting after the C position is performed under the same processing conditions as the laser cutting up to the A position. is there.

  A laser cutting apparatus for performing laser cutting of a steel plate as a workpiece, the laser oscillator, a laser processing head for condensing and irradiating the workpiece with laser light oscillated from the laser oscillator, and the laser Assist gas supply means capable of switching nitrogen gas or oxygen as assist gas supplied to the machining head, control means capable of controlling the laser output of the laser oscillator and the relative movement speed of the laser machining head with respect to the workpiece, and assist gas When laser cutting of thick workpieces using nitrogen gas as a small radius arc part in the minimum range of radius 0.8mm to 1.2mm and / or larger than the radius of the minimum range than the radius of 1/2 of the plate thickness Is a first processing condition in which laser cutting processing conditions are stored in advance when laser cutting processing is performed on a small-diameter arc portion having a small radius in a small range. A table, and a small-diameter arc portion of a minimum range of 0.8 to 1.2 mm in radius and / or larger than the radius of the minimum range at the time of laser cutting of a thick workpiece using oxygen as an assist gas. A second machining condition table in which laser cutting machining conditions are stored in advance when performing laser cutting of a small-diameter arc portion having a small radius smaller than the radius of 2, and input from the input means for performing laser cutting of the workpiece A program prefetching means for prefetching the processed machining program, an assist gas selection means for selecting an assist gas corresponding to the material of the work prefetched by the program prefetching means, and a content prefetched by the program prefetching means. When the small-diameter arc portion is included, the first or second machining condition table is selected corresponding to the material of the workpiece read ahead. The machining condition table selection means and the laser oscillator output and workpiece with the machining conditions stored in the machining condition table selected by the machining condition table selection means when performing laser cutting of the small-diameter arc portion. And a control means for controlling a relative moving speed of the laser processing head with respect to the above.

  A laser cutting apparatus for performing laser cutting of a steel plate as a workpiece, the laser oscillator, a laser processing head for condensing and irradiating the workpiece with laser light oscillated from the laser oscillator, and the laser Assist gas supply means capable of switching nitrogen gas or oxygen as assist gas supplied to the machining head, control means capable of controlling the laser output of the laser oscillator and the relative movement speed of the laser machining head with respect to the workpiece, Program prefetching means for prefetching a machining program input from the input means for performing laser processing, assist gas selection means for selecting an assist gas corresponding to the material of the work prefetched by the program prefetching means, The content prefetched by the program prefetching means has a radius of 0.8 mm to 1.2 mm. Laser cutting of the small-diameter arc portion when the small-diameter arc portion in the minimum range and / or the small-diameter arc portion in the small range radius larger than the radius of the minimum range and smaller than ½ radius of the plate thickness are included. The input means for inputting the laser cutting processing conditions for performing processing, the processing condition memory for storing the laser cutting processing conditions input by the input means, and the processing conditions stored in the processing condition memory Therefore, the control means for controlling the output of the laser oscillator and the relative moving speed of the laser processing head with respect to the workpiece is provided.

  According to the present invention, even when laser cutting of a small-diameter arc portion is performed on a thick plate with respect to a thick plate, a recess, burning, or rough surface is generated below the cut surface immediately after passing through the corner portion. Can be prevented, and the cut surface of the workpiece can be laser processed into a good surface.

It is the functional block diagram which showed notionally and schematically the function of the whole structure of the laser cutting processing apparatus which concerns on embodiment of this invention. It is the functional block diagram which showed the function of the control apparatus which controls a laser cutting processing apparatus. It is explanatory drawing of a small diameter circular arc part. It is explanatory drawing of the data of a process condition table. It is explanatory drawing which showed the relationship between the laser actual output when performing the laser cutting process of the small diameter circular arc part in SUS as a workpiece | work, and a laser cutting process speed. It is explanatory drawing which showed the relationship between the laser actual output when performing the laser cutting process of the small diameter circular arc part in SS material as a workpiece | work, and a laser cutting process speed.

  As conceptually and schematically shown in FIG. 1, a laser cutting apparatus 1 according to an embodiment of the present invention includes a work table 3 that supports a work W made of a steel plate having a thickness of about 8 mm to 32 mm, for example. A laser processing head 5 for performing laser cutting processing of the workpiece W by irradiating W with laser light LB is provided. The work table 3 is provided so as to be relatively movable and positionable in the X and Y axis directions with respect to the laser processing head 5, and positioning for relatively moving and positioning the work table 3 in the X and Y axis directions. A motor 7 is provided. Further, a Z-axis motor 9 is provided for moving and positioning the laser processing head 5 in the Z-axis direction, which is a direction in which the laser processing head 5 is relatively moved toward and away from the workpiece W.

  The laser cutting device 1 is provided with a laser oscillator 11, and a reflecting mirror 13 that reflects the laser beam LB oscillated from the laser oscillator 11 in the workpiece W direction is provided in the laser processing head 5. And a condensing lens 15 that condenses the laser beam LB and irradiates the workpiece W. Further, the laser cutting apparatus 1 is provided with oxygen supply means 17 for supplying oxygen as an assist gas when the workpiece W is an SS material or the like, and when the workpiece W is SUS. A nitrogen gas supply means 19 for supplying nitrogen gas as an assist gas is provided. A switching valve 21 is provided that can switch the assist gas supplied corresponding to the material of the workpiece W to oxygen or nitrogen gas. That is, the oxygen supply means 17, the nitrogen gas supply means 19, and the switching valve 21 constitute one kind of assist gas supply means 23 that can switch between oxygen and nitrogen gas as an assist gas supplied to the laser processing head 5. .

  Further, the laser cutting device 1 is a control device 25 that controls the relative movement and positioning of the laser processing head 5 with respect to the workpiece W, controls the laser output in the laser oscillator 11, and controls the assist gas supply means 23. Is provided. The control device 25 is constituted by a computer and includes a CPU 27, a ROM 29, a RAM 31, an input means 33 and an output means 35.

  The control device 25 includes a first machining condition table 37 and a second machining condition table 39. As shown in FIG. 3, the first and second processing condition tables 37 and 39 are formed, for example, in a corner portion of a thick workpiece W having a thickness t of about 8 mm to 32 mm, for example, a radius R of 0.8 mm to 1.2 mm. Laser cutting when laser cutting is performed on a small-diameter arc portion AR having a minimum range or a radius that is larger than the radius of the minimum range and smaller than about ½ of the plate thickness of the workpiece W, that is, a small-diameter arc portion AR having a small range radius. Conditions are stored in advance.

  That is, when viewed in the traveling direction of the workpiece W in the laser cutting processing direction (the arrow direction in FIG. 3), the laser cutting processing straight traveling portion (straight portion) 41 or the curved portion having a large curvature radius (the straight portion 41 is lasered under the same conditions) Since it is a part where cutting is performed, the connection position between the small-diameter arc part AR) belonging to the straight line part 41 when viewed under the laser cutting process conditions is defined as A position, and passes through the A position and the next When the laser beam cutting process is performed from the A position to the C position, where the connection position with the straight line portion 41 or the curved line section is the B position, and the position at a predetermined distance in the direction of laser cutting processing from the B position is the C position. These laser cutting processing conditions are stored in the first and second processing condition tables 37 and 39 in advance.

  The first processing condition table 37 stores laser cutting processing conditions when performing laser cutting processing of the small-diameter arc portion AR of the thick workpiece W using nitrogen gas as the assist gas. The second processing condition table 39 stores laser cutting processing conditions when performing laser cutting processing of the small-diameter arc portion AR of the thick workpiece W using oxygen as the assist gas.

  As shown in FIG. 4, the processing condition tables 37 and 39 are each provided with a processing condition table for each of the thick plates t1, t2, t3,. Further, as processing conditions, there are conditions 1 and 2 in which a radius R of a minimal range where the radius of the corner portion is 0.8 mm to 1.2 mm is set in a predetermined large and small range, and more than the radius of the minimal range. There are conditions 3, 4, and 5 in which a small range that is large and smaller than about t / 2 of the thickness t of the workpiece W is divided into large, medium, and small ranges. The conditions are not limited to the conditions 1 to 5, but can be further subdivided.

  For each of the conditions 1, 2, 3, 4 and 5, the processing speed, laser output, frequency, and duty as laser cutting processing conditions between the positions AB are experimentally obtained and set in advance. Further, as the processing conditions, the distance L between the BCs for each of the conditions 1 to 5 is experimentally obtained and set in advance for each plate thickness. Further, as processing conditions, processing speed, laser output, frequency, and duty as laser cutting processing conditions between BCs are experimentally obtained and set in advance.

  Therefore, when the material of the workpiece W to be laser cut is SUS, the first machining condition table 37 or the second machining condition table 39 is selected corresponding to the case of the SS material, and the plate thickness t1, An appropriate machining condition table is selected corresponding to t2, t3,. The laser cutting of the small-diameter arc portion AR can be performed under the processing conditions stored in the selected processing table.

  The control device 25 is provided with a program storage memory 43 for storing a machining program (a program whose contents can be changed) input from the input means 33 in order to perform laser cutting of the workpiece W. In addition, a program prefetching means 45 for prefetching the machining program stored in the memory 43 is provided. And the assist gas selection means 21 as said switching valve which selects oxygen or nitrogen gas as assist gas corresponding to the material of the workpiece | work W read by the said program prefetching means 45 is provided.

  Further, there is provided discriminating means 47 for discriminating whether or not the small-diameter arc portion AR is included in the contents of the machining program prefetched by the program prefetching means 45. The discriminating means 47 discriminates whether or not the radius value of the arc portion included in the machining program is included in the radius of the minimum range or the radius of the small range set in advance. When it is determined by the determination means 47 that the radius of the small-diameter arc portion AR is included in the minimum range or the small range, the A position is determined based on the equation indicating the straight portion 41 and the equation indicating the small-diameter arc portion AR. The control device 25 is provided with calculation means 49 for calculating the coordinate position of the B position. A second memory 51 for storing data of the calculation result calculated by the calculation means 49 is provided.

  Further, the control device 25 is provided with machining condition table selection means 53. The machining condition table selection means 53 selects and reads the first machining condition table 37 when the material of the workpiece W read is SUS because the program prefetching means 45 prefetches the machining program. When the material of the workpiece W is SS material, it has a function of selecting the second processing condition table 39. Then, when the first machining condition table 37 or the second machining condition table 39 is selected, a machining condition table corresponding to the plate thickness t of the workpiece W is retrieved by the retrieval means 55 provided in the control device 25. The searched machining condition data in the machining condition table is stored in the third memory 57, the data of the A position and B position stored in the second memory 51, and the machining conditions stored in the third memory 57. Under the control of the control means 59, relative movement positioning of the laser processing head 5 with respect to the laser output of the laser oscillator 11 and the workpiece W is performed based on the data of the processing conditions of the table.

  By the way, when performing laser cutting of a workpiece that is a thick steel plate having a thickness of about 8 mm to 32 mm, laser cutting of a small arc portion having a small radius with a radius R of the corner of about 0.8 mm to 1.2 mm is performed. It is difficult to do. Therefore, an experiment was conducted to determine what kind of problem would occur when laser cutting of a small small-diameter arc portion was performed. As an experimental work, SUS having a thickness of 10 mm was used, and nitrogen gas was used as an assist gas.

  Then, at a laser actual output 3000 W (output 4000 W, 800 Hz, duty 60%), the laser cutting processing is performed at a laser cutting speed of 650 mm / min, and the radius of the small arc portion is set to R = 1 mm. Laser cutting was performed on the small-diameter circular arc part over 90 ° under the same conditions as the straight line part. In this case, the cut surface after bending the small-diameter arc portion was the same as the cut surface of the straight line portion, but generation of dross was observed. That is, the disturbance that affects the laser cutting process when the small-diameter arc part is laser-cut is small.

  Next, when the laser output was maintained under the same conditions and the laser cutting processing speed was increased to 700 mm / min, plasma was generated near the lower surface (near reference numeral 61 shown in FIG. 3) immediately after bending the small-diameter arc portion. However, as the laser cutting progressed, the original laser cut surface was restored soon. However, when laser cutting was performed at a higher laser cutting speed of 750 mm / min, surface roughness occurred immediately after the small-diameter arc portion was bent, and it did not return to the original cut surface. In other words, when laser cutting is performed on a small-diameter arc portion while keeping the laser output constant, the disturbance that affects laser cutting increases as the processing speed increases (faster).

  Therefore, when laser cutting of a thick steel plate workpiece is performed, if a small-diameter arc portion is included, it is necessary to appropriately control the laser output and the laser cutting processing speed in the small-diameter arc portion.

  By the way, the experiment was a case where the laser cutting speed was changed while keeping the laser output constant, but the laser cutting speed of the straight portion and the laser cutting speed of the small-diameter arc portion were constant. . Therefore, when the laser cutting processing speed is 650 mm / min, the processing speed is slow, and the irradiation amount of the laser beam per unit length of the cutting length in the traveling direction of the laser cutting processing is sufficiently performed, so that the work upper surface is cut. The delay of the cutting progress on the lower surface of the workpiece relative to the progress is small, and it is presumed that the surface roughness of the cutting surface did not occur even after the small-diameter arc portion was bent.

  However, when the laser cutting processing speed is as high as 700 mm / min, the amount of laser light irradiation per unit length in the direction of laser cutting processing decreases, so the cutting progress direction of the workpiece lower surface relative to the workpiece upper cutting direction. The delay becomes larger. Therefore, even when laser cutting is performed along the small-diameter arc portion on the upper surface of the workpiece, the shape of the arc trajectory is larger than the radius of the small-diameter arc portion on the upper surface due to the delay on the lower surface of the workpiece. It will collapse. As described above, it is presumed that plasma is generated in the vicinity of the lower surface 61 and surface roughness is generated in the vicinity of the lower surface 61 due to the collapse of the circular arc locus due to the delay of the laser cutting process on the lower surface with respect to the upper surface of the workpiece. .

  When the small diameter circular arc portion passes and the process shifts to the laser cutting of the straight portion again, the workpiece lower surface delay is larger than that at the processing speed of 650 mm / min, and there is disturbance due to the lower surface side delay. The disturbance affecting the laser cutting process is small, and it is estimated that the disturbance disappeared with the progress of the laser cutting process and returned to the original state of the laser cutting process.

  However, when the laser cutting processing speed becomes 750 mm / min, the amount of laser light irradiation per unit length in the laser cutting processing direction becomes smaller, and the laser cutting processing on the lower surface of the workpiece with respect to the progress of the laser cutting processing on the upper surface of the workpiece. The delay becomes larger. Therefore, when laser cutting of a small-diameter arc portion is performed, the collapse of the arc locus on the lower surface of the workpiece is larger than the radius of the small-diameter arc portion on the upper surface of the workpiece. Therefore, although the laser cutting process of the straight part until reaching the small-diameter arc part was possible, the disturbance due to the delay on the lower surface side when the laser cutting process of the small-diameter arc part was large, the laser of the small-diameter arc part It is presumed that after the cutting process, the original laser cutting process state could not be restored without the disturbance disappearing.

  That is, the major cause of the disturbance that the rough surface is generated on the laser cut surface of the small-diameter arc portion is that the laser cutting process on the lower surface of the work is delayed with respect to the progress of the laser cutting process on the upper surface of the work. As described above, the disturbance is caused by the delay of the laser cutting process on the lower surface of the work with respect to the upper surface of the work during the laser cutting process of the work. When the laser output and the laser cutting processing speed as laser cutting processing conditions are kept constant, for example, when laser cutting of a straight portion is performed, the delay of the laser cutting processing on the lower surface of the workpiece with respect to the upper surface of the workpiece Even if there is no problem without adversely affecting the laser cutting surface, the radius of curvature of the upper surface and the radius of curvature of the lower surface are, for example, during laser cutting of a small-diameter arc portion having a radius of about 0.8 mm to 1.2 mm. Is larger than the allowable value, the delay of the laser cutting process on the lower surface of the workpiece relative to the upper surface of the workpiece is a disturbance that generates a rough surface on the laser cutting surface that is continuously laser-cut after the small-diameter arc portion is cut. It works.

  In addition, although the said experiment was a case where the workpiece | work was SUS and the nitrogen gas was used as an assist gas, when SS cutting was used as a workpiece | work and oxygen was used as an assist gas, the same experimental result was obtained. Obtained. Since oxygen is used as the assist gas, burning and dents occurred in the vicinity of the lower surface 61.

  As understood from the experimental results, when the laser cutting process of a thick workpiece having a plate thickness of 8 mm or more includes a small-diameter arc portion having a radius of about 0.8 mm to 1.2 mm, the laser output is constant. If the laser cutting processing speed is further increased by holding the workpiece, the disturbance due to the larger delay of the lower surface with respect to the laser processing position of the upper surface of the workpiece becomes larger at the time of laser cutting processing of the small-diameter arc portion. is there. Even in the case of a small-diameter arc portion having a radius in a small range that is larger than the minimum range of about 0.8 mm to 1.2 mm and less than or equal to about 1/2 of the plate thickness t, the corner portion has a rough surface. Although there is a difference, a rough surface may be similarly formed on the cut surface after passing through the small-diameter arc portion.

  As already understood, when performing laser cutting of a thick steel plate workpiece having a thickness of about 8 mm to 32 mm, the radius of the corner portion is 0.8 mm to 1. mm in the laser cutting path (laser cutting locus). When a small-diameter arc portion having a radius of about 2 mm or less than t / 2 is included, the work lower surface side is delayed with respect to the progress of the laser cutting process on the work upper surface, so that the cut surface of the laser cutting process is roughened. Disturbances can occur.

  Therefore, similarly to the workpiece used in the above-described experiment, SUS having a thickness of 10 mm is used, and nitrogen gas is used as an assist gas. As shown in FIG. In order to perform laser cutting processing of the linear portion at 750 mm / min and suppress the delay of laser cutting processing of the lower surface of the workpiece relative to the upper surface of the workpiece in the small-diameter arc portion, the laser cutting speed at the position A is set to 500 mm / min. Controlling to a low speed, holding this low speed of 500 mm / min to the C position, and returning to the original processing speed of 750 mm / min from this C position, the cut surface of laser cutting does not become the rough surface as described above. It was. The distance from the B position to the C position was 4 mm. However, when the experiment was carried out by extending the distance from the B position to the C position to 10 mm, generation of dross was gradually observed.

  That is, when laser cutting of a 10 mm thick SUS straight section, the actual laser output of 3000 W and the laser cutting speed of 750 mm / min are appropriate laser cutting processing conditions. By maintaining the laser cutting speed as low as possible and controlling the laser cutting speed to a low speed of 500 mm / min, the laser beam irradiation amount per unit cutting length at the time of laser cutting processing of the linear portion can be reduced at the time of laser cutting processing at the small-diameter arc portion. growing. Therefore, the delay in laser cutting of the lower surface of the workpiece relative to the upper surface of the workpiece is smaller than the delay of the linear portion in the small-diameter arc portion. Therefore, the disturbance affecting the laser cutting process is reduced, and a good laser cut surface is obtained.

  By the way, if the distance from the B position to the C position is increased to, for example, 10 mm, the portion of 4 mm or more becomes a laser cutting process of a straight part, and an appropriate laser cutting process with a laser actual output of 3000 W and a laser cutting speed of 750 mm / min. The generation of dross was observed due to the laser cutting process being performed out of the conditions.

  Next, at the time of laser cutting processing at the small-diameter arc portion, the amount of laser light irradiation per unit cutting length is made larger than at the time of laser cutting processing at the straight portion, and In order to reduce the delay in the laser cutting position and reduce the difference in the delay between the upper surface and the lower surface of the workpiece, as shown in FIG. 5B, the laser cutting speed is constant at 750 mm / min throughout. When the laser actual power at the time of laser cutting processing from the A position to the C position was increased to 3700 W while maintaining the speed, the laser cutting surface after the laser cutting processing of the small-diameter arc portion did not become rough.

  Next, using a SS material with a plate thickness of 19 mm as the workpiece, using oxygen as the assist gas, laser cutting processing including a small-diameter arc portion under laser cutting conditions with a laser output of 3000 W and a cutting speed of 800 mm / min. Similarly to the conditions shown in FIG. 5A, when the laser cutting process was performed by controlling the speed from the A position to the C position to a cutting speed of 400 mm / min which is 1/2, the small-diameter arc portion was bent. Immediately after, burning occurred near the lower surface of the laser cut surface of the workpiece. Therefore, as shown in FIG. 6A, the laser processing cutting speed from the B position to the C position is controlled to a cutting speed of 600 mm / min, which is an intermediate speed between the cutting speeds of 800 mm / min and 400 mm / min. When laser cutting was performed, the laser cut surface was a good cut surface without producing a rough surface.

  In this case, since the workpiece is an SS material and the assist gas is oxygen, not only the laser energy generated by the laser beam irradiation but also the heat of oxidation reaction between the workpiece and oxygen is applied to the laser cutting portion of the workpiece. This will contribute to fusing. Therefore, at the time of laser cutting of the small-diameter arc portion, the delay of the work lower surface with respect to the laser cutting of the work upper surface is suppressed, the difference in the delay of the work lower surface with respect to the work upper surface is reduced, and the difference is increased. The disturbance that roughens the cut is small.

  However, if the low-speed arc of 400 mm / min is maintained even at the position B immediately after cutting the small-diameter arc portion, the contribution of the oxidation reaction heat increases, and it is assumed that the cut surface becomes rough. Therefore, when the speed is increased to the intermediate speed of 600 mm / min at the B position immediately after cutting the small-diameter arc portion, the contribution of the oxidation reaction heat is suppressed and the disturbance is gradually lost. Then, high-speed laser cutting can be performed by returning to the original cutting speed of 800 mm / min from the position C where the disturbance has disappeared.

  The data of the laser cutting processing conditions shown in FIGS. 5 and 6 are stored in the first processing condition table 37 and the second processing condition table 39, respectively. The first and second machining condition data tables 37 and 39 are stored for each plate thickness of each workpiece and for each different laser machining condition.

  As already understood, when performing laser cutting of a steel plate made of carbon steel such as SS material as a workpiece, if oxygen is used as an assist gas, the oxidation reaction heat will also contribute to the fusing of the steel plate, so that the small diameter When performing laser cutting of the arc portion, it is necessary to consider not only the laser beam irradiation energy but also the contribution of the oxidation reaction heat. Therefore, when performing laser cutting of an SS material having a thickness of 19 mm, the laser cutting speed is maintained at a constant speed of 800 mm / min and laser cutting including a small-diameter arc portion is performed. In accordance with the laser cutting processing conditions shown in FIG. 6B, as shown in FIG. 6B, the laser output during laser cutting processing from the A position to the B position is controlled to the maximum output, and from the B position to the C position. When laser cutting is performed by controlling the laser output at the time of laser cutting to a medium output between the maximum output and the small output at the time of laser cutting of the linear portion, the laser after passing through the small-diameter arc portion A rough surface was not observed on the cut surface, and the cut surface was a good cut surface.

  As will be understood from the above description, when the corner portion in the laser cutting path of a thick steel plate having a thickness of, for example, 8 mm to 32 mm includes a small-diameter arc portion having a radius of, for example, 0.8 mm to 1.2 mm. The small-diameter arc portion is obtained by suppressing the difference in the delay in the laser cutting process on the lower surface of the workpiece relative to the progress position in the laser cutting process on the upper surface of the workpiece to be smaller than the difference in the delay in the laser cutting process on the linear portion. It is possible to suppress the generation of a rough surface on the laser cut surface after the elapse of. The reason why the rough surface is generated on the laser cutting surface is caused by a large cutting delay of the work lower surface with respect to the work upper surface when performing laser cutting of the small diameter arc portion. At the time of processing, the laser cutting processing conditions may be controlled in order to reduce the cutting delay of the work lower surface relative to the work upper surface.

  As already understood, when a necessary processing program is input from the input means 33 and stored in the first memory 43 in order to perform laser cutting of a carbon steel plate such as SUS or SS, the program Pre-reading means 45 pre-reads the machining program. When the work corresponding to the laser cutting process is SUS, the assist gas selection means 21 selects the nitrogen gas supply means 19, and when the work is an SS material, the oxygen supply means 17 is selected. It will be.

  When the laser cutting machining path in the machining program prefetched by the program prefetching means 45 includes a small-diameter arc portion, the first machining condition table 37 or the second machining condition table 39 corresponding to the material of the workpiece. Is selected. Then, the machining condition table corresponding to the workpiece thickness t specified in the machining program read in the selected machining condition table 37 or 39 and one of the conditions 1 to 5 corresponding to the radius of the small-diameter arc portion are selected. Then, the processing condition data of the selected processing condition table is stored in the third memory 57. Further, the radius R of the pre-read small-diameter arc part and the connection positions A and B with the straight line part or the curved part before and after the small-diameter arc part are calculated by the calculating means 49. The calculation result data is stored in the second memory 51.

  As described above, when the position data of the A position and the B position is stored in the second memory 51 and the selected processing condition data is stored in the third memory 57, the second and third memories 51 and 57 store the selected processing condition data. Based on the stored data, the laser output of the laser oscillator 11 and the relative movement and positioning of the laser processing head 5 with respect to the workpiece W are performed under the control of the control means 59 to perform laser cutting processing of the workpiece W. It is what is said.

  That is, processing condition tables 37 and 39 of laser cutting processing conditions obtained experimentally in advance corresponding to the material, plate thickness, and small-diameter arc portion of the workpiece W are provided, and the laser cutting processing conditions of the processing condition tables 37 and 39 are set as the laser cutting processing conditions. Based on this, since the laser cutting process is performed on the small-diameter arc part, it is possible to effectively suppress the occurrence of a rough surface on the laser cutting surface immediately after the laser cutting process on the small-diameter arc part.

  By the way, as understood from the above description, when performing laser cutting processing of a small-diameter arc portion of a thick workpiece, one of the laser output and the laser cutting processing speed is controlled appropriately, so that an appropriate processing condition is obtained. The experiment is easy. In addition, it is easy to collect data on appropriate machining conditions for the small-diameter arc portion corresponding to the workpiece material and plate thickness.

DESCRIPTION OF SYMBOLS 1 Laser cutting processing apparatus 5 Laser processing head 11 Laser oscillator 17 Oxygen supply means 19 Chisso gas supply means 21 Switching valve (assist gas selection means)
23 assist gas supply means 25 control device 37 first processing condition table 39 second processing condition table 43 first memory 45 program pre-reading means 49 arithmetic means 51 second memory 53 processing condition table selection means 55 search means 57 third memory 59 control means

Claims (6)

  During laser cutting of a thick steel plate workpiece using nitrogen gas as the assist gas, a small-diameter arc portion with a radius of 0.8 mm to 1.2 mm and / or larger than the radius of the minimum range is 1 / th of the plate thickness. A laser cutting method for cutting a small-diameter arc portion having a radius in a small range smaller than the radius of 2 and connecting the linear portion or curved portion to the small-diameter arc portion when viewed in the traveling direction of the laser-cutting direction The position is the A position, the connection position between the small-diameter arc portion and the next straight line portion or the curved portion passing through the A position is the B position, and a position at a predetermined distance from the B position in the direction of laser cutting processing Is the laser output at the time of laser cutting to the A position and the laser cutting processing speed, while maintaining the laser output from the A position to the C position at the same output, the laser cutting processing speed The Laser cutting is performed at a low speed, and the laser cutting after the C position is performed under the same processing conditions as the laser cutting up to the A position. .   During laser cutting of a thick steel plate workpiece using nitrogen gas as the assist gas, a small-diameter arc portion with a radius of 0.8 mm to 1.2 mm and / or larger than the radius of the minimum range is 1 / th of the plate thickness. A laser cutting method for cutting a small-diameter arc portion having a radius in a small range smaller than the radius of 2 and connecting the linear portion or curved portion to the small-diameter arc portion when viewed in the traveling direction of the laser-cutting direction The position is the A position, the connection position between the small-diameter arc portion and the next straight line portion or the curved portion passing through the A position is the B position, and a position at a predetermined distance from the B position in the direction of laser cutting processing Is set to the C position, the laser output while the laser cutting processing speed from the A position to the C position is maintained at the same speed as the laser output at the time of laser cutting processing to the A position and the laser cutting processing speed. The Laser cutting is performed under control of high output, and laser cutting after the C position is performed under the same processing conditions as laser cutting up to the A position. Method.   At the time of laser cutting of a thick steel plate workpiece using oxygen as an assist gas, a small-diameter arc portion having a radius of 0.8 mm to 1.2 mm and / or larger than the radius of the minimum range is 1 / th of the plate thickness. A laser cutting processing method for cutting a small-diameter arc portion having a radius in a small range smaller than the radius of 2, which is a connection position between the linear portion or the curved portion and the small-diameter arc portion as viewed in the progress direction of the laser cutting processing. Is the A position, the connection position between the small-diameter arc portion and the next straight line portion or curved portion passing through the A position is the B position, and a position at a predetermined distance from the B position in the direction of laser cutting processing is When the C position is set, the laser output from the A position to the B position is maintained at the same output with respect to the laser output and the laser cutting speed at the time of laser cutting to the A position. Control at low speed The laser cutting process is performed, and the laser output from the B position to the C position is kept at the same output, while the laser cutting process speed to the A position is between the laser cutting process speed to the B position. Laser cutting is performed by controlling the speed, and the laser cutting after the C position is performed under the same processing conditions as the laser cutting up to the A position. .   At the time of laser cutting of a thick steel plate workpiece using oxygen as an assist gas, a small-diameter arc portion having a radius of 0.8 mm to 1.2 mm and / or larger than the radius of the minimum range is 1 / th of the plate thickness. A laser cutting processing method for cutting a small-diameter arc portion having a radius in a small range smaller than the radius of 2, which is a connection position between the linear portion or the curved portion and the small-diameter arc portion as viewed in the progress direction of the laser cutting processing. Is defined as A, and the connection position between the small-diameter arc portion and the next straight line portion or curved portion passing through the A position is defined as the B position, and the position at a predetermined distance in the laser cutting processing direction from the B position is defined as C. The laser output is increased while maintaining the laser cutting speed from the A position to the B position at the same speed as the laser output and laser cutting speed at the time of laser cutting to the A position. Control to output The laser cutting process is carried out, and the laser is cut to a medium output between the laser output up to the A position and the laser output up to the B position while maintaining the same laser cutting processing speed from the B position to the C position. Laser cutting is performed by controlling output, and laser cutting after the C position is performed under the same processing conditions as laser cutting up to the A position. .   A laser cutting processing apparatus for performing laser cutting processing of a steel sheet as a workpiece, a laser oscillator, a laser processing head for condensing and irradiating the workpiece with laser light oscillated from the laser oscillator, and the laser processing head Assist gas supply means capable of switching nitrogen gas or oxygen as assist gas supplied to the apparatus, control means capable of controlling the laser output of the laser oscillator and the relative movement speed of the laser processing head with respect to the workpiece, and nitrogen gas as the assist gas When cutting a thick workpiece using a laser, a small-diameter arc portion of a minimum range of 0.8 to 1.2 mm in radius and / or larger than the radius of the minimum range and smaller than a radius of 1/2 of the plate thickness A first machining condition table pre-stored with laser cutting machining conditions when performing laser cutting of a small-diameter arc portion of a small radius range And a small-diameter arc portion of a minimum range of radius 0.8 to 1.2 mm and / or larger than the radius of the minimum range at the time of laser cutting of a thick workpiece using oxygen as an assist gas. A second machining condition table in which laser cutting machining conditions are stored in advance when performing laser cutting of a small-diameter arc portion having a small radius smaller than the radius of 2, and input from the input means for performing laser cutting of the workpiece Program prefetching means for prefetching the processed machining program, assist gas selection means for selecting an assist gas corresponding to the material of the work prefetched by the program prefetching means, and contents prefetched by the program prefetching means Machining conditions for selecting the first or second machining condition table corresponding to the workpiece material prefetched when the small-diameter arc portion is included. When performing laser cutting processing of the table selection means and the small-diameter arc portion, the output of the laser oscillator and the workpiece with respect to the work conditions stored in the processing condition table selected by the processing condition table selection means And a control means for controlling the relative moving speed of the laser processing head.   A laser cutting processing apparatus for performing laser cutting processing of a steel sheet as a workpiece, a laser oscillator, a laser processing head for condensing and irradiating the workpiece with laser light oscillated from the laser oscillator, and the laser processing head Assist gas supply means capable of switching nitrogen gas or oxygen as assist gas supplied to the apparatus, control means capable of controlling the laser output of the laser oscillator and the relative movement speed of the laser machining head with respect to the work, and laser machining of the work Program prefetching means for prefetching the machining program input from the input means for performing the operation, assist gas selection means for selecting the assist gas corresponding to the material of the work prefetched by the program prefetching means, and the program The content pre-read by the pre-reading means has a minimum radius of 0.8mm to 1.2mm. When the small-diameter arc portion of the range and / or the small-diameter arc portion of the small range radius larger than the radius of the minimum range and smaller than the radius of 1/2 of the plate thickness are included, the laser cutting of the small-diameter arc portion is performed. With the input means for inputting the laser cutting processing conditions for performing, the processing condition memory for storing the laser cutting processing conditions input by the input means, and the processing conditions stored in the processing condition memory, And a control means for controlling an output of the laser oscillator and a relative moving speed of the laser processing head with respect to a workpiece.

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