JP2012000678A - Laser machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser machining method for cutting a workpiece with a laser beam, wherein the diameter of a piercing hole is reduced, while the dispersing amount of molten metal is reduced, and a through hole is formed in a short time.SOLUTION: Piercing machining is executed by a first step for irradiating a beam in first piercing conditions, a second step for temporarily stopping the irradiation of beam, and a third step for irradiating the beam again in second piercing conditions. Thus, oxidation combustion reaction is suppressed during piercing to reduce the dispersing amount of molten metal.

Description

  The present invention relates to a laser processing method for forming a through hole serving as a starting point of cutting at a predetermined position of a workpiece when the workpiece is cut by a laser beam.

In a process of forming a through hole (hereinafter also referred to as a piercing hole) as a starting point of cutting at a predetermined position of a workpiece, and performing a laser beam cutting process from this through hole, a through hole is generally formed at the starting point. It comprises a piercing step for opening and a cutting step for cutting the through hole into an arbitrary shape after the piercing step.
Conventionally, in laser processing on thick plates such as carbon steel and stainless steel, it has been common to use pulse output that has the effect of suppressing heat input in the piercing conditions, but with this method, as the plate thickness increases Piercing time increases exponentially, hindering productivity improvement, and various methods have been proposed for shortening piercing time.

  For shortening the piercing time, it is effective to promote the oxidative combustion reaction of the metal by beam irradiation or defocused beam irradiation in CW (Continuous Wave) mode that outputs the beam continuously. While the piercing time is shortened, there are many problems that impede the cutting process, such as an increase in the diameter of the piercing hole, an increase in scattered melt (hereinafter referred to as spatter), and an increase in heat storage on the workpiece. Specifically, the increase in the diameter of the piercing hole increases the diameter of the cut hole and worsens the material yield. The increase in spatter increases the probability of processing failure at the time of cutting due to deposition on the workpiece, and may cause damage to processing machines such as optical path system parts and drive system parts. In addition, an increase in heat storage on the workpiece causes abnormal combustion during cutting after piercing, and increases the probability of defective cutting.

  FIG. 13 is a schematic view of a hole cross section formed by piercing processing in a PW (Pulse Wave) mode and a CW mode. In general, in the piercing process in the PW mode by repeating ON / OFF of the pulse, the amount of heat input to the work piece is obtained by focusing the laser beam L near the surface of the work piece W as shown in FIG. Can be processed with a hole diameter of about 0.5 to 1 mm. However, there is a disadvantage that energy absorption at the workpiece wall surface in the middle of the piercing hole h cannot be ignored, and the piercing time increases exponentially as the plate thickness increases. On the other hand, the piercing in the CW mode irradiates the defocused laser beam L in order to accelerate the oxidation combustion reaction of the workpiece W as shown in FIG. Can be penetrated. However, since the workpiece has a large amount of molten metal, the diameter of the piercing hole h is as large as 5 to 10 mm, and there is a problem that spatter accumulates around the piercing hole h.

  Therefore, by setting the laser output to continuous output at the start of piercing, and changing the laser output to pulse output during the piercing process, the spattering generated from the workpiece is reduced and the piercing time is reduced. A processing method is disclosed (for example, see Patent Document 1).

JP-A-10-323781

  Certainly, according to the method disclosed in Patent Document 1, it is possible to reduce spatter as compared with the processing method using the CW mode, and it is possible to reduce the processing time compared to the PW mode. However, in Patent Document 1, since the laser output condition is immediately and continuously changed from the CW mode to the PW mode while the piercing is in progress, the heat amount due to the CW mode beam irradiation remains even in the processing in the PW mode. It is difficult to effectively suppress the oxidative combustion reaction in the processing in the mode. For this reason, even if the pulse output is changed to continuous pulse output immediately during piercing, there is a problem that the spatter is relatively large and the diameter of the piercing hole becomes large. Moreover, since the PW mode is used together, there is a limit to shortening the processing time, and further improvement is necessary.

  In addition, since the piercing process is performed by changing only the laser beam output conditions, the spatter generated during the piercing process remains and adheres around the piercing hole. Therefore, in the cutting process, which is the next process of the piercing process, there still remains a problem that the cutting performance is greatly deteriorated, such as contact between the sputter and the nozzle, reflection of the laser beam caused by the spatter, and disturbance of assist gas.

  The present invention has been made to solve the above problems, and enables piercing processing in which the diameter of the piercing hole is reduced, the amount of spatter is reduced, and the piercing time is shortened.

  In the laser processing method according to the present invention, in the laser processing method for performing piercing processing, a first step of performing piercing processing by irradiating a workpiece with a laser beam under a first piercing condition, and after the first step The second step of stopping the irradiation of the laser beam, and after the second step, the part processed in the first step is irradiated with the laser beam on the workpiece under the second piercing condition to complete the piercing process. A time for stopping the irradiation of the laser beam in the second step, and a time when the sputtering amount decreases from a constant value and reaches a constant value again with respect to the increase of the stopping time. It is what.

  In the present invention, by providing a beam stop period during piercing processing, the amount of spatter generated during piercing processing can be reduced, through holes can be formed in a short time, and the processing time of the entire laser processing can be shortened. it can.

It is a block diagram of the laser processing apparatus which shows Embodiment 1 of this invention. It is a graph which shows time changes, such as a laser output for enforcing the laser processing method which is Embodiment 1 of this invention. It is a flowchart which shows the flow of the operation | movement for implementing the laser processing method which is Embodiment 1 of this invention. It is a schematic diagram which shows the piercing hole cross section at the time of implementing the laser processing method which is Embodiment 1 of this invention. It is a graph which shows the relationship between the beam stop time and sputter | spatter amount in the laser processing method which is Embodiment 1 of this invention. It is a comparison table | surface with the process by the laser processing method which is Embodiment 1 of this invention, and the process in the conventional CW mode. It is a block diagram of the laser processing apparatus which shows Embodiment 2 of this invention. It is a graph which shows time changes, such as a laser output for enforcing the laser processing method which is Embodiment 2 of this invention. It is a flowchart which shows the flow of the operation | movement for implementing the laser processing method which is Embodiment 2 of this invention. It is the figure which compared the piercing quality by the laser processing method which is Embodiment 2 of this invention, and Embodiment 1. FIG. It is a graph which shows time changes, such as a laser output for enforcing the laser processing method which is Embodiment 3 of this invention. It is a comparison table | surface with Embodiment 1 and 2 of the process by the laser processing method which is Embodiment 3 of this invention. It is a schematic diagram which shows the piercing hole cross section at the time of implementing the laser processing method by the conventional PW mode and CW mode.

Embodiment 1 FIG.
FIG. 1 is an apparatus configuration diagram showing a laser processing apparatus used in a laser processing method according to Embodiment 1 for carrying out the present invention.
In FIG. 1, a laser beam L emitted from a laser oscillator 1 is guided through a predetermined optical path by one or a plurality of mirrors 2 and is incident on a machining head 3. A lens 4 for condensing the laser beam L on the workpiece W is provided in the processing head 3. The laser beam L is condensed by the lens 4 and irradiated onto the workpiece W from the nozzle 5 provided at the tip of the processing head 3. The output and ON / OFF of the laser oscillator 1 are controlled by a laser oscillation control circuit 14 based on a command value from an NC apparatus to which a machining program is input.
The workpiece W is placed on a processing table (not shown), and the processing table and the processing head 3 are relatively moved in the X, Y, and Z axis directions by a servo motor or the like as a driving source (not shown). And the desired processing is performed. The servo motor and the like are controlled by the servo control circuit 12 based on a command value from the NC device to which the machining program is input.
The distance between the nozzle 5 and the workpiece W is detected by a nozzle sensor (not shown) provided in the vicinity of the nozzle 5 or the nozzle 5. The detected information is sent to the gap controller 11, which compares the command value from the NC device 13 with the measured value, sends a correction command to the servo control circuit 12, and always commands the height of the nozzle 5. Match the value.
Further, the assist gas supply device 6 supplies a predetermined pressure and type of assist gas A into the machining head according to a command value from the NC device 13. The supplied assist gas A is ejected coaxially with the laser beam L from the tip of the nozzle 5 and is used for promoting the melting of the workpiece W and removing the molten metal.

  FIG. 2 is a workpiece controlled by the laser oscillation output of the laser oscillator, the vertical movement of the machining head, and the vertical movement of the machining head to show the laser machining method in the first embodiment for carrying out the present invention. It is the figure which showed the time change of the upper beam spot diameter. FIG. 3 is a flowchart for explaining the operation flow. Hereinafter, the operation related to the piercing process will be described in detail with reference to FIGS.

  In FIG. 2, the time t1 from the start of piercing is called the first step, the time t2 after the first step is called the second step, and the time t3 after the second step is called the third step. . That is, in this embodiment, the piercing process is completed by the first to third steps. Further, the piercing process performed in the first step is referred to as a first piercing process, and the processing condition is referred to as a first piercing condition. Furthermore, the piercing process performed in the third step is called a second piercing process, and the processing condition is called a second piercing condition. In FIG. 3, steps S01 and S02 correspond to the first step, step S03 corresponds to the second step, and steps S04 to S06 correspond to the third step.

In the first step, melt drilling is started by irradiating the workpiece W with the laser beam L under the first piercing condition and injecting the assist gas A (S01), in order to enhance the effect of removing the molten metal, The beam spot diameter is increased by raising the processing head to a predetermined height (S02). Here, the vertical movement of the machining head 3 is raised from the just focus position (Hjf) to the defocus position (Hdf) as shown in FIG. The defocus position (Hdf) is a position equivalent to the defocus position when piercing is performed only in the conventional CW mode. In the first step, since it is necessary to enhance the effect of removing the molten metal, the processing may be performed at the defocus position. However, as described above, the defocus is changed from the just focus position to the defocus position. The amount of sputtering can be further reduced as compared with processing only at the position.
In the subsequent second step, the beam irradiation and the assist gas injection are temporarily stopped and the stop time t2 is provided in order to block the oxidation combustion reaction before the piercing process is completed. At this stage, the melt drilling phenomenon stops and the expansion of the diameter of the piercing hole is suppressed (S03).
Subsequently, in the third step, the portion processed in the first step is irradiated with the laser beam L again from a predetermined height (Hdf) and the assist gas A is injected under the second piercing condition. The melt drilling phenomenon is resumed, but in order to prevent the hole diameter from expanding due to excessive oxidation combustion reaction, the machining head 3 is again brought close to the just focus position (Hjf) to complete the penetration (S05). In the third step, since it is necessary to reduce the amount of spatter, processing may be performed at the just focus position, but only the just focus position can be obtained by changing from the defocus position to the just focus position as described above. The processing time can be further reduced as compared with the case of processing.
With the above operation, the piercing process is completed (S06), and thereafter, cutting is started under the cutting conditions (S07).

  FIG. 4 is a schematic view of a cross section of a piercing hole processed by the above method, FIG. 4 (a) is a view after the first step, and FIG. 4 (b) is a view after the third step. . As shown in FIG. 4A, the piercing hole h is formed halfway through the thickness of the workpiece W according to the first piercing condition selected in the first step. Since the beam irradiation is temporarily stopped in the subsequent second step, the oxidative combustion reaction that has progressed halfway is interrupted. In the subsequent third step, the laser beam L is irradiated again, but since there is no excessive heat input, a small diameter piercing hole h can be formed as shown in FIG. Thereby, the amount of spatter can be reduced and the processing time can be shortened.

  These processes, including the machining conditions, are all input as a program to the NC device 13, and based on the command value from the NC device 13, the irradiation and output of the laser beam L are controlled by the laser oscillation control circuit 14, and the gap controller 11 and the servo control circuit 12 control the vertical movement of the machining head 3, and the assist gas supply device 6 controls the injection of the assist gas A.

  Here, if the beam stop time in the second step is too short, the amount of heat generated in the first step remains, and an excessive melting phenomenon is induced by beam irradiation in the subsequent third step. It is necessary to set time. However, if the beam stop time in the second step is too long, as a result, the time required for piercing processing and further the processing time for the entire laser processing become longer, which hinders the productivity of laser processing. Therefore, the time t2 of the second step needs to be set appropriately.

FIG. 5 shows the experimental results of measuring the amount of sputtering when the beam stop time in the second step is changed. The conditions of the workpiece used in this experiment, the first piercing condition, and the second piercing condition are as follows.
<Common conditions>
Workpiece material and plate thickness: Mild steel (SS400) t19mm
Processing lens: Focal length f190.5mm
Nozzle diameter: φ1.7mm
<First piercing condition>
Laser beam output: 2000W (CW mode)
Z-axis moving speed: 15000mm / min
Assist gas type: oxygen Assist gas pressure: 0.08 MPa
Beam on time: 0.4 sec
Processing head height at the start of beam irradiation: 4.0 mm (Hjf) from the material surface
Processing head height at the end of beam irradiation: 19.0 mm (Hdf) from the material surface
<Second piercing condition>
Laser beam output: 4000W (CW mode)
Z-axis moving speed: 1000 mm / min
Assist gas type: oxygen Assist gas pressure: 0.07 MPa
Beam on time: 0.9 sec
Processing head height at the start of beam irradiation: 19.0 mm (Hdf) from the material surface
Processing head height at the end of beam irradiation: 4.0 mm (Hjf) from material surface

As can be seen from FIG. 5, when t2 exceeds 0.3 seconds, the amount of spatter starts to decrease and becomes substantially constant after 0.5 seconds or more. Therefore, from the viewpoint of reducing the amount of sputtering, the beam stop time in the second step may be about 0.5 seconds or more. Furthermore, considering shortening of the processing time, it is appropriate to set t2 to about 0.5 seconds.
5 shows the processing result of mild steel (SS400) with a plate thickness of 19 mm, but the same experiment was performed with plate thicknesses of 12 mm, 16 mm, and 22 mm, and the same results as in FIG. 4 were obtained. It can be said that the optimum value of t2 is about 0.5 seconds regardless of the plate thickness.

Here, the first piercing condition and the second piercing condition are examples of the processing method according to the present embodiment, and are not particularly limited to the above conditions, and depend on the plate thickness and material of the workpiece. What is necessary is just to set suitably. However, it is desirable to satisfy the following conditions in consideration of the processing quality and processing time.
In the first piercing condition, in order to increase the beam spot diameter rapidly and drilling to the middle of the plate thickness, compared with the second piercing condition, the output speed is increased and the moving speed upward of the Z-axis is increased. It is desirable to set the irradiation time short. Further, the second piercing condition promotes the oxidative combustion reaction again for the piercing hole in which the drilling has progressed to the middle of the plate thickness, and increases the drilling efficiency. Therefore, compared with the first piercing condition, the high output and It is desirable to set the beam irradiation time longer by decreasing the moving speed below the Z axis.

Next, the effect of the processing method in the present embodiment will be described. FIG. 6 compares the diameter of the piercing hole, the amount of spatter generated during piercing, and the processing time between the piercing process in the conventional CW mode and the piercing process according to the present embodiment. The processing conditions of the present embodiment were the above processing conditions, and the time t2 of the second step was 0.5 seconds. As a workpiece, a mild steel SS400 material having a plate thickness of 19 mm similar to the above was used. Conventional piercing conditions are as follows.
<Conventional piercing conditions>
Laser beam output: 4000W (CW mode)
Assist gas type: oxygen assist gas pressure: 0.08 MPa
Beam on time: 1.0 sec
Processing head height during beam irradiation: 19.0 mm (constant) from material surface

The processing time of this embodiment is
0.4 seconds (first step) +0.5 seconds (second step) +0.9 seconds (third step) = 1.8 seconds, as shown in FIG. 6, according to the conventional CW mode. Compared with the processing time of 1.0 second of the processing method, it is a little worse. However, the diameter of the piercing hole is reduced by 40%, so that the amount of spatter can be reduced by about 30% or more.

  Further, when a through hole is machined in a mild steel SS400 having a plate thickness of 19 mm under the piercing process conditions in the conventional PW mode, the machining time is about 20 seconds, and this embodiment is 1/10 or less compared to the PW mode. Through holes can be machined in time.

  In this way, in the piercing processing method of making a through hole that is a starting point of cutting processing at a predetermined position of the workpiece, the first step of irradiating the beam under the first piercing condition, and once beam irradiation By using the processing method including the second step of stopping and the third step of irradiating the beam again under the second piercing condition, the diameter of the piercing hole can be reduced and the amount of spatter can be reduced. . Furthermore, the processing time can be shortened and the productivity can be improved.

Embodiment 2. FIG.
In the first embodiment, during the piercing process, the beam spot diameter on the workpiece that can be controlled by the laser output and the vertical movement of the machining head is changed, the beam stop time is provided, and the sputtering amount is reduced. In the present embodiment, in addition to these operations, air and spatter adhesion preventive agent are sprayed near the piercing hole, thereby preventing spatter remaining and adhering around the piercing hole.

FIG. 7 is an apparatus configuration diagram showing a laser processing apparatus used in the laser processing method according to Embodiment 2 for carrying out the present invention. The structure of FIG. 1 of the laser processing apparatus of the first embodiment is configured by adding a mechanism for injecting air from a side nozzle and a mechanism for injecting a spatter adhesion preventing agent. Hereinafter, additional portions from FIG. 1 will be described.
In FIG. 7, the side gas supply device 8 supplies air S having a predetermined pressure to the side nozzle 7 in accordance with a command value from the NC device 13. The supplied air S is jetted around the piercing hole h on the workpiece W from the side nozzle 7 and used to remove spatter around the piercing hole h. Here, the side nozzle 7 is fixed to the processing head 3 and moves up and down together with the processing head 3.
Further, according to a command value from the NC device 13, the spatter adhesion preventing agent supply device 9 supplies spatter adhesion preventive agent O having a predetermined pressure to the spatter adhesion preventive agent injection nozzle 10. Here, the spatter adhesion preventing agent includes a release agent or an oil component for preventing spatter sticking to the workpiece W. The supplied spatter adhesion preventing agent O is sprayed around the piercing hole h on the workpiece W from the spatter adhesion preventing agent spray nozzle 10 and used for preventing spatter adhesion around the piercing hole. The side nozzle 7 moves up and down together with the processing head 3, but the spatter adhesion preventing agent spray nozzle 10 is independently fixed so that the spatter adhesion preventing agent O does not adhere to the nozzle 5 and the like. When the spatter adhesion preventing agent O is sprayed, the processing head 3 is raised to the retracted position.

  FIG. 8 shows a workpiece controlled by the laser oscillation output of the laser oscillator, the vertical movement of the machining head, and the vertical movement of the machining head to show the laser machining method in the second embodiment for carrying out the present invention. It is the figure which showed the time change of the beam spot diameter irradiated, the spraying pressure of a spatter adhesion inhibitor, and the side nozzle air pressure. FIG. 9 is a flowchart for explaining the operation flow.

  In FIG. 8, as in the first embodiment, the times of the first to third steps correspond to t1 to t2, respectively. In FIG. 9, steps S20 to S02 correspond to the first process, steps S21 and S22 correspond to the second process, and steps S04 to S06 correspond to the third process. The difference from the first embodiment is that the spatter adhesion preventing agent is injected before the first piercing process in the first step, the air and the spatter adhesion preventive agent are injected in the second step, It is a point which injects air after the 2nd piercing process by 3 processes.

Hereinafter, operations related to the piercing process will be described in detail with reference to FIGS. 8 and 9.
First, in the first step, the machining head 3 is raised to the retracted position (He), and the spatter adhesion preventive agent O is ejected from the spatter adhesion preventive spray nozzle 9 (S20). Next, melt drilling is started by irradiating the workpiece with the laser beam L under the first piercing condition and injecting the assist gas A (S01). Then, by raising the machining head 3 to a predetermined height during drilling, the beam spot diameter is increased and the melt drilling phenomenon is promoted (S02). The setting of the height for moving the machining head 3 up and down is the same as in the first embodiment.
In the subsequent second process, the beam irradiation and the assist gas injection are temporarily stopped, the air S is ejected from the side nozzle 7, and the sputter generated in the first process is removed from the processing part (S21). At this stage, the melt drilling phenomenon stops and the expansion of the diameter of the piercing hole is suppressed. Thereafter, the machining head 3 is raised to the retracted position (He), and the spatter adhesion preventing agent O is again sprayed onto the machining portion (S22). This is because the spatter adhesion preventing agent O injected first is volatilized and removed by beam irradiation and assist gas injection in the first piercing process.
Subsequently, in the third step, the machining head 3 is set to a predetermined height (Hdf), the portion processed in the first step is irradiated again with the laser beam L, and the assist gas A is injected, thereby causing the melt drilling phenomenon. In order to prevent the hole diameter from expanding due to excessive oxidation combustion reaction, the machining head 3 is again brought close to the just focus position (Hjf) to complete the penetration (S05). Thereafter, the beam irradiation and the assist gas injection are stopped. And the sputter | spatter which generate | occur | produced by the beam irradiation of the 2nd piercing process is removed from a process part by injecting the air S from the side nozzle 7 (S23). With the above operation, the piercing process is completed (S06), and thereafter, cutting is started under the cutting conditions (S07).

  As described above, before each processing of the first piercing processing and the second piercing processing, it is made difficult to adhere spatter by spraying a spatter adhesion preventing agent, and after each processing, air is sprayed from the side nozzle to cause spattering. Blowing off and removing can effectively prevent the spatter remaining around the piercing hole and sticking.

  Next, an implementation result of the present embodiment will be described. The processing conditions are the same as those in the first embodiment for the workpiece and the first piercing condition and the second piercing condition. Processing time is as follows. The first step requires about 1.2 seconds for the spatter adhesion preventing agent injection step, so the total t1 = 1.2 + 0.4 = 1.6 seconds, and the third step includes the air injection step. Since about 1.0 seconds are required, the total t3 = 0.9 + 1.0 = 1.9 seconds. In the second step, about 1.9 seconds are required for the spatter adhesion preventing agent and the air injection step, but from FIG. 5, if the beam stop time is 0.5 seconds or more, the amount of spatter does not change, so t2 = Set to 1.9 seconds. Therefore, the processing time is t1 + t2 + t3 = 5.4 seconds, which is three times longer than the processing time of 1.8 seconds in the first embodiment. Further, the diameter of the piercing hole and the amount of sputtering are the same as those in the first embodiment.

  FIG. 10 is a comparison of spatter adhesion around the piercing hole in the first embodiment and the present embodiment. From this, it can be confirmed that, under the piercing conditions of the first embodiment, large amounts of spatter remain and adhere around the piercing holes, whereas in the second embodiment, they are extremely small.

  As described above, in the second embodiment, the processing time increases as compared with the first embodiment, but it is possible to effectively suppress the spatter remaining around the pierced hole and sticking generated during the piercing process. . As a result, in the cutting process, which is the next process of the piercing process, the factors that significantly reduce the cutting performance, such as contact between the molten scattered matter and the nozzle, reflection of the laser beam caused by sputtering, and disturbance of assist gas, are eliminated. Quality and stable laser processing can be realized.

Embodiment 3 FIG.
In the first and second embodiments, the first piercing condition and the second piercing condition are both in the CW mode. In the present embodiment, the diameter of the piercing hole is made smaller than those in the first and second embodiments, and a processing method giving priority to improving the quality of the piercing hole is provided, and the second piercing condition is set to the PW mode. It is.

FIG. 11 is a workpiece controlled by the laser oscillation output of the laser oscillator, the vertical movement of the machining head, and the vertical movement of the machining head to show the laser machining method in the third embodiment for carrying out the present invention. It is the figure which showed the time change of the upper beam spot diameter. When compared with FIG. 2 of the first embodiment, the third step is different. In the second piercing process in the first embodiment, the CW mode changed from defocus to just focus is used, but in this embodiment, the PW mode using the focused beam that is just focused in the second piercing process. It is a feature to use.
By using the PW mode in the third step, the diameter of the piercing hole in the third step can be further reduced, and the quality of the piercing hole can be improved.

Next, experimental results of the present embodiment will be described. The workpiece and the like used in the experiment and the first piercing conditions are the same as those in the first embodiment. Also, the beam stop time in the second step is set to 0.5 seconds as in the first embodiment. The second piercing condition is as follows.
<Second piercing condition>
Laser output: 1000W (PW mode)
Pulse frequency: 100Hz
Pulse duty: 20%
Assist gas type: oxygen Assist gas pressure: 0.07 MPa
Beam on time: 3.0 sec
Processing head height during beam irradiation: 4.0 mm (constant) from material surface

FIG. 12 is a table comparing the piercing time, the piercing hole diameter, and the sputtering amount of the processing under the above conditions with the first and second embodiments. Here, the diameter of the piercing hole is the diameter of the surface of the workpiece W. Since the first piercing condition is the same up to the first to third embodiments, the diameter is the same. However, since this embodiment employs the PW mode as the second piercing condition, the hole diameter on the bottom surface of the workpiece is smaller than in other embodiments, and the amount of spatter is reduced. ing. The piercing processing time determined here is a time including a process other than the beam irradiation time.
In the first to third embodiments, the spatter amount tends to decrease as the piercing time is longer. However, an appropriate piercing method can be selected according to the required processing time, processing quality, and processing stability. It is. For example, when the number of times of piercing is increased due to a large number of holes, it is desirable to adopt the first embodiment in order to shorten the processing time, and the processing head is located near the piercing holes for complicated cutting lines. In processing that often crosses, in order to prevent deterioration in processing quality due to fixed spatter and collision between the fixed sputter and the processing head, Embodiment 2 with less spatter adherence or a small amount of spatter itself is performed. It is desirable to adopt the third form.

  In the third embodiment, the side air injection for the purpose of removing spatter as in the second embodiment, and the spatter adhesion preventing agent injection for the purpose of preventing spatter remaining and sticking are executed. However, it goes without saying that the inclusion of these operations has the effect of further improving the piercing capability.

DESCRIPTION OF SYMBOLS 1 Laser oscillator, 2 Mirror, 3 Processing head, 4 Lens, 5 Nozzle, 6 Assist gas supply device, 7 Side gas nozzle, 8 Side gas supply device, 9 Spatter adhesion prevention agent supply device, 10 Spatter adhesion prevention agent injection nozzle, 11 Gap controller, 12 Servo control circuit, 13 NC unit, 14 Laser oscillation control circuit, L Laser beam, A assist gas, W Work piece, h Piercing hole, S air, O Spatter adhesion inhibitor

Claims (12)

In the laser processing method for piercing processing,
A first step of irradiating a workpiece with a laser beam under a first piercing condition to form a piercing hole halfway through the thickness of the workpiece;
A second step of stopping irradiation of the laser beam for a predetermined time after the first step;
After the second step, and a third step of completing the processing of irradiating the laser beam to the portion processed in the first step under the second piercing condition to penetrate the piercing hole,
The predetermined time in the second step is
A relation in which the amount of spatter generated by the piercing processing in the first to third steps decreases from a constant value and changes to a constant value again with an increase in the time during which the laser beam irradiation is stopped in the second step. In the laser processing method, the time when the amount of sputtering decreases and reaches a predetermined value again is set as the predetermined time. The laser processing method according to claim 1, wherein a continuous waveform mode is selected under the first piercing condition. 3. The laser processing method according to claim 2, wherein a beam spot diameter is changed under the first piercing condition. 4. The laser processing method according to claim 3, wherein the beam spot diameter is changed from a just focus state to a defocus state. The laser processing method according to any one of claims 1 to 4, wherein a continuous waveform mode is selected under the second piercing condition. 6. The laser processing method according to claim 5, wherein a beam spot diameter is changed under the second piercing condition. 7. The laser processing method according to claim 6, wherein the beam spot diameter is changed from a defocus state to a just focus state. The laser processing method according to any one of claims 1 to 4, wherein a pulse waveform mode is selected under the second piercing condition. 9. The laser processing method according to claim 8, wherein a beam spot diameter is constant under the second piercing condition. In the first step, before the laser beam irradiation, a spatter adhesion preventing agent is sprayed near the processed portion of the workpiece,
10. The laser processing method according to claim 1, wherein air is jetted near a processing portion of the workpiece when the laser is stopped in the second step. When the laser is stopped in the second step, a spatter adhesion preventing agent is sprayed near the processed portion of the workpiece,
The laser processing method according to claim 1, wherein air is jetted near a processing portion of the workpiece after the laser beam irradiation in the third step. In the laser processing method for piercing processing,
A first step of irradiating a workpiece with a laser beam in a continuous waveform mode under a first piercing condition to form a piercing hole halfway through the thickness of the workpiece;
A second step of stopping irradiation of the laser beam for a predetermined time after the first step;
After the second step, a third step of completing the process of irradiating the workpiece with the laser beam in the continuous waveform mode on the part processed in the first step under the second piercing condition to penetrate the piercing hole; With
The predetermined time in the second step is
A relation in which the amount of spatter generated by the piercing processing in the first to third steps decreases from a constant value and changes to a constant value again with an increase in the time during which the laser beam irradiation is stopped in the second step. In the laser processing method, the time when the amount of sputtering decreases and reaches a predetermined value again is set as the predetermined time.