JP2000042768A - Method and device for detecting end of material to be cut - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the end of a plate material even if the shape of the end is deformed in the material. SOLUTION: In a state where a plate 7 to be cut is placed on a cutting base 8, cutting is started for the plate 7 by holding a laser cutting torch 1 near the end of the plate 7 with a specific space apart from the plate while an assist gas is supplied; then, a micro differential pressure detecting sensor 6 successively detects the inner pressure of an injecting pressure collecting cover 5, sending it to the comparator of a plate end detecting part. During the movement of a laser cutting torch 1, the comparator makes a comparison between the inner pressure of the injecting pressure collecting cover 5 detected by the micro differential pressure detecting sensor 6 and a preliminarily set threshold value; and, if the inner pressure is detected becoming smaller than the threshold value, the comparator transmits a signal showing the change in the inner pressure to a plate end discriminating part. The plate end discriminating part, receiving the signal showing the change in the inner pressure, decides that the nozzle of the laser cutting torch 1 has reached the end of the plate 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting a plate edge of a laser cutting machine used for cutting a thick plate or the like.

[0002]

2. Description of the Related Art When cutting a thick plate or the like with an automatic laser cutting machine, a cutting route is input in advance, and the position of the plate on the cutting platen is determined by a plurality of lines C according to the input data.
The laser cutting machine automatically cuts the position by recognizing the position by an automatic position recognizing device provided with a CD camera or the like or by manually recognizing the position of the board by a person. In cutting this plate, it is necessary to always keep a constant distance between the tip of the cutting torch and the plate in order to stably cut even if there is a level difference in the platen or the plate is undulating. For this reason, the cutting torch is made to follow the plate. As this copying method, a method of keeping the capacitance between the tip of the cutting torch of the laser cutting machine and the plate constant or the like is used.

[0003] In the case of cutting with this laser cutting machine, as a method of inputting the overall dimensions of the base material and the dimensions of the plate to be cut and recognizing the actual position, for example, Japanese Patent Laid-Open No. 8-267 is disclosed.
As shown in Japanese Patent Publication No. 232 and Japanese Patent Application Laid-Open No. 1-95872, a plurality of CCD cameras are mounted on a cutting machine so as to cover the entire width of the cutting platen, and the cutting platen is scanned over its entire length.
There are a method for recognizing the arrangement state and the plate shape of the plate, and a method for recognizing the position of two or three positions with respect to one plate by teaching. The cutting is started after the board to be actually cut is recognized. When cutting the plate, lower the cutting torch while operating the copying machine from the top inside the plate a few millimeters from the end of the plate at the cutting start position, and keep the distance between the cutting torch and the plate constant. When the copy size can be confirmed for holding, the cutting torch is put out of the plate several tens mm.
Moving, cutting at a slow speed while squirting laser and oxygen from the outside position without the board,
The cutting is continued by increasing the speed from the position cut by about 30 mm. When the cutting is performed to the target length by this cutting, the cutting operation is repeated by moving to the next cutting position, and the cutting operation is completed when the cutting is performed to the predetermined size and shape. When cutting to the opposite side of the plate width and escaping, the tracing to the plate edge is 30m
The automatic copying is stopped from a distance of about m before cutting at a constant height.
The cutting length is longer than a preset length, that is, the actual plate width, and is, for example, about 30 m to a position where there is no plate.
The cutting is continued for about m longer, and then moved to the next cutting position.

In the above operation, when manually teaching the position of the base material, when inputting the dimensions of the base material, the actual plate shape may vary depending on the manufacturing process of the base material, that is, the cut plate material or the material as rolled. There is also a material that is curved, so that it is safe not to be uncut, seeing the safety and visually inspecting the cutting allowance and the cutting allowance, setting it as a plate with a size larger than the actual plate size, for example, a size larger by about 30 mm or more I have.

[0005]

When the position of the plate is to be manually taught as described above, the first base material plate-shaped teaching is set with a margin larger than the actual plate size. Therefore, it takes time for the empty cutting, and the cutting time is lengthened by that much, and the cutting ability is reduced. Conversely, if the margin of the plate to be cut is small, the plate will be in an uncut state, and an operation process for cutting the uncut portion will be further required, and the cutting capability will also be reduced.

Further, when recognizing the arrangement state and the plate shape of a plate by optical image processing using a line CCD camera, it is necessary to perform a huge amount of position recognition data processing at high speed, which makes the apparatus expensive. turn into. Furthermore, when these image processing devices are mounted on an existing laser cutting machine, there are restrictions on the arrangement of the CCD camera and lighting, etc.
It may not be easy to install and may be difficult to install in practice. Also, if the material to be cut is a small piece, the plate may be deformed by cutting, and the plate may move from the position initially set and recognized. It is necessary to cut afterwards, and the cutting ability is reduced.

The present invention has improved such disadvantages. Even if the end of the plate is deformed, the end of the plate can always be detected accurately and the position of the plate moves during cutting. It is another object of the present invention to provide a method and an apparatus for detecting an end of a workpiece, which can always accurately detect a plate edge.

[0008]

According to a method of detecting an end portion of a material to be cut according to the present invention, the nozzle of the laser cutting torch causes the nozzle of the material to be cut to change due to a change in pressure around the nozzle caused by auxiliary gas injected from the nozzle of the laser cutting torch. It is characterized by detecting whether or not it is at the end.

[0009] The object to be cut end detecting device according to the present invention comprises:
A cutting edge detecting device for cutting a cutting material while injecting an auxiliary gas from a nozzle of a laser cutting torch, having an injection pressure collecting cover, a differential pressure detecting sensor, and an end detecting unit. The injection pressure collecting cover is provided at the tip of the laser cutting torch around the nozzle of the laser cutting torch, and the differential pressure detection sensor collects the injection pressure when the auxiliary gas is injected from the nozzle of the laser cutting torch. The pressure in the cover is detected, and the end detection unit determines whether the nozzle of the laser cutting torch is at the end of the material to be cut based on the pressure change in the injection pressure collection cover detected by the differential pressure detection sensor. It is characterized by detecting.

In another embodiment of the present invention, a position detecting sensor is provided at each of four equally spaced positions on the outer periphery of a laser cutting torch, and at least three of the four position detecting sensors are provided. When the position detection sensors do not detect the material to be cut, the end of the material to be cut is determined to be detected, and the laser cutting torch is stopped.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An apparatus for detecting an end of a material to be cut according to the present invention has an injection pressure collecting cover, a differential pressure detecting sensor, and an end detecting section. The injection pressure collecting cover is provided at the tip of the laser cutting torch, surrounding the nozzle of the laser cutting torch for cutting a plate to be cut while ejecting auxiliary gas from the nozzle. The small pressure difference detection sensor detects the pressure in the injection pressure collecting cover when the auxiliary gas is injected from the nozzle of the laser cutting torch. The edge detection unit has a comparison unit and a plate edge determination unit. The comparing section compares a change in the internal pressure in the injection pressure collecting cover detected by the slight differential pressure detection sensor with a predetermined threshold. The plate edge determination unit determines the edge of the plate based on the comparison result of the comparison unit.

With the plate to be cut placed on the cutting platen,
When the cutting of the plate is started while supplying the auxiliary gas with a laser cutting torch at a certain distance from the plate near the end of the plate, the differential pressure detection sensor detects the internal pressure in the injection pressure collecting cover sequentially and detects the plate edge. It is sent to the comparison unit of the detection unit. In this state, when the laser cutting torch is moved in the direction outside the plate by the drive control unit, the comparison unit sets the internal pressure in the injection pressure collecting cover detected by the differential pressure detection sensor to a preset value. When the internal pressure is compared with the threshold value and it is detected that the internal pressure has become smaller than the threshold value, a signal indicating a change in the internal pressure is sent to the plate edge determination unit. The plate edge determination unit determines that the nozzle of the laser cutting torch has reached the edge of the plate when receiving a signal indicating a change in the internal pressure from the comparison unit.

[0013]

FIG. 1 is a block diagram of one embodiment of the present invention.
As shown in the figure, a laser cutting torch (hereinafter, referred to as a cutting torch) 1 is connected to an auxiliary gas supply device 2, and a nozzle 4 coaxial with a beam focused by a condenser lens 3, for example, an auxiliary gas such as oxygen or air. By injecting into the workpiece and using the heat of reaction of the oxidation reaction between the workpiece and the auxiliary gas to be injected to improve the processing efficiency and to smoothly remove and remove the generated melt from the cut groove The quality of the cut surface is improved. An injection pressure collecting cover 5 surrounding the nozzle 4 is provided at the tip of the cutting torch 1. A small differential pressure detection sensor 6 for detecting the pressure in the injection pressure collecting cover 5 is attached to the injection pressure collecting cover 5. The cutting platen 8 on which the plate 7 to be processed is placed is formed in a saw-like shape having a plurality of grooves 9.

As shown in the block diagram of FIG. 2, a plate edge detecting unit 10 of the cutting torch 1 includes a comparing unit 11 and a plate edge determining unit 12.
Having. The comparing unit 11 compares the internal pressure P in the injection pressure collecting cover 5 detected by the differential pressure detection sensor 6 with a predetermined threshold value Pt. The plate edge determination unit 12 determines the edge of the plate 7 based on the comparison result of the comparison unit 11 and sends the edge to the drive control unit 13 of the laser cutting device.

In describing the operation of detecting the end of the plate 7 placed on the cutting platen 8 by the plate end detecting unit 10 of the cutting torch 1 configured as described above, the principle of operation will be described first. . When the auxiliary gas is injected from the nozzle 4 in a state where the plate 7 is placed on the cutting surface plate 8 by the cutting torch 1, when the injected auxiliary gas does not hit the plate 7, the differential pressure detection sensor 6 detects the auxiliary gas. As shown in FIG. 3, the internal pressure P in the injection pressure collecting cover 5 becomes the pressure P0, and when the auxiliary gas being injected hits the plate 7, it is drawn by the auxiliary gas hitting the plate 7 and the pressure P1 is reduced. Subtle changes. The change in the internal pressure P detected by the small differential pressure detection sensor 6 varies depending on the shape of the injection pressure collecting cover 5. For example, the original pressure of the auxiliary gas supplied from the auxiliary gas supply device 2 is 1.5 kgf / cm ^2.
The auxiliary gas is supplied to the plate 7 at a certain distance from the nozzle 4.
When it is injected above, the pressure P1 of 20 mmH ₂ O at negative pressure
Next, if injected onto the cutting plate 8 off the plate 7 has a pressure P0 of 0 mm H ₂ O. The end of the plate 7 can be detected by detecting a change in the internal pressure P in the injection pressure collecting cover 5.

The operation of detecting the end of the plate 7 based on this operation principle will be described with reference to the flowchart of FIG. With the plate 7 to be cut placed on the cutting platen 8,
When the cutting torch is started at a predetermined distance from the plate 7 and the auxiliary gas is supplied from the auxiliary gas supply device 2 near the end of the plate 7, the small differential pressure detection sensor 6 The internal pressure P is sequentially detected and sent to the comparison unit 11 of the plate edge detection unit 10 (Step S1). In this state, the drive torch 13 moves the cutting torch 1 in a direction outside the plate 7 (step S2). While moving the cutting torch 1, the comparing unit 11 compares the internal pressure P in the injection pressure collecting cover 5 detected by the slight differential pressure detection sensor 6 with a preset threshold value Pt, When it is detected that the internal pressure P has become smaller than the threshold value Pt, for example, a high-level signal is sent to the plate edge determination unit 12 (step S3). Board edge determination unit 12
When a high-level signal is input from the comparison unit 11, it is determined that the cutting torch 1 has reached the end of the plate 7, and a plate end detection signal is sent to the drive control unit 13 (step S4). When receiving the plate edge detection signal, the drive control unit 13 moves the cutting torch 1 by a clearance allowance, for example, about 0 to 5 mm and stops it (step S5). Then, the drive control unit 13 moves the cutting torch 1 in the direction of the plate 7 and starts cutting by irradiating the cutting torch 1 with a laser beam (step S6). When the cutting torch 1 moves and detects that the internal pressure P in the injection pressure collecting cover 5 that has been detected by the differential pressure detection sensor 6 and input to the comparison unit 11 exceeds the threshold value Pt, the comparison unit 11
Switches the high-level signal sent to the plate edge determination unit 12 to a low-level signal (step S7). When a low-level signal is input from the comparison unit 11, the plate edge determination unit 12 determines that the cutting torch 1 has reached the start end of the plate 7, and sends a plate edge detection signal to the drive control unit 13 (step S8).
The drive control unit 13 moves the cutting torch 1 at a predetermined cutting speed to advance the cutting of the plate 7 (Step S9). When the cutting of the plate 7 proceeds and detects that the internal pressure P in the injection pressure collecting cover 5 input to the comparison unit 11 has become smaller than the threshold value Pt, the comparison unit 11 The low-level signal being sent is switched to a high-level signal (step S10). When a high-level signal is input from the comparing unit 11, the cutting edge torch 1
Is determined to have been reached, and the cutting is terminated (step S
11, S12).

As described above, the internal pressure P in the injection pressure collecting cover 5 due to the auxiliary gas injected from the nozzle 4 of the cutting torch 1
Of the plate 7 to be cut is detected from the change in
Even if the shape of the end is deformed, the end of the plate 7 can be accurately detected. Further, even if the position of the plate 7 moves, the end of the plate 7 can be detected accurately and stably.

In the above embodiment, the cutting torch 1 cuts the plate 7
In the above description, the cutting torch 1 is stopped by moving by 0 to 5 mm, for example, by a clearance allowance predetermined by the drive control unit 13 after reaching the end of the cutting torch 1, but as shown in FIG. For example, a position detection sensor, for example, a reflective photoelectric switch 14 is provided at each of the four equally-divided positions, for example, in the front, rear, left, and right directions in the traveling direction of the cutting torch 1, and at least three photoelectric switches 14 among the four photoelectric switches 14 It may be determined that the end of the plate 7 has been detected when the state has not been detected. When the cutting torch 1 moves in an arbitrary direction in this way, the nozzle 4 of the cutting torch 1
Has reached the end of the plate 7 can be easily detected.

[0019]

As described above, according to the present invention, the end of the material to be cut is detected from the change in the internal pressure in the injection pressure collecting cover due to the auxiliary gas injected from the nozzle of the cutting torch. Even when the material is deformed, the end of the material to be cut can always be accurately detected. Further, even if the position of the material to be cut moves during the cutting, the end portion can always be accurately detected, so that the cutting efficiency can be increased and the productivity can be improved.

Further, position detecting sensors are provided at equally-divided positions on the outer peripheral portion of the cutting torch, and three of the four position detecting sensors do not detect the workpiece. When the cutting torch moves in an arbitrary direction, it can be easily detected that the end of the workpiece has been reached by determining that the edge of the workpiece has been detected.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a plate edge detection unit.

FIG. 3 is a characteristic diagram showing a change in an internal pressure in an injection pressure collecting cover.

FIG. 4 is a flowchart showing the operation of the embodiment.

FIG. 5 is a configuration diagram of another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser cutting torch (cutting torch) 2 Auxiliary gas supply device 3 Condensing lens 4 Nozzle 5 Injection pressure collection cover 6 Small differential pressure detection sensor 7 Plate 8 Cutting platen 10 Plate end detection unit 11 Comparison unit 12 Plate end judgment unit 13 Drive control unit 14 Photoelectric switch

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Akiyoshi Tsuji 1-2-1 Marunouchi, Chiyoda-ku, Tokyo F-term in Nihon Kokan Co., Ltd. 2F069 AA15 BB19 BB20 CC06 DD12 GG04 GG20 GG62 GG65 HH30 JJ07 LL04 NN12 4E068 AE00 CA17 CB01 CC00 CC06 CH01 CH02 DA14

Claims (3)

[Claims] 1. A material to be cut, wherein whether or not the nozzle of the laser torch is at an end of the material to be cut is detected based on a change in pressure around the nozzle due to an auxiliary gas injected from the nozzle of the laser cutting torch. Edge detection method. 2. A device for detecting an end portion of a material to be cut when cutting a material to be cut while injecting an auxiliary gas from a nozzle of a laser cutting torch, comprising: an injection pressure collecting cover, a differential pressure detection sensor, and an end portion. It has a detection unit, the injection pressure collecting cover is provided at the tip of the laser cutting torch surrounding the nozzle of the laser cutting torch, and the small differential pressure detection sensor is when auxiliary gas is injected from the nozzle of the laser cutting torch The pressure in the injection pressure collecting cover is detected at the end, and the end detector detects the nozzle in the laser cutting torch from the end of the material to be cut based on the pressure change in the injection pressure collecting cover detected by the differential pressure detection sensor. An end detecting device for a material to be cut, characterized in that it detects whether or not the part is present in a part. 3. A state in which a position detection sensor is provided at each of four equally-spaced positions on the outer peripheral portion of the laser cutting torch, and at least three of the four position detection sensors do not detect the workpiece. An edge detection device for cutting a workpiece, wherein the laser cutting torch is stopped when it is determined that the edge of the workpiece has been detected.