JP2790166B2 - Piercing end detection device for laser beam machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting the end of piercing of a laser beam machine, and more particularly to detecting the end of machining of a workpiece from a pulse signal generated at the time of cutting of the workpiece. The present invention relates to a piercing end detection device for a laser beam machine.

[0002]

2. Description of the Related Art Conventionally, as a laser processing machine, a laser oscillator for emitting a laser beam, a focus head for irradiating a workpiece with a laser beam emitted from the laser oscillator, and a focus head and a workpiece for processing the laser beam. A capacitance sensor for measuring an interval, a drive motor for raising and lowering the focus head, and a signal from the capacitance sensor for inputting a signal to control the drive motor, and for piercing to set the laser oscillator in a pulse mode. A device having a control device for causing oscillation is known. When the laser oscillator is oscillated in the pulse mode at the time of the piercing process, a plasma is generated in a pulse shape each time a laser beam is irradiated on the workpiece in a pulse shape, and thereby the capacitance is also in a pulse shape. To fluctuate.
As a result, in a laser processing machine using a capacitance sensor,
If the capacitance fluctuates in a pulse shape during piercing, the control device that inputs the pulse signal controls the drive motor to move the focus head finely up and down. The control of raising and lowering the focus head by the drive motor is stopped. By the way, when judging the end of the piercing process, usually, the time required for the piercing process is measured in advance for various workpieces having different materials and plate thicknesses, and a predetermined time is measured by a timer. When the time has elapsed, it is determined that the piercing process has been completed. Alternatively, there has been proposed a piercing end detection device which determines that the piercing operation has been completed when the reflected laser beam reflected from the workpiece disappears or the pulse-like processing sound disappears. .

[0003]

However, when the above timer is used, even if the timer can be manufactured at low cost, the set time of the timer needs to be set long so that the piercing process is surely completed. In particular, when a large number of piercing processes are performed, there is a disadvantage that the entire processing time becomes long. On the other hand, if the latter piercing processing completion detecting device is used, the time required for the piercing processing can be minimized, but on the other hand, there is a disadvantage that it is expensive. The present invention has been made in view of such circumstances, and provides an inexpensive piercing processing end detecting device.

[0004]

That is, according to the present invention, in a conventional laser beam machine provided with the above-mentioned capacitance sensor, the control device detects a pulse signal input from the capacitance sensor. And a determination unit for determining that the piercing processing has been completed when the input of the pulse signal has been completed.

[0005]

In the above configuration, the piercing process is determined to be completed when the input of the pulse signal input from the capacitance sensor is completed by the determination unit. It can be detected immediately, and the time required for the piercing process can be minimized. Further, since the capacitance sensor is used as a sensor for detecting the end of the piercing process, and the determination unit of the control device only needs to detect the presence or absence of a pulse signal input from the capacitance sensor. It can be manufactured at a lower cost as compared with a conventional piercing processing completion detecting device.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiment. In FIG. 1, a laser processing machine includes a laser oscillator 1 for oscillating and emitting a laser beam L, and a laser beam L emitted from the laser oscillator 1 for focusing. The laser oscillator 1 is controlled by an output control unit 4 of a control device 3 and is oscillated during piercing processing, and is subsequently cut. Sometimes, continuous oscillation is performed. The focus head 2 includes a control device 3
The distance D between the workpiece 6 and the workpiece 6 is controlled by a lifting / lowering control unit 5. The focus head 2 has an electrostatic force for measuring the distance D between the focus head 2 and the workpiece 6. A capacitance sensor 7 is provided. The signal detected by the capacitance sensor 7 is amplified through a capacitance sensor amplifier 8 and then input to the calculation unit 9 of the control device 3. An output value obtained from the capacitance sensor 7 via the capacitance sensor amplifier 8 when the focus head 2 is at a predetermined height position is input to the calculation unit 9 in advance. Reference numeral 9 compares the output value with the output value actually obtained from the capacitance sensor 7 and supplies a signal representing the difference to the elevation control unit 5 via a gate unit 12 described later. I have. On the other hand, the elevation control unit 5 controls the drive motor 11 via the servo motor amplifier 10 so that the difference signal input from the calculation unit 9 becomes zero, so that the difference becomes zero. By controlling the height position of the focus head 2, the focus head 2 can be positioned at the predetermined height position. By the way, when the laser oscillator 1 is oscillated in the pulse mode at the time of piercing, the plasma is generated in a pulsed manner each time the laser beam L is irradiated on the workpiece 6 in a pulsed manner as described above. As a result, the capacitance also fluctuates in a pulse shape (see FIG. 2). And this pulse signal R is
This occurs at the same time as the start of the irradiation of the workpiece 6 with the laser beam L, and disappears when the laser beam L passes through the workpiece 6. The capacitance after the disappearance of the pulse signal R becomes a signal Q having a magnitude corresponding to the distance D between the focus head 2 and the workpiece 6. When the pulse-shaped signal R is input to the arithmetic unit 9, the signal output from the arithmetic unit 9 also becomes a pulse-shaped signal R. When the pulse-shaped signal R is input to the elevation control unit 5, As a result, the drive motor 11 is reciprocated to move the focus head 2 up and down. To prevent this, the control device 3 includes a gate unit 12. As the gate unit 12, a switch circuit that cuts off the circuit between the arithmetic unit 9 and the elevation control unit 5 during the piercing process and connects the circuit when the piercing process is completed can be used. Of course, this switch circuit can be manufactured by hardware, but the same object can be achieved by software of the control device 3. More preferably, for example, the gain of the pulse signal R output from the arithmetic unit 9 is set to 1 until the focus head 2 does not substantially move up and down during the piercing process.
It is possible to use a gain adjustment circuit that reduces the gain to about / 4 (see reference symbol R ′ in FIG. 2) and returns the gain to 1 when the piercing processing is completed. In particular, if the above-described gain adjustment circuit is used, it is possible to detect the distance D between the focus head 2 and the workpiece 6 even during piercing. Further, the control unit 3 is provided with a determination unit 14 for detecting the presence or absence of the pulse signal R input from the capacitance sensor 7, and this determination unit 14 switches or branches the circuit of the gate unit 12. It can be controlled. In the above configuration, when piercing is performed, the signal input from the capacitance sensor 7 to the calculation unit 9 before the piercing is started is not the pulse signal R, but the focus head 2 and the workpiece 6. , The determination unit 14 sets the circuit of the gate unit 12, for example, the gain of the gain adjustment circuit 12 to 1. In this state, the arithmetic unit 9 of the control device 3 outputs the signal of the difference between the output value and the reference output value to the elevation control unit 5 while receiving the signal Q from the capacitance sensor 7, The elevation control unit 5 controls the drive motor 11 based on the difference signal to position the focus head 2 at a height suitable for piercing. In this state, the control device 3 causes the laser oscillator 1 to perform pulse oscillation via the output control unit 4 and irradiates the workpiece 6 with a pulsed laser beam L to start piercing. Then, since the determination unit 14 detects the pulse signal R from the capacitance sensor 7, the determination unit 14 reduces the gain of the gain adjustment circuit 12 to 1/4. In this state, the pulse signal R is input from the arithmetic unit 9 to the elevation control unit 5, but since the gain thereof is 1/4, the elevation control unit 5 substantially eliminates the focus. The head 2 is not finely moved up and down. On the other hand, the elevation control unit 5 does not finely move the focus head 2 up and down, but the signal of the output difference based on the signal Q from the capacitance sensor 7 is continuously input via the calculation unit 9. Therefore, the focus head 2
The distance D between the workpiece and the workpiece 6 can be detected, and as the piercing process progresses, the focus head 2 gradually decreases.
Can be controlled. After this,
When the laser beam L penetrates the workpiece 6 and the pulse signal R disappears, the determination unit 14 determines that the piercing processing has been completed at that time, and returns the gain of the gain adjustment circuit 12 to the original value of 1. Let it. Thereby, the control device 3
The elevation control unit 5 receives an output difference signal based on the signal Q from the capacitance sensor 7 from the calculation unit 9 and controls the position of the focus head 2 to a position suitable for cutting based on the signal. Then, the output control unit 4 of the control device 3 switches the laser oscillator 1 to continuous oscillation, continuously irradiates the laser beam L to the workpiece 6, and starts the cutting process. In the above embodiment, the cutting process is performed by the continuous oscillation of the laser oscillator 1. However, the cutting process may be performed with the pulse oscillation. In this case, a gain adjustment circuit is used as the gate unit 12, and the focus head 2 is lowered to a position suitable for piercing at the time of piercing and cutting, in which the laser oscillator 1 performs pulse oscillation, in other words, before piercing. Except for cases, the gain may be set to, for example, the above-described １ ／.

[0007]

As described above, according to the present invention, when the end of the piercing processing is detected, it is possible to immediately proceed to the next step. Therefore, the conventional apparatus which detects the end of the piercing processing by using a timer is used. In this case, the piercing time can be shortened as compared with the above, and therefore, the production efficiency can be improved. In addition, since it is sufficient to provide a determination unit for detecting a pulse-like signal input from the capacitance sensor, an effect that the piercing end detection device of the laser processing machine can be manufactured at a lower cost than in the past. Is obtained.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of the present invention.

FIG. 2 shows a pulse signal R generated during piercing processing.
FIG.

[Description of sign]

 REFERENCE SIGNS LIST 1 laser oscillator 2 focus head 3 control device 4 output control unit 5 elevating control unit 7 capacitance sensor 11 drive motor 12 gate unit 14 determination unit L laser beam R pulse signal

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-81286 (JP, A) JP-A-4-91880 (JP, A) JP-A-6-218569 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) B23K 26/00 G01B 7/00 G01B 7/14

Claims (2)

(57) [Claims] A laser oscillator for emitting a laser beam;
A focus head that irradiates a workpiece with a laser beam emitted from the laser oscillator; a capacitance sensor that measures an interval between the focus head and the workpiece; a drive motor that moves the focus head up and down; A laser processing machine comprising a control device for inputting a signal from a capacitance sensor to control the drive motor and oscillating the laser oscillator in a pulse mode at the time of piercing processing. A piercing process end detection of a laser beam machine, comprising a determination unit that detects a pulse signal input from a capacitance sensor and determines that the piercing process has ended when the input of the pulse signal ends. apparatus. 2. The apparatus according to claim 2, wherein the control device further comprises a gain adjustment circuit for reducing the gain of the signal to a level at which the focus head does not finely move up and down by a pulse signal from the capacitance sensor at least during piercing processing. The piercing end detection device for a laser beam machine according to claim 1.