JPH06210476A - Laser beam machining device - Google Patents

Abstract

PURPOSE:To hold a distance between an object to be worked and a laser beam machining head constant during a laser beam machining, and to prevent a defect caused by working by allowing a signal adder circuit to add an opposite phase signal to a detected signal, and allowing a control device to control the operation of an elevating/lowering mechanism based on a resultant signal. CONSTITUTION:An operating part 7A calculates a detected signal by a capacitance sensor 9 influenced by plasma generated on an object 2 to be worked, and transfers the detected signal to a signal generator 7B. The signal generator 7B generates an opposite phase signal to the detected signal to input it into a signal adder circuit 7C. A control device 7 controls the operation of an elevating/lowering mechanism 6 to adjust the height position of a working head 3 according to a resultant signal obtained by the signal adder circuit 7C. Consequently, even in the case of an object 2 to be worked generating plasma, a distance between an object 2 to be worked and the laser beam machining head 3 can be held constant during a laser beam machining, and a satisfactory laser beam machining can be performed without a defect caused by working.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing apparatus,
More specifically, the present invention relates to improvement of a laser processing apparatus including a capacitance sensor that detects a distance between a workpiece and a processing head.

2. Description of the Related Art Conventionally, as a laser machining apparatus, a machining head for irradiating a workpiece with a laser beam, an elevating mechanism for elevating the machining head, a controller for controlling the operation of the elevating mechanism, and a workpiece. And a machining head are detected, and a capacitance sensor that inputs the detection signal to the control device is provided, and the distance between the workpiece and the machining head is maintained at a predetermined interval. It is known that a workpiece is subjected to required laser processing.

However, in the above-mentioned conventional laser processing apparatus, when aluminum or stainless steel is processed in an oxygen-free state, plasma is generated in the processed portion of the workpiece, and the plasma causes the above-mentioned static electricity. The detection signal by the capacitance sensor becomes inaccurate. More specifically, when the laser beam is a pulse laser, the detection signal by the capacitance sensor is also a periodic signal having a waveform corresponding to the pulse period of the laser beam. As described above, in the conventional device, the electrostatic capacitance sensor is adversely affected by the plasma generated in the processed portion of the workpiece, and when the operation of the lifting mechanism is controlled by the control device based on the detection signal of the electrostatic capacitance sensor, There is a drawback in that the distance between the work piece and the working head cannot be maintained at a predetermined interval, so that the work piece suffers a processing failure.

In view of the above-mentioned circumstances, the present invention controls a working head for irradiating a workpiece with a laser beam, a lifting mechanism for lifting the working head, and an operation of the lifting mechanism. A control device and a capacitance sensor that detects the distance between the workpiece and the processing head and inputs the detection signal to the control device are provided to measure the distance between the workpiece and the processing head. In a laser processing apparatus that performs a required laser processing on a work piece while maintaining a predetermined interval, the electrostatic capacitance for each material and plate thickness of the work piece in which plasma is generated when performing the laser processing. The control device is provided with a calculation unit for calculating a detection signal input from the sensor to the control device, and a signal having a phase opposite to the detection signal is generated based on the detection signal calculated by the calculation unit. Actually processed When laser processing is started for the detection signal is input to the control device from the capacitance sensor, the control device is provided with a signal addition circuit that adds a signal having the opposite phase to the detection signal. The operation of the elevating mechanism is controlled based on a combined signal obtained as a result of addition by the signal adding circuit. A second invention provides a machining head for irradiating a workpiece with a laser beam, an elevating mechanism for elevating the machining head, a controller for controlling the operation of the elevating mechanism, the workpiece and the machining head. And a capacitance sensor for detecting the distance between them and inputting the detection signal to the control device,
In a laser processing apparatus configured to perform a required laser processing on a workpiece while maintaining a distance between the workpiece and a processing head at a predetermined interval, a workpiece in which plasma is generated during laser processing For each material and plate thickness of the above, the detection signal input to the control device from the capacitance sensor is obtained and stored in the control device in advance. Once entered into the controller,
From the pre-stored detection signals, select the detection signal corresponding to the material of the workpiece to be input, the plate thickness, and generate a signal of the opposite phase based on the selected detection signal,
When laser processing is actually started on the workpiece and a detection signal is input from the capacitance sensor to the control device, the control device is provided with a signal addition circuit that adds the signal having the opposite phase to the detection signal. The control device is configured to control the operation of the lifting mechanism based on a combined signal obtained as a result of addition by the signal addition circuit.

According to this structure, when laser-machining a workpiece in which plasma is generated during laser machining, even if the detection signal of the capacitance sensor is inaccurate due to plasma, the control device is The operation of the lifting mechanism is controlled based on the combined signal obtained as a result of addition by the signal adding circuit. Thus, laser processing can be performed while maintaining the distance between the workpiece and the processing head at a predetermined interval without being affected by the plasma generated in the processed portion of the workpiece. Therefore, it is possible to perform good laser processing without causing processing defects even on a workpiece in which plasma is generated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. In FIG. 1, reference numeral 1 is a processing table on which a workpiece 2 is placed and which can be moved in XY directions.
A processing head 3 for irradiating the workpiece 2 with the laser beam L is provided above the position. The machining head 3 is moved up and down by an elevating mechanism 6 including a motor 4 and a screw shaft 5 provided on a support frame (not shown), whereby the distance between the lower end of the machining head 3 and the workpiece 2 is increased. Can be adjusted. A drive source (not shown) for moving the processing table in XY directions and the lifting mechanism 6
The operation of the motor 4 constituting the above is controlled by the controller 7, and the operation of the laser oscillator 8 which emits the laser beam L is also controlled by the controller 7. A conventionally known electrostatic capacity sensor 9 is provided at the lower end of the processing head 3, and the electrostatic capacity sensor 9 includes the workpiece 2 placed on the processing table 1 and the lower end of the processing head 3. The distance between the two is detected, the detected distance is converted into a signal, and the signal is input to the control device 7. The control device 7 includes an optimum output of the laser beam L and a pulse cycle according to processing conditions such as a material of the workpiece 2, a plate thickness, a type of laser processing, a moving speed of the processing table in the XY directions, and Data such as the distance between the workpiece 2 and the lower end of the processing head 3 is stored in advance. Then, in the above-described configuration, when laser processing such as cutting is performed on the workpiece 2, processing conditions such as the material of the workpiece 2, the plate thickness, and the type of laser processing are determined, and these are controlled by the controller 7. Then, the control device 7 selects the data corresponding to the input laser processing conditions from the data stored in advance. Next, the control device 7 controls the operation of the drive source of the machining table 1 to move the machining table 1 in the XY directions, and position the machining head 3 above the machining start position on the workpiece 2. Let After this, the controller 7
The work 2 and the processing head 3 are controlled by controlling the operation of the lifting mechanism 6.
The processing head 3 is stopped at a height position such that the distance from the lower end of the is a predetermined distance. Next, the control device 7 operates the laser oscillator 8 and simultaneously moves the machining table 1 in the XY directions via the drive source of the machining table 1, so that the laser beam L causes the workpiece 2 on the machining table 1 to move. Since the workpiece 2 and the processing head 3 are moved relative to each other in the XY directions while being irradiated, the required laser processing such as cutting and welding can be performed on the workpiece 2. During the laser processing, the distance between the workpiece 2 and the lower end of the processing head 3 is detected by the capacitance sensor 9, and the detected value is converted into a signal and input to the control device 7. It Then, the control device 7 can confirm the distance between the workpiece 2 and the lower end portion of the processing head 3 by the detection signal of the electrostatic capacity sensor 9 input from the electrostatic capacity sensor 9. When the distance is different from the predetermined distance, the height position of the processing head 3 is adjusted by controlling the operation of the elevating mechanism 6 so that the distance becomes the predetermined distance. The configuration described above and the operation based thereon are the same as those of the conventionally known laser processing apparatus. By the way, in the conventional apparatus having the above-described configuration, when the workpiece 2 in which plasma is generated during laser processing is processed, the electrostatic capacitance sensor 9 is adversely affected by the plasma, which causes the workpiece 2 to be processed. There was a processing defect in the. More specifically, for example, when the workpiece 2 is aluminum or stainless steel and is subjected to non-oxidative cutting, plasma is generated during the cutting of the workpiece 2, and the plasma causes the capacitance sensor. The value detected by 9 becomes inaccurate. Then, particularly as in this embodiment, the laser beam L for irradiating the workpiece 2
2 is a pulsed laser, the detection signal of the capacitance sensor 9 affected by the plasma is the pulse cycle of the laser beam L emitted from the laser oscillator 8 as shown in the second stage from the bottom of FIG. Is a periodic signal with a waveform corresponding to. Therefore, in the conventional device, the detection signal of the electrostatic capacity sensor 9 affected by such plasma is directly input to the control device 7. Then, the control device 7 controls the operation of the elevating mechanism 6 based on the detection signal input from the capacitance sensor 9 to adjust the height position of the processing head 3. Therefore, conventionally, it has been pointed out that when performing laser processing in which plasma is generated on the workpiece 2, the workpiece 2 may be cut or welded poorly. In consideration of such a conventional problem, the present embodiment is configured so that, when performing laser processing on the workpiece 2 in which plasma is generated, excellent laser processing can be performed without being affected by plasma. It is a thing. Before giving a detailed description of the present embodiment, first, the above-mentioned conventional problems that are the premise of the present invention will be described in more detail. That is, when the inventor of the present application analyzed the influence of plasma generated during laser processing, the results shown in FIGS. 3A to 3D were obtained. That is, as shown in FIG. 3A, the pulse cycle VL of the laser beam and the vibration cycle FCG of the detection signal of the capacitance sensor 9 affected by the plasma are expressed by a straight line on the upper right. It turned out to be proportional. In other words, since the pulse cycle VL of the laser beam L is constant when performing a certain laser processing, it means that the vibration cycle FCG of the detection signal of the capacitance sensor 9 is also constant. Further, between the amplitude VCG of the vibration of the detection signal of the electrostatic capacity sensor 9 affected by the plasma and the distance D between the lower end of the processing head 3 and the workpiece 2, as shown in FIG. As shown, there is a relationship shown by a downward-sloping curve, and as the distance D between the lower end of the processing head 3 and the workpiece 2 decreases, the amplitude VCG of the vibration of the detection signal of the capacitance sensor 9 increases. Is shown. Furthermore, the amplitude VCG of the vibration of the detection signal of the capacitance sensor 9 which is affected by the plasma
Between the peak value P of the pulse of the laser beam L and the peak value P of the pulse of the laser beam L as shown in the upper right curve of FIG. It has been found that the amplitude VCG of the vibration of the detection signal of the sensor 9 and the pulse width W of the laser beam L have a relationship represented by the upper right curve as shown in FIG. . The relationships shown in FIGS. 3A to 3D can be expressed as the following functions. The relationship shown in FIG. 3A (the relationship between the pulse cycle VL of the laser beam L and the vibration cycle FCG of the detection signal of the capacitance sensor 9) is
FCG = f (VL). In addition, the relationship shown in FIG. 3B (amplitude VCG of vibration of the detection signal of the capacitance sensor 9)
And the relationship between the lower end of the processing head 3 and the distance D between the workpiece 2) is VCG1 = f (D). Further, the relationship (relationship between the amplitude VCG of the vibration of the detection signal of the electrostatic capacity sensor 9 and the peak value P of the pulse of the laser beam L) shown in FIG. 3C is VCG2 = f (P). . Furthermore, FIG.
The relationship shown in (D) (the relationship between the amplitude VCG of the vibration of the detection signal of the electrostatic capacity sensor 9 and the pulse width W of the laser beam L) is VCG3 = f (W). Then, as already described above, the relationship between the cycle VL of the pulse of the laser beam L and the cycle FCG of the vibration of the detection signal of the capacitance sensor 9 (the relationship of (A) of FIG. 3) is FCG = f (VL ), And the pulse period V of the laser beam L during laser processing
Since L is constant, the cycle FCG of vibration of the detection signal of the electrostatic capacity sensor 9 is also constant, and therefore FCG = f (V
The calculation result by L) is constant. Where this FCG
= F (VL) is the first expression. On the other hand, the capacitance sensor 9
The amplitude VCG of the vibration of the detection signal can be further expressed as follows. That is, VCG = VC
G1 * VCG2 * VCG3 = f (D) * f (P) * f
(W) Here, this is set as the second equation. The values (distance D, pulse peak value P, pulse width W) taken along the horizontal axis in FIGS. 3B to 3D are different depending on the material and plate thickness of the workpiece 2. Therefore, VCG = VCG1 * VCG2 * VCG3 = f (D) * f
The value obtained by (P) * f (W), that is, the amplitude VCG of the detection signal of the capacitance sensor 9 differs depending on each material and plate thickness of the workpiece 2. To briefly express the conclusion obtained from the analysis results expressed in (A) to (D) of FIG. 3 described above, since the pulse period VL of the laser beam L when performing a certain laser processing is constant, If the cycle FCG of the wave of the detection signal by the affected capacitance sensor 9 is constant and the plate thickness and material of the workpiece 2 can be specified,
The amplitude VCG of the wave of the detection signal by the capacitance sensor 9 can be specified, and thus the detection signal by the capacitance sensor 9 can be specified. Then, in the present embodiment, based on such knowledge, the control device 7 is improved so as to perform favorable laser processing even on the workpiece 2 in which plasma is generated during the laser processing. It is a thing. That is, the control device 7 of the present embodiment includes a calculation unit 7A, a signal generator 7B, and a signal addition circuit 7C. When the material and plate thickness of the workpiece 2 are input to the control device 7, the calculation unit 7A calculates a detection signal from the capacitance sensor 9 when plasma is generated corresponding to the material. That is, the arithmetic unit 7A uses the above-mentioned first equation F
CG = f (VL) and the second equation VCG = f (D) * f
Based on (P) * f (W), a predetermined calculation module 7a calculates a detection signal from the capacitance sensor 9.
As described above, since the pulse period VL of the laser beam L is constant during laser processing, the above first equation FCG = f (VL)
The calculation result (the cycle FCG of the detection signal by the capacitance sensor 9) is constant. On the other hand, since the amplitude VCG of the detection signal by the capacitance sensor 9 differs depending on the material and plate thickness of the workpiece 2, the amplitude is calculated according to the second formula according to the material and plate thickness of each workpiece 2 to be processed. The VCG is calculated, and the detection signal from the capacitance sensor 9 is calculated by the predetermined calculation module 7a based on the amplitude VCG and the cycle FCG of the detection signal. In this way, the calculation unit 7A calculates the detection signal by the capacitance sensor 9 which is affected by the plasma generated in the workpiece 2 to be processed, and transmits the detection signal to the signal generator 7B. Signal generator 7
When the detection signal is transmitted from the arithmetic unit 7A, the B generates a signal S1 having a phase opposite to the detection signal as shown in the second stage from the top of FIG. 2 and the generated signal S1. To the signal addition circuit 7C. Signal addition circuit 7C
Stores the signal S1 input from the signal generator 7B, and when the detection signal actually detected by the capacitance sensor 9 after the laser processing is actually started is input to the control device 7, The signal S1 from the signal generator 7B is added to the detection signal input from the capacitance sensor 9 to the control device 7, and a combined signal S2 obtained thereby is obtained. In other words, the signal addition circuit 7C
A signal S1 having a phase opposite to that of the detection signal input from the capacitance sensor 9 to the control device 7 is added to obtain a combined signal S2. As a result, as shown in the lowermost part of FIG. 2, it is possible to obtain a combined signal S2 having no waveform vibration. Then, the control device 7 controls the operation of the elevating mechanism 6 based on the combined signal S2 obtained by the signal adding circuit 7C to adjust the height position of the processing head 3. Therefore, even for the workpiece 2 in which plasma is generated, the distance between the workpiece 2 and the processing head 3 can be kept constant during the laser processing, and therefore a processing defect does not occur. Good laser processing can be performed. In the above embodiment, the material and plate thickness of the work piece 2 to be processed are input to the control device 7 and then the calculation unit 7A is operated.
Although the signal detected by the capacitance sensor 9 is calculated by the above, the following configuration may be used.
That is, the calculation unit 7A calculates signals detected by the capacitance sensor 9 for each material and plate thickness of the workpiece 2 to be processed in advance, and stores them in the calculation unit 7A in advance, and actually When the material and the plate thickness of the workpiece 2 to be processed are input to the control device 7, the capacitance sensor 9 corresponding to the material and the plate thickness input to the control device 7 from the above-mentioned stored signals. Signal is transmitted to the signal generator 7B described above, and thereafter, the processing by the signal generator 7B and the signal addition circuit 7C may be performed as in the first embodiment. Even with such a configuration, it is possible to obtain the same operation and effect as those of the above-described embodiment.

As described above, according to the present invention, it is possible to obtain an effect that good laser processing can be performed on a workpiece in which plasma is generated without causing processing defects.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a relationship of signals generated in each component of the present invention.

FIG. 3 is a diagram showing a relationship between a detection signal of a capacitance sensor and a pulse period of a laser beam, etc.

[Explanation of symbols]

2 Workpiece 3 Processing head 6 Lifting mechanism 7 Control device 7A Calculation unit 7B Signal generator 7C Signal addition circuit 9 Capacitance sensor

Claims (2)

[Claims] 1. A machining head for irradiating a workpiece with a laser beam, an elevating mechanism for elevating the machining head, a controller for controlling the operation of the elevating mechanism, and a machining head between the workpiece and the machining head. A laser that is required for the workpiece by including a capacitance sensor that detects the distance and inputs the detection signal to the control device and maintains the distance between the workpiece and the processing head at a predetermined interval. In a laser processing apparatus designed to perform processing, a calculation for calculating a detection signal input from the above capacitance sensor to the control device for each material and plate thickness of a workpiece in which plasma is generated when performing laser processing A part is provided in the control device, and a signal having a phase opposite to the detection signal is generated based on the detection signal calculated by the calculation part, and laser processing is actually started on the workpiece. The capacitance When a detection signal is input from the control device to the control device, the control device is provided with a signal addition circuit for adding the signal having the opposite phase to the detection signal, and the control device is a composite signal obtained as a result of addition by the signal addition circuit. A laser processing apparatus for controlling the operation of the elevating mechanism based on the above. 2. A machining head for irradiating a workpiece with a laser beam, an elevating mechanism for elevating the machining head, a controller for controlling the operation of the elevating mechanism, and a machining head between the workpiece and the machining head. A laser that is required for the workpiece by including a capacitance sensor that detects the distance and inputs the detection signal to the control device and maintains the distance between the workpiece and the processing head at a predetermined interval. In a laser processing device that is designed to perform processing, the detection signal input to the control device from the capacitance sensor is calculated for each material and plate thickness of the workpiece where plasma is generated when performing laser processing. Is stored in the control device in advance, and when the material and plate thickness of the workpiece when laser processing is input to the control device, the input material of the workpiece from the previously stored detection signals, Inspection corresponding to plate thickness A signal is selected, a signal having a phase opposite to that of the selected detection signal is generated, laser processing is actually started for the workpiece, and the detection signal is input from the capacitance sensor to the control device. Then, the control device is provided with a signal addition circuit for adding the signal having the opposite phase to the detection signal, and the control device operates the elevating mechanism based on a combined signal obtained as a result of addition by the signal addition circuit. A laser processing apparatus characterized by controlling the.