JP2773912B2 - Copying control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a copying control device used in a laser processing device or the like, and particularly relates to a method of controlling a processing nozzle and a workpiece in a normal processing state. The present invention relates to a copying apparatus that performs copying control for maintaining a distance at a predetermined constant value.

(Prior Art) For example, in a laser processing apparatus, a processing nozzle that emits laser light and ejects an assist gas is used to maintain a focal position of laser light on a workpiece and an assist gas pressure to be constant. It is necessary to keep the distance between the workpiece and the workpiece constant.

In view of this, a distance detection means such as an overcurrent type is provided at the tip of the processing nozzle, and the distance between the processing nozzle and the workpiece is constantly detected by the distance detection means. A copying control device configured to control a relative position between a processing nozzle and a workpiece by a servo control means so as to maintain a distance between the nozzle and the workpiece at a predetermined constant value has already been proposed. Are described, for example, in JP-A-62-22
No. 2101 discloses this.

(Problems to be solved by the invention) In a laser processing apparatus or the like, an appropriate distance between a processing nozzle and a workpiece is often as short as several millimeters,
Therefore, when molten metal such as spatter generated during processing is scattered, there is a possibility that a phenomenon that the molten metal adheres to the distance detecting means provided at the tip of the processing nozzle may occur. When a molten metal or the like adheres to the distance detecting means, the distance detecting means cannot normally detect the distance between the processing nozzle and the workpiece due to the metal, and the copying control is not properly performed. For this reason, conventionally, when the above-mentioned situation occurs, the copying control is stopped. However, if a large amount of sputter melted at this time remains on the distance detecting means for a long time, the distance detection is stopped. The internal temperature of the means rises significantly, which reduces the durability of the distance detecting means and may cause it to break.

In laser processing, when the laser beam oscillating part is not properly adjusted, when the adjustment of the laser beam reflecting mirror, condenser lens, etc. is insufficient, especially when processing a thick workpiece, or when piercing. In such a case, there is a possibility that a large amount of spatters may occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to provide an improved copying control device that can protect a distance detecting unit from spattering and the like and can prevent deterioration and breakage of the durability of the distance detecting unit. I have.

[Structure of the Invention] (Means for Solving the Problems) The present invention has been made in view of the conventional problems as described above. As shown in FIG. 1, the present invention relates to a processing nozzle A of a laser processing apparatus. A distance detecting means B provided at the tip of the processing nozzle A for detecting the distance between the processing nozzle A and the workpiece W; and the processing nozzle A and the workpiece according to the distance detected by the distance detecting means B. Servo control means C for controlling the position of the processing nozzle A in order to keep the distance between the processing nozzle W and a predetermined value
In the copying control device having the distance detecting means B,
Abnormality detection means D for comparing the detection value detected by the above with the predetermined value to detect an abnormality when the predetermined value> the detection value, and the processing nozzle A when the abnormality detection means D detects an abnormality. A retreat control means E for moving the workpiece away from the workpiece W is provided, and the laser beam irradiation is stopped when the abnormality is detected.

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 shows an example of a laser processing apparatus to which the copying control device according to the present invention is applied. In FIG.
Indicates the entire laser processing apparatus, and the laser processing apparatus 1
Is a device main body 9 having a laser beam generating device 3, a laser intensity adjusting device, a control device 7, etc .;
An upper horizontal arm 13 extending from the apparatus main body 9 and extending horizontally above the work table 11;
13, a laser processing head 15 provided at the tip of the laser processing head 13, a processing nozzle 17 attached to the lower end of the laser processing head 15 so as to be vertically movable, and a plate-shaped workpiece W on the work table 11.
Work clamp device 19 for supporting and moving the workpiece in a plane
And

The processing nozzle 17 applies the laser beam from the laser beam generator 3 to the intensity adjuster 5, the reflecting mirror 21, and the condenser lens 23.
Is supplied to the work W on the work table 11 and the assist gas from an assist gas supply device (not shown) is blown to the work W.

As shown in FIG. 3, a distance sensor 25 is attached to the tip of the processing nozzle 17. The distance sensor 25 is
It is an overcurrent type and has a frusto-conical shape having a conical cavity inside by an inner member 25a made of graphite and an outer member 25b made of ceramics, and is mounted concentrically on a conical portion 17a of a processing nozzle 17. ing. A distance detecting coil L is provided on the conical portion formed by the inner member 25a and the outer member 25b.
Are arranged concentrically with each other ₁ the temperature and compensating coil L ₂ is at a predetermined distance above and below.

Coil L ₁ and L ₂ are bridge circuit by a signal cable 27
29 (see FIG. 4). Bridge circuit 29
Consists of a bridge circuit with a general structure, and a coil
Amplifying a voltage signal corresponding to the distance L ₁ and the workpiece W circuit 65
It adapted to provide to the input terminal T _1. If a more detailed description of the overcurrent distance sensor 25 and the bridge circuit 29 is required, refer to Japanese Patent Application Laid-Open No. 62-222101.

FIG. 4 shows an example of a control device 7 of a laser processing apparatus including a copying control device according to the present invention. The control device 7
Main control unit 31 including microcomputer of general structure
, A work position control unit 33, a nozzle height control unit 35, and a pulse signal processing unit 37.

The main control section 31 outputs a control command signal to each control section based on a predetermined control program. The main control section 31 outputs a work position command signal S (X, Y) to the work position control section 33, and the work position command signal S (X, Y) controls the workpiece W. In order to cut the work into a predetermined shape, the work clamp device 19 is commanded to move in a plane. The main control unit 31 outputs a nozzle height command signal S (Z) to the nozzle height control unit 35, and the nozzle height command signal S
(Z) designates the height of the processing nozzle 17 with respect to the work table 11, and generally assumes that there is no warpage in the work W, and the height on the work table 11 in the normal processing state. The nozzle height is instructed so that the laser beam is focused on the height of the workpiece W placed on the workpiece.

The work position control unit 33 receives a command signal S (X, Y), performs predetermined interpolation, and outputs a drive signal to each of the X-axis drive unit 39 and the Y-axis drive unit 41. The X-axis drive section 39 and the Y-axis drive section 41 are each constituted by a servo amplifier, and are controlled based on a drive signal from the work position control section 33.
The axis servo motor Mx and the Y axis servo motor My are driven. Servo motors Mx and My are servo motors that move the work clamp device 19 back and forth, left and right,
Rotary encoders Ex and Ey are attached to each of them, and the rotary encoders Ex and Ey return the movement result to the X-axis drive unit 39 or the Y-axis drive unit 41. As a result, the workpiece W supported by the work clamp device 19 is moved to the designated X and Y positions at a predetermined speed under feedback control.

The nozzle height control unit 35 is provided with a height command signal S (Z) from the main control unit 31, and in a normal machining state, applies a correction value (deviation value) ± ΔZ to a predetermined command height Zo. Then, a driving signal is output to the Z-axis driving unit 43 so that the nozzle height predetermined value Z = Zo ± ΔZ. Z axis drive unit 43
Is composed of a servo amplifier, and the nozzle height control unit 35
The Z-axis servo motor Mz is driven based on the control signal. Z-axis servo motor Mz is a processing nozzle
The servomotor Mz is provided with a rotary encoder Ez. The rotary encoder Ez returns the result of the vertical movement of the processing nozzle 17 to the Z-axis drive unit 43. As a result, the processing nozzle 17 is moved up and down under a feedback control at a predetermined speed so that the nozzle height Z becomes Z = Zo ± ΔZ.

The pulse signal processing section 37 is for giving a correction value ± ΔZ to the nozzle height control section 35, and is selectively connected to either the manual pulse generator 41 or the pulse control circuit 43A by a switch 39. Pulse signal Ph or Pa, and the pulse signal Ph or Pa input within a predetermined time.
The correction value ± ΔZ is calculated on the basis of the integral value of.

A specific example of the pulse control circuit 43A is shown in FIG. The pulse control circuit 43A includes an addition amplifier 45, an absolute value amplifier 47, a direction discriminator 49, an upper limit setting device 51, a lower limit setting device 53, a V / F converter 55, a scanning width amplifier 57, and a NAND. Gate circuit 59, frequency divider 61, and another NAND gate circuit
63.

Summing amplifier 45, the input amplifier 65 to the terminal T ₂ of the detection distance voltages ea than (see FIG. 4), so that the standard voltage for copying distance setting to another input terminal T ₃ es is input I have. This standard voltage ea is a voltage output when the distance sensor 25 is at this height when the copying distance between the distance sensor 25 attached to the processing nozzle 17 and the workpiece W is to be set to, for example, 1.5 mm. It is set to the corresponding voltage.

Incidentally, the amplification circuit 65 (see FIG. 4) is a general one, and outputs a detection distance voltages ea amplifies the voltage signal from the bridge circuit 29 applied to the input terminal T ^1.

Summing amplifier 45 is above as the input terminal T ₂ to the detection distance voltage
The ea, difference voltage with respect to the standard voltage es of the detection distance voltages ea given each standard voltage es to the other input terminal T ₃ .DELTA.e
Is output.

The absolute value amplifier 47 amplifies the absolute value of the deviation voltage Δe,
This is output to each of the V / F converter 55 and the scanning width setting device 57.

The V / F converter 55 converts the amplified voltage from the absolute value amplifier 47 into a pulse signal having a frequency proportional to the voltage, and outputs the pulse signal to one input terminal of a two-input terminal type NAND gate circuit 59. It has become.

The scanning width setting device 57 outputs the amplified voltage from the absolute value amplifier 47,
Given a predetermined voltage ef defining the copying width from the input terminal T _6,
When the amplified voltage is in the range of the predetermined voltage ef, the output signal is set to “0”, and when the amplified voltage exceeds the predetermined voltage ef, “1” is output.

Therefore, the NAND gate circuit 59 outputs the pulse signal of the predetermined frequency from the V / F converter 55 to the frequency divider 61 only when the voltage output from the absolute value amplifier 47 is within the scanning range, for example, the voltage ef that defines ± 1 mm. Output to

The direction discriminator 49 calculates the deviation voltage Δ output from the addition amplifier 45.
The sign of e is detected and output to one input terminal of the NAND gate circuit 63.

The NAND gate circuit 63 is supplied with a pulse signal from the frequency divider 61 to another input terminal, and gives a positive or negative sign to the pulse signal supplied from the frequency divider 61 based on the sign of the direction discriminator 49. become.

Figure 6 shows the output characteristics of a pulse signal Pa for outputting NAND gate circuit 63 to the output terminal T _7. NAND gate circuit 63
The frequency of the pulse signal Pa that is output changes steeply in proportion to the detection distance voltage ea with the standard voltage es as the zero point, and V / F
It changes with a symmetrical change characteristic with respect to the zero (originating point) that saturates at a distance corresponding to the regulated voltage of the converter 55.
Numerically, the frequency of the pulse signal Pa is the control width CD (±
It may be about nKHz (n: about 1 to 3) for about 200 μm). Pulse signal Pa of NAND gate circuit 63 outputs is supplied to the output terminal T _7, which is selectively provided to the pulse signal processing unit 37 by the switch 39.

Upper limit set value 51 is given a deviation voltage Δe from the summing amplifier 45 together with the given voltage eu corresponding to the upper limit distance control scanning from the input terminal T _4, a distance sensor 25 and the workpiece W from the comparison of the two voltages distance is adapted to determine the greater or not than a predetermined upper limit value, when larger outputs a signal which becomes high level to the output terminal T ₈ between.

Lower limit set value 53 is given a deviation voltage Δe from the summing amplifier 45 together with the given voltage ed corresponding to the lower limit distance control scanning from the input terminal T _5, the distance sensor 25 and the workpiece W from the comparison of the two voltages the distance between it is determined whether or not smaller than the lower limit value, when said distance is smaller than the lower limit and outputs a high level signal to the output terminal T _9.

Signal at the output terminal T ₈ and T ₉ are flowcharts such are shown respectively provided to the main control unit 31, it exceeds the upper limit value in accordance with at control program to the main control unit 31 controls, in control or Figure 6 exceeds the lower limit value The emergency evacuation control is performed according to the following.

The main control unit 31 so as to output the normal processing conditions sometimes nozzle height control unit 35 a predetermined command level signal Zo when not given a high-level signal than either of the output terminal T ₈ and T ₉ Has become. Due to this, under this condition,
The nozzle height control unit 35 is provided with a predetermined command height signal Zo from the main control unit 31 and the correction value signal is provided with ± ΔZ from the pulse signal processing unit 37, whereby the distance sensor 25, in other words, the processing is performed. It works so that the distance between the nozzle 17 and the workpiece W is always kept at the standard distance.

The main control unit 31 is adapted to perform beyond the upper limit value in place of the normal control, such as the above-described control when the given a high-level signal from the output terminal T _8, when control execution exceeds this limit distance This is when the sensor 25, in other words, the processing head 17 is at a position substantially higher than the workpiece W, and at this time, control is performed to move the processing nozzle 17 at a relatively high speed to the standard distance in the copying control. Is done.

When the main control unit 31 is a distance sensor 25 when given a high-level signal from the output terminal T _9, i.e. processing nozzle 17 if it is determined that close to the lower limit with respect to the workpiece W In this case, the processing nozzle 17 is positioned on an opening such as a hole of the workpiece W. The normal copying control is prohibited, the nozzle height is maintained at this time, and the processing nozzle 17 is The workpiece W can pass over the opening.

FIG. 7 is a flowchart showing an abnormality detection method at the time of piercing.

When piercing is started in step 701, the processing nozzle 17
Irradiates the workpiece W with a laser beam.

At this time, in step 702, the distance is detected, and this distance l
Is given to the main control unit 31. This distance should generally be a set value lo.

Therefore, in step 703, the predetermined value lo is compared with the detection value l. When l <lo, the spatter adhesion is detected in step 704, and an abnormal process is executed in step 705.

The abnormality processing includes notification to the CRT and a step of stopping the laser beam irradiation and raising the processing nozzle 17.

The abnormality detection in step 703 may not be a mere distance comparison but may be a comparison of the speed of change or a monitoring of a curve (pattern) of change.

In the mode other than the piercing mode, steps 801 to 8 in FIG.
As shown in FIG. 05, spatter adhesion can be detected and abnormal processing can be performed in the same procedure as described with reference to FIG.

In the above, the present invention has been described in detail with respect to a specific embodiment. However, the present invention is not limited to this, and various embodiments can be made within the scope of the present invention. It will be clear to those skilled in the art.

[Effects of the Invention] As can be understood from the above description of the embodiments, in short, the present invention is provided at the tip of the processing nozzle (A) of the laser processing apparatus and the processing nozzle (A) and the workpiece (W). )
And a distance between the processing nozzle (A) and the workpiece (W) according to the distance detected by the distance detection means (B). In a scanning control device having servo control means (C) for controlling the position of a processing nozzle (A) to maintain a predetermined value, a detection value detected by the distance detection means (B) is compared with the predetermined value. Abnormality detection means (D) for detecting an abnormality when the predetermined value> the detection value, and the abnormality detection means (D)
A retreat control means (E) for moving the processing nozzle (A) in a direction away from the workpiece (W) when detecting an abnormality, and stopping the laser beam irradiation when the abnormality is detected. It is a configuration.

As is clear from the above configuration, in the present invention, the distance between the tip of the processing nozzle of the laser processing apparatus and the workpiece is detected by the distance detecting means, and the detected value is compared with a predetermined value to determine the predetermined value. When the value is greater than the detection value, it is detected as abnormal, the laser beam irradiation is stopped, and the processing nozzle is moved in a direction away from the workpiece. When an abnormality is detected, the irradiation of the laser beam is stopped, and the processing nozzle is separated from the workpiece, thereby preventing a large amount of spatter from adhering to the distance detection means and improving safety. You can do it.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the copying control device according to the present invention,
FIG. 2 is a front view showing an example of a laser processing apparatus to which the copying control apparatus according to the present invention is applied, FIG. 3 is a longitudinal sectional view showing an example of a distance sensor provided in a processing nozzle of the laser processing apparatus, and FIG. Is a block diagram showing an example of a control device of a laser processing apparatus including the copying control device according to the present invention, FIG. 5 is a block diagram showing an example of a pulse control circuit used in the control device shown in FIG. 4, FIG. 6 is a graph showing the frequency characteristics of the pulse signal, and FIGS. 7 and 8 are flowcharts showing an example of a control program used in the copying control device according to the present invention. 1 laser processing device 11 work table 17 processing nozzle 25 distance sensor 29 bridge circuit 31 main control unit 35 nozzle height control unit 37 pulse signal processing unit 43 …… Pulse control circuit, 65 …… Amplifier circuit

Claims (1)

(57) [Claims] 1. A distance detecting means (B) provided at a tip of a processing nozzle (A) of a laser processing apparatus and detecting a distance between the processing nozzle (A) and a workpiece (W); Servo control for controlling the position of the processing nozzle (A) to keep the distance between the processing nozzle (A) and the workpiece (W) at a predetermined value according to the distance detected by the detection means (B). Means (C) for comparing the detection value detected by the distance detection means (B) with the predetermined value, and detecting an abnormality when the predetermined value> the detection value (abnormality detection means ( D) and retreat control means (E) for moving the processing nozzle (A) in a direction away from the workpiece (W) when the abnormality detection means (D) detects an abnormality. Laser beam irradiation is stopped when the above abnormality is detected. It is configured so as to copying control device and said.