JP7466051B1 - Assist gas control device, laser processing machine, and assist gas control method - Google Patents

Abstract

[Problem] To provide an assist gas control device that does not consume the same amount of assist gas during fast-forward movement as during machining, thereby reducing the amount of assist gas consumed during fast-forward movement. [Solution] An assist gas control device 9 calculates the movement time required for a machining head 5 to move from the machining end point to the machining start point, acquires a pressure command value for the assist gas at the machining start point, and sets a reduced pressure command value, which is a pressure command value for reducing the pressure of the assist gas while the machining head 5 moves from the machining end point to the machining start point, based on the movement time and the pressure command value, reduces the pressure of the assist gas to the reduced pressure command value when the machining head 5 starts moving from the machining end point, and increases the pressure of the assist gas to the pressure command value by the time the machining head 5 reaches the machining start point. [Selected Figure] Figure 1

Description

The present invention relates to an assist gas control device, a laser processing machine, and an assist gas control method.

A conventional assist gas pressure control method for shortening takt time is disclosed in Patent Document 1. In the assist gas pressure control method disclosed in Patent Document 1, the assist gas pressure is feedback controlled so that the detected pressure value of the assist gas near the nozzle port becomes the target pressure value. In this conventional assist gas pressure control method, if the assist gas pressure is reduced when fast-forwarding between processing points, it takes time to restore the pressure, resulting in a wait time before processing can begin at the processing point after the movement. Therefore, in order to prevent a wait time from occurring at the processing point after the movement, the pressure command value for the processing point after the movement is switched to the pressure command value at the start of the fast-forward movement.

JP 2003-251487 A

However, in the conventional assist gas pressure control method described above, the assist gas is controlled by the pressure command value of the processing point after the movement even during fast-forward movement between processing points, so there was a problem in that the same amount of assist gas was consumed during fast-forward movement as during processing. In particular, when the processing conditions at the processing point after the movement were to cut with high-pressure gas, a large amount of assist gas continued to be consumed during the fast-forward movement.

An assist gas control device according to one aspect of the present invention is an assist gas control device that controls the pressure of the assist gas while the processing head of a laser processing machine moves from the processing end point to the processing start point, calculates the movement time during which the processing head moves from the processing end point to the processing start point, obtains a pressure command value for the assist gas at the processing start point, and sets a reduced pressure command value, which is a pressure command value for reducing the pressure of the assist gas while the processing head moves from the processing end point to the processing start point, based on the movement time and the pressure command value, reduces the pressure of the assist gas to the reduced pressure command value when the processing head starts moving from the processing end point, and increases the pressure of the assist gas to the pressure command value by the time the processing head reaches the processing start point.

An assist gas control method according to one aspect of the present invention is an assist gas control method for an assist gas control device that controls the pressure of the assist gas while the processing head of a laser processing machine moves from the processing end point to the processing start point, and the assist gas control device calculates the movement time during which the processing head moves from the processing end point to the processing start point, obtains a pressure command value for the assist gas at the processing start point, and sets a reduced pressure command value, which is a pressure command value for reducing the pressure of the assist gas while the processing head moves from the processing end point to the processing start point, based on the movement time and the pressure command value, and when the processing head starts moving from the processing end point, reduces the pressure of the assist gas to the reduced pressure command value, and increases the pressure of the assist gas to the pressure command value by the time the processing head reaches the processing start point.

In the assist gas control device and method configured as described above, when the processing head starts moving from the processing end point, the pressure of the assist gas is reduced to the reduced pressure command value, and the pressure of the assist gas is increased to the pressure command value by the time the processing head reaches the processing start point. Therefore, the same amount of assist gas is not consumed during fast forward movement as during processing.

According to an assist gas control device and method according to one aspect of the present invention, the amount of assist gas consumed during fast-forward movement is reduced because the same amount of assist gas is not consumed during fast-forward movement as during processing.

FIG. 1 is a diagram showing the configuration of a laser processing machine equipped with an assist gas control device according to a first embodiment. FIG. 2 is a diagram for explaining a method for calculating a travel time for the machining head to move between machining points by the assist gas control device according to the first embodiment. FIG. 3 is a diagram for explaining a method for calculating a travel time for the machining head to move between machining points by the assist gas control device according to the first embodiment. FIG. 4 is a diagram showing an example of a pressure reduction range setting table used by the assist gas control device according to the first embodiment. FIG. 5 is a diagram showing an example of a return time setting table used by the assist gas control device according to the first embodiment. FIG. 6 is a diagram for explaining a method of controlling the pressure of the assist gas by the assist gas control device according to the first embodiment. FIG. 7 is a flowchart showing a procedure of the assist gas pressure control process performed by the assist gas control device according to the first embodiment. FIG. 8 is a diagram for explaining a method of controlling the pressure of the assist gas by the assist gas control device according to the first embodiment. FIG. 9 is a diagram showing the relationship between the post-reduced pressure ratio and the pressure reduction time. FIG. 10 is a diagram showing the relationship between the reduced pressure ratio and the recovery time. FIG. 11 is a diagram showing the relationship between the travel time and the reduced pressure ratio used by the assist gas control device according to the second embodiment. FIG. 12 is a diagram showing the relationship between the movement time and the return time used by the assist gas control device according to the second embodiment. FIG. 13 is a flowchart showing a procedure of assist gas pressure control processing by the assist gas control device according to the second embodiment. FIG. 14 is a diagram for explaining a method of controlling the pressure of the assist gas by the assist gas control device according to the modified example.

[First embodiment]
A first embodiment of the present invention will now be described with reference to the drawings. In the description of the drawings, the same parts are given the same reference numerals and detailed description will be omitted.

[Configuration of laser processing machine]
Fig. 1 is a diagram showing the configuration of a laser processing machine equipped with an assist gas control device according to this embodiment. As shown in Fig. 1, the laser processing machine 1 includes a laser oscillator 3, a processing head 5, an NC device 7, an assist gas control device 9, a servo amplifier 11, a servo motor 13, an assist gas supplier 15, an electropneumatic regulator 17, and a pressure gauge 19.

The assist gas control device 9 according to this embodiment is an assist gas control device that controls the pressure of the assist gas while the processing head 5 of the laser processing machine 1 moves from the processing end point to the processing start point, calculates the movement time during which the processing head 5 moves from the processing end point to the processing start point, obtains a pressure command value for the assist gas at the processing start point, and sets a reduced pressure command value, which is a pressure command value for reducing the pressure of the assist gas while the processing head 5 moves from the processing end point to the processing start point, based on the movement time and the pressure command value. When the processing head 5 starts moving from the processing end point, the pressure of the assist gas is reduced to the reduced pressure command value, and the pressure of the assist gas is increased to the pressure command value by the time the processing head 5 reaches the processing start point.

The laser processing machine 1 moves the processing head 5 using a movement mechanism (not shown) and performs laser processing such as laser cutting on a metal workpiece. The laser oscillator 3 is a fiber laser oscillator or a YAG laser oscillator, and oscillates a laser beam and supplies it to the processing head 5.

The processing head 5 is connected to the laser oscillator 3 via a transmission fiber, and irradiates the laser beam supplied from the laser oscillator 3 toward the workpiece. Inside the processing head 5, a collimating lens that collimates the laser beam and a focusing lens that focuses the collimated laser beam are provided.

The NC (Numerical Control) device 7 performs numerical control of the laser processing machine 1 and is equipped with an assist gas control device 9. Specifically, the NC device 7 outputs a control target value to a servo amplifier 11 to drive a movement mechanism, thereby moving the processing head 5. The NC device 7 also outputs a control signal to an electro-pneumatic regulator 17 to control the pressure of the assist gas.

The servo amplifier 11 compares the control target value input from the NC device 7 with the feedback signal from the servo motor 13, and drives the servo motor 13 so that the machining head 5 moves in the X-, Y-, and Z-axis directions (left-right, front-back, and up-down directions). The servo motor 13 drives the movement mechanism under the control of the servo amplifier 11. In addition, the servo motor 13 has a built-in encoder that detects the rotation angle, and feeds back the detected rotation angle to the servo amplifier 11.

The assist gas supplier 15 supplies assist gas such as nitrogen, argon, or oxygen to the machining head 5. The electro-pneumatic regulator 17 operates an internal solenoid valve or proportional control valve in response to a control signal from the NC device 7 to control the pressure of the assist gas supplied from the assist gas supplier 15. The pressure gauge 19 measures the pressure of the assist gas supplied to the machining head 5 and outputs the result to the electro-pneumatic regulator 17.

The assist gas control device 9 is mounted on the NC device 7 and controls the pressure of the assist gas while the processing head 5 of the laser processing machine 1 moves from the processing end point to the processing start point. The assist gas control device 9 includes a movement time calculation unit 21, a pressure reduction width setting unit 23, a return time setting unit 25, and a pressure control unit 27.

The movement time calculation unit 21 calculates the movement time required for the processing head 5 to move from the processing end point to the processing start point. When the processing head 5 moves from the processing end point to the next processing start point, the movement of the processing head 5 is fast-forwarded compared to when the processing head 5 moves from the processing start point to the processing end point while performing laser processing along the processing path. There are three types of operation control patterns for the processing head 5 during this fast-forward movement. Therefore, the movement time calculation unit 21 switches the calculation method of the movement time depending on the operation control pattern.

First, as shown in Figure 2, a method for calculating the movement time when the machining head 5 moves from the machining end point in the Z-axis direction (up and down) and then in the X and Y-axis directions (left and right, front and back directions) will be described. The movement time calculation unit 21 calculates the movement time after the ascent in the Z-axis direction is completed, because the fast-forward movement time Txy in the X and Y-axis directions is known after the ascent in the Z-axis direction. At this time, the ascent movement time Tz1 and the descent movement time Tz2 in the Z-axis direction are approximately equal, so the movement time calculation unit 21 calculates the movement time T as T = Txy + Tz1.

As shown in FIG. 3, the motion control patterns include a medium-speed motion control pattern 41 in which the machining head 5 moves from the machining end point in the Z-axis direction and in the X- and Y-axis directions simultaneously. In this case, the movement time in the Z-axis direction is included in the movement time in the X- and Y-axis directions, so the movement time calculation unit 21 calculates the movement time T as T=Txy. There is also a high-speed motion control pattern 43 in which the machining head 5 moves from the machining end point in the Z-axis direction without rising. In this case, there is no movement in the Z-axis direction, so the movement time calculation unit 21 calculates the movement time T as T=Txy.

The pressure reduction width setting unit 23 acquires the pressure command value of the assist gas at the machining start point after the machining head 5 has moved. When moving from the machining end point to the next machining point, taking into account the assist gas switching time, the pressure reduction width setting unit 23 acquires the pressure command value required at the next machining start point before starting the fast-forward movement. The pressure command value at each machining point is recorded in the machining conditions stored in a storage unit such as the memory or database of the NC device 7, so the pressure reduction width setting unit 23 acquires the pressure command value at the next machining start point from the NC device 7.

When the pressure command value is acquired, the pressure reduction range setting unit 23 sets a pressure reduction range for reducing the pressure of the assist gas while the machining head 5 moves from the machining end point to the machining start point, based on the acquired pressure command value and the movement time calculated by the movement time calculation unit 21. This pressure reduction range is the reduction range from the acquired pressure command value for the machining start point, and the pressure of the assist gas is reduced by 10 to 30% while the machining head 5 moves from the machining end point to the next machining start point.

Furthermore, the pressure reduction width setting unit 23 sets a reduced pressure command value by reducing the pressure reduction width from the pressure command value at the processing start point. This reduced pressure command value is a pressure command value for reducing the pressure of the assist gas while the processing head 5 moves from the processing end point to the processing start point. Therefore, the pressure reduction width setting unit 23 sets a reduced pressure command value, which is a pressure command value for reducing the pressure of the assist gas while the processing head 5 moves from the processing end point to the processing start point, based on the movement time and the pressure command value at the processing start point.

Specifically, the pressure reduction width setting unit 23 sets the pressure reduction width using the pressure reduction width setting table shown in FIG. 4. In the pressure reduction width setting table, the pressure reduction width is set according to the length of the movement time and the magnitude of the pressure command value. In other words, the pressure reduction width setting unit 23 sets the pressure reduction width based on the pressure reduction width setting table in which the pressure reduction width is set according to the length of the movement time and the magnitude of the pressure command value. The pressure reduction width setting table is recorded in the memory of the assist gas control device 9.

As shown in FIG. 4, in the pressure reduction width setting table, the pressure command value is classified into large, medium, and small according to preset thresholds 1 and 2. Similarly, the movement time is classified into large, medium, and small according to preset thresholds 3 and 4. The pressure reduction width setting unit 23 compares the acquired pressure command value with thresholds 1 and 2 to determine whether it is large, medium, or small. Similarly, the pressure reduction width setting unit 23 compares the movement time calculated by the movement time calculation unit 21 with thresholds 3 and 4 to determine whether it is large, medium, or small. As a result, the pressure reduction width setting unit 23 selects one of the pressure reduction widths A to I according to the pressure command value (large, medium, or small) and the movement time (large, medium, or small), and sets the selected pressure reduction width. Among the pressure reduction widths A to I, the pressure reduction width A is the largest, for example 30%, and the pressure reduction width I is the smallest, for example 10%. That is, the pressure reduction width is set to a larger value as the pressure command value increases, and is set to a larger value as the movement time increases.

The return time setting unit 25 acquires the pressure command value of the assist gas at the processing start point after the processing head 5 has moved. Then, based on the acquired pressure command value and the pressure reduction width set by the pressure reduction width setting unit 23, it sets the return time required to increase the pressure of the assist gas, which has decreased by the pressure reduction width, to the pressure command value.

Specifically, the return time setting unit 25 sets the return time using the return time setting table shown in FIG. 5. In the return time setting table, the return time is set according to the magnitude of the pressure reduction width and the magnitude of the pressure command value. The return time setting table is recorded in the memory of the assist gas control device 9.

As shown in FIG. 5, in the return time setting table, the pressure command value is classified into large, medium, and small by the preset threshold value 5 and threshold value 6. Similarly, the pressure reduction width is classified into large, medium, and small by the preset threshold value 7 and threshold value 8. However, threshold value 5 and threshold value 6 may be the same as threshold value 1 and threshold value 2 in FIG. 4. The return time setting unit 25 compares the acquired pressure command value with threshold value 5 and threshold value 6 to determine whether it is large, medium, or small. Similarly, the return time setting unit 25 compares the pressure reduction width set by the pressure reduction width setting unit 23 with threshold value 7 and threshold value 8 to determine whether it is large, medium, or small. As a result, the return time setting unit 25 selects one of the return times A to I according to the pressure command value (large, medium, or small) and the pressure reduction width (large, medium, or small), and sets the selected return time. Among the return times A to I, the return time A is the longest, and the return time I is the shortest. In other words, the return time is set to a larger value as the pressure command value increases, and is set to a larger value as the pressure reduction width increases.

The pressure control unit 27 calculates the difference between the movement time calculated by the movement time calculation unit 21 and the return time set by the return time setting unit 25, and calculates the pressure reduction time for reducing the pressure of the assist gas. Then, when the processing head 5 starts to move from the processing end point to the next processing start point, the pressure of the assist gas is reduced to the reduced pressure command value, and the pressure of the assist gas is increased to the pressure command value for the processing start point by the time the processing head 5 reaches the processing start point.

Specifically, the method of controlling the pressure of the assist gas by the pressure control unit 27 will be described with reference to FIG. 6. As shown in FIG. 6, the pressure control unit 27 acquires the pressure command value S at the processing start point after movement before the processing end point at time t1, and switches to the acquired pressure command value S. Then, when the cutting processing ends at the processing end point at time t1, the pressure control unit 27 reduces the pressure command value S by the pressure reduction width. That is, the pressure control unit 27 reduces the pressure command value S to the reduced pressure command value. As a result, the pressure P of the assist gas gradually decreases during the pressure reduction time and decreases by the pressure reduction width. After this, when the pressure reduction time has elapsed and it reaches time t2, the pressure control unit 27 sets the pressure command value S to the pressure command value at the next processing start point. As a result, the pressure P of the assist gas gradually increases, and increases to the pressure command value at the next processing start point at time t3 when the return time has elapsed. In this way, the pressure control unit 27 reduces the pressure of the assist gas while the processing head 5 moves in fast forward from the processing end point to the next processing start point.

The assist gas control device 9 is a controller that includes general-purpose electronic circuits, including a microcomputer, a microprocessor, and a CPU, and peripheral devices such as memory. The assist gas control device 9 has a computer program installed therein for executing the assist gas pressure control process. Each function of the assist gas control device 9 can be implemented by one or more processing circuits. The processing circuit may include, for example, a programmed processing device including an electrical circuit, and may also include devices such as application specific integrated circuits (ASICs) or conventional circuit components arranged to perform the functions described in the embodiments.

[Assist gas pressure control process]
Next, the assist gas pressure control process by the assist gas control device 9 according to this embodiment will be described with reference to Fig. 7. Fig. 7 is a flow chart showing the procedure of the assist gas pressure control process by the assist gas control device 9.

As shown in FIG. 7, in step S101, the movement time calculation unit 21 calculates the movement time during which the processing head 5 fast-forwards from the processing end point to the next processing start point. The movement time calculation unit 21 calculates the movement time according to the operation control pattern of the processing head 5.

In step S103, the pressure reduction width setting unit 23 acquires a pressure command value for the assist gas at the processing start point after the processing head 5 has moved. In step S105, the pressure reduction width setting unit 23 sets a pressure reduction width for reducing the pressure of the assist gas while the processing head 5 moves from the processing end point to the processing start point, based on the pressure command value acquired in step S103 and the movement time calculated in step S101. The pressure reduction width setting unit 23 sets the pressure reduction width using the pressure reduction width setting table shown in FIG. 4. Furthermore, the pressure reduction width setting unit 23 sets a reduced pressure command value by decreasing the pressure command value at the processing start point by the pressure reduction width.

In step S107, the return time setting unit 25 acquires the pressure command value of the assist gas at the processing start point after the processing head 5 has moved. Then, based on the acquired pressure command value and the pressure reduction width set in step S105, the return time required to increase the pressure of the assist gas, which has been reduced by the pressure reduction width, to the pressure command value is set. The return time setting unit 25 sets the return time using the return time setting table shown in FIG. 5.

In step S109, the pressure control unit 27 acquires the minimum reduction time. The minimum reduction time is the minimum value of the pressure reduction time for reducing the pressure of the assist gas. The minimum reduction time is a predetermined value set according to the performance of the electropneumatic regulator 17, and if the minimum reduction time is too short, the assist gas pressure may increase suddenly when it is increased. For this reason, the minimum reduction time is set by experiment or simulation as the time necessary and sufficient to reduce the pressure of the assist gas by the pressure reduction amount. The minimum reduction time is recorded in the memory of the assist gas control device 9.

In step S111, the pressure control unit 27 determines whether the movement time calculated in step S101 is less than the sum of the minimum reduction time acquired in step S109 and the return time set in step S107. If the movement time is less than the sum of the minimum reduction time and the return time (YES in step S111), the process proceeds to step S113, and if the movement time is equal to or greater than the sum of the minimum reduction time and the return time (NO in step S111), the process proceeds to step S115.

In step S113, the pressure control unit 27 sets the pressure reduction width to 0%. As shown in FIG. 8, if the movement time is less than the sum of the minimum reduction time and the return time, the assist gas pressure P cannot increase to the pressure command value S at the end of the movement time. Therefore, the pressure control unit 27 sets the pressure reduction width to 0% so as not to execute the process of reducing the assist gas pressure.

In step S115, the pressure control unit 27 executes a pressure reduction command. Specifically, as shown in FIG. 6, when the cutting process ends at the processing end point, the pressure control unit 27 sets the pressure command value S at time t1 to a reduced pressure command value that is reduced by the pressure reduction width.

In step S117, the pressure control unit 27 calculates the difference between the movement time calculated in step S101 and the return time set in step S107, and calculates the pressure reduction time for reducing the pressure of the assist gas.

In step S119, the pressure control unit 27 determines whether the pressure reduction time calculated in step S117 has elapsed. If the pressure reduction time has not elapsed, it repeatedly determines whether the pressure reduction time has elapsed, and if the pressure reduction time has elapsed, the process proceeds to step S121.

In step S121, the pressure control unit 27 executes the pressure command value for the next processing start point. As shown in FIG. 6, when the pressure reduction time has elapsed and it reaches time t2, the pressure control unit 27 increases the pressure command value S to the pressure command value for the next processing start point. As a result, the assist gas pressure P gradually increases, and at time t3 when the return time has elapsed, it increases to the pressure command value for the next processing start point. In this way, the assist gas pressure control process according to this embodiment ends.

[Effects of the First Embodiment]
As described above in detail, the assist gas control device 9 according to this embodiment calculates the movement time during which the machining head 5 moves from the machining end point to the machining start point, acquires the pressure command value of the assist gas at the machining start point, and sets the reduced pressure command value, which is the pressure command value for reducing the pressure of the assist gas while the machining head 5 moves from the machining end point to the machining start point, based on the movement time and the pressure command value. Then, when the machining head 5 starts moving from the machining end point, the pressure of the assist gas is reduced to the reduced pressure command, and the pressure of the assist gas is increased to the pressure command value by the time the machining head 5 reaches the machining start point. This prevents the same amount of assist gas from being consumed during fast-forward movement as during machining, and also prevents the occurrence of waiting time at the machining start point after movement. Therefore, the assist gas control device 9 according to this embodiment can maintain productivity and also reduce the consumption of assist gas during fast-forward movement.

The assist gas control device 9 according to this embodiment sets a pressure reduction width for reducing the pressure of the assist gas while the machining head 5 moves from the machining end point to the machining start point based on the movement time and the pressure command value, and sets a reduced pressure command value by reducing the pressure command value by the pressure reduction width. This reduces the amount of assist gas consumed during fast-forward movement by setting the reduced pressure command value, and therefore prevents the same amount of assist gas from being consumed during fast-forward movement as during machining.

Furthermore, the assist gas control device 9 according to this embodiment sets the pressure reduction width based on a pressure reduction width setting table in which the pressure reduction width is set according to the length of the movement time and the magnitude of the pressure command value. This allows the pressure reduction width to be set using a preset table, making it easy to control the assist gas.

The assist gas control device 9 according to this embodiment also sets the recovery time required to raise the pressure of the assist gas, which has been reduced by the pressure reduction width, to the pressure command value based on the pressure command value and the pressure reduction width. This allows a recovery time of an appropriate length to be set according to the pressure command value and the pressure reduction width, so that the reduced pressure of the assist gas can be stably raised to the pressure command value.

Furthermore, the assist gas control device 9 according to this embodiment calculates the difference between the movement time and the return time to calculate the pressure reduction time for reducing the pressure of the assist gas. This allows the pressure of the assist gas to be reduced after ensuring the return time, so that the reduced pressure of the assist gas can be reliably increased to the pressure command value.

The assist gas control device 9 according to this embodiment also acquires the minimum reduction time, which is the minimum value of the pressure reduction time, and does not execute the process of reducing the pressure of the assist gas if the movement time is less than the sum of the minimum reduction time and the return time. This prevents the assist gas pressure from being unable to increase to the pressure command value within the movement time, thereby preventing waiting time at the start point of the next processing and maintaining productivity.

Furthermore, in this embodiment, a laser processing machine 1 is provided that is equipped with an assist gas control device 9. This makes it possible to provide a laser processing machine that can maintain productivity and reduce the amount of assist gas consumed during fast-forward movement.

[Second embodiment]
Hereinafter, the laser processing machine according to the present embodiment will be described with reference to the drawings. In the drawings, the same parts are given the same reference numerals, and detailed description will be omitted. In the first embodiment, the pressure reduction width is set using a pressure reduction width setting table. However, in the second embodiment, the difference from the first embodiment is that the pressure reduction width is set by calculating a post-reduction pressure ratio, which is the ratio of the pressure after pressure reduction to the pressure command value, based on the movement time.

In the first embodiment, if the fast-forward movement time is short and the assist gas pressure fluctuates significantly, the pressure will not be stable when restored, so the pressure reduction range is set within a range that allows restoration even with a short movement time.

However, when the movement time is long and there is ample time for recovery, the pressure of the assist gas may not be reduced sufficiently even though it could be reduced further. Therefore, in the second embodiment, the amount of pressure reduction can be set according to the length of the movement time.

The pressure reduction width setting unit 23 acquires a pressure command value for the assist gas at the processing start point after the processing head 5 has moved. Furthermore, when the pressure reduction width setting unit 23 acquires the pressure command value, it sets a pressure reduction width for reducing the pressure of the assist gas while the processing head 5 moves from the processing end point to the processing start point, based on the acquired pressure command value and the movement time calculated by the movement time calculation unit 21. Furthermore, the pressure reduction width setting unit 23 sets a reduced pressure command value by decreasing the pressure command value at the processing start point by the pressure reduction width.

Specifically, the method for setting the pressure reduction width according to this embodiment will be described with reference to the drawings. FIG. 9 is a diagram showing the relationship between the reduced pressure ratio and the pressure reduction time. The reduced pressure ratio is the ratio of the pressure after the pressure reduction to the pressure command value at the processing start point after fast-forward movement. That is, when the pressure command value is P and the pressure reduction width is ΔP, the reduced pressure ratio is (P-ΔP)/P×100. For example, when the reduced pressure ratio is 70%, it indicates that the pressure after being reduced by the pressure reduction width is 70% of the pressure command value at the processing start point. Also, the pressure reduction time in FIG. 9 is the time required to reduce the pressure of the assist gas by the pressure reduction width.

However, if the assist gas pressure is increased or decreased significantly in a short period of time, the pressure will overshoot, which will affect the laser processing. Therefore, Figure 9 shows the relationship when the amount of overshoot when the pressure is reduced and then restored within a certain period of time is calculated so that it falls within a certain range with respect to the pressure command value.

ただし、ｙは低減後圧力比、ｘは圧力低減時間、ａ０、ｂ０、ｘ０、ｙ０は定数である。 As shown in Fig. 9, the pressure reduction time increases as the post-reduction pressure ratio decreases. In other words, when the pressure of the assist gas is significantly reduced, the pressure reduction time increases. Here, the approximate value D2 obtained from the actual measurement value D1 shown in Fig. 9 can be expressed by the following formula (1).

where y is the post-reduced pressure ratio, x is the pressure reduction time, and a0, b0, x0, and y0 are constants.

ただし、ｙは復帰時間、ｘは低減後圧力比、ａ１、ｂ１は定数である。式（２）に示すように、図１０に示す低減後圧力比と復帰時間との関係は１次式で近似することができる。 Furthermore, there is a relationship between the reduced pressure ratio and the return time as shown in Figure 10. The return time is the time required to raise the pressure of the assist gas, which has been reduced by the pressure reduction amount, to the pressure command value. As shown in Figure 10, the return time increases as the reduced pressure ratio decreases. In other words, this shows that if the pressure of the assist gas is reduced significantly, the return time increases. Here, the approximate value D2 calculated from the actual measurement value D1 shown in Figure 10 can be expressed by the following formula (2).

where y is the return time, x is the reduced pressure ratio, and a1 and b1 are constants. As shown in formula (2), the relationship between the reduced pressure ratio and the return time shown in FIG.

Next, a method for setting the pressure reduction width and the return time from the movement time will be described using equations (1) and (2). First, the movement time shown in Fig. 6 is set to t0, the pressure reduction time to t1, and the return time to t2. Since x in equation (1) is the pressure reduction time, x is replaced with t1, and equation (1) is rewritten as equation (3).

In equation (2), y is the return time and x is the reduced pressure ratio, so these are replaced by t2 and y, respectively, and equation (2) is rewritten as equation (4).

Here, the relationship between the movement time t0, the pressure reduction time t1, and the return time t2 is t1=t0-t2 as shown in FIG. 6, so by inputting equation (4) into this equation, equation (5) is obtained.

This equation (5) is input into t1 of equation (3) to obtain equation (6).

ただし、Ｗ（ｘ）はランベルトのＷ関数である。 Solving equation (6) for y gives equation (7), which makes it possible to calculate the reduced pressure ratio y from the travel time t0.

where W(x) is the Lambert W function.

Figure 11 shows the relationship between the movement time t0 and the reduced pressure ratio y based on equation (7). As shown in Figure 11, the longer the movement time, the smaller the reduced pressure ratio becomes. In other words, the longer the movement time, the greater the reduction in the pressure of the assist gas can be achieved.

Here, when the pressure command value at the machining start point after the fast-forward movement is P and the pressure reduction width is ΔP, the reduced pressure ratio y is given by equation (8).
[Number 8]
y = (P - ΔP) / P × 100 (8)
Therefore, when the reduced pressure ratio y is calculated from the movement time t0 based on the formula (7), the pressure reduction width ΔP can be calculated by inputting the pressure command value P into the formula (8).

Therefore, the pressure reduction width setting unit 23 calculates the reduced pressure ratio y from the movement time t0 based on formula (7), and calculates and sets the pressure reduction width ΔP from the reduced pressure ratio y and the pressure command value P based on formula (8). That is, the pressure reduction width setting unit 23 calculates the reduced pressure ratio, which is the ratio of the pressure after pressure reduction to the pressure command value, based on the movement time, and sets the pressure reduction width based on the reduced pressure ratio and the pressure command value.

Furthermore, by inputting equation (7) into equation (4), the relationship between the return time t2 and the movement time t0 can be obtained. FIG. 12 is a diagram showing the relationship between the return time t2 and the movement time t0. As shown in FIG. 12, the return time can be increased as the movement time increases. However, for example, in FIG. 12, the return time is approximately 240 ms when the movement time is 700 ms. This return time of 240 ms is the return time when the reduced pressure ratio is 40%, since the reduced pressure ratio is 40% when the movement time is 700 ms as shown in FIG. 11.

Therefore, the return time setting unit 25 sets the return time t2 from the movement time t0 based on the formulas (4) and (7). That is, the return time setting unit 25 sets the return time required to increase the pressure of the assist gas, which has decreased by the pressure reduction width, to the pressure command value based on the movement time.

[Assist gas pressure control process]
Next, the assist gas pressure control process by the assist gas control device 9 according to this embodiment will be described with reference to Fig. 13. Fig. 13 is a flow chart showing the procedure of the assist gas pressure control process by the assist gas control device 9.

As shown in FIG. 13, in step S201, the movement time calculation unit 21 calculates the movement time during which the processing head 5 fast-forwards from the processing end point to the next processing start point. The movement time calculation unit 21 calculates the movement time according to the operation control pattern of the processing head 5.

In step S203, the pressure reduction width setting unit 23 acquires a pressure command value for the assist gas at the processing start point after the processing head 5 has moved. In step S205, the pressure reduction width setting unit 23 sets a pressure reduction width for reducing the pressure of the assist gas while the processing head 5 moves from the processing end point to the processing start point, based on the pressure command value acquired in step S203 and the movement time calculated in step S201. Specifically, the pressure reduction width setting unit 23 calculates a post-reduction pressure ratio from the movement time using the relationship shown in FIG. 11, and calculates and sets the pressure reduction width from this post-reduction pressure ratio and the pressure command value. Furthermore, the pressure reduction width setting unit 23 sets a reduced pressure command value by decreasing the pressure command value at the processing start point by the pressure reduction width.

In step S207, the return time setting unit 25 sets the return time required to increase the pressure of the assist gas, which has decreased by the pressure reduction width, to the pressure command value based on the movement time calculated in step S201. Specifically, the return time setting unit 25 sets the return time from the movement time using the relationship shown in FIG. 12.

In step S209, the pressure control unit 27 executes a pressure reduction command. Specifically, as shown in FIG. 6, when the cutting process ends at the processing end point, the pressure control unit 27 sets the pressure command value S at time t1 to a reduced pressure command value that is reduced by the pressure reduction width.

In step S211, the pressure control unit 27 calculates the difference between the movement time calculated in step S201 and the return time set in step S207, and calculates the pressure reduction time for reducing the pressure of the assist gas.

In step S213, the pressure control unit 27 determines whether the pressure reduction time calculated in step S211 has elapsed. If the pressure reduction time has not elapsed, it repeatedly determines whether the pressure reduction time has elapsed, and if the pressure reduction time has elapsed, the process proceeds to step S215.

In step S215, the pressure control unit 27 executes the pressure command value for the next processing start point. As shown in FIG. 6, when the pressure reduction time has elapsed and it reaches time t2, the pressure control unit 27 increases the pressure command value S to the pressure command value for the next processing start point. As a result, the assist gas pressure P gradually increases, and at time t3 when the return time has elapsed, it increases to the pressure command value for the next processing start point. In this way, the assist gas pressure control process according to this embodiment ends.

[Modification]
In the above embodiment, the pressure command value at the machining start point after fast-forward movement is the same as the pressure command value at the machining end point, but the pressure command value at the machining start point may differ from the pressure command value at the machining end point. For example, when piercing is performed at the next machining point after fast-forward movement and then cutting is performed, the pressure command value at the machining end point at time t1 differs from the pressure command value at the machining start point at time t2, as shown in Fig. 14. Generally, a higher pressure assist gas is required for cutting than for piercing, so the pressure command values can be set separately for piercing and cutting.

Therefore, when piercing is performed at the next processing point, when the cutting process ends at time t1, the pressure command value for the piercing process and the pressure command value for the cutting process are obtained as the pressure command value for the processing start point after the fast-forward movement. Then, as in the above-described embodiment, the reduced pressure ratio is calculated from the movement time using the relationship shown in FIG. 11, and the pressure reduction width is calculated and set from this reduced pressure ratio and the pressure command value for the piercing process.

At time t2, the pressure control unit 27 increases the pressure command value S to the pressure command value for piercing, and when the machine moves to the next processing point at time t3, the piercing starts. After that, when the piercing ends at time t4, the pressure control unit 27 increases the pressure command value S to the pressure command value for cutting.

However, since a waiting time occurs due to the change in gas pressure when transitioning from piercing to cutting, the pressure command value for piercing and the pressure command value for cutting may be set to the same pressure to prevent a decrease in productivity.

[Effects of the second embodiment]
As described above in detail, the assist gas control device 9 according to this embodiment calculates a post-reduced pressure ratio, which is the ratio of the pressure after pressure reduction to the pressure command value, based on the movement time, and sets the pressure reduction width based on the post-reduced pressure ratio and the pressure command value. This makes it possible to set the pressure reduction width according to the length of the movement time, so that when the movement time is long, the pressure of the assist gas can be reduced more greatly.

The assist gas control device 9 according to this embodiment also sets the return time required to raise the pressure of the assist gas, which has been reduced by the pressure reduction amount, to the pressure command value based on the movement time. As a result, the return time is set according to the length of the movement time, so if the movement time is long, a longer return time can be set.

However, the above-described embodiment is merely an example of the present invention. Therefore, the present invention is not limited to the above-described embodiment, and various modifications can be made to the design, etc., even if the embodiment is different from the above-described embodiment, as long as the modifications do not deviate from the technical concept of the present invention.

REFERENCE SIGNS LIST 1 Laser processing machine 3 Laser oscillator 5 Processing head 7 NC device 9 Assist gas control device 11 Servo amplifier 13 Servo motor 15 Assist gas supply device 17 Electropneumatic regulator 19 Pressure gauge 21 Movement time calculation section 23 Pressure reduction range setting section 25 Recovery time setting section 27 Pressure control section 41, 43 Operation control pattern D1 Actual measurement value D2 Approximation value S Pressure command value P Assist gas pressure Txy Fast forward movement time in X and Y axis directions Tz1 Z axis upward movement time Tz2 Z axis downward movement time

Claims (10)

An assist gas control device that controls the pressure of an assist gas while a processing head of a laser processing machine moves from a processing end point to a processing start point,
Calculating a travel time for the processing head to move from the processing end point to the processing start point;
Acquire a pressure command value of the assist gas at the processing start point;
Based on the movement time and the pressure command value, a reduction pressure command value is set, which is a pressure command value for reducing the pressure of the assist gas while the processing head moves from the processing end point to the processing start point;
When the processing head starts moving from the processing end point, the pressure of the assist gas is reduced to the reduced pressure command value,
An assist gas control device that increases the pressure of the assist gas to the pressure command value before the processing head reaches the processing start point. The assist gas control device according to claim 1, wherein a pressure reduction width for reducing the pressure of the assist gas while the processing head moves from the processing end point to the processing start point is set based on the movement time and the pressure command value, and the reduced pressure command value is set by reducing the pressure command value by the pressure reduction width. The assist gas control device according to claim 2, wherein the pressure reduction range is set based on a pressure reduction range setting table in which the pressure reduction range is set according to the length of the movement time and the magnitude of the pressure command value. The assist gas control device according to claim 3, which sets a recovery time required to raise the pressure of the assist gas, which has decreased by the pressure reduction width, to the pressure command value based on the pressure command value and the pressure reduction width. The assist gas control device according to claim 2, which calculates a post-reduction pressure ratio, which is the ratio of the pressure after pressure reduction to the pressure command value, based on the travel time, and sets the pressure reduction width based on the post-reduction pressure ratio and the pressure command value. The assist gas control device according to claim 5, which sets the recovery time required to raise the pressure of the assist gas, which has decreased by the pressure reduction width, to the pressure command value based on the movement time. The assist gas control device according to claim 4 or 6, which calculates the difference between the movement time and the return time to calculate the pressure reduction time for reducing the pressure of the assist gas. The assist gas control device according to claim 7, which acquires a minimum reduction time, which is the minimum value of the pressure reduction time, and does not execute a process to reduce the pressure of the assist gas if the movement time is less than the sum of the minimum reduction time and the return time. A laser processing machine equipped with an assist gas control device according to any one of claims 1 to 6. An assist gas control method for an assist gas control device that controls the pressure of an assist gas while a processing head of a laser processing machine moves from a processing end point to a processing start point, comprising:
The assist gas control device includes:
Calculating a travel time for the processing head to move from the processing end point to the processing start point;
Acquire a pressure command value of the assist gas at the processing start point;
Based on the movement time and the pressure command value, a reduction pressure command value is set, which is a pressure command value for reducing the pressure of the assist gas while the processing head moves from the processing end point to the processing start point;
When the processing head starts moving from the processing end point, the pressure of the assist gas is reduced to the reduced pressure command value,
An assist gas control method for increasing the pressure of the assist gas to the pressure command value before the processing head reaches the processing start point.

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