JPH09174275A - Method for using assist gas in heat cutting machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the running cost and improve the working ratio of a machine by using a pressure variation absorbing system assist gas producing device and selectively using the obtd. gaseous nitrogen or gaseous oxygen as the assist gas. SOLUTION: An absorbing vessels 23a and 23b are alternately used in each specified time and while one side of the absorbing vessel 23 separates the gaseous nitrogen and the gaseous nitrogen is stored into a product vessel 24, the gaseous oxygen, etc., absorbed in the other side of the absorbing vessel 23 is sucked with a vacuum pump and stored into a gaseous oxygen product vessel 32. This operation is repeated and the gaseous nitrogen concn. in a gaseous nitrogen product vessel 24 gradually becomes high and the stored gaseous nitrogen is discharged from an outlet line B through a valve. When the gaseous nitrogen concn. does not becomes a specified value or higher, a solenoid valve 4 is changed over to (a) position with a control unit 12 and low purity gaseous nitrogen is exhausted. When this gas concn. becomes the specified value or higher, the valve 4 is changed over to (b) position and a valve 3 is changed over to (a) position and the gaseous nitrogen is supplied as the assist gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of using an assist gas for a heat cutting machine, and more particularly to a method of using nitrogen gas and oxygen gas which are separated from the air and stored.

[0002]

2. Description of the Related Art A thermal cutting machine using a laser beam or a plasma arc is widely used in various fields as a machine capable of sharply cutting an iron plate such as stainless steel and accurately machining a work having a complicated shape. Has been done. The method of cutting a metal plate or the like by a thermal cutting machine is to irradiate a metal plate to be processed with a laser beam or a plasma arc from a nozzle at the tip of a processing head along a trajectory of a predetermined graphic input to the metal to be processed. Melt and cut. At the same time, so-called assist gas such as oxygen gas or nitrogen gas is also jetted from the nozzle to perform cutting processing.

The assist gas supply device used in the thermal cutting machine is equipped with an oxygen gas cylinder and a nitrogen gas cylinder, and the gas is used while being selected according to the purpose of cutting and the use of the workpiece. For example, Japanese Patent Laying-Open No. 16783/1997 proposes a laser beam machine as shown in FIG. 3, which will be described below with reference to FIG. A nozzle 9 is provided at the tip of the processing head 8. A through hole (not shown) penetrating from the inside of the processing head 8 to the tip of the nozzle 9 is provided, and a laser beam is emitted from an external laser oscillator (not shown) through a predetermined optical path in the laser processing machine and the through hole. I am trying. Further, a passage for supplying an assist gas is provided inside the processing head 8, and the assist gas is supplied to this passage via a gas pipe 44 connected to the processing head 8. Then, the supplied assist gas is ejected from the tip of the nozzle 9 together with the irradiation of the laser beam.

A low pressure gas pipe 47 and a high pressure gas pipe 50 are connected to the gas pipe 44 via a low pressure pressure regulator 48 and a high pressure pressure regulator 49, respectively. Gas supply paths from the oxygen gas cylinder 45a, the nitrogen gas cylinder 45b, and the air compressor 45c are connected to the high-pressure gas pipe 50 via switching valves 46a, 46b, and 46c, respectively. Further, a gas supply path from the oxygen gas cylinder 45a is connected to the low pressure gas pipe 47 via a switching valve 46d. Further, each of the switching valves 46a, 46b, 46
c, 46d operation solenoid, and low pressure pressure regulator 4
8. The operating solenoid of the high pressure regulator 49 is connected to a control device (not shown). This control device switches the switching valves 46a, 46b, 46c, 46d, and the low pressure regulator 48 and the high pressure regulator 49.
The pressure value of is set.

Next, the operation of the laser beam machine having such a configuration will be described. The operator inputs the type of assist gas to be used, the plate thickness of the work 41 to be processed, and the like into the control device before starting the processing. When the processing is started, this control device moves the processing head 8 to a predetermined start position of the workpiece 41 to be processed, irradiates the laser beam from the nozzle 9 at this position, and at the same time ejects oxygen gas from the nozzle 9 as assist gas.

Assuming that the gas pressure at the time of piercing is set to a low pressure, the control device has a switching valve 46.
A switching command is output to the operation solenoid of d to supply oxygen gas to the low pressure gas pipe 47. Further, the control device sends a command signal according to the set pressure value to the low pressure regulator 48.
The pressure of the assist gas supplied to the gas pipe 44 from the low pressure gas pipe 47 is adjusted to the above pressure value. As a result, piercing is performed with a predetermined pressure value.

After the piercing is completed, the control device switches the switching valve 46 according to the type of the assist gas input above.
By switching a, 46b, and 46c, the required assist gas is sent to the high-pressure gas pipe 50. At this time, the control device outputs a command signal corresponding to the pressure value preset corresponding to the input plate thickness of the workpiece 41 to the high pressure regulator 49. As a result, the pressure of the assist gas supplied from the high pressure gas pipe 50 to the gas pipe 44 is adjusted to the above pressure value. In this way, the selected assist gas is jetted from the nozzle 9 at a predetermined pressure value to perform processing.

[0008]

However, in the above thermal cutting machine, since the exclusive nitrogen gas cylinder and oxygen gas cylinder are used, the running cost is high. Further, since it requires manpower each time these gas cylinders are replaced, and this replacement time is also required, the maintenance cost for gas cylinder replacement becomes high. In addition, since a large-sized and heavy-weight cylinder is often used, a safe operation at the time of replacement must be taken into consideration, which is a heavy burden on the operator. Further, when the used capacity of the assist gas increases, the number of times the gas cylinder is replaced increases, and the operation of the thermal cutting processing machine must be interrupted each time, which causes a problem that the operating rate of the processing machine decreases.

Further, the cutting quality depends on the purity of the assist gas, but the conventional gas cylinders are not stable in terms of quality due to variations in purity. For example, in cutting using a nitrogen gas cylinder, the nitrogen purity is preferably 99.
Although the appearance quality after cutting is better when 98% or more is used, the nitrogen gas cylinders are 99.5% or more in the standard and 99.95 to 99.99% in practice. Therefore, when cutting is actually performed using a nitrogen gas cylinder, variations in appearance quality may occur, resulting in poor quality. Therefore, there is a demand for a thermal cutting machine capable of cutting with a stable nitrogen purity.

The present invention has been made in view of the above problems, can reduce the running cost, can be maintenance-free such as cylinder replacement, can improve the operating rate of the processing machine, and can reduce nitrogen gas and It is an object of the present invention to provide a method of using an assist gas for a thermal cutting machine, which can secure the purity of oxygen gas at a predetermined value or more and stabilize the cutting quality.

[0011]

In order to achieve the above object, the invention according to claim 1 is a thermal cutting process in which nitrogen gas or oxygen gas is selectively switched and used as an assist gas. In the method of using assist gas of a machine, a nitrogen gas or an oxygen gas obtained by using an assist gas generator 20 of pressure fluctuation adsorption type that separates nitrogen gas from the air using an adsorption bed made of molecular sieve coal is selectively used. Is used as an assist gas.

According to the first aspect of the present invention, the nitrogen gas separated from the air is accumulated, and the remaining gas (mainly oxygen gas) is stored as oxygen gas. Is selectively used as an assist gas in accordance with cutting processing conditions. Therefore, it is not necessary to replace the cylinder, the running cost is reduced, and the maintenance cost is reduced because the maintenance is free. Further, the machine operating rate can be improved, the work safety can be improved, and the burden on the operator can be reduced.

Further, in the second aspect of the present invention, in the method of using the assist gas for the thermal cutting machine, the concentration of the nitrogen gas separated from the air by the assist gas generator 20 and stored is not less than a predetermined value. When this happens, the stored nitrogen gas is used as an assist gas.

According to the second aspect of the present invention, the nitrogen gas having a high purity can be used because it is used as the assist gas after waiting until the concentration of the nitrogen gas becomes a predetermined value or more. Therefore, it is possible to perform cutting with stable appearance quality after cutting.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an assist gas generator 20 for a laser beam machine according to the present invention will be described in detail with reference to the drawings. Here, the same components as those described with reference to FIG. 3 of the related art are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 is a schematic diagram of an assist gas generator 20. The air compressor 1 that compresses and pressure-feeds air, which is a raw material of the assist gas, includes an assist gas generator 2
0 is connected to the inlet side. Assist gas generator 2
0 separates and extracts nitrogen gas from compressed air, and outputs this nitrogen gas and the remaining gas (mainly oxygen gas, hereinafter referred to as oxygen gas). The nitrogen gas output line of the assist gas generator 20 is connected to the inlet side of the nitrogen gas product tank 24, and the oxygen gas output line of the assist gas generator 20 is connected to the inlet side of the oxygen gas product tank 32.

The outlet line B of the nitrogen gas product tank 24 is, via the filter 25a, a nitrogen gas concentration detecting means 2 for detecting the gas concentration, a solenoid valve 3 for opening and closing the gas supply line, and a solenoid for exhausting means. It is connected in parallel with the valve 4. Similarly, the outlet line C of the oxygen gas product tank 32 is connected via the filter 25b,
Solenoid valve 35 as gas supply line opening / closing means
And a solenoid valve 34, which is an exhaust means, are connected in parallel.

Since the assist gas generator 20 operates within a predetermined pressure range, the air compressor 1 is provided with an unload valve so that the pressure of the compressed air of the air copressor 1 does not exceed a predetermined value. Etc. are built in.

The nitrogen gas concentration detecting means 2 is for detecting whether or not the nitrogen gas concentration in the output line B of the nitrogen gas product tank 24 has exceeded a predetermined value. To detect the nitrogen gas concentration, for example, the nitrogen gas concentration may be directly detected, or the oxygen gas concentration in the remaining gas after separating the nitrogen gas may be detected and used as a substitute. As described above, as the assist gas for the thermal cutting machine, a nitrogen gas concentration that is preferable in terms of quality is generally required to have a purity of 99.98% or higher. Therefore, as the nitrogen gas concentration detecting means 2, when the nitrogen gas concentration is directly detected by the nitrogen gas concentration meter, the lower limit setting value of the nitrogen gas concentration is 99.98%, and when the nitrogen gas concentration is detected by the oxygen gas concentration meter. The upper limit set value of the oxygen gas concentration is 0.02%. In addition,
When the oxygen gas concentration in the outlet line C of the oxygen gas product tank 32 is used at a predetermined value or higher, an oxygen gas concentration detecting means may be provided in the output line of the filter 25b.

The output gas pipe line from the solenoid valve 3 is provided with an assist gas supply line (not shown) inside the machining head 8 of the laser beam machine through the static electricity regulator 7 for adjusting the gas pressure supplied to the machining head 8. Connected). A nozzle 9 is provided at the tip of the processing head 8.
The valve of the solenoid valve 3 is biased by the spring force so as to be in the b position when the command signal is not input to the operation solenoid portion. At this position b, a check valve is built in so that the nitrogen gas does not flow from the nitrogen gas product tank 24 to the static electricity regulator 7 side.

The output gas piping from the solenoid valve 4 is led to the atmosphere via a pressure reducing valve 5 and a silencer 6. This is because when the nitrogen gas concentration of the gas output from the nitrogen gas product tank 24 has not reached a predetermined value, this gas is depressurized and is exhausted into the atmosphere while soundproofing. Similarly to the above, the valve of the solenoid valve 4 is biased by the spring force so as to be in the b position when the command signal is not input to the operation solenoid portion. Further, a check valve is built in this position b so as not to flow from the nitrogen gas product tank 24 to the exhaust line into the atmosphere.

The output gas piping from the solenoid valve 35 is provided with an assist gas supply path () for the assisting gas inside the machining head 8 of the laser beam machine via an air-electric regulator 36 for adjusting the gas pressure supplied to the machining head 8. (Not shown). The valve of the solenoid valve 35 is biased by the spring force so as to be in the b position when the command signal is not input to the operation solenoid portion. At the position b, from the oxygen gas product tank 32 to the static regulator 36
A check valve is built in so that oxygen gas does not flow into the side.

Further, the output gas pipeline from the solenoid valve 34 is led to the atmosphere via a pressure reducing valve 37 and a silencer 38. This is because, in the initial stage where the oxygen gas concentration of the gas output from the oxygen gas product tank 32 has not reached the predetermined value, this gas is depressurized and exhausted into the atmosphere while soundproofing. The valve of the solenoid valve 34 is biased by the spring force so as to be in the position b when the command signal is not input to the operation solenoid portion, as described above. At this position b, the oxygen gas product tank 3
2 so as not to flow into the exhaust line into the atmosphere,
Built-in check valve.

A pressure gauge 10 and a pressure switch 11 are connected between the air compressor 1 and the assist gas generator 20 as means for detecting the pressure of compressed air.
The pressure switch 11 turns on an output contact signal, for example, when the pressure of the compressed air exceeds a predetermined pressure value that is set, and this output contact signal is input to the control device 12 as a pressure signal. As the pressure detecting means, for example, a pressure sensor that outputs pressure value data may be used.

The assist gas generator 20 comprises a solenoid valve 21, an activated carbon tank 22, an adsorption tank 23, and a filter 25. The pipeline of compressed air from the air compressor 1 is connected to the input side of the activated carbon tank 22 via the solenoid valve 21, and the output side of the activated carbon tank 22 is connected to the adsorption tank 23 via the filter 25. Of the two outputs of the adsorption tank 23, the nitrogen gas output line is connected to the nitrogen gas product tank 24, and the oxygen gas output line is connected to the oxygen gas product tank 32. The valve of the solenoid valve 21 is biased by the spring force so as to be in the b position when the command signal is not input to the operation solenoid portion. In addition, a check valve is built in this position b so that air does not enter the assist gas generator 20 from the air compressor 1.

Since the purity of nitrogen gas and oxygen gas at the beginning of the operation of the assist gas generator 20 is low, it takes time to reach a predetermined usable purity. In order to perform the cutting work during the waiting time, in parallel with the nitrogen gas supply line and the oxygen gas supply line by the assist gas generator 20, respectively, a nitrogen gas supply line by a nitrogen gas cylinder and an oxygen gas by an oxygen gas cylinder are provided. A supply line is provided. In FIG. 1, for example, a nitrogen gas cylinder 30 (an oxygen gas supply line by an oxygen gas cylinder is not shown) is connected to an input port of a solenoid valve 31 which is a cylinder gas supply line opening / closing means via a filter 25c. The output gas line from the solenoid valve 31 is connected in parallel with the output gas line of the solenoid valve 3 to the input port side of the pneumatic regulator 7. The valve of the solenoid valve 31 is biased by the spring force so as to be in the b position when the command signal is not input to the operation solenoid portion. At this position b, a check valve is incorporated so that nitrogen gas does not flow from the nitrogen gas cylinder 30 to the static electricity regulator 7 side.

A pressure signal from the pressure switch 11 and a gas concentration signal from the nitrogen gas concentration detecting means 2 are input to the control device 12 which controls the assist gas generator 20. Further, the control device 12 includes a solenoid valve 3,
It is connected to each operation solenoid 4, 21, 31, 34, 35, and outputs a switching signal to each operation solenoid to switch the corresponding solenoid. Further, the control device 12 outputs a command signal corresponding to the pressure set value of the assist gas at the time of disconnection described in the prior art to the respective solenoid portions of the pneumatic regulators 7 and 36. Further, the control device 12 outputs a start command to the compressor 1. The control device 12 is formed by, for example, a computer system mainly composed of a general microcomputer.

FIG. 2 shows an adsorption tank 23 and a nitrogen gas product tank 24.
3 is a diagram showing the details of the oxygen gas product tank 32, and a detailed description will be given below based on the same figure. The air inlet line A is
They are connected to the inlet side of the adsorption tank 23a and the inlet side of the adsorption tank 23b via valves 55 and 57, respectively. The outlet side of the adsorption tank 23a and the outlet side of the adsorption tank 23b are connected to the nitrogen gas product tank 24 via valves 59 and 60, respectively. An outlet line B is connected to the outlet side of the nitrogen gas product tank 24 via a valve 67.

The inlet side of the adsorption tank 23a and the inlet side of the adsorption tank 23b are connected to the suction side of the vacuum pump 54 via valves 56 and 58, respectively. Also, the vacuum pump 5
The output side of 4 is connected to the inlet side of the oxygen gas product tank 32,
An outlet line C is connected to the outlet side of the oxygen gas product tank 32 via a valve 65.

The inside of the adsorption tanks 23a and 23b is filled with molecular sieve charcoal which is a gas adsorbent. A method of separating nitrogen gas from a mixed gas such as air by a pressure fluctuation adsorption method using an adsorbent composed of molecular sieve charcoal has been generally used conventionally. The method for separating nitrogen gas by the adsorption tank 23a and the adsorption tank 23b of the present invention is also based on this pressure fluctuation adsorption method. That is, when compressed air is input to the adsorption tank 23a and the adsorption tank 23b filled with the molecular sieve charcoal, oxygen gas, carbon dioxide gas in the air by the molecular sieve charcoal,
Nitrogen gas that adsorbs moisture and the like within a short time and is hardly adsorbed during that time is output from the adsorption tank 23a and the adsorption tank 23b. The nitrogen gas is stored in the nitrogen gas product tank 24 and used as an assist gas.

Next, the operation of the assist gas generator 20 will be described. Here, it is assumed that the valve 57 and the valve 60 are closed. The pressurized air enters the adsorption tank 23a from the air inlet line A through the valve 55, and the components such as oxygen gas to be removed are adsorbed by the molecular sieve charcoal in the adsorption tank 23a.
The separated nitrogen gas is passed through the valve 59 to the nitrogen gas product tank 2
Stored in 4.

After the above adsorption for a predetermined time, the adsorption tank 2
Since the adsorption rate of oxygen gas or the like by the molecular sieve coal of 3a decreases, the controller 12 closes the valves 55 and 59 to once complete the separation of nitrogen gas by the adsorption tank 23a. After that, the controller 12 opens the valves 57 and 60 to input the pressurized air from the air inlet line A into the adsorption tank 23b. In the adsorption tank 23b, the nitrogen gas is separated similarly to the adsorption tank 23a, and the separated nitrogen gas is stored in the nitrogen gas product tank 24 via the valve 60. Also, during this time, valve 5
By opening 6 and operating the vacuum pump 54, oxygen gas or the like adsorbed by the molecular sieve charcoal in the adsorption tank 23a is sucked and stored in the oxygen gas product tank 32.

In this way, the adsorption tanks 23a and 23b are alternately used every predetermined time, and one adsorption tank 23a is used.
While the nitrogen gas is separated and stored in the nitrogen gas product tank 24, the oxygen gas or the like adsorbed in the other one adsorption tank 23 is sucked by the vacuum pump 54 and the oxygen gas product tank Stored at 32. By repeating this, the nitrogen gas concentration in the nitrogen gas product tank 24 gradually increases, and the stored nitrogen gas is output from the outlet line B via the valve 67. When the nitrogen gas concentration does not exceed the predetermined value, the control device 12 sets the solenoid valve 4 to a
When the nitrogen gas of low purity is exhausted to the atmosphere by switching to the position, and when the value exceeds a predetermined value, the solenoid valve 4 is switched to the b position, and the solenoid valve 3 is switched to the a position to connect to the nitrogen gas supply line. Nitrogen gas is supplied as an assist gas.

Similarly, the oxygen gas concentration in the oxygen gas product tank 32 gradually increases, and the stored oxygen gas is released from the valve 65.
Is output from the exit line C via the. During the initial period when the oxygen gas concentration does not reach the predetermined value or more, the control device 12 switches the solenoid valve 34 to the position a to exhaust oxygen gas of low purity to the atmosphere, and when the oxygen gas concentration exceeds the predetermined value, , The solenoid valve 34 is switched to the b position, and the solenoid valve 35 is switched to the a position to supply oxygen gas as an assist gas to the oxygen gas supply line.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an assist gas generator of the present invention.

FIG. 2 is a block diagram of an adsorption tank and a product tank of the assist gas generator of the present invention.

FIG. 3 is a block diagram of an assist gas generator in a conventional laser processing machine.

[Explanation of symbols]

1 ... Air compressor, 2 ... Nitrogen gas concentration detecting means,
3, 4 ... Solenoid valve, 5 ... Pressure reducing valve, 6 ... Silencer, 7 ... Pneumatic regulator, 8 ... Machining head, 9 ... Nozzle, 10 ... Pressure gauge, 11 ... Pressure switch, 12 ... Control device, 20 ... Assist gas Generator, 21 ... Solenoid valve, 22 ... Activated carbon tank, 23a, 23b ... Adsorption tank, 24
... Nitrogen gas product tank, 25, 25a, 25b, 25c ... Filter, 30 ... Nitrogen gas cylinder, 31 ... Solenoid valve, 32 ... Oxygen gas product tank, 34, 35 ... Solenoid valve, 36 ... Pneumatic regulator, 37 ... Pressure reducing valve , 38 ...
Silencer, 41 ... Work to be processed, 44 ... Supply pipe, 4
5a ... Oxygen gas cylinder, 45b ... Nitrogen gas cylinder, 45
c ... Air compressor, 46a, 46b, 46c, 46
d ... Switching valve, 47 ... Low-pressure gas pipe, 47 ... Low-pressure pressure regulator, 49 ... High-pressure pressure regulator, 50 ... High-pressure gas pipe,
54 ... Vacuum pump, 55, 56, 57, 58, 59, 6
0, 64, 65, 67 ... Valves.

Claims (2)

[Claims] 1. A method for using an assist gas of a thermal cutting machine, which selectively switches nitrogen gas or oxygen gas to use as an assist gas, wherein a pressure for separating nitrogen gas from the air by using an adsorbent composed of molecular sieve charcoal is used. Fluctuating adsorption type assist gas generator (20)
A method of using an assist gas in a thermal cutting machine, characterized by selectively using nitrogen gas or oxygen gas obtained by using as an assist gas. 2. The stored nitrogen gas is used as an assist gas when the concentration of the nitrogen gas separated from the air by the assist gas generator (20) and stored exceeds a predetermined value. The method of using an assist gas for a thermal cutting machine according to claim 1.