JPH0825015B2 - Plasma cutting method and apparatus thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma cutting method and an apparatus thereof, and more particularly to a plasma cutting method and an apparatus thereof suitable for use in automatic cutting and remote cutting of thick plates. Is.

[Conventional technology]

For the conventional plasma cutting method, "Basics and practice of plasma cutting" edited by Japan Welding Association (Industrial publication, 1983)
There is a plasma arc cutting method and a plasma jet cutting method described in a book called as. These principles are shown in FIGS. 5 and 6, respectively. FIG. 5 is a principle diagram of the plasma arc cutting method. A high frequency generator 11, a pilot power source 12, and a main power source 13 are connected to a nozzle 301, an electrode 302, and a cutting material 20 as shown in the figure. The cutting material 20 needs to be a conductive material, but since arc is generated between the cutting material 20 and the electrode 302 and the thermal efficiency is high, it is possible to cut a thick plate. At the time of start-up, since the main arc is generated, the high frequency generator 11 and the pilot power supply 12 generate the pilot arc between the nozzle 301 and the electrode 302. After the main arc is ignited,
The switch 15 is opened and the pilot current and high frequency current are generally cut off. On the other hand, FIG. 6 is a principle diagram of the plasma jet cutting method, in which the high frequency generator 11 and the main electrode 13 are connected to the nozzle 301.
And to the electrode 302 as shown. In this case, the cutting material 20 does not need to be a conductive material, but has low thermal efficiency and is not suitable for cutting thick materials. However, since a plasma jet is generated regardless of the cutting material 20, automatic cutting,
Positioning control of the torch related to remote cutting and control of the timing of firing the main arc are unnecessary and easy to handle. A composite cutting method that combines a plasma arc cutting method and a plasma jet cutting method is also known, and is practically used for cutting a book plate.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma cutting method and apparatus capable of cutting a thick plate using a composite cutting method combining a plasma arc cutting method and a plasma jet cutting method.

[Means for solving problems]

The configuration of the present invention made to achieve the above-mentioned object is, in the plasma cutting method, in the plasma cutting method in which the plasma arc and the plasma jet are combined, the plasma arc current increases as the plate thickness of the material to be cut increases. When the plasma arc current is increased, the plasma jet current is also set to be larger in accordance with the increase of the plasma arc current, and the plasma jet current is held even when the plasma arc current is cut off. In, in a plasma cutting device having a main power supply for plasma arc and a main power supply for plasma jet,
A nozzle and an electrode arranged in contact with the material to be cut, a setter for the plasma arc power supply value, and the plasma jet current value so that the ratio of the plasma jet current value to the plasma arc current value becomes a predetermined value. A current setting device for setting and a parallel circuit capable of holding the plasma jet current even when the plasma arc current is cut off are provided.

[Action]

Since the present invention uses the above means, optimum cutting can be performed. In order to cut a given plank, a cutting ability corresponding to it is necessary. The cutting ability can be increased by increasing the current value, but conversely, when the current value is increased, the consumption of the electrode and the nozzle becomes severe. Therefore, when the minimum required current value is selected, it is necessary to determine two types of current values, a plasma arc current value and a plasma jet current value. In the present invention, the cutting ability is basically considered to be related to the plasma arc current value, and the plasma arc current value is kept constant, and the plasma jet current value is variously changed to perform a comparative test of the cutting ability, and as a result, It was confirmed that the plasma jet current did not contribute to the cutting ability. Rather, it was found that when the plasma jet current was increased, the cutting ability was slightly reduced. On the other hand, the advantage of using a composite cutting method that combines the plasma arc cutting method and the plasma jet cutting method for thick plate cutting is that the plasma arc is ignited again even after the plasma arc is extinguished once by using the plasma jet together. I think it is to keep it easy. That is, in the plasma arc cutting method, this corresponds to leaving the pilot arc even after the main arc is extinguished. According to the method of the present invention, the minimum required plasma jet current for maintaining the pilot arc (plasma jet) during plasma arc ignition and plasma arc extinction is related to the magnitude of the plasma arc current value. This method focuses on the fact that when the arc current is large, the minimum required plasma jet current at that time also becomes large. Also for this, under the same cutting conditions, the inventor conducted a test in which the plasma arc current value was kept constant and the plasma arc current value was gradually increased under various plasma arc current value conditions. Becomes larger,
It has been confirmed that the minimum plasma jet current for maintaining the pilot arc (plasma jet) also increases. For example, when the plasma arc current is 150A, the minimum required current of the plasma jet is 20A, and when the plasma arc current is 200A, the minimum required current of the plasma jet is 40A. Later Pilot Arc (Plasma Jet)
I also confirmed that it would be extinguished.

Also, the plasma cutting power supply device is provided with a main power supply for plasma arc and a main power supply for plasma jet, and by setting the plasma arc current value, the plasma arc current value and the plasma shet current value at the plasma arc current value are set. Since the automatic setting device for automatically setting the ratio of 1 to a predetermined ratio is provided, optimum cutting can be easily performed.

According to the above-mentioned test results, the optimum plasma arc current value is determined by the required cutting ability, and the optimum plasma jet current value is determined by the plasma arc current value. It can be performed.

〔Example〕

The present invention will be described in detail below with reference to the embodiments shown in FIGS. 1, 2, and 4 and FIG.

FIG. 1 is a wiring diagram showing an embodiment in which two plasma cutting power supply devices are used to explain the plasma cutting method of the present invention, and FIG. 2 shows an embodiment of the power supply device. It is a circuit block diagram.

In FIG. 2, two main power supplies 13, 13 ', a pilot power supply 12, and a high frequency generator 11 are connected to the nozzle 301, the electrode 302, and the cutting material 20 as shown in the drawing. Main power supply 13 ′, 1
Main electrode setters 101 and 201 are respectively connected to 3, and these are composed of, for example, a variable resistor and the like, and the main power supplies 13 ', 1 are formed by a divided voltage signal.
The output current of 3 is controlled. here,
When the main current setting device 101 is adjusted, the electrode 302 and the cutting material 20
The plasma arc current flowing between the two can be set arbitrarily. Further, by adjusting the main current setting device 201, the plasma jet current flowing between the nozzle 301 and the electrode 302 can be arbitrarily set.

Next, a specific cutting method will be described with reference to the configuration diagram shown in FIG. First, the main current setting device 101 sets a plasma arc current value that provides a required cutting ability based on conditions such as the thickness of the cutting material 20 and the cutting speed. next,
The main current setting device 201 sets a minimum required plasma jet current value according to the set plasma arc current value. Next, by closing the switches 16 and 17, and further closing the switch 15, the high frequency generator 11 and the pilot power supply are closed.
12 and main power supply 13 make the plasma jet nozzle
It occurs between 301 and electrode 302. If a plasma jet is generated, the plasma jet will not be extinguished by the main power supply 13 even if the switch 15 is opened. Then the nozzle
When the electrode 302 and the cutting material 20 come close to a predetermined distance by moving the torch or the cutting material 20 composed of 301 and the electrode 302, a plasma arc is generated between the electrode 302 and the cutting material 20. The cutting material 20 is cut as described above. However, when the distance between the cutting material 20 and the electrode 302 is large, or when the main power source 13 ′ is used.
When the switch 17 is opened, the plasma arc is extinguished and only the plasma jet is generated between the electrode 302 and the nozzle 301. Here, if the switch 17 is closed again and the electrode 302 is brought closer to the cutting material 20, the plasma arc is ignited again.

This pattern is shown in FIG. FIG. 3A shows a state in which the torch 300 in the state where the plasma jet is generated horizontally moves in the direction of the cutting material 20. FIG. 3 (b) shows that when the torch 300 approaches the cutting material 20 and reaches a predetermined distance, a plasma arc is generated between the electrode 302 inside the torch 300 and the cutting material 20. .
Fig. 3 (c) shows the cutting material with plasma arc generated.
Shows cutting 20. FIG. 3 (d) shows a state in which the switch 17 of FIG. 2 is opened to extinguish the plasma arc,
It shows that only the plasma jet remains. FIG. 3 (e) shows a state in which the torch 300 is moved in the state where only the plasma jet is generated. As described above, in the composite cutting method in which the plasma arc cutting method and the plasma jet cutting method are combined, once the pilot arc (plasma jet) is generated by the high frequency generator 11,
The plasma arc can be ignited and extinguished any number of times, and when applied to automatic cutting and remote cutting, the operability is good and the advantage that it is easy to apply can be utilized. Also,
Generating a high frequency adversely affects the life of the electrode 302 and the nozzle 301, and thus it is desirable to reduce the number of occurrences from the viewpoint of life.

In FIG. 2, the pilot power supply 12 is actually unnecessary. Here, description is given assuming that the cutting method of the present invention is performed using two plasma cutting power supply devices A100 and B200 (see FIG. 1) for plasma arc cutting. The actual wiring diagram in this case is shown in FIG. Since the plasma cutting power supply device A100 is used as a power supply for generating a plasma arc, the main current output terminal 112 is connected to the cutting material 20 and the common negative terminal 111 is connected.
Is connected to the torch electrode 302. The plasma disconnection power supply device B200 is used as a power supply for generating high frequency and plasma jet, so the main current output terminal
222 and the high frequency and pilot current output terminal 223 are connected to the nozzle 301 of the torch, and the common negative terminal 221 is connected to the electrode 302 of the torch. Optimal cutting can be performed by setting the plasma arc current value by the main current setting device 101 and the plasma jet current value by the main current setting device 201. Although the water tank 10 is shown in FIG. 1, the working gas supply system, the structure of the torch, and the like are not directly related to the present invention, and are not shown.

FIG. 4 is a block diagram showing an embodiment of a plasma cutting power supply device having an automatic setting device for automatically setting the ratio of the plasma arc current value and the plasma jet current value to a predetermined ratio. The main current setting device 101 of the plasma cutting power supply device A100 which is the main power supply for plasma arc is a variable resistor, and the variable resistor of the main current setting device 201 of the plasma cutting power supply device B200 which is the main power supply for plasma jet and the connecting shaft. It is connected at 98, and by turning the setting dial 99, both the main current setting devices 101 and 201 can be adjusted. Here, the main current setting device 10
The characteristics of the variable resistors 1 and 201 can be automatically set easily by setting the preset voltage of the plasma jet current value according to the magnitude of the plasma arc current value as the partial voltage of the variable resistor. You will be able to do it. In addition, in order to perform automatic setting, it may be connected via a gear instead of the connecting shaft 98, or a direct acting type variable resistor may be used instead of the rotary type variable resistor. Is the same. In addition, a minimum plasma jet current value corresponding to various plasma arc current values may be stored in advance in a storage device such as a microcomputer, and may be automatically set according to the input plasma arc current value. .

〔The invention's effect〕

As described above, according to the present invention, it is possible to perform the thick plate cutting in the composite cutting method in which the plasma arc cutting method and the plasma jet cutting method are combined under the optimum condition for the nozzle life, and the plasma jet is always cut. Since the condition for maintaining the condition is satisfied, there is an effect that it can be easily applied to automatic cutting and remote cutting without requiring highly accurate positioning control of the torch or cutting material.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the plasma cutting method of the present invention.
FIG. 2 is a wiring diagram showing an embodiment in which a plasma cutting power supply device of one unit is used, FIG. 2 is a circuit configuration diagram showing an embodiment of the power supply device, and FIG. A cutting situation diagram, FIG. 4 is a configuration diagram showing an embodiment of a plasma cutting power supply device having an automatic setting device of the plasma jet current value corresponding to the plasma arc current value, and FIG. 5 is a principle diagram of the plasma arc cutting method, FIG. 6 is a principle diagram of the plasma jet cutting method. 10 ... Water tank, 11 ... High frequency generator, 12 ... Pilot power supply, 1
3,13 '... Main power supply, 15,16,17 ... Switch, 20 ... Cutting material, 98 ... Coupling shaft, 99 ... Setting dial, 100,200 ... Plasma cutting power supply device, 101,201 ... Main current setting device, 111,221
… Common negative terminal, 112,222… Main current output terminal, 1
13,223 ... High frequency and pilot current output terminals, 301 ... Nozzle, 302 ... Electrodes.

Claims (2)

[Claims] 1. A plasma cutting method in which a plasma arc and a plasma jet are combined, wherein when the plasma arc current is increased as the plate thickness of a material to be cut increases, the plasma arc current is increased. A plasma jet current is also set to a large value, and the plasma jet current is maintained even when the plasma arc current is cut off. 2. A plasma cutting apparatus having a main power supply for plasma arc and a main power supply for plasma jet, a nozzle and an electrode arranged in contact with a material to be cut, and a plasma arc current value setting device. A current setting device that sets the plasma jet current value so that the ratio of the plasma jet current value to the plasma arc current value becomes a predetermined value, and holds the plasma jet current even when the plasma arc current is cut off. And a parallel circuit capable of controlling the plasma cutting apparatus.