JP3231899B2 - Plasma cutting method and plasma cutting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling an arc current in response to a change in the flow rate of a plasma gas, and a method and an apparatus for controlling the flow rate of a plasma gas in response to a change in an arc current. is there.

[0002]

2. Description of the Related Art In plasma cutting, an appropriate plasma arc discharge phenomenon can be continuously generated only when a delicate correlation is established between a plasma gas flow rate and an arc current value. For example, if the arc current decreases for some reason or if the plasma gas flow rate increases, the arc cannot be held and the arc discharge stops. On the other hand, if the arc current increases or the plasma gas flow rate decreases for some reason, the arc generation point from the electrode becomes unstable and a series arc that generates a plurality of arcs occurs, which causes damage to the electrode.

[0003] In particular, an example of a factor that causes a change in the arc current is attributable to a change in the distance between the electrodes and the material to be cut. In addition to changing the height of the plasma torch, the thickness of the material to be cut changes, the material to be cut becomes distorted during cutting, and the distance between the electrodes changes. When the torch straddles the cutting groove, the arc current value changes rapidly due to the instability of the discharge current.

In addition, a change in the inclination angle of the plasma torch with respect to the material to be cut, a change in the cutting movement speed of the torch, etc.
The arc current value changes with various changes in cutting conditions. It is necessary to adjust the arc current in response to such a change in the arc current or to adjust the plasma gas flow rate accordingly. Conventionally, the operator empirically adjusts the arc current and the plasma gas flow rate individually. As a result, an appropriate plasma arc was formed.

[0005]

However, when the operator individually adjusts the plasma gas flow rate and the arc current in response to various changes in the cutting conditions as described above, it is difficult to cope with minute changes in the cutting conditions. There is no present. Normally, since cutting is performed in a uniform cutting process in which cutting information is set in advance, cutting according to the cutting state of each cut material cannot be performed. Further, when cutting a material to be cut having complicated cutting conditions, there is a problem that individual setting is troublesome and setting takes time.

SUMMARY OF THE INVENTION It is an object of the present invention to perform efficient plasma cutting by automatically controlling a plasma gas flow rate and an arc current relatively to each cutting condition to form an appropriate plasma arc.

[0007]

[0008]

[0009]

SUMMARY OF THE INVENTION A plasma cutting apparatus according to the present invention supplies a plasma gas around an electrode and ejects a plasma arc from a nozzle to cut a material to be cut. A flow rate measuring unit for detecting the flow rate of the plasma gas supplied to the cut material, a first storage unit for temporarily storing plasma gas flow rate information from the flow rate measuring unit, and an input for inputting preset flow rate information Unit, a second storage unit that stores the preset flow rate information, a current measurement unit that detects an arc current injected to the workpiece, and temporarily stores the arc current information from the current measurement unit. A third storage unit, a fourth storage unit for temporarily storing the arc current information temporarily stored in the third storage unit, a flow rate information from the plasma gas flow rate measurement unit, and the preset value. A plasma comprising: a calculation unit that compares and calculates the flow rate information with the calculated flow rate information and a change calculation of the current information from the arc current measurement unit; and an arc current control unit that controls the arc current based on the calculation information. It is a cutting device.

[0010] Further, the plasma cutting apparatus according to the present invention comprises:
In a plasma cutting method for cutting a material to be cut by supplying a plasma gas around an electrode and spraying a plasma arc from a nozzle, a current measuring unit for detecting an arc current injected to the material to be cut, and the current measurement A first storage unit for temporarily storing arc current information from the unit, an input unit for inputting preset arc current information, a second storage unit for storing the preset arc current information, A flow rate measurement unit for detecting a flow rate of the plasma gas supplied to the material, a third storage unit for temporarily storing plasma gas flow rate information from the flow rate measurement unit, and a third storage unit for temporarily storing the plasma gas flow rate information A fourth method for temporarily storing the plasma gas flow rate information
A storage unit for comparing and calculating the current information from the arc current measurement unit and the preset current information, and comparing and calculating a change in flow rate information from the plasma gas flow rate measurement unit; and And a plasma gas flow controller for controlling a flow rate of the plasma gas based on information.

[0011]

[0012]

In the plasma cutting apparatus according to the present invention, as described above, the flow rate information obtained by measuring the plasma gas flow rate by the flow rate measuring section is temporarily stored in the first storage section, and the flow rate information and the second storage section are stored in advance in the second storage section. By comparing and calculating the flow rate information set and stored by the calculation unit, the change amount of the gas flow rate according to the cutting condition can be calculated, and the arc current control unit corresponds to the gas flow rate change amount. Therefore, the arc current and the plasma gas flow rate can always be maintained in an appropriate correlation.

Further, the controlled arc current is measured by an arc current measuring section, and the arc current information before the measurement is temporarily stored in a fourth storage section, and the arc current information after the measurement is temporarily stored in a third storage section, respectively. After transmitting the respective current information to the calculation unit and performing the comparison calculation, the arc current control unit controls the arc current according to the calculation information, measures again by the arc current measurement unit, and repeats the above feedback operation. Since the control is performed so as to obtain a desired arc current, an appropriate arc current value can be obtained.

[0014] Further, the plasma cutting apparatus according to the present invention comprises:
As described above, the current information obtained by measuring the arc current in the current measurement unit is temporarily stored in the first storage unit, and the current information and the current information preset and stored in the second storage unit are calculated by the calculation unit. By performing the comparison operation, the change amount of the arc current according to the cutting condition can be calculated, and the plasma gas flow rate control unit controls the plasma gas flow rate in accordance with the change amount of the arc current. It is possible to always maintain a proper correlation with the plasma gas flow rate.

Further, the controlled plasma gas flow rate is measured by the plasma gas flow rate measuring section, and the plasma gas flow rate information before the measurement is stored in the fourth storage section, and the plasma gas flow rate information after the measurement is stored in the third storage section. After temporarily storing and transmitting the respective flow rate information to the calculation unit and performing the comparison calculation, the plasma gas flow rate control unit controls the plasma gas flow rate according to the calculation information, and the plasma gas flow rate measurement unit measures again, Since the above-mentioned feedback operation is repeated so as to obtain a desired plasma gas flow rate, an appropriate plasma gas flow rate can be obtained.

[0016]

FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 3 is a block diagram illustrating the configuration of a central information processing unit, FIG. 3 is a block diagram illustrating a second embodiment of the present invention, FIG. 4 is a block explanatory diagram illustrating the configuration of a central information unit in the second embodiment; FIG. 5 and FIG. 6 are graphs showing how the arc current and the plasma gas flow rate are controlled in accordance with the temporal changes of the plasma gas flow rate and the arc current, respectively.

In FIGS. 1 and 3, a plasma torch 1
A power supply 4 and an arc current measuring unit 5 are connected in series between the electrode 2 detachably attached to the tip of the electrode and the workpiece 3, and an arc is formed between the electrode 2 and the workpiece 3. It is configured to discharge. The power supply 4 is connected to an arc current control unit 10 for controlling an arc current. Further, a nozzle member 6 is mounted on the outer periphery of the plasma torch 1 and is connected to the power supply 4. A cylinder 8 for supplying a plasma gas is connected to the nozzle member 6 via a plasma gas flow rate measurement unit 7 and a plasma gas flow rate control unit 12 in series.

The procedure for starting the cutting device will be briefly described. First, the cylinder 8 is opened, and the plasma gas flow controller 12 is opened.
Is operated to supply a plasma gas at a predetermined flow rate, the plasma gas passes through the plasma gas flow rate measuring unit 7 and is then injected to the workpiece 3 via the nozzle member 6. Next, the arc current control unit 10 and the power supply 4 are driven to generate a pilot arc between the electrode 2 attached to the tip of the plasma torch 1 and the nozzle member 6, and the plasma gas flow control unit 12 is operated to operate the plasma arc. When the flow rate of the plasma gas is gradually increased, the pilot arc grows in the direction of the workpiece 3 and reaches the surface of the workpiece 3.

Next, when a voltage is applied between the electrode 2 and the workpiece 3 by operating the arc current control unit 10 and the power supply 4, an arc discharge is formed between the electrode 2 and the workpiece 3. . Thereafter, the pilot arc is stopped. Further, by operating the arc current control unit 10 to gradually increase the arc current and operating the plasma gas flow rate control unit 12 to gradually increase the flow rate of the plasma gas, a plasma arc that can be cut is formed.

Next, the mechanism of the control system of the first embodiment will be described with reference to FIGS. 1 and 2. In FIG. 1, the plasma gas flow rate measuring unit 7, the arc current measuring unit 5, and the arc current control unit 10 Each is connected to the central information processing section 9. As shown in FIG. 2, the central information processing section 9 includes a first storage section 21 for temporarily storing flow rate information from the plasma gas flow rate measurement section 7, and an input section 23 for inputting preset plasma gas flow rate information. Is connected to the input unit 23,
A second memory for storing the preset plasma gas flow rate information;
, A third storage unit 25 for temporarily storing the current information from the arc current measurement unit 5, and temporarily storing the current information from the arc current measurement unit 5 temporarily stored in the third storage unit 25. A fourth storage unit 26 to be stored, the first storage unit 21, the second storage unit 22, the third storage unit 25, and the fourth storage unit 26 are connected to each other to compare and calculate information. Calculation unit 20
And an output unit 24 connected to the calculation unit 20 and outputting calculation information from the calculation unit 20 to the arc current control unit 10.

As described above, the arc current control unit 10 controls the power supply 4 based on the calculation information output from the central information processing unit 9.
Is controlled to adjust the arc current value.

Considering, for example, a case where the flow rate of the plasma gas changes for some reason while cutting the workpiece 3 using the above-described cutting apparatus, the flow rate information g1 measured by the plasma gas flow rate measuring section 7 is stored in the central information processing section. 9, the flow rate information g1 is temporarily stored in the first storage unit 21. on the other hand,
The flow rate information g2 preset by the input unit 23 is input and stored in the second storage unit 22, and the flow rate information g2 and the flow rate information g1 stored in the first storage unit 21 are respectively calculated by the arithmetic unit 20. Then, the arithmetic unit 20 compares the two, and transmits the operation information o1 to the output unit 24.

When the operation information o1 is output from the central information processing unit 9 via the output unit 24 and transmitted to the arc current control unit 10, the arc current control unit 10 controls the power supply 4 to A predetermined arc current according to the calculation information o1 is caused to flow between the workpiece 3 and the workpiece 3. The controlled arc current is measured by the arc current measuring unit 5, and the current information e 1 is fed back to the central information processing unit 9.

After the current information e1 is temporarily stored in the third storage unit 25, it is transmitted to the calculation unit 20. The arithmetic unit 20 calculates the current information e1, the flow rate information g1, and the flow rate information g.
2 and transmits the calculation information o2 to the output unit 24 and the current information e1 to the fourth storage unit 26. The fourth storage unit 26 temporarily stores the current information e1. I do.

When the operation information o2 is output from the central information processing unit 9 via the output unit 24 and transmitted to the arc current control unit 10, the arc current control unit 10 controls the power supply 4 to A predetermined arc current is passed between the workpiece 3 and the workpiece 3 in accordance with the calculation information o2. The controlled arc current is measured again by the arc current measuring unit 5, and the current information e 2 is fed back to the central information processing unit 9.

The current information e2 is temporarily stored in the third storage unit 25 and transmitted to the calculation unit 20 and the fourth storage unit 26
Is transmitted to the arithmetic unit 20. The arithmetic unit 20 calculates the current information e2, the current information e
1. A comparison operation is performed based on the flow rate information g1 and the flow rate information g2, and the calculation information o3 is transmitted to an output unit 24, and the current information e2 is transmitted to a fourth storage unit 26. The unit 26 temporarily stores the current information e2.

When the calculation information o3 is output from the central information processing unit 9 via the output unit 24 and transmitted to the arc current control unit 10, the arc current control unit 10 controls the power supply 4 to A predetermined arc current according to the calculation information o3 is caused to flow between the workpiece 3 and the workpiece 3. The controlled arc current is measured again by the arc current measuring unit 5, and the current information e 3 is fed back to the central information processing unit 9. Similarly, the present control system automatically performs the above-described feedback so as to obtain an appropriate arc current.

Further, when the flow rate of the plasma gas changes,
The flow rate information measured by the plasma gas flow rate measurement unit 7 is the first
After a temporary storage in the storage unit 21, the above-described series of control systems is operated to automatically control so as to obtain an appropriate arc current corresponding to the changed plasma gas flow rate.

Next, the mechanism of the control system of the second embodiment will be described with reference to FIGS. 3 and 4. Referring to FIG. 3, the arc current measuring unit 5, the plasma gas flow measuring unit 7, and the plasma gas flow controlling unit 12 will be described. Are connected to the central information processing section 11, respectively. As shown in FIG. 4, the central information processing section 11 includes a first storage section 28 for temporarily storing current information from the arc current measurement section 5, an input section 30 for inputting preset arc current information, and A second storage unit 29 connected to the input unit 30 for storing the preset arc current information;
And a third storage section 32 for temporarily storing flow rate information from the plasma gas flow rate measurement section 7 and temporarily storing current information from the plasma gas flow rate measurement section 7 temporarily stored in the third storage section 32. A fourth storage unit 33 and the first storage unit 28;
, The second storage unit 29, the third storage unit 32, and the fourth
Calculation units connected to the storage unit 33 for comparing and calculating information
27, and an output unit 31 connected to the calculation unit 27 and outputting calculation information from the calculation unit 27 to the plasma gas flow control unit 12.

The plasma gas flow control unit 12 is configured to perform predetermined control based on the calculation information output from the central information processing unit 11 to adjust the plasma gas flow rate as described above.

Considering, for example, that the arc current changes for some reason while cutting the workpiece 3 using the above-described cutting device, the current information e11 measured by the arc current measuring unit 5 is transmitted to the central information processing unit 11. Then, the current information e11 is temporarily stored in the first storage unit 28. On the other hand, the current information e12 set in advance by the input unit 30 is input to the second storage unit 29.
When the current information e12 and the current information e11 stored in the first storage unit 28 are transmitted to the calculation unit 27, the calculation unit 27 compares the two and outputs the calculation information o11. The information is transmitted to the unit 31.

The calculation information o11 is output from the central information processing section 11 via an output section 31 and is output to the plasma gas flow control section 12
Is transmitted, the plasma gas flow control unit 12 is configured to supply a predetermined plasma gas flow according to the calculation information o11. The controlled plasma gas flow rate is measured by the plasma gas flow rate measuring section 7 and the plasma gas flow rate information g11 is fed back to the central information processing section 11.

After the flow rate information g11 is temporarily stored in the third storage section 32, it is transmitted to the arithmetic section 27. The calculation unit 27 calculates the flow rate information g11, the current information e11, and the current information e11.
A comparison operation is performed on the basis of 12 and operation information o12 is transmitted to an output unit 31 and the flow rate information g11 is transmitted to a fourth storage unit 33. The fourth storage unit 33 temporarily stores the flow rate information g11. I do.

The calculation information o12 is output from the central information processing section 11 via an output section 31 and is output to the plasma gas flow control section 12
Is transmitted, the plasma gas flow controller 12 supplies a predetermined plasma gas flow according to the calculation information o12. The controlled plasma gas flow rate is measured again by the plasma gas flow rate measuring section 7 and the flow rate information g12 is fed back to the central information processing section 11.

The flow rate information g12 is temporarily stored in the third storage unit 32 and transmitted to the calculation unit 27, and the fourth storage unit 33
Is transmitted to the calculation unit 27. The calculation unit 27 calculates the flow rate information g12 and the flow rate information g.
11, a comparison operation is performed based on the current information e11 and the current information e12, and operation information o13 is transmitted to an output unit 31; and the flow rate information g12 is transmitted to a fourth storage unit 33, and the fourth storage The unit 33 temporarily stores the flow rate information g12.

The calculation information o13 is output from the central information processing section 11 via the output section 31 and is output to the plasma gas flow control section 12
The plasma gas flow controller 12 supplies a predetermined plasma gas flow according to the calculation information o13. The controlled plasma gas flow rate is measured again by the plasma gas flow rate measuring section 7 and the flow rate information g13 is fed back to the central information processing section 11. In the same manner, the control system automatically performs the feedback so as to obtain an appropriate plasma gas flow rate by repeating the feedback.

When the arc current further changes, after the current information measured by the arc current measuring section 5 is temporarily stored in the first storage section 28, the above-described series of control systems operate to operate the changed arc current. Automatic control is performed to obtain an appropriate plasma gas flow rate corresponding to the current.

FIG. 5 is a graph showing how the arc current is automatically controlled in accordance with the plasma gas flow rate that changes with time using the cutting apparatus shown in the first embodiment of the present invention. Elapsed time on the horizontal axis starting from the origin o,
The solid line on the vertical axis indicates the changing plasma gas flow rate, and the dotted line indicates the following arc current.

On the graph, between o and a indicates a pilot arc at the time of starting. When the plasma gas flow rate gradually increases with time and rises to a predetermined cuttable flow rate, the arc current is automatically controlled to follow the rising curve and rises to a predetermined arc current value that can be cut along substantially the same curve. I do.

A section between a and b and a section between cd show different cutting conditions under different cutting conditions. In addition, between bc indicates the time of transition to the different cutting. After de and e, the cutting is completed, and the plasma gas flow rate is adjusted in two stages. As shown in this graph, the arc current is automatically controlled in accordance with the change in the flow rate of the plasma gas, so that appropriate cutting can always be performed.

FIG. 6 is a graph showing how the flow rate of the plasma gas is automatically controlled in accordance with the arc current that changes with time using the cutting device shown in the second embodiment of the present invention. Elapsed time on the horizontal axis starting from the origin o,
The solid line on the vertical axis shows the changing arc current, and the dotted line shows the following plasma gas flow rate.

On the graph, a portion between o and a indicates a pilot arc at the time of starting. When the arc current gradually increases with time and rises to a predetermined cuttable current, the plasma gas flow rate is automatically controlled to follow the rising curve and rises to a predetermined plasma gas flow rate that can be cut along substantially the same curve. I do.

A section between a and b and a section between b and c indicate different cutting conditions under different cutting conditions. Between a and i, cutting between a and c is repeated four times. The cutting after ij and j is the end of cutting, and two-stage arc current adjustment is performed. As shown in this graph, the flow rate of the plasma gas is automatically controlled in accordance with the change in the arc current, so that appropriate cutting can always be performed.

[0044]

Since the plasma cutting apparatus according to the present invention has the above-described configuration and operation, when cutting a material to be cut having individual complicated cutting conditions, the plasma gas flow rate and the arc current are relatively controlled. By automatically controlling the plasma arc and forming an appropriate plasma arc, the operator need not make complicated and cumbersome settings for individual cutting conditions, and can perform efficient plasma cutting.

Further, even if the arc current decreases for some reason or the flow rate of the plasma gas increases, the arc can be maintained, so that there is no need to restart the starting operation. Further, even if the arc current increases for some reason or the flow rate of the plasma gas decreases, a series arc that generates a plurality of arcs does not occur, so that the maintenance of the electrode can be improved and the life can be extended.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a central information processing unit according to the first embodiment.

FIG. 3 is an explanatory block diagram showing a second embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of a central information processing unit according to a second embodiment.

FIG. 5 is a graph showing a state in which an arc current is controlled according to a temporal change of a plasma gas flow rate.

FIG. 6 is a graph showing a state in which a plasma gas flow rate is controlled in response to a time change of an arc current.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Plasma torch 2 ... Electrode 3 ... Material to be cut 4 ... Power supply 5 ... Arc current measuring part 6 ... Nozzle member 7 ... Plasma gas flow rate measuring part 8 ... Cylinder 9 ... Central information processing part 10 ... Arc current control part 11 ... Center Information processing unit 12 Plasma gas flow control unit 20 Operation unit 21 First storage unit 22 Second storage unit 23 Input unit 24 Output unit 25 Third storage unit 26 Fourth storage unit 27 arithmetic unit 28 first storage unit 29 second storage unit 30 input unit 31 output unit 32 third storage unit 33 fourth storage unit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23K 10/00 H05H 1/28

Claims (2)

(57) [Claims] In a plasma cutting apparatus for cutting a material to be cut by supplying a plasma gas around an electrode and spraying a plasma arc from a nozzle, a flow rate of the plasma gas supplied to the material to be cut is controlled. A flow rate measuring section to be detected, a first storage section for temporarily storing plasma gas flow rate information from the flow rate measuring section, an input section for inputting preset flow rate information, and a second section for storing the preset flow rate information. 2
Storage unit, a current measurement unit that detects an arc current injected to the workpiece, a third storage unit that temporarily stores arc current information from the current measurement unit, and a third storage unit A fourth storage unit for temporarily storing the arc current information temporarily stored in, and a flow rate information of the plasma gas from the flow rate measurement unit and the previously set flow rate information are compared and calculated, and from the arc current measurement unit A plasma cutting device, comprising: a calculation unit for comparing and calculating a change in current information; and an arc current control unit for controlling the arc current based on the calculation information. 2. A current measuring unit for detecting an arc current injected into a material to be cut in a plasma cutting apparatus for cutting a material to be cut by supplying a plasma gas around an electrode and jetting a plasma arc from a nozzle. A first storage unit for temporarily storing arc current information from the current measurement unit, an input unit for inputting preset arc current information, and a second storage unit for storing the preset arc current information A flow rate measuring unit for detecting a flow rate of the plasma gas supplied to the material to be cut; a third storage unit for temporarily storing plasma gas flow rate information from the flow rate measuring unit;
A fourth storage unit for temporarily storing the plasma gas flow rate information temporarily stored in the storage unit, and comparing and calculating the current information from the arc current measurement unit and the preset current information, A plasma cutting device, comprising: a calculation unit for comparing and calculating a change in flow rate information from a measurement unit; and a plasma gas flow rate control unit for controlling a flow rate of the plasma gas based on the calculation information.