JPH0839257A - Stand off controller of plasma torch - Google Patents

Abstract

PURPOSE:To avoid collision of a torch with a work and to facilitate mainte nance and check of a torch, work, etc., by outputting correction signal and retreating a torch from work when the deviation between reference voltage and detected voltage exceeds the prescribed value set beforehand in stand off control. CONSTITUTION:An electrode 12, nozzle 14 and material 18 to be cut are connected to voltage detectors 24, 26. The voltage detector 24 detects the voltage e1 between an electrode 12 and material 18 to be cut, the voltage detector 26 detects the arc voltage e2 between a nozzle 14 and material 18 to be cut, the detected value are inputted into a stand off correction computing element 28. The stand off correction computing element 28 obtains correcting values of torch elevating direction/speed, etc., from the detected voltages e1, e2 inputted and the correction values are inputted into a controller 30 connected to output side. The controller 30 drives an elevating device 32 of torch 10 based on the controlling value from the stand off correction computing element 28 so as to keep the interval between the torch 10 and material 18 to be cut in the prescribed stand off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gap between a plasma torch and a material to be processed in a plasma cutting machine or the like for generating a plasma arc between an electrode and the material to be cut to cut the material to be cut. The present invention relates to a standoff control device for a plasma torch that controls the temperature.

[0002]

2. Description of the Related Art A plasma cutting machine is provided with a nozzle around an electrode to form a flow path for a working gas, and at the same time, the plasma generated between the electrode and the material to be cut is narrowed in front of the tip of the electrode to generate a plasma. The temperature of the plasma arc is kept high and the size of the plasma arc is kept constant so that a good cut surface shape can be obtained. However, if the distance between the torch consisting of the electrode and the nozzle and the material to be cut changes, the plasma arc
The arc cannot be sustained, or the size of the plasma arc changes, and a good cut shape cannot be obtained. Therefore, in the plasma cutting machine, the distance between the torch and the material to be cut (so-called torch height, standoff) is kept constant so that good cutting can be performed.

When controlling the standoff, it is known that the voltage (arc voltage) between the electrode or the nozzle and the workpiece is proportional to the standoff, and this is often used. 2. Description of the Related Art A stand-off control device that detects a voltage between an electrode and a material to be cut or a voltage between a nozzle and a material to be cut and maintains these voltages at a constant value is used (for example, Japanese Patent Application Laid-Open No. H11-163873). No. 57-1955582).

[0004]

However, the above-mentioned conventional apparatus for detecting the arc voltage and holding the standoff constant does not correspond to the deviation of the detected arc voltage from the reference voltage. Therefore, it takes time to set a predetermined standoff when the deviation is large, and a response delay occurs, so that sufficient cutting accuracy cannot be obtained. Further, when the deviation becomes abnormally large, the abnormal voltage is detected by an abnormal voltage detection circuit different from the circuit for performing the stand-off control, and the arc is turned off, thereby reducing the efficiency of the cutting operation. Moreover,
Conventionally, when the deviation voltage greatly swings to the negative side,
Since the torch starts to descend at a high speed, there is a danger that the torch will continue to descend and collide with the workpiece, damaging the torch and the workpiece.

An object of the present invention is to provide a plasma torch stand-off control device capable of quickly correcting a deviation of a stand-off from a set value. And

[0006]

In order to achieve the above object, a plasma torch standoff controller according to the present invention has a voltage for detecting a voltage between a torch electrode or a nozzle around the electrode and a workpiece. The detector and the standoff controller of the plasma torch that controls the standoff interval by comparing the detection voltage output by the voltage detector with the reference voltage are configured as follows.

First, when the deviation between the reference voltage and the detected voltage reaches or exceeds a predetermined value, the torch is retracted from the work material.

Secondly, the amount of movement of the torch that moves based on the deviation between the reference voltage and the detected voltage is made different between when the torch approaches the workpiece and when it does not approach the workpiece. It is characterized by that.

Thirdly, the amount of movement of the torch based on the deviation between the reference voltage and the detected voltage is configured to reduce or stop the amount of movement of the torch near a predetermined standoff. Is characterized by.

Fourth, when the deviation between the reference voltage and the detected voltage is less than a predetermined value, the deviation is regarded as zero, and the deviation is larger than the predetermined value and is predetermined. When the deviation is larger than the second predetermined value and smaller than the second predetermined value, the moving amount of the torch is increased as the deviation increases, and when the deviation reaches or exceeds the second predetermined value, the torch is moved. Is configured to be retracted from the work material.

[0011]

According to the first aspect, when the deviation reaches the predetermined value or more, the correction signal for retracting the torch from the work material is output. That is, the inconvenience of the torch colliding with the work material as in the prior art is eliminated. Further, since the torch is retracted from the work material, maintenance and inspection of the torch and the work material can be performed without any trouble.

According to the second aspect, the amount of movement of the torch that moves based on the deviation is made different when the torch approaches the work material and when it does not approach. That is, the standoff control is a control that causes the torch to perform the operation of returning to the target standoff when the torch approaches and does not approach the workpiece, but the target standoff is extremely small. Since it is normal, it is desirable to naturally perform different control when approaching and when not approaching. For example, when approaching, to avoid collision between the torch and the work material, be careful or blunt (that is, to reduce the amount of movement per unit deviation, for example), while when not approaching, the collision between the torch and the work material should be avoided. Since it does not exist, it is preferable to make it rough or quick (that is, increase the movement amount per unit deviation). Of course, it may be carefully or blunted (that is, the movement amount per unit deviation may be reduced) only when approaching the target standoff or less. By doing this,
Highly efficient processing can be achieved.

According to the third aspect, when the torch movement amount based on the deviation is near the predetermined standoff (that is, near the target standoff), the correction signal for reducing or stopping the torch movement amount. Is output. That is, if the actual standoff is the target standoff, optimum processing (for example, high-quality cutting) should be naturally obtained. However, if the standoff control is performed at this time as well, the change in the cutting width due to the change in the heat input to the workpiece due to the change in the previous torch, the rise of the plasma gas and the melting of the molten metal caused by the small target standoff, Deviations due to non-uniform blow-off and the like occur, the stand-off control acts and the target stand-off cannot be maintained, and as a result, larger deviations occur and stable machining cannot be performed. Therefore,
In the third embodiment, the torch movement amount is reduced or stopped in the vicinity of the target standoff where the target processing accuracy is obtained. Thereby, stable processing is secured.

The above-mentioned fourth is obtained by incorporating the above-mentioned third and the first and further adding intermediate control. That is, fourth, when the deviation is equal to or less than a predetermined value, the deviation is regarded as zero and the correction signal is not output (that is, in accordance with the third configuration), and the deviation is the predetermined value. Greater than the value,
And when it is smaller than the second predetermined value which is larger than the predetermined value set in advance, a correction signal for increasing the movement amount of the torch is output as the deviation becomes larger (that is, the intermediate control), and the deviation becomes When it reaches the second predetermined value or more, a correction signal for retracting the torch from the workpiece is output (that is, the first configuration). According to the fourth aspect, in the intermediate control, for example, the ascending / descending speed of the torch increases as the deviation increases, so that the torch can be quickly returned to the target standoff. In other words, as the deviation decreases, the torch ascending / descending speed decreases.
Torch overshoot can be avoided. The operation of the other front and rear configurations has been described above, and will be omitted.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plasma torch stand-off control apparatus according to the present invention will be described in detail along with a plasma torch stand-off control method with reference to the accompanying drawings.

FIG. 2 is a block diagram showing an example of an apparatus embodying the stand-off control apparatus of the present invention.

In FIG. 2, a torch 10 of a transfer arc type plasma cutting machine robot is provided with a nozzle 14 for forming a working gas flow path (not shown) around an electrode 12. The electrode 12 is electrically connected to the nozzle 14 and the workpiece 18 via a DC power supply 16,
A pilot arc is generated with the nozzle 14 and a main plasma arc 20 is generated with the workpiece 18. On the other hand, the lower end of the nozzle 14 is narrowed narrowly, and the plasma arc 20 is narrowed to obtain high-temperature plasma.

The electrode 12 and the nozzle 14 and the workpiece 18 are connected to voltage detectors 24 and 26, respectively. The voltage detector 24 includes the electrode 12 and the workpiece 18.
Is detected, and the detected voltage e1 is input to a stand-off correction calculator 28 which will be described in detail later. Then, the voltage detector 26 detects a voltage (arc voltage) between the nozzle 14 and the workpiece 18 and detects the voltage e.
2 is input to the standoff correction calculator 28.

The stand-off correction calculator 28 obtains the correction amounts such as the ascending / descending direction, the ascending / descending speed, and the ascending / descending amount of the torch from the input detected voltages e1 and e2, and outputs them to the controller 30 connected to the output side. input. The control device 30 controls the robot robot based on the control amount from the stand-off correction calculator 28.
The lifting device 32 for raising and lowering the torch 10 is driven to drive the torch 10
Is raised and lowered so that the distance between the torch 10 and the workpiece 18 becomes a predetermined standoff Ho.

As shown in FIG. 1, the stand-off correction calculator 28 includes an electrode wear / stand-off detector 34, a reference voltage calculation setter 36, a deviation calculator 37 to which these signals are inputted, and a deviation calculator 37. A correction amount calculator 38 for obtaining a correction amount for raising and lowering the torch 10 based on the deviation output from the calculator 37.

The electrode consumption / stand-off detector 34 receives the detection voltages e1 and e2 output from the voltage detectors 24 and 26 to obtain the consumption amount of the electrode 12 as described later, and outputs the electrode consumption signal according to the consumption amount. Is output to a display device or the like (not shown), the actual standoff amount H is obtained, and the corresponding standoff signal EH is output to the deviation calculator 37.

Further, the reference voltage calculation setter 36 determines the plate thickness, material, nozzle diameter and target standoff Ho of the material 18 to be cut.
, The reference voltage Eo based on the cutting speed data is output to the deviation calculator 37.

The correction amount calculator 38 has a table as shown in FIG. 3, and based on the deviation ΔE of the standoff signal EH from the reference voltage Eo output from the deviation calculator 37, The controller 30 supplies a correction voltage ΔEH having a magnitude corresponding to the deviation ΔE for returning the switch 10 to the standoff Ho.
Output to. That is, the text of the correction amount calculator 38
Does not output the correction voltage .DELTA.EH in a predetermined first deviation range. +-. E1. If the deviation .DELTA.E is between + .DELTA.E1 and + .DELTA.E2, the deviation increases. To
When the correction voltage ΔEH is output so as to increase the rising speed of the torch 10, and the deviation ΔE is between −ΔE1 and −ΔE2, the lowering speed of the torch 10 is increased as the deviation increases. The correction voltage -ΔEH is output. Further, when the deviation ΔE exceeds ± ΔE2, the table shows a correction voltage ± ΔE in which the rate of change in the ascending or descending speed of the torch 10 is increased according to the magnitude of the deviation.
Outputs H. When the deviation ΔE exceeds a predetermined third value ± ΔE3, it is determined that an abnormality has occurred in the device.
The torch 10 is separated from the workpiece.

The standoff control method by the apparatus configured as described above is performed as follows.

The arc voltage e changes depending on the value of the standoff H, and there is a proportional relationship with the standoff H as shown in FIG. And set the standoff Ho
Is the material and thickness of the material to be cut 18, the nozzle 1 of the torch 10.
4 and the cutting speed V. Therefore, the reference voltage calculation setting unit 36 of the stand-off correction calculation unit 28 determines the material and thickness of the workpiece 18, the diameter of the nozzle 14 of the torch 10,
When the target standoff Ho or the like is inputted from a keyboard or an operation panel (not shown), an arc voltage eo with respect to a standard cutting speed Vo (for example, 1 m / s) is calculated by the following equation (1). Is output to the deviation calculator 37 as the reference voltage Eo.

[0026]

Eo = {Ks1 + Ks2 (Ho + Kt)} xKn

Here, Ks1, Ks2, Kt, Kn
Is previously obtained by an experiment or the like according to the material and thickness of the material to be cut 18, and is stored in the reference voltage calculation setter 36 as a table as shown in FIG.

The reference voltage calculation setting unit 36 internally stores a table as shown in FIG. 4 corresponding to a standoff determined by the values of the material, the thickness, the nozzle diameter, and the cutting speed of the material 18 to be cut. When the material and the nozzle diameter of the material to be cut 18 and the set standoff Ho are given by an operation panel or the like, a table corresponding to the material of the material to be cut 18 and the value of the nozzle diameter is stored. May be selected to output a reference voltage Eo determined by the input standoff Ho.

The control device 30 is provided with a cutting program such as a shape for cutting the material 18 to be cut, a cutting speed, and the like. The robot 30 is moved to a position where the voltage between the electrode 12 and the material 18 becomes the arc voltage eo. The torch 10 is lowered via the lifting device 32 to start cutting.

On the other hand, when the cutting is started, the voltage detectors 24 and 26 detect the detection voltage e1 between the electrode 12 and the workpiece 18 and the torch 10 and the workpiece 18 at predetermined time intervals such as 10 ms.
The detected voltage e2 is detected and input to the electrode wear / standoff detector 34 of the standoff correction calculator 28.

Incidentally, the arc voltages e1 and e2 detected by the voltage detectors 24 and 26 change as shown in FIG. 6 even if the stand-off Ho is kept constant, because the electrodes are consumed. Therefore, the electrode wear / standoff detector 34 calculates the electrode wear component Ep from the following equation 2 and the standoff component Es from the following equation 3, and wears the electrode 12 obtained from these equations 2 and 3. The amount is calculated, and an electrode consumption signal corresponding to the consumption amount is output to a display device (not shown) or the like for display.

[0032]

[Equation 2] Ep = ae1 + be2

[0033]

## EQU3 ## Es = a'e1 + b'e2

Then, the voltage detector 24 outputs to the deviation calculator 37 a standoff signal EH obtained by removing the detected voltage e1 from the increase in voltage due to the consumption of the electrode 12 shown in FIG.

The reference voltage calculation setting unit 36 includes a torch 10
Starts cutting, a cutting speed detected by a cutting speed detector (not shown) or cutting speed data (cutting speed V) from the control device 30 is input. Then, when the cutting speed V is input, the reference voltage calculation setting unit 36 corrects the arc voltage eo according to the cutting speed V and outputs it as the reference voltage Eo.

That is, the arc voltage e has a relationship as shown in FIG. 7 with the cutting speed V. The arc voltage e decreases as the cutting speed V increases, and increases as the cutting speed V decreases. Therefore, even if the torch 10 is held at the set standoff Ho, if the cutting speed V changes, the deviation output from the deviation calculator 37 increases, and the correction amount calculator 38 operates the torch 10. A correction signal for raising and lowering is output, and the torch 10 deviates from the standoff Ho, and the cutting shape is deteriorated. Therefore, the reference voltage calculation setter 36 determines the material of the material to be cut 18, the plate thickness, the nozzle diameter, and the standoff Ho.
From the table of FIG. 7 stored corresponding to each value of
A correction voltage Δe _V corresponding to a change in the cutting speed V of the arc voltage e obtained in accordance with the stand-off Ho is obtained, and the reference voltage Eo is obtained.

[0037]

Equation 4] was calculated as Eo = eo ± △ e _v and outputs the deviation calculator 37. That is, when the cutting speed is slower than the reference, and outputs a value obtained by subtracting the rise △ e _v of the voltage from eo as the reference voltage Eo, if the cutting speed is faster than the reference, the voltage drop in eo outputs a frequency △ e _v plus value as the reference voltage Eo. However, the value is the cutting speed V, for example, when it exceeds 2m / s, the correction amount △ e _v is constant. Note that the correction of the reference voltage Eo based on the cutting speed V may be performed by the following equation (5) or (6).

[0038]

When 0 <V ≦ K _V2 , Eo = eo−K _V1 × (V−1)

[0039]

When V> K _V2 , Eo = eo−K _V1 × (K _V2 −1)

Here, K _V1 and K _V2 are the correction coefficients shown in FIG.

The deviation calculator 37 calculates a deviation ΔE of the stand-off signal EH output from the electrode wear / stand-off detector 34 with respect to the reference voltage Eo, and outputs it to the correction amount calculator 38. That is, when the stand-off amount of the torch 10 is larger than the set value Ho and the stand-off signal EH is larger than the reference voltage Eo, the deviation calculator 37 calculates a negative value according to the magnitude of the stand-off signal EH. Is output, and in the opposite case, a positive error + ΔE is output.

The correction amount calculator 38 is a table shown in FIG.
Tolerance corresponding to the input deviation ΔE
And outputs a correction voltage .DELTA.EH to the control device 30 for quickly returning to the stand 10 and the standoff Ho. And the control device 3
When 0 receives the correction voltage ΔEH, the ascending / descending speed of the torch 10 and the ascending / descending amount of the torch 10 are obtained, and the elevating device 32 is driven to elevate / lower the torch 10 at a speed corresponding to ΔEH. , Set standoff to Ho.

As described above, in the embodiment, the electrode 12
-In order to increase the elevating speed of the torch 10 in accordance with the deviation ΔE of the detection voltage e1 between the workpieces 18 with respect to the reference voltage Eo, when the torch 10 deviates from the set standoff Ho. , Is promptly returned to the standoff Ho, and a good cutting can be performed. Moreover, since the dead zone where the correction signal is not output is provided in the portion where the deviation ΔE is small, it is possible to prevent an unstable fluctuation of the torch 10 in the vicinity of the set standoff Ho and to improve the cutting surface. Further, in the embodiment, since the change in the arc voltage due to the consumption of the electrode 12 and the change in the arc voltage with respect to the change in the cutting speed V are corrected, more excellent cutting can be performed. Further, since the rate of change in the ascending / descending speed of the torch 10 is reduced in the portion where the deviation ΔE is small,
The overshoot of the torch 10 can be prevented.

In the above embodiment, the case where the stand-off H is controlled by using the detection voltage e1 between the electrode 12 and the workpiece 18 as the arc voltage has been described. The stand-off H may be controlled using the detected voltage e2.

FIG. 8 is a flow chart for explaining another embodiment. The reference voltage calculation setter 36 of the standoff correction calculator 28 receives the detection voltages e1 and e2 from the voltage detectors 24 and 26, as shown by the broken line in FIG. Then, the reference voltage calculation setter 36
Is designed to obtain the reference voltage Eo based on the input detection voltage e1 or detection voltage e2.

That is, when a command to start cutting is given, the controller 30 lowers the torch 10 from the workpiece 18 to a predetermined height (step 50 in FIG. 8). When the torch 10 descends and reaches a predetermined height, a limit switch (not shown) is activated (step 52), and it is detected that the torch 10 has reached the predetermined height. Thereafter, the control device 30 lowers the descending speed of the torch 10 and
To pierce height and pierce (step 54,
56). Then, when the piercing is completed, the control device 30 further lowers the torch 10 and starts cutting at the cutting height (steps 58 and 60).

The cutting height, that is, the set standoff Ho depends on the material and thickness of the material to be cut 18 and the diameter of the nozzle 14 of the torch 10 as described above. The information is provided to the control device 30 from a keyboard, an operation panel, or the like.

When the torch 10 is kept at the stand-off Ho and the cutting is started, the voltage detectors 24 and 26 detect the voltage at a predetermined time (for example, every 0.1 second) and detect the detected voltage. e1 and e2 are input to the reference voltage calculation / setting unit 36 and the electrode wear / standoff detector 34. The reference voltage calculation setting unit 36 is the first several (for example, three) detection voltages e1 or e2 input from the voltage detectors 24 and 26.
Is read (step 62), the average value of them is calculated and output as the reference voltage Eo (step 64).

Then, as the cutting proceeds, the reference voltage calculation / setting device 36 outputs a reference voltage Eo corrected for the change in the cutting speed V (step 68).
On the other hand, the electrode wear / standoff detector 34 outputs the standoff signal EH corrected by the wear of the electrode 12 to the deviation calculator 37, as described above. Thereafter, cutting is performed in the same manner as in the above-mentioned embodiment, and when the cutting is completed,
The chi 10 is raised (steps 70, 72).

As described above, when the arc voltage at the start of cutting is the reference voltage Eo, the influence of electrode wear can be eliminated, and the reference voltage Eo can be easily set.

Although the transfer arc type plasma cutting machine has been described in the above embodiment, the plasma cutting machine may be a non-transfer arc type. In the above-described embodiment, the description has been given of the plasma cutting machine. However, the present invention can be applied to a plasma welding machine. Further, in the above-mentioned embodiment, the case where the table of the correction amount computing unit 38 is point-symmetrical about the origin has been described, but it is not necessary to be point-symmetrical, and especially the absolute value of -ΔE3 is used. Is preferably smaller than the absolute value of + ΔE3 to surely prevent the torch 10 from coming into contact with the material 18 to be cut. The ± ΔE1, ± ΔE2, ± ΔE3 and the inclinations of the respective line segments of the table shown in FIG. 1 can be appropriately determined by experiments or the like.

[0052]

As is clear from the description of the above embodiment,
If necessary, the present invention takes the measures described in the claims, and as is clear from the description of the above embodiment, the deviation of the standoff with respect to the set value can be promptly corrected. Details are as follows.

According to the first configuration, when the deviation reaches a predetermined value or more, a correction signal for retracting the torch from the work material is output. That is, the inconvenience of the torch colliding with the work material as in the prior art is eliminated. Also,
Since the torch is retracted from the work material, maintenance and inspection of the torch and work material can be performed without any problems.

According to the second structure, the amount of movement of the torch that moves based on the deviation is made different between when the torch approaches the workpiece and when it does not approach the workpiece. That is, the standoff control is a control that causes the torch to perform the operation of returning to the target standoff when the torch approaches and does not approach the workpiece, but the target standoff is extremely small. Is normal. For this reason, it is desirable to perform different controls naturally when approaching and when not approaching. For example, when approaching, be careful or dull to avoid collision between the torch and the workpiece (ie,
(For example, the movement amount per unit deviation is small), and when there is no approach, there is no collision between the torch and the workpiece, so that the torch is rough or quick (that is, the movement amount per unit deviation is large). is there. Of course, only when approaching below the target standoff, the distance may be carefully or dull (that is, for example, the amount of movement per unit deviation may be reduced). By doing so, highly efficient processing can be achieved.

According to the third configuration, when the torch movement amount based on the deviation is near the predetermined standoff (that is, near the target standoff), the correction signal for reducing or stopping the torch movement amount. Is output. That is, if the actual stand-off is the target stand-off, optimal processing (for example, high-quality cutting) should be obtained naturally. Variations in the cutting width due to changes in heat input to the workpiece due to fluctuations in the temperature, deviations due to plasma gas blowing up due to the small target standoff and uneven blowing of the molten metal, etc., maintain the target standoff No longer,
As a result, a larger deviation occurs and stable machining cannot be performed. Therefore, in the third embodiment, the movement amount of the torch is reduced or stopped in the vicinity of the target standoff where the target processing accuracy is obtained. Thereby, stable processing is secured. This is the so-called dead zone control, but the above-described unique effect in the stand-off control of the plasma torch can be obtained.

The fourth structure incorporates the third structure and the first structure, and further takes intermediate control into consideration.
That is, according to the fourth configuration, when the deviation is less than or equal to a predetermined value, the deviation is regarded as zero and the correction signal is not output (that is, according to the third configuration). When it is larger than the predetermined value and smaller than the second predetermined value which is larger than the predetermined value set in advance, a correction signal for increasing the amount of movement of the torch is output as the deviation becomes larger (that is, as described above). When the deviation reaches or exceeds the second predetermined value, a correction signal for retracting the torch from the workpiece is output (that is, the first configuration). According to the fourth aspect, in the intermediate control, for example, the ascending / descending speed of the torch increases as the deviation increases, so that the torch can be quickly returned to the target standoff. In other words, since the ascending / descending speed of the torch decreases as the deviation decreases, it is possible to avoid the overshoot of the torch.

[Brief description of drawings]

FIG. 1 is a detailed explanatory diagram of a stand-off correction arithmetic unit of a plasma cutting device.

FIG. 2 is a block diagram of a plasma cutting device for carrying out the method of the embodiment.

FIG. 3 is a diagram illustrating a relationship between a deviation and an ascending / descending speed of a torch for explaining a standoff control method according to an embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a standoff amount and an arc voltage.

FIG. 5 is a diagram showing an example of a table for a reference voltage calculation setter of a stand-off correction calculator to calculate an arc voltage.

FIG. 6 is a diagram showing the relationship between the degree of electrode wear and the arc voltage.

FIG. 7 is a diagram showing a relationship between a cutting speed and an arc voltage.

FIG. 8 is a flowchart for explaining another embodiment of a method of setting a reference voltage.

[Explanation of symbols]

 10 torch 12 electrode 14 nozzle 18 material to be cut 20 plasma arc 24, 26 voltage detector 28 standoff correction calculator 30 controller 32 lifting device 34 electrode consumption / standoff detector 36 reference voltage calculator 37 Deviation calculator 38 Correction amount performance

Claims (4)

[Claims] 1. A voltage detector for detecting a voltage between a torch electrode or a nozzle around the electrode and a work material, and a detection voltage output from the voltage detector is compared with a reference voltage to determine a standoff interval. In a plasma torch stand-off control device to control, the deviation between the reference voltage and the detected voltage,
A stand-off control device for a plasma torch, characterized in that the torch is retracted from a work piece when a predetermined value or more is reached. 2. A voltage detector for detecting the voltage between the electrode of the torch or the nozzle around the electrode and the material to be processed, and the detection voltage output by the voltage detector is compared with a reference voltage to determine the standoff interval. In a plasma torch stand-off control device to be controlled, the moving amount of a torch that moves based on the deviation between the reference voltage and the detected voltage is made different when the torch approaches and does not approach the workpiece. A stand-off control device for a plasma torch, which is configured as described above. 3. A voltage detector for detecting a voltage between a torch electrode or a nozzle around the electrode and a work material, and a detection voltage output from the voltage detector is compared with a reference voltage to determine a standoff interval. In a plasma torch standoff control device for controlling, a movement amount of the torch based on a deviation between the reference voltage and the detected voltage is reduced or stopped in the vicinity of a predetermined standoff. A stand-off control device for a plasma torch, which is characterized by being configured. 4. A voltage detector for detecting a voltage between a torch electrode or a nozzle around the electrode and a workpiece, and a detection voltage output from the voltage detector is compared with a reference voltage to determine a standoff interval. In the plasma torch stand-off control device for controlling, when the deviation between the reference voltage and the detected voltage is equal to or less than a predetermined value, the deviation is regarded as zero, and the deviation is larger than the predetermined value. When the deviation is greater than the second predetermined value and the deviation is greater than the second predetermined value, the torch movement amount is increased as the deviation increases. , A torch standoff control device configured to retract the torch from the work material.