JPH04111977A - Method and device for plasma piercing - Google Patents

Abstract

PURPOSE:To prevent the blow-up of slag or to improve piercing capacity by setting the current value to be applied to a plasma torch at the time of execution of piercing at the value different from the current value to be applied at the time of execution of cutting. CONSTITUTION:A rower source 5 is controlled by a power source controller 7 in such a manner that the current value to be applied to the plasma torch 1 in a piercing region (p) is increased gradually to attain the value equal to the current value at the time of the execution of the cutting upon ending of piercing. A variable resistor is provided in the power source controller 7 and the data on the piercing work time corresponding to the thickness of a work A and the data on the current value corresponding to the lapse of the work time are previously stored in order to execute the piercing method relating to this embodiment. The above-mentioned power source controller 7 is operated according to the start signal of the piercing operation to control the resistance value of the variable resistor so as to change this value with lapse of time, by which the current to be impressed to the plasma torch 1 from the power source 5 is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method and apparatus for piercing a workpiece such as a steel plate or a stainless steel plate using a plasma torch.

<Prior art> When precision cutting is performed on a workpiece such as a steel plate or stainless steel plate using a plasma torch, piercing (
Then, cutting is started using this hole as a reference point.

When performing the above-mentioned piercing, the workpiece at the position where the plasma arc is injected melts from the surface, and a molten product (slag) is generated. Since this slag has no escape route until the hole is penetrated into the workpiece, it blows upward and causes damage to the plasma torch.

In order to solve the above problem, piercing is performed by retracting the plasma torch upward, or beer song is performed by increasing the pressure of the working gas injected from the plasma torch. After the hole is formed in the workpiece, the plasma torch is lowered if it has been retracted upward, or the gas pressure is lowered to the normal pressure if the pressure of the working gas has been increased. Cutting is carried out using

Furthermore, when performing piercing, the current value applied to the plasma torch is generally equal to the current value applied when cutting the workpiece.

<Problems to be Solved by the Invention> In the above conventional technology, when the height of the plasma torch relative to the workpiece is changed during piercing,
- A drive device is required to raise and lower the chi, and a control device is required to control this drive device.

This makes the entire device complicated. Further, when changing the pressure of the working gas injected from the plasma torch during piercing, a control device is required to control the pressure of the working gas. Generally, controlling gas pressure is a relatively difficult technology, and the structure of the pressure regulating device and control device for the working gas is complicated.

Further, since the current value applied to the plasma torch during piercing is equal to the current value during cutting, the thickness of the plate that can be pierced is set to be equal to the thickness of the plate that can be cut. Therefore, by raising the plasma torch during piercing, the piercing ability becomes inferior to the cutting ability, and there is a problem in that piercing takes a long time.

An object of the present invention is to provide a plasma piercing method that can prevent slag from blowing up or improve piercing ability, and to provide a plasma piercing device for carrying out the method.

<Means for Solving the Problems> In order to solve the above problems, a plasma piercing method according to the present invention is a method for piercing a workpiece using a plasma torch. The current value applied to the plasma torch is set to a value different from the current value applied to the plasma torch when performing cutting.

Further, a plasma piercing device is a device for piercing a workpiece using a plasma torch, and includes a plasma torch, a power supply device for applying current to the plasma torch, and a device for piercing a workpiece using a plasma torch. and a power supply control device for controlling the power supply device so that the current value and the current value at the time of cutting are different values.

<Operation> The above plasma piercing method (hereinafter referred to as r piercing method J)
According to the above, by setting the current value applied to the plasma torch during piercing to a value different from the current value applied during cutting, it is possible to prevent slag from blowing up or improve the piercing ability. I can do it.

That is, the current value applied to the plasma torch during piercing is gradually increased so that when a hole is formed in the workpiece, the current value applied to the plasma torch is equal to the current value during cutting. or if the current value applied to the plasma torch during piercing is set to a value larger than the current value during cutting, and this current is applied in a pulsed manner that is intermittent over time, Blow-up can be prevented or reduced.

Furthermore, if the current value applied to the plasma torch during piercing is set to a larger value than the current value during cutting, it is possible to improve the piercing ability, and therefore, when the plasma torch is raised, However, the piercing time can be shortened.

The above plasma piercing device (hereinafter referred to as “piercing device”)
), the above piercing method can be easily carried out.

That is, by controlling the power supply device using the power supply control device so that the current value during piercing and the current value during cutting are different values, the current value applied to the plasma torch during piercing can be adjusted to the desired value. can be controlled to the value of

<Example> A piercing method and device to which the above-mentioned means are applied will be explained below.

Figure 1 is a block diagram of the piercing device, Figures 2 to 4 are diagrams of current values during piercing and cutting, and Figures 5 (a) to (C) are diagrams for piercing the workpiece. It is an explanatory diagram when carrying out.

First, piercing will be explained with reference to FIGS. 5(a) to 5(C).

Piercing is the process of forming a through hole in the thickness direction of the workpiece A, and by cutting the workpiece A into a predetermined shape using this hole as a reference point, a product with less distortion can be obtained. This makes it possible.

When performing piercing using plasma 1-chi 1, when plasma arc 2 is injected onto workpiece A, the same figure (
As shown in a) and (b), the surface of the workpiece A is melted at the injection part of the arc 2, and slag B is generated. This slag B is blown upward from the surface of the workpiece +A by the kinetic energy of the plasma arc 2 and is removed. When the melting of the workpiece A and the removal of the slag B proceed and a hole C is formed in the workpiece A, the slag B passes through the hole C and is removed downward.

During the above-mentioned piercing process, while the hole C penetrates the workpiece A, the slag B is removed upward from the surface of the workpiece A, and the slag B adheres to the plasma torch 1 or the plasma torch It may adhere to the through hole of the plasma arc 2 formed at the tip of the plasma arc 1 and block the through hole.

Therefore, one of the purposes of the piercing method according to the present invention is to prevent slag B from blowing up during the piercing process,
Alternatively, the purpose is to prevent the slag B from adhering to the plasma torch 1 by reducing the amount.

Next, a piercing device according to the present invention will be explained using FIG. 1.

In the figure, a plasma torch 1 includes an electrode 3 and a nozzle 4.
is provided. The electrode 3 is connected to a negative electrode of a power supply device 5, and the nozzle 4 is connected to an operating gas supply device 6 consisting of a gas supply section 6a, a pressure adjustment section 6b, and a solenoid valve 6C. The positive electrode of the power supply device 5 is connected to the workpiece A and the nozzle 4. Note that the workpiece A is grounded.

The configuration is the same as a known plasma cutting device.

In the piercing device according to the present invention, a power supply control device 7 is connected to the power supply device 5, and the power supply control device 7 changes the current value applied to the plasma torch 1 between the value at the time of piercing and the value at the time of cutting. The power supply device 5 is controlled to have different current values.

Next, the current value applied to the plasma torch 1 when piercing the workpieces t and I'A will be explained.

In FIGS. 2 to 4, area p indicates the piercing area, and area C indicates the cutting area.

Further, the vertical axis shows the current ■, and the horizontal axis shows the time.

FIG. 2 is an explanatory diagram regarding the first embodiment of the piercing method according to the present invention, in which the current value applied to the plasma torch 1 in the piercing area p is gradually increased, and the current value at the time of cutting at the end of piercing is This is a piercing method in which the power supply 5 is controlled by the power supply control device 7 so that the value becomes equal to the current value.

In this embodiment, it is possible to gradually deepen the melting depth of the workpiece during piercing in accordance with the increase in the current value.Therefore, a large amount of slag does not occur all at once. Therefore, it is possible to prevent or reduce the blowing up of slag.The piercing method of this embodiment does not allow slag to adhere to the plasma torch 1, although the piercing operation time may be a little longer.

In order to carry out the piercing method according to the present embodiment, a variable resistor is provided in the power supply control device 7, and a variable resistor is provided in the power supply control device 7.
Piercing work time data corresponding to the thickness of the workpiece A and current value data corresponding to the elapse of the work time are stored in advance in the machine, and the power supply control device 7 is activated in response to a piercing work start signal. This can be achieved by controlling the resistance value of the variable resistor to change over time, and by changing the current applied to the plasma torch 1 from the power source 5.

In the piercing method according to this example, the starting current (
The current value at point a in Figure 2 was set to 100A, the time in the piercing area P was set to 2.5 seconds, and by increasing the current value within this time, it was possible to perform a good piercing work. .

FIG. 3 is an explanatory diagram regarding a second embodiment of the piercing method according to the present invention, in which the current value in the piercing area p is set to a value larger and a value smaller than the current value in the cutting area C. This is a piercing method in which the power supply 5 is controlled by the power supply control device 7 so as to apply these currents in a pulsed manner.

In this embodiment, it is possible to prevent or reduce the blowing up of slag from the workpiece A, as in the first embodiment described above.

That is, by applying a current to the plasma torch 1 in a pulsed manner, the energy of the plasma arc 2 ejected from the torch 1 also changes in a pulsed manner. Therefore, at the injection position of the plasma arc 2 on the workpiece A, melting of the base material by the plasma arc 2 and removal of slag by the working gas are performed alternately in a short time, so a large amount of slag is removed at once. Therefore, it is possible to prevent or reduce the blow-up of slag.

With the piercing method of this embodiment, it is possible to perform the piercing operation in a shorter time than the piercing operation time in the first embodiment described above.

In order to carry out the piercing method according to this embodiment, the power supply control device 7 is provided with a current value setting switching circuit that can apply a current when performing piercing and a current when cutting. The current intermittent pitch data and the piercing time according to the thickness of the workpiece are stored when piercing is performed, and the power supply control device 7 is operated in response to a piercing start signal to pulse current to the plasma torch 1. This can be done by controlling the power supply device 5 so as to apply the power in the desired manner.

In the piercing method according to the present example, the maximum current (current value at point a in Fig. 3) is 1.50 A, and the minimum current (the third The current value at point b in the figure) is 100 A, and the current intermittent pitch in area p is 200 m5ec,
By setting the time in area P to 1.5 seconds, it was possible to perform a good piercing work.

FIG. 4 is an explanatory diagram regarding a third embodiment of the piercing method according to the present invention, in which the power supply control device 7 is used to set the current value in the piercing region p to be larger than the current value in the cutting region C. This is a piercing method that controls the power source 5.

The piercing method according to this embodiment differs from the previous embodiments in that the cutting ability of the plasma arc 2 during the piercing operation is increased so that the piercing operation can be completed in a short time. This piercing method is effective when the plasma torch I is retracted from the workpiece A during the piercing operation, and is advantageous when used in an automatic cutting device such as a numerically controlled cutting device, for example.

That is, by setting the current value in the piercing region p to a sufficiently larger value than the current value in the cutting region C, it is possible to melt the workpiece Δ all at once.

At this time, the generated slag is blown upward, but each time the plasma torch 1 is retracted upward from the workpiece A, the blown up slag is prevented from adhering.

The beer song method according to this embodiment shortens the piercing work time because the current applied to the torch is equal to the current during cutting, although the conventional piercing method involves retracting the plasma torch from the workpiece. This is a solution to problems that are difficult to do.

In order to carry out the piercing method according to this embodiment, the power supply control device 7 is provided with each current setting switching circuit capable of applying a current during piercing and a current during cutting. This is possible by storing the piercing time etc. according to the thickness of the material and controlling the power supply device 5 so as to operate the power supply control device 7 in response to a piercing start signal and apply current to the plasma torch 1. It is.

In the piercing method according to this embodiment, the plate thickness is 12InI1
The maximum current (current value at point a in Fig. 4) is 200 A for the steel plate No. 1 (current 150 A during cutting), the distance between the plasma torch 1 and the workpiece A is 10 mm, and the area p By setting the time Q to 5 seconds, it was possible to perform a good piercing operation.

This piercing time is reduced by about 0.7 seconds compared to the time taken by conventional piercing methods.

In each of the embodiments described above, the operation gas is supplied from the operation gas supply device 6 to the nozzle 4 during the piercing operation in the same manner as when cutting is performed.

As described above, by controlling the current value in the piercing region P to a value different from the current value in the cutting region C, it is possible to prevent or reduce the blow-up of slag that occurs during piercing. Alternatively, it becomes possible to shorten the piercing work time.

In the piercing device configured as described above, after piercing the workpiece A with the plasma torch 1, the current value applied from the power supply device 5 to the electrode 3 is adjusted to cut the workpiece A. The current required for the workpiece A
By relatively moving the plasma torch 1 and the plasma torch 1, it is possible to cut the workpiece A into a desired shape.

<Effects of the Invention> As explained in detail above, according to the piercing method according to the present invention, the current value applied to the plasma torch during piercing is set to a value different from the current value applied during cutting, thereby reducing the slag. The blow-up can be prevented or reduced to prevent damage to the plasma torch, or the piercing ability can be improved and the piercing operation can be shortened.

Furthermore, the piercing device according to the present invention is characterized in that the piercing method described above can be carried out rationally by controlling the power supply device by the power supply control device.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the piercing device, Figures 2 to 4 are diagrams of current values during piercing and cutting, and 511ffl(a) to (C) are diagrams for piercing the workpiece. It is an explanatory diagram at the time of implementation. A is the workpiece, B is the slag, C is the hole, 1 is the plasma torch, 2 is the plasma arc, 3 is the electrode, 4 is the nozzle, 5 is the power source, 6 is the operating gas supply device, and 7 is the power control device . Patent applicant Koike Oxygen Industry Co., Ltd.

Claims (2)

[Claims] (1) A method for piercing a workpiece using a plasma torch, in which the current value applied to the plasma torch during piercing is set to a different value from the current value applied to the plasma torch during cutting. A plasma piercing method characterized by: (2) A device for piercing a workpiece using a plasma torch, which includes a plasma torch, a power supply device for applying a current to the plasma torch, and a current value and cutting during piercing. A plasma piercing device comprising: a power supply control device for controlling the power supply device so that the current value at the time of execution becomes a different value.