JPH07115191B2 - Plasma cutting machine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma cutting machine that cuts by attaching one of a torch and an object to be cut to a self-propelled carriage.

2. Related Art A conventional plasma cutting machine of this type is shown in FIG. Here, 1 is a self-propelled trolley, to which a torch 2 for ejecting a plasma arc 4 is attached. Reference numeral 3 denotes an object to be cut, and a power source 5 for supplying a cutting current is connected between the torch 2 and the object to be cut 3. In addition, the to-be-cut object 3 may be attached to the self-propelled carriage 1 instead of the torch 2.

In such a configuration, a continuous cutting current as shown in FIG. 6 is applied between the power source 5 and the torch 2 and the object 3 to be cut,
Automatically disconnect. In this way, the distance between the torch 2 and the object to be cut 3 is always kept constant, and the cutting speed can be made constant, so that a relatively clean cutting surface can be obtained as compared with manual cutting performed by holding the torch by hand. Obtainable.

However, in such a conventional one, when low-speed cutting is required such as when cutting a corner portion, there is a lot of adhered metal and there is a lot of burning, and a cut surface is clean. There is a problem that high quality cutting cannot be done because it cannot be done. Even if the cutting current is reduced to reduce the heat input to the object to be cut, the above problem cannot be solved.

Therefore, an object of the present invention is to solve such a problem and to enable high quality cutting even at low speed cutting.

Means for Solving the Problems In order to solve the above problems, the present invention installs one of a torch and an object to be cut on a self-propelled carriage, and supplies a pulse cutting current between the torch and the object to be cut. A pulse frequency setting circuit for setting the frequency of the pulse cutting current and a speed setting circuit for the self-propelled carriage, and between the output of the pulse frequency setting circuit and the output of the speed setting circuit of the self-propelled carriage. Has a proportional relationship with.

Effect According to such a configuration, the heat input required for cutting is given to the object to be cut only by the period of the peak current of the pulse cutting current. Therefore, if the frequency is high, the cutting speed is fast, and conversely if the frequency is low The cutting speed will also decrease. Moreover, since the peak cutting current during low speed cutting is the same as that during high speed cutting, high quality cutting with high energy density is possible.

Embodiment FIG. 1 shows a plasma cutting machine according to an embodiment of the present invention. Here, a power supply 5 similar to that shown in FIG. 5 is provided with a frequency setting circuit 6 for the pulse cutting current. This frequency setting circuit 6 is connected to the proportional signal generating circuit 7,
The proportional signal generating circuit 7 is connected to the speed setting circuit 8 provided in the self-propelled carriage 1 similar to the case of FIG.
Other configurations are the same as those shown in FIG. 5, and either one of the torch and the object to be cut is attached to the self-propelled carriage 1.

The output of the frequency setting circuit 6 is input to the proportional signal generating circuit 7, and the output of this circuit 7 is input to the speed setting circuit 8.
The speed of the self-propelled carriage 1 is set. Here, the speed v of the self-propelled carriage and the pulse frequency f of the cutting current are set in a proportional relationship as shown in FIG.

With this setting, the heat input required for cutting is applied to the object to be cut only during the peak current of the pulse cutting current, so if the frequency is high, the cutting speed is fast, and conversely, if the frequency is low, the cutting speed is also Will go down. FIGS. 3 and 4 illustrate this. Here, it is assumed that the hole 9 having the radius R is machined in the object to be cut by one "pulse cutting current". In the figure, "base cutting current" is for ensuring that the next "pulse cutting current" flows, and means a small current for heating the electrode. Therefore, no disconnection occurs during this "base disconnection current" period.

FIG. 3 shows the case where the pulse frequency f is low, and FIG. 4 shows the case where it is high. Now, if the speeds v of the self-propelled carriages are equal, the pitch d of the cutting hole 9 with the radius R is d = v / f.
And the higher the pulse frequency f, the pitch d of the cutting hole 9
The smaller the size, the denser the cutting becomes possible. On the other hand, it can be seen that the lower the pulse frequency f is, the coarser the cutting becomes. On the contrary, the higher the pulse frequency f, the faster the cutting becomes possible, and the lower the pulse frequency f, the slower the cutting becomes.

Moreover, since the peak cutting current during low speed cutting is the same as that during high speed cutting, high quality cutting with high energy density becomes possible.

Therefore, when cutting is performed with the above device, the pulse frequency f of the cutting current is reduced during low-speed cutting, and the average heat input to the object to be cut is reduced, but the peak current does not change, so high energy density and high quality are achieved. It becomes possible to disconnect. Therefore, the corner portion can be easily cut with good quality.

EFFECTS OF THE INVENTION As described above, according to the present invention, by providing a proportional relationship between the speed of the self-propelled carriage and the pulse frequency of the cutting current, appropriate heat input to the object to be cut, particularly at low speed cutting The control becomes possible, and high quality cutting at low speed cutting, which is the biggest problem in automatic cutting work, becomes possible.

[Brief description of drawings]

FIG. 1 is a block diagram of a plasma cutting machine according to an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between the speed of a self-propelled carriage and the pulse frequency of the cutting current in the plasma cutting machine of FIG. 3 and 4 are model diagrams of a pulse cutting current waveform and a cutting state for explaining the present invention, FIG. 5 is a front view of an example of a conventional plasma cutting machine, and FIG. 6 is cutting in FIG. It is a figure which shows the waveform example of an electric current. 1 ... self-propelled cart, 5 ... power supply, 6 ... frequency setting circuit,
7: Proportional signal generation circuit, 8: Speed setting circuit.

Claims (1)

[Claims] 1. A pulse frequency for mounting one of a torch and an object to be cut on a self-propelled carriage, supplying a pulse cutting current between the torch and the object to be cut, and setting a frequency of the pulse cutting current. A plasma cutting machine comprising a setting circuit and a speed setting circuit for the self-propelled carriage, wherein the output of the pulse frequency setting circuit and the output of the speed setting circuit of the self-propelled carriage have a proportional relationship.