JPH0669628B2 - Plasma cutting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an oxygen plasma cutting apparatus used for cutting a steel plate or the like.

[Prior Art] In the plasma cutting method, as shown in FIG. 9, an electrode 1 is arranged in a nozzle 2 and a cutting gas 5 is ejected during arc discharge to generate a plasma 4, and the plasma is applied to a steel plate. It is cut by hitting the material 3 to be cut, etc., and the one using oxygen as a cutting gas is the mainstream (see Welding Technology, June 1984, pages 46 to 49).

In plasma cutting, a bevel angle φ occurs on the cut surface due to its characteristics, and a vertical cut end surface cannot be obtained. Therefore, as a means to prevent the occurrence of the bevel angle φ,
As shown in FIG. 9, there is a method in which the bevel angle φ is preliminarily considered and the plasma torch 6 is inclined by a predetermined torch angle θ and cut.

[Problems to be solved by the invention]

In this case, in relation to the material 3 to be cut, the plasma arc 4 tries to flow over a distance having the least resistance, and as a result, the side 2a of the nozzle 2 closer to the material 3 to be cut.
Is significantly consumed, and the plasma arc 4 is deflected from its original intended position. This phenomenon further promotes the consumable portion 2a of the nozzle 2 and causes an error in the cutting dimension. In order to keep the cutting dimension within a predetermined tolerance range, the nozzle 2 must be frequently replaced or the torch angle must be changed.

Frequent replacement of the nozzle 2 causes the following problems. First
In addition, the nozzle 2 uses pure copper having good thermal conductivity and conductivity due to the characteristics of plasma cutting, and requires precise processing to direct the plasma arc 4 to an accurate position, which is very expensive. Frequent replacement of such an expensive product causes a significant increase in cutting cost. Second
In addition, replacement of the nozzle 2 requires a lot of time, and frequent replacement of the nozzle 2 significantly reduces the operating rate of the equipment.

Further, it is difficult to change the cutting position due to the consumption of the nozzle 2 accurately because it is difficult to quantitatively detect the consumption amount of the nozzle 2, and it takes a lot of time to perform the precise adjustment. I need.

Furthermore, it is almost impossible at present to fundamentally prevent the uneven consumption of the nozzle 2 from the characteristics of plasma cutting.

Therefore, it is an object of the present invention to provide a plasma cutting device that enables accurate cutting on the premise that uneven consumption of nozzles is caused by plasma cutting.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention comprises a moving means for orienting a plasma torch at a predetermined torch inclination angle with respect to a material to be cut and moving the plasma torch along a set cutting line. In the plasma cutting device, a measuring device for measuring the dimensions of the cut material after each cutting, a comparison means for obtaining a deviation between the measured value and a reference dimension, and a deviation value for each of the obtained cut materials. And means for feeding back to the torch moving means.

[Action]

According to the above configuration of the present invention, the dimensions of the cut material after cutting are measured for each of the cut materials, and the measured values are obtained by comparing the deviations with the reference dimensions, and the obtained deviation values are torch moved. Since the deviation value is corrected by feeding back to the means, even if the nozzle is unevenly worn, it is possible to correct the dimensional error due to the wear, and therefore it is possible to accurately cut the dimension. In addition, as a result of this correction, it is possible to continue the cutting work up to the nozzle usage limit, suppress frequent nozzle replacement, and continue cutting, thus improving work efficiency and equipment operation rate. Can be improved.

〔Example〕

Next, an embodiment of the plasma cutting apparatus according to the present invention will be described with reference to the drawings.

FIG. 2 shows an outline of the embodiment. In FIG. 2, reference numeral 7 denotes a cutting robot, which uses an NC (numerical control) type and is attached to the tip of the arm 8 at a set torch angle θ at a set cutting position. The plasma torch 6 is moved in the cutting direction (for example, in the case of straight line cutting). The material 3 to be cut is mounted on a mounting jig 9 arranged at a position adjacent to the cutting robot 7. Adjacent to the mounting jig 9 is provided a measuring device 10 for measuring the dimensions of the cut material 3 after cutting. Measuring instrument
The dimension measurement value of each material 3 after cutting by 10 is fed back to the comparator (not shown) in the NC control circuit of the cutting robot 7, and the dimension measurement value after the last cutting of the material is preset and set in advance. The deviation from the standard dimension (or target dimension) that has been set is obtained and used as a correction value for the next cutting. As a result, the dimensional error due to the consumption of the nozzle 2 can be eliminated. The above control concept is shown in FIG.

Next, an example of the measuring device 10 is shown in FIG. As shown in FIG. 3, a cylinder 11 capable of expanding and contracting is provided facing the cut end surface of the material 3 to be measured, and the piston rod 12 thereof is provided.
At the tip of the probe, a probe 13 that can abut the cut end surface of the material 3
Is installed. A dog bar 14 extending rearward is connected to the probe 13, and a dog 15 is attached to the tip of the dog bar 14. The length between the longitudinal end faces of the dog 15 corresponds to the distance between the rolling contact rollers 18 and 19 of the first limit switch 16 and the second limit switch 17 described below. That is, the first and second limit switches
Reference numerals 16 and 17 use normally open contacts, which are closed (ON) when the rolling contact rollers 18 and 19 contact the dog 15. When both the first and second limit switches 16 and 17 are ON,
The material to be cut 3 has a regular size. The first limit switch 16
If it is ON and the second limit switch 17 is OFF, the probe 13
Indicates that the cutting dimension is short because it has moved forward that much. On the contrary, the first limit switch 16 is OF
If the second limit switch 17 is ON at F, it means that the probe 13 is retracted by that much, which means that the cutting dimension is long. The table below summarizes this.

Each contact 16 of the above first and second limit switches 16 and 17
As shown in FIG. 4, a and 17a are incorporated in a sequence in the NC control circuit of the cutting robot 7 and fed back as a feedback signal of the measuring instrument 10. Therefore, the operation of the first relay coil 20 in the sequence of FIG. 4 depends on the first contact 16a, and the operation of the second relay coil 21 depends on the second contact 17a.

FIG. 5 shows a mode of the cutting position set with respect to the material 3 to be cut (a virtual locus set in the NC control circuit, not actually drawn). 22 is the exact size,
23 indicates the short dimension, and 24 indicates the long dimension position. These dimensional positions 22, 23, 24 correspond to the length of the dog 15 in the moving direction, and thus correspond to the operation of the first and second limit switches 16, 17.

In this way, the dog 15 and the first and second limit switches 1
The combination with 6, 17 constitutes the measuring device 10 and also serves as a comparison means, and the combination of the first and second contacts 16a, 17a and the first and second relay coils 20, 21 is the cutting robot 7. To form a feedback means to.

As shown in FIG. 6, the probe 13 is used as a clamp 26 for holding the member 25 to be welded to the material 3 to be cut, and is measured at the same time when the member 25 is welded to the material 3 to be cut. May be. By doing so, a chain of work can be secured and efficiency can be improved.

Next, a series of operations in the above configuration will be described.

An operator or an automatic machine cuts the material 3 to be cut set in the jig 9 by using the plasma torch 6 and the cutting robot 7. After the cutting is completed, the measuring device 10 measures the dimension of the material 3 to be cut.
To measure.

If the cutting of the material 3 to be cut is now completed, it is still held by the jig 9. In this state, the tracing stylus 13 in the original position during cutting advances by the cylinder 11 and stops in a state of hitting the cut surface of the material 3 to be cut. A dog bar 14 is attached to the probe 13, and a dog 15 is attached to the dog bar 14 to turn ON and OFF the first and second limit switches 16 and 17.
It is as described above that it is made to FF.

As for the positional relationship between the dog 15 and the limit switches 16 and 17, both 16 and 17 are turned on if the size of the cut material 3 is in the acceptable range, and if it is longer than the acceptable range, only 17 is turned on. If it is short, only 16 will be turned on. (See the above table) The signals of the limit switches 16 and 17 are converted into relay contact outputs 20 and 21, as shown in FIG. 4, and these output signals are input to the NC control device.

A judgment program as shown in FIGS. 7 and 8 is input to the NC device in advance. Measure the workpiece dimensions after cutting, and if, for example, 20 and 21 are both ON (the cutting dimensions are positive), continue the currently used JOB and only 20 is ON (normal If it is not possible to switch, the job is switched to the longer job (orbit 24 in FIG. 5). Similarly, if only 21 is ON (longer than the exact size), the shorter JOB (5th
If the switch is not possible, the error is displayed. If both 20 and 21 are off, an error display will be displayed.

For each JOB, as shown in Fig. 5, JOB1 teaches the locus 22 such that the work size after cutting becomes the exact size.
B2 teaches a locus 24 in which the dimension after cutting is longer than the true size, and a locus 23 in which JOB3 is shorter than the actual size.

In the above outline, the process of actually modifying the trajectory will be described next.

First, the nozzle 2 and the electrode 1 are changed to new ones, and plasma cutting is started. In the initial stage, there is no wear of the nozzle 2, so the work 3
After cutting, the dimensions are correct, and when measured with the measuring device 10, both relays 20 and 21 are turned on, and the locus for the next cutting is cut along the correct size locus 22 (Fig. 5). .

However, as the number of cuttings increases, the consumable part shown in Fig. 11
The wear of 2a progresses, and the plasma arc 4 is gradually deflected. Therefore, the dimension after cutting is longer than the true dimension, and as a result of measurement by the measuring device 10, only the second relay 21 is turned on. In such a situation, the locus at the time of the next cutting is changed to the locus 23 (Fig. 5) shorter than the normal size,
The changed work 3 will be corrected to the correct size again.

After changing the locus to 23, the consumable part 2a of the nozzle 2 further advances and the plasma arc 4 is further deflected, so that only the second relay 21 is turned on again. In such a case, since it is impossible to make further correction, an abnormal condition is output and the operator is prompted to replace the nozzle 2.

As described above, the life is about twice as long as that in the case where the nozzle 2 is replaced without moving from the regular size locus 22. Obviously, increasing the number of offset trajectories (22,23) will extend the life.

Further, the longer cutting locus 24 is used when the work length after cutting becomes short due to the mounting error of the nozzle 2 and the variation of the processing accuracy. Also in this case, if the function shown in the present correction system is not provided, the nozzle 2 must be reattached or the nozzle 2 itself must be discarded as a defective product. This system is also effective in this case.

Further, in the above embodiments, the limit switch is used as a means for converting the dimensions of the material to be cut after cutting into an electric signal, but not to mention other detectors (for example, proximity switch, photoelectric tube), By using a detector such as a pulse generator, it is possible to arbitrarily change the set dimension.

Further, in the above embodiments, the correction locus is created as a separate program in advance, and the method of switching the program is shown, but it is also possible to shift the true locus by an input signal.

〔The invention's effect〕

As described above, according to the present invention, even if uneven wear of the nozzle occurs due to plasma cutting, the consumed amount can be corrected sequentially, so that accurate cutting is possible and the life of the nozzle is reduced. It can be extended to the limit of use, and further work efficiency and equipment operation rate can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control concept of the present invention, FIG. 2 is an elevation view showing an embodiment of the present invention, FIG. 3 is an elevation view showing an example of a measuring instrument, and FIG. 4 is each limit switch. Fig. 5 is a circuit diagram showing a sequence circuit using a relay coil, Fig. 5 is a perspective view showing a limit locus with respect to a regular size locus, Fig. 6 is an elevation view showing another example of a measuring instrument, and Fig. 7 is an NC control program. Fig. 8 is a flowchart showing an example, Fig. 8 is the same explanatory diagram, Fig. 9 is an explanatory diagram showing the principle of plasma cutting, Fig. 10 is an explanatory diagram showing the bevel method, and Fig. 11 is an explanatory diagram showing uneven consumption of nozzles. is there. 1 ... Electrode, 2 ... Nozzle, 3 ... Material to be cut, 4 ... Plasma arc, 5 ... Cutting gas, 6 ... Torch, 7 ... Cutting robot, 8 ... Arm, 9 ... Placed Jig, 10 ... Measuring instrument, 16 ... First limit switch, 17 ... Second limit switch, 20 ... First relay coil, 20 ... Second relay coil, 22 ... Side cutting line locus, 23 ... Short cutting line locus, 24 ... Long cutting line locus.

Claims (1)

[Claims] 1. A plasma cutting apparatus having a moving means for directing a plasma torch at a predetermined torch inclination angle with respect to a material to be cut and moving the plasma torch along a set cutting line. A measuring device for measuring the dimensions of the material after each cutting,
A plasma cutting apparatus comprising: a comparison unit that obtains a deviation between the measured value and a reference dimension; and a unit that feeds back the obtained deviation value of each material to be cut to the torch moving unit.