JP2601724B2 - Reference voltage setting method for plasma cutting - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a reference voltage setting method in plasma cutting.

[Conventional technology]

Conventionally, in plasma cutting, the setting of a reference arc voltage for keeping the standoff constant is generally performed directly by an operator. This will be described with reference to FIG. 4. The reference voltage Eo can be any desired target standoff h, nozzle diameter φ, work material ρ, work plate thickness t,
The operator himself / herself determines the cutting speed 消耗, the temperature, the degree of wear of the nozzle, and other various conditions by trial and error based on a reference voltage data table prepared in various combinations of these in advance. The determined value Eo is input to the plasma cutting machine (not shown) by an operator, for example, using the dial 10, and is set as a fixed value. In a specific example, the plasma torch 40 includes an electrode 41,
It is roughly constituted by a nozzle 42 surrounding the outer periphery (see FIG. 5). The plasma torch 40 has a predetermined height hc (the nozzle diameter φc, the work material ρc, the work plate thickness tc, the cutting speed Δc, the temperature, The height is determined based on the degree of wear of the nozzle and other predetermined conditions, and this height is maintained as a stand-off. The same applies hereinafter.), And the workpiece 43 is plasma-cut. In the figure, E1 is an electrode
The potential difference between 41 and the work 43 is shown, and E2 is the nozzle 42 and the work
The potential difference from 43 is shown. By the way, the cutting quality of the plasma cutting machine largely depends on the fluctuation of the standoff hc. The causes of the fluctuation ± Δh are, for example, the unevenness, bending, and bending of the cut surface of the work 43, and the cutting of a curved portion in three-dimensional cutting.
In this case, there are changes with time such as wear of the tip of the electrode 41 and damage to the tip of the nozzle 42. Take standoff hc
According to the prior art, the plasma torch 40 is slightly moved based on the variation ± e of the arc voltage E (E1 or E2) to keep the stand-off hc constant, while the cutting quality is reduced based on the variation ± Δh of the cutting voltage. ing. More specifically, as shown in FIG. 4, the actual voltage E (E1 or E2) is compared with the reference voltage Eo (Eo−E = Δe), and the stand-off correction is performed based on the plus / minus and magnitude of the difference Δe. The amount ± Δh is obtained, and based on this, the plasma torch 40 is moved toward or away from the work 43. For example, if Δe <0,
Assuming that the actual standoff is larger than the predetermined standoff hc, the plasma torch 40 is slightly moved so as to be close to the surface of the work 43 by Δh. On the contrary, if Δe> 0, the actual standoff is set to the predetermined standoff hc. Assuming that it is smaller than the off-hc, control is performed to finely move the plasma torch 40 so as to be away from the surface of the work 43 by Δh. 4th
In the figure, reference numeral 20 denotes a correction value converter which outputs a correction command value ± Δh, and 30 denotes a plasma torch according to the command.
A robot that activates 40.

[Problems to be solved by the invention]

The above-mentioned prior art automatically moves the plasma torch 40
The advantage is that the stand-off is maintained at a predetermined value hc at least to compensate for the cutting quality. However, as described above, in the related art, the reference voltage Eo, which is one of the comparison standards, is fixed after being initialized by manual operation. However, as described above, for example, work 43
In the cutting at the curved portion of the cutting line, since the cutting speed changes, the arc voltage changes, and the standoff hc also changes with this change. Therefore, the cutting quality is reduced, and the life of the plasma torch is reduced. More specifically, for example, in a curved portion of a cutting line, a plasma torch 40
40 is stopped for a moment, decelerated or accelerated. However, as described above, in the related art, the standoff of such a portion is controlled to be a constant value hc.However, since the reference arc voltage is changed due to the cutting speed change, the change of the standoff occurs. There is a disadvantage that the cutting quality of an unusual transmission portion is reduced.

The present invention focuses on the problems of the conventional technique described above, and can output a reference voltage that can be self-corrected substantially according to the cutting speed, thereby stabilizing the standoff and improving the cutting quality. An object of the present invention is to provide a reference voltage setting method in plasma cutting suitable for automation.

[Means for solving the problem]

In order to achieve the above object, the method for setting a reference voltage in plasma cutting according to the present invention includes the steps of: (1) setting a predetermined cutting speed _{ｃ c} , a nozzle diameter φ _c , and a work material ρ The relationship between the actual standoff hχ and the first arc voltage E _y1 at the time of _c and the work plate thickness t _c is captured as a first linear function κ ₁ , (2) For the above-mentioned predetermined work material ρ _c The relationship between the actual cutting speed Vχ and the second arc voltage E _{y2 at} an arbitrary cutting speed υ, nozzle diameter φ, and work plate thickness t is captured as a _second linear function κ2, and its inclination α is obtained. determined, (3) defines a predetermined target standoff hc, (4) in the above first linear function kappa ₁ coordinate system, the coordinates of the first arc voltage E _y1 in point Pc to coordinate the target standoff hc Ec at the beginning of the plasma cutting Reference voltage Ec
And then, (5) in the second linear function kappa _second coordinate system, provided with a said inclination alpha, third including Pcc points to the initial reference voltage Ec to the predetermined cutting speed υ and _c coordinates A linear function κ _c is provided, and the coordinate Ey of the second arc voltage E _{y2 at} the point Pcχ with the actual cutting speed Vｃ in the third linear function κ _c is used as the reference voltage for the plasma cutting. . Note that the procedure (3) may be a procedure before the procedure (1) or the procedure (2).

[Operation] At first glance, the above configuration itself is simple. However, the introduction process of this configuration is based on various experimental values, and is complicated and characteristic. Actual arc voltage shown in Fig. 1A
The relationship between E _y1 (vertical axis) and the actual standoff hχ (horizontal axis) is that the cutting speed υ, the nozzle diameter φ, the work material ρ, the work plate thickness t, and the consumption of the electrode are constant (that is, a predetermined cut). If the velocity υ _C , the nozzle diameter φ _C , the work material ρ _C and the work plate thickness t _C ), the linear function κ _{1 as} shown in FIG.
Indicated by Next, the relationship between the actual arc E _y2 (vertical axis) and the actual cutting speed Vχ (horizontal axis) shown in FIG. 1B is based on other conditions (cutting speed υ, nozzle diameter even φ and workpiece thickness t) is optionally represented by a linear function kappa ₂ in as shown in FIG. In particular, according to the latter association characteristic, once the linear function κ ₂ is known, and if this is stored, the linear function κ _c for specifically obtaining the reference voltage Ey according to the present application is obtained. It can be easily obtained. That is, in the coordinate system of Figure 1B, determined initial reference voltage Ec of the output becomes the Figure 1A, the Pcc points to 1 condition comprising cutting speed upsilon _C and the coordinates of Figure 1A, then the this point Pcc The linear function κ _c can be easily obtained by translating the linear function κ ₂ . Briefly, it is sufficient to describe the primary function kappa ₂ of the slope line of the same slope α and α on the point Pcc. The present invention is one in which such actions are arranged in order.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, in order to facilitate the description of the embodiment and to understand its effects, an overall block diagram of a reference voltage setting, which is an example of using the present invention, will be briefly described with reference to FIG.
A specific embodiment will be described based on the drawings (FIGS. 2A and 2B). An example of use is as shown in FIG. 3, where the actual arc voltage E (E1 or E1) from the plasma torch 40 (see FIG. 5) is used.
2. _Ey1 described later) is first compared with a reference voltage Ey from the reference voltage setting device 10A configured using the embodiment (Ey1).
y−E = Δe). This comparison output Δe is output from the correction value converter 20A.
In the above, the standoff correction command value ± Δh is output to the robot 30A based on a predetermined standoff correction reference table stored in advance (for example, the table 21A or 21B shown in the frame 21), and the plasma torch 40 is You will be slightly moved. Note that the robot 30A has a predetermined cutting speed υ
The change ± _C of _C is fed back to the reference voltage setting device 10A. An embodiment in such a usage example will be described below. Beginning of the procedure of Example, in the actual coordinate system of standoff hχ (horizontal axis) and its arc voltage E _y1 (vertical axis), is to set a linear function kappa ₁ in a predetermined condition. The predetermined conditions in the present embodiment are a cutting speed 1.0 _C of 1.0 m / min, a nozzle system φ _{C of} 0.6 mm, a work material ρc of SS material, and a work plate thickness t _{C of} 3.2 mm. The linear function κ ₁ under the conditions is shown in FIG. 2A. It should be noted that even if other conditions υ, φ, ρ, t, the linear function κ
_1, although in slightly different positions and tilt this coordinate system shows the characteristic as a linear function kappa ₁ in the Figure 2A. The following procedure is actually to the coordinate system of the cutting speed Vχ (horizontal axis) and the actual arc voltage E _y2 (vertical axis), to set a linear function kappa ₂ in a given workpiece material [rho _C. Predetermined condition in the present embodiment is only the work material ρc of the above SS material, a linear function kappa ₂ in this condition is shown in Figure 2B. Regarding other conditions υ, φ, and t, the gradient α (α = −10 in the present embodiment) is, as shown by the linear functions κ ₂ and κ ₂ , no matter how they change. It is the same (in the above comparison, only two examples κ ₂ and κ ₂ are described, but the same result can be obtained in experiments under other various conditions). However it should be noted that exceeds the value Ps which has cutting speed Vχ is that the voltage E _y2 becomes constant. In this embodiment, 2.0 m / min is the value Ps. As described above, the linear functions κ ₁ and κ ₂ can be obtained by approximating experimental measurement values.

More particularly, ○ marks in the graph of FIG. 2B, △ mark is a measure, from the measurement values, the range of the actual cutting speed Vχ is 1.0~2.0m / min, gradient of the linear function kappa ₂ alpha (= -10), in the range where the actual cutting speed Vχ exceeds 2.0 m / min, it can be seen that it is possible to (approximated by two polygonal line in this example) approximates the slope of the linear function kappa ₂ alpha (= 0) .

For actual cutting speed Vχ speed range below 1.0 m / min in this example, it would not seeking the slope of the linear function kappa ₂ alpha, which is the range of practical cutting speed (actually used Judging from the speed range, which is not required, when it is deemed unnecessary, there is no need to obtain it. If, when it is determined to be necessary, decide the scope of applying approximate expression calculated measurements from experiments and that expression, it may be added to the primary function kappa ₂ fold line.

The same applies to a linear function kappa _1. The next procedure is a predetermined target standoff hc (2.0 m in this embodiment).
The coordinates Ec (the embodiment of a linear function kappa ₁ arc voltage E _y1 in m) is to a 120V) and the initial reference voltage Ec of the plasma cutting. The final step, in the coordinate system of the linear function kappa _2, the initial reference voltage Ec (120V) and the cutting speed upsilon _C and _(1.0 m / min) to Pcc point of the coordinates, the slope of the linear function kappa ₂ α (α is −10 in this embodiment) is converted to a linear function κ _c (E _y2 = −10 Vχ + 130 in this embodiment, where 0
≦ Vχ ≧ 2.0, V _y > 2.0, E _y2 = −10 × 2 + 130 = 11
0), and outputs a reference voltage Ey that takes into account the fluctuation of the arc voltage ± Δe corresponding to the fluctuation of the predetermined cutting speed υ _C (1.0 m / min) ± Δυ.

In the embodiments of claims 2 and 3, in the structure of claim 1, even if the procedure (3) is positioned before the procedure (1) or before the procedure (2), the operation and the effect are the same. It just indicates that.

According to the above embodiment, when cutting the same work because the reference voltage Ey is corrected according to the cutting speed Vχ, the stand-off is kept constant, and a reference voltage setting method in plasma cutting more suitable for automation. Has become.

〔The invention's effect〕

As described above, according to the reference voltage setting method in the plasma cutting according to the present invention, it may be considered that only the cutting speed changes in the plasma cutting of the same work. Since the configuration is such that the reference voltage is automatically obtained, the self-corrected reference voltage can be automatically output according to the cutting speed. For this reason, the standoff can be made more constant and the cutting quality can be improved. Therefore, according to the present invention, a suitable reference voltage setting method can be provided for plasma cutting in which stand-off is set to a constant value and plasma cutting is performed.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a configuration of a reference voltage setting method in plasma cutting according to the present invention. FIG. 1A is a characteristic graph of an actual arc voltage and an actual standoff, and FIG. 1B is an actual arc voltage and an actual cutting. FIG. 2 is a diagram for explaining the configuration of a reference voltage setting method in the embodiment. FIG. 2A is a characteristic graph of an actual arc voltage and an actual standoff, and FIG. 2B is a diagram of the actual arc voltage. Characteristic graph with actual cutting speed, FIG. 3 is a schematic block diagram of a reference voltage setting circuit in plasma cutting as an application example of the embodiment, and FIG. 4 illustrates a configuration of a reference voltage setting method in plasma cutting in a conventional technique. FIG. 5 is an enlarged sectional view of the tip of the plasma torch. hc Target standoff φ Arbitrary nozzle diameter φ _C Specified nozzle diameter ρ _C Specified work material t Arbitrary work plate thickness t _C Specified work plate thickness h ワ ー ク Actual standoff Ec initial reference voltage Ey ...... reference voltage E _y1, E _y2 ...... actual arc voltage Vχ ...... actual cutting speed υ ...... any cutting speed υ _{C ......} predetermined cutting speed Δυ ...... cutting speed fluctuation κ _1, κ _2, κ _c ... linear function Pc, Pcc, Pcχ ... point α ... slope of linear function κ _c

Claims (3)

(57) [Claims] 1. Setting a reference voltage Ey in plasma cutting: (1) Actual stand-off hχ at a predetermined cutting speed _{ｃ c} , nozzle diameter φ _c , work material ρ _c and work plate thickness t _c. And the first arc voltage E _y1 as a first linear function κ _1. (2) For a given work material ρ _c , an arbitrary cutting speed υ, nozzle diameter φ, and work plate thickness At time t, the relationship between the actual cutting speed Vχ and the second arc voltage E _y2 is captured as a _second linear function κ ₂ to determine its slope α. (3) A predetermined target standoff hc is determined, 4) in the first linear function kappa ₁ coordinate system, the target coordinates Ec of the first arc voltage E _y1 standoff hc in point Pc to the coordinates of the plasma cutting initial reference voltage Ec
And then, (5) in the second linear function kappa _second coordinate system, provided with a said inclination alpha, third including Pcc points to the initial reference voltage Ec to the predetermined cutting speed υ and _c coordinates A linear function κ _c is provided, and a coordinate Ey of the second arc voltage E _y2 at a point Pcχ having an actual cutting speed Vχ in the third linear function κ _c as a coordinate is used as a reference voltage for the plasma cutting. Reference voltage setting method for plasma cutting. 2. The method according to claim 1, wherein the step (3) is performed before the step (1). 3. The method according to claim 1, wherein the step (3) is between the step (1) and the step (2).