JPH06234019A - Method for correcting of displacement to bending load in press brake - Google Patents

Abstract

PURPOSE:To precisely and inexpensively obtain a relation between a displacement and a bending load in a bending process of a press brake. CONSTITUTION:At first, in a state where a work is not lain, a load over than a requiring load for bending the work is applied on a space between a punch 5 and a die 3, data of the displacement against the bending load of that time is stored, and the data between the displacement and the bending load stored in such a way is approximated with a prescribed functional equation, for example, like a n-th order equation and a constant of the functional equation is operated. Next, the bending of the work is practically executed with the punch 5 and the die 3, the data between the displacement and the bending load in that time is stored, then the correcting displacement amount is operated by substituting each load value of the data between the displacement and bending load stored in such a way for the functional equation, further, the correcting value of each displacement value is operated by subtracting the correcting displacement amount from each displacement value corresponding to each load value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of correcting bending load vs. displacement data in a press brake for bending a plate-shaped work at a required angle by a punch and a die.

[0002]

2. Description of the Related Art Conventionally, when a plate-shaped work is bent using a bending machine such as a press brake, the NC device is used to input machining information such as the plate thickness, material and target bending angle of the work. It is known that a desired processed product is obtained by calculating the amount of punch lowering based on these input information. However, in actual bending, even if the amount of lowering of the punch is controlled as described above, it is desired due to variations in characteristic values such as the plate thickness of the material itself, Young's modulus, n value, and various processing conditions. In many cases, the bending angle cannot be obtained. Therefore, in practice, prior to bending, trial bending is manually performed to determine the adjustment amount of the punch lowering amount, and the adjustment amount is input to the NC device. Further, such fine adjustment of the amount of lowering of the punch needs to be performed every time when the material lot is changed, which is a very complicated work.

Therefore, in order to eliminate the bending angle error caused by the variation of the material as described above and realize highly accurate bending, the material characteristic value is identified by the bending load-displacement data during the bending process. It has been proposed to predict the bending angle and the like.

By the way, as a method of measuring the bending load of a work for obtaining such bending load-displacement data, the following method is usually adopted. That is, the first is a method in which a strain gauge is attached to the frame of the press brake body, and the bending load of the work is measured from the deflection of the frame. The second is to install a load cell above the punch or below the die. This is a method of measuring the bending load of the work by this load cell. Of these methods, the former method using a strain gauge is generally used because it is inexpensive and simple, but has a drawback in that the measurement accuracy is not sufficient. On the other hand, in the latter method using the load cell, the measurement accuracy is relatively good, and there is no particular problem in measuring only the bending load.

[0005]

However, when the bending load-displacement data is to be measured in addition to the bending load, the deflection of the load cell itself, the mounting backlash of the mold, and the press can be achieved even if the above-mentioned method using the load cell is used. Due to the effect of bending due to insufficient rigidity of the brake body,
The displacement data inevitably contains an error. here,
Regarding the deflection of the load cell itself, it is possible to improve by using a high rigidity piezoelectric element type load cell instead of a strain gauge type load cell, but this piezoelectric element type load cell is very expensive. In addition, there is a problem that the effect cannot be exerted against the error caused by the above.

The present invention has been made in order to solve the above-mentioned problems, and the relationship between the bending load and the displacement in the bending process of the press brake is determined by the deflection of the load cell itself, the play of the die, and the machine body. It is an object of the present invention to provide an accurate and inexpensive method that is not affected by bending or the like due to lack of rigidity.

[0007]

In order to achieve the above object, a method for correcting bending load vs. displacement data in a press brake according to the present invention is a press for bending a plate-shaped work at a required angle with a punch and a die. In braking,
(A) A first step of applying a load larger than a load necessary for bending the work between the punch and the die in the absence of the work, and storing bending load vs. displacement data at that time.
(B) A second step of approximating the bending load vs. displacement data stored in this first step by a predetermined functional expression and calculating the constant of the functional expression, (c) Bending of the work by the punch and die. And (d) each load value of the bending load versus displacement data stored in this third step is calculated in the second step. Comprising a fourth step of calculating the correction displacement amount by substituting it into the functional expression and calculating the correction value of each displacement value by subtracting this correction displacement amount from each displacement value corresponding to each load value It is characterized by that.

Here, as the functional expression, F = Y
It may be expressed by ⁿ (F: load, Y: displacement, n: constant), or F = a in the region of Y ≦ δ.
In the region of Y, Y> δ, F = bY + c (F: load,
Y: displacement, a, b, c: constant).

[0009]

In the present invention, first, a load larger than the load necessary for bending the work is applied between the punch and the die in the state where the work does not exist before the actual bending.
The bending load versus displacement data at that time is stored. Next, the bending load vs. displacement data stored in this way is approximated by a predetermined functional expression, and the constant of the functional expression is calculated.
Next, the work is actually bent by the punch and the die, and the bending load versus displacement data at that time is stored.
Then, the corrected displacement amount is calculated by substituting each load value of the bending load vs. displacement data stored in this way into the functional expression, and the corrected displacement amount is calculated from each displacement value corresponding to each load value. By subtracting, the correction value of each displacement value is calculated.

In this way, it becomes possible to obtain the relationship between the bending load and the displacement, in which the deflection of the load cell itself, the play of the die, the deflection due to insufficient rigidity of the machine body, etc. are corrected by an inexpensive method.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of a method for correcting bending load vs. displacement data in a press brake according to the present invention will be described with reference to the drawings.

FIG. 1 is a side view of a press brake according to an embodiment of the present invention. The press brake 1 of this embodiment includes a die (lower die) 3 supported by a pedestal 2.
And a punch (upper die) 5 attached to a lower portion of a ram 4 which is provided above the die 3 so as to be able to move up and down, and a metal is provided between the punch 5 and the die 3. A work made of a plate is inserted, and the ram 4 is lowered with the work placed on the die 3 to punch the work 5
The work is bent by pressing it with the die 3. Although the punch 5 is a straight punch in the illustrated example, a gooseneck punch may also be used.

Above the punch 5, a plurality of (for example, three) load cells 6 are attached along the longitudinal direction of the press brake 1, and the bending load is measured by these load cells 6. . On the other hand, at a predetermined position on the gantry 2 side, a displacement meter (not shown) such as a potentiometer for detecting the tip position of the punch 5 is provided.
The displacement of the punch 5 is measured by this displacement meter.

Next, a procedure for obtaining the relationship (correction data) between the bending load and the displacement in the bending process using the press brake 1 having such a configuration will be described. First, in a state where no work is present before actual bending, the punch 5 is brought into contact with the die 3 by lowering the ram 4, and a load larger than the load necessary for bending is applied to the die 3 at this time. The load vs. displacement data is stored in the storage unit of the computer (not shown) by the output from the load cell 6 and the displacement meter of FIG. An example of a diagram showing the relationship between load and displacement thus obtained is shown in FIG. In FIG. 2, the area A is due to the backlash of the mold.
It is considered that the region B is due to the deflection of the load cell 6 itself and the deflection due to insufficient rigidity of the press brake body.

Next, the relationship between the load and the displacement (FIG. 2) of the press brake 1 obtained in the above-described manner during idling is expressed by F
Is a load, and Y is a displacement, and is approximated by an ⁿ -order formula F = Y ⁿ , and the value of n in this n-order formula is obtained. The value of n is calculated, for example, by obtaining the area ratios above and below the curve of FIG.

Next, the work is actually set between the die 3 and the punch 5 to perform bending, and the bending load versus displacement data at that time is stored in the storage unit. An example of a diagram showing the relationship between bending load and displacement thus obtained is shown in FIG. However, in FIG. 3, the vertical axis represents the bending load per unit bending length (kg / mm).

Since the bending load vs. displacement data shown in FIG. 3 includes the above-mentioned play of the die, the deflection of the load cell 6 itself and the deflection due to insufficient rigidity of the press brake body, it is obtained first. N-order formula F = Y ⁿ
It is necessary to correct the bending load vs. displacement data in consideration of the above. Therefore, in the next step, the correction displacement amount is calculated by substituting each load value in FIG. 3 into the n-th order formula F = Y ⁿ , and the correction displacement amount is subtracted from each displacement value corresponding to each load value. By doing so, the correction value of each displacement value is calculated.

The relationship between the bending load and the displacement thus obtained is shown by an arrow Q in FIG. The arrow P is a diagram showing the relationship between bending load and displacement based on the data before correction. As shown in the figure, the line diagram based on the corrected data indicated by the arrow Q is shifted to the left as a whole as compared with the line diagram indicated by the arrow P before the correction.

According to the method for correcting the bending load vs. displacement data of the present embodiment, it is possible to correct the deflection of the load cell itself, the play of the die attachment, and the deflection due to insufficient rigidity of the machine body with an inexpensive device. It is also possible to correct the difference in punch rigidity due to different punch types. Therefore, the relationship between the bending load and the displacement in the bending process using the press brake can be accurately obtained. In the present embodiment, when there is no change in the mold, the step of storing the load vs. displacement data of the above-described press brake 1 during idling, and the stored data are stored as n.
The step of approximating with the following formula F = Y ⁿ to obtain the value of n can be omitted.

In the above-mentioned embodiment, the load-displacement data when the press brake 1 is in the idle operation is approximated by the ⁿ -th order formula F = Y ⁿ , but this load-displacement data is shown in the area A of FIG. The displacement value of the boundary point (inflection point) between the region B and the region B can be set to δ and can be approximated by the following linear expression. Note that these linear expressions are first obtained by the square method.

Area A: F = aY (when Y ≦ δ) Area B: F = bY + c (when Y> δ) Then, when correcting the bending load vs. displacement data in the actual bending process, Y These two equations are selectively used according to the value of, and the correction displacement amount is calculated by substituting each load value into each equation as in the above-described embodiment, and the correction displacement amount is calculated for each displacement corresponding to each load value. The correction value of each displacement value is calculated by subtracting from the value.

[0022]

As described above, according to the present invention, the press brake is preliminarily idled, and the relationship between the bending load and the displacement when the actual work is bent is based on the relationship between the load and the displacement during the idling. Since the correction is performed, it is possible to obtain a corrected accurate bending load-displacement relationship such as the deflection of the load cell itself, the play of the mold, the deflection due to insufficient rigidity of the machine body, and the like.

In this case, the accuracy of correction can be further improved by approximating the load-displacement relationship during idling by an n-order expression or two linear expressions with the inflection point as a boundary.

[Brief description of drawings]

FIG. 1 is a side view of a press brake according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between load and displacement during idling of the press brake according to the embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between load and displacement when a work is bent in a press brake according to an embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between load and displacement after correction in a press brake according to an embodiment of the present invention in comparison with that before correction.

[Explanation of symbols]

 1 Press brake 3 Die 4 Ram 5 Punch 6 Load cell

Claims (3)

[Claims] 1. In a press brake for bending a plate-shaped work at a required angle by a punch and a die, (a) a load greater than a load required for bending the work between the punch and the die in the absence of the work. A first step of applying a load and storing the bending load-displacement data at that time, (b) The bending load-displacement data stored in this first step is approximated by a predetermined functional expression, and a constant of the functional expression The second step of computing
(C) Bending of the work is performed by the punch and the die, and the third step of storing bending load versus displacement data at that time, and (d) Each of the bending load versus displacement data stored in the third step. The correction displacement amount is calculated by substituting the load value into the functional expression calculated in the second step, and each displacement is calculated by subtracting the correction displacement amount from each displacement value corresponding to each load value. A method of correcting bending load vs. displacement data in a press brake, comprising a fourth step of calculating a correction value of the value. 2. The functional formula is such that F is a load, Y is a displacement, and n is
The method for correcting bending load vs. displacement data in a press brake according to claim 1, wherein F = Y ⁿ is defined as a constant. 3. The functional formula is such that F is a load, Y is a displacement,
The bending load in the press brake according to claim 1, wherein a, b, c, and δ are constants, and F = aY in a region of Y ≦ δ and F = bY + c in a region of Y> δ. Correction method for pair displacement data.