JP3288102B2 - Correction method of load versus displacement data in press brake - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates relates to a method of correcting load heavy versus displacement data in the press brake bending to a desired angle a plate-shaped workpiece by the punch and the die.

[0002]

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

[0003] Therefore, in order to realize highly accurate bending to eliminate the bend angle error caused by variations in materials, such as described above, the load during the bending process heavy - the material characteristic values identified by displacement data , Bending angles and the like have been proposed.

[0004] Such load heavy - as method for measuring the bending load of the work for obtaining the displacement data, it is usual then the method as shown is employed. That is, the first method is to attach a strain gauge to the frame of the press brake body and measure the bending load of the work from the deflection of the frame. The second method is to install a load cell above the punch or below the die. This is a method of measuring a bending load of a work using the load cell. Among these methods, the former method using a strain gauge is generally used because it is inexpensive and simple, but has a disadvantage that the measurement accuracy is not enough. On the other hand, in the latter method using a load cell, the measurement accuracy is relatively good, and there is no particular problem in measuring only the bending load.

[0005]

However, when measuring not only the bending load but also the load-displacement data, even if the above-described method using the load cell is used, the deflection of the load cell itself, the play of the mold, the press brake, and the like. Due to the influence of bending or the like due to insufficient rigidity of the main body, the displacement data necessarily includes an error. Here, the deflection of the load cell itself can be improved 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 In addition to being expensive, there is a problem that it cannot exert its effect on the error caused by the above.

[0006] The present invention has been made to solve the above problems, the relationship between load weight versus displacement for the bending process of the press brake, the mounting backlash and machine body of the flexure and mold load cell itself It is an object of the present invention to obtain an accurate and inexpensive method without being affected by bending or the like due to insufficient rigidity of the device.

[0007]

To SUMMARY OF THE INVENTION To achieve the above object, a method of correcting load heavy versus displacement data in the press brake according to the present invention, folding the required angle the plate-shaped workpiece by the punch and die press In the brake, (a) a first step of applying a load equal to or more than a load required for bending the work between the punch and the die in a state where the work does not exist, and storing load versus displacement data at that time; (b) A second step of approximating the load versus displacement data stored in the first step by a predetermined function formula and calculating a constant of the function formula; (c) performing bending of the work by the punch and the die; substituted in the third step and (d) function formula which is calculated each load value of the load weight versus displacement data stored in the third step in the second step for storing a load weight versus displacement data at that time Correction by doing And a fourth step of calculating a displacement amount and subtracting the corrected displacement amount from each displacement value corresponding to each of the load values to calculate a correction value of each displacement value. .

Here, the function formula is F = Y
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]

According to the present invention, a load greater than the load required for bending the work is applied between the punch and the die in the absence of the work before the actual bending.
The load versus displacement data at that time is stored. Next, the load versus displacement data thus stored is approximated by a predetermined function formula, and the constant of the function formula is calculated. Next, actual workpiece bent by the punch and the die is performed, the load at that time heavy versus displacement data is stored. Then, thus correcting the displacement amount by the load value is assigned to the function expression of the stored load heavy vs. displacement data are calculated, further, the respective displacement values the correction amount of displacement corresponding to the respective load value By performing the subtraction, a correction value of each displacement value is calculated.

[0010] Thus the relationship of the load cell itself deflection and load the like deflection due to insufficient rigidity of the mounting backlash and machine body is corrected mold heavy versus displacement, it is possible to obtain an inexpensive way.

[0011]

Next, a press brake according to the present invention will be described.
Specific examples of the method for correcting the load weight versus displacement data,
This 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 according to the present embodiment includes a die (lower die) 3 supported by a gantry 2.
And a punch (upper die) 5 attached to the lower part of a ram 4 provided above and opposite to the die 3 so as to be movable up and down. A work made of a plate is inserted, the ram 4 is lowered while the work is placed on the die 3, and the work is punched 5.
The work is bent by clamping the work with the die 3. In the illustrated example, the punch 5 is a straight punch, but a gooseneck punch may also be used.

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

[0014] Next, using a press brake 1 having such a configuration, the procedure for obtaining the relationship between the load weight versus displacement (correction data) in the bending process will be described. First,
Before the actual bending, the punch 5 is brought into contact with the die 3 by lowering the ram 4 in a state where there is no work, and a load greater than the load required for bending is applied to the die 3. 6 and the output from the displacement meter, the load versus displacement data is stored in a storage unit of a computer (not shown). An example of a diagram showing the relationship between the load and the displacement obtained in this way is shown in FIG. In FIG. 2, the region A is considered to be caused by the play of the mold, and the region B is considered to be caused by the bending of the load cell 6 itself and the bending of the press brake body due to insufficient rigidity.

Next, the relationship between the load and displacement (FIG. 2) of the press brake 1 during idling operation obtained as described above is expressed by F
Is approximated by an ⁿ -th order equation F = Yn, where Y is a displacement and Y is a displacement, and the value of n in the n-th order equation is obtained. The value of n is calculated, for example, by calculating the area ratio of the upper and lower areas of the curve in FIG.

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

The load weight versus displacement data shown in FIG. 3, the above-described mold mounting backlash, because it is the deflection of the load cell 6 itself and those including the deflection due to insufficient rigidity of the press brake main body, obtained previously was n by adding the following equation F = Y ⁿ it is necessary to correct the load weight versus displacement data. Therefore, in the next step, calculates a correction amount of displacement by substituting each load values in FIG. 3 to the n-th order equation F = Y ^n, subtracting this correction displacement amounts from respective displacement values corresponding to the respective load value Then, the correction value of each displacement value is calculated.

The relationship thus obtained load weight versus displacement is indicated by the arrow Q in FIG. 4. The arrow P is a graph showing the relationship between load weight versus displacement based on uncorrected data. As shown in the figure, the diagram based on the corrected data indicated by the arrow Q is shifted to the left as a whole as compared with the uncorrected data indicated by the arrow P.

According to the correction method of loading heavy versus displacement data of the present embodiment, by an inexpensive apparatus, it is possible to correct the deflection by insufficient rigidity of the mounting backlash and machine body of the flexure and mold load cell itself, A difference in punch stiffness due to different types of punches can also be corrected.
Therefore, in the bending process using the press brake
The relationship between the load weight versus displacement can be accurately determined. In addition,
In the present embodiment, when there is no change in the mold, the step of storing the load-displacement data during the idle operation of the press brake 1 described above, and the stored data is converted into an n-dimensional expression F = Y
^The step of approximating with ⁿ and obtaining the value of n can be omitted.

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

The area A: F = aY (when Y ≦ [delta]) region B: F = bY + c ( Y> when the [delta]) and, when correcting the load weight versus displacement data in the actual bending process, Y The corrected displacement amount is calculated by substituting each of the load values into the respective formulas in the same manner as in the above embodiment, by using these two formulas depending on the values of the above. The correction value of each displacement value is calculated by subtracting from the value.

[0022]

According to the present invention, as described above, were pre-air-operated press brake, the idle operation on the basis of the relationship of the load versus displacement during bending of the actual workpiece processed load weight versus displacement relationship when because be corrected, and the corrected relationship of the correct load weight versus displacement such as deflection due to insufficient rigidity of the mounting backlash and machine body of the flexure and mold load cell itself may be obtained in a cheap way .

In this case, the accuracy of correction can be further improved by approximating the relationship between the load and the displacement during the idling operation by the n-th order equation or two linear equations at the inflection point.

[Brief description of the 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 the relationship between load and displacement during idle operation in the press brake of one embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between load and displacement during bending of a workpiece in a press brake according to one embodiment of the present invention.

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

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-105714 (JP, A) JP-A-59-144527 (JP, A) JP-A-5-329553 (JP, A) 15929 (JP, A) JP-A-5-293550 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21D 5/02

Claims (3)

(57) [Claims] 1. A press brake for bending a plate-like work to a required angle by a punch and a die, wherein: (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 load-displacement data at that time; (b) approximating the load-displacement data stored in the first step by a predetermined function formula and calculating a constant of the function formula second step, (c) said punch and performs bending work by a die, the third step and (d) load weight stored in the third step for storing a load weight versus displacement data of the time of A corrected displacement amount is calculated by substituting each load value of the displacement data into the function formula calculated in the second step, and the corrected displacement amount is subtracted from each displacement value corresponding to each load value. By its each displacement Correction method of the load weight versus displacement data in the press brake, characterized in that it comprises a fourth step of calculating the correction value. 2. The function formula is as follows: F is load, Y is displacement, n
As a constant correction method of loading heavy versus displacement data in the press brake according to claim 1 which is represented by the F = Y ^n. 3. The function formula is such that F is a load, Y is a displacement,
a, b, c, and a constant, respectively [delta], loading in the press brake according to claim 1 in the region of Y ≦ δ F = aY, are those represented by in the region of Y> δ F = bY + c heavy Correction method for displacement data.