JPH1157865A - Spring back angle estimation method and, method of and device for bending using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the bending process with high angle accuracy by precisely estimating the spring back angle even if material characteristic values fluctuate between the material lots. SOLUTION: During a work bending operation, actual bending angles are detected at the at least two temporary last spurt points of a driving mold. Based on the relationship between a change of the last spurt value related to each temporary last spurt positions and a change of the actual bending angle, the work spring back angle is estimated by using a pre-memorized data about the spring back behavior under the processing condition of the specific bending.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating a springback angle of a work when a plate-like work is pressed and bent by a driving die and a fixed die, and a bending process using the method. The present invention relates to a method and a bending device.

[0002]

2. Description of the Related Art Generally, when a plate-shaped workpiece is subjected to V-bending using a bending machine such as a press brake, the behavior related to the plastic deformation of the workpiece changes according to the characteristic value of the material. It is known that even if the same material is used, the bending angle greatly changes due to variations in the characteristic values between lots. For this reason, it is extremely difficult to control the drive-in amount of the driving die with high accuracy, and in actual bending work, the actual situation often depends on the intuition of a skilled operator.

[0003] In order to cope with such a problem, a press brake which detects a bending angle of a workpiece during a bending process and controls a drive-in amount of a driving die based on the detected bending angle. Have been proposed and put into practical use. An example of such a technique is disclosed in Japanese Patent Application Laid-Open No. 7-265957. In the press brake described in this publication, attention is paid to the fact that the variation of the springback angle is small between material lots, and the data of the springback angle is stored separately for each material and plate thickness of the work. It is configured to calculate the final driving amount based on the following. According to this control method, there is an effect that the bending can be performed with high accuracy only by detecting the angle once without performing complicated control of the driving die.

[0004]

However, as shown in FIG. 8, the springback angle actually has a slight variation due to a variation in material characteristic values between lots. FIG. 8 shows the springback angles at various bending angles in six types of cold-rolled steel sheets of the same kind but different lots.
This indicates that the dispersion varies by about 0.3 °. From this, when performing bending with an accuracy of ± 0.3 ° or less,
It is required to accurately estimate or detect the springback angle.

As a method of detecting the springback angle, there is also a method of temporarily moving the upper and lower dies relatively apart during the bending process and detecting the difference from the bending angle before and after this movement. According to the detection method, there is a problem that when the mold is moved closer to the workpiece again after the separation movement, the contact point between the mold and the workpiece changes, and the processing accuracy is deteriorated.

The present invention has been made in order to solve such a problem, and a springback capable of accurately estimating a springback angle even if material characteristic values vary between lots of materials. An object of the present invention is to provide an angle estimating method, and a bending method and a bending apparatus capable of realizing bending with extremely high angle accuracy.

[0007]

Means for Solving the Problems and Action / Effect The present invention is to store the behavior data of the springback angle stratified for each bending condition, and to carry out a correction according to the variation of the material characteristic value. This makes it possible to perform extremely high-precision bending without depending on the variation of the springback angle caused by the variation of the material characteristic value between lots of the material.

That is, the springback angle estimating method according to the first invention is a method for estimating a springback angle of a work when a plate-like work is pressed and bent by a driving die and a fixed die. During the bending of the workpiece, the actual bending angles of the work are detected at at least two temporary driving positions of the driving die, and the relationship between the change in the driving amount and the change in the actual bending angle for each of the temporary driving positions. Based on the above, the springback angle of the workpiece is estimated using data on the behavior of springback under the bending processing conditions stored in advance.

In the present invention, at the time of bending the work, the driving die is first driven to the first temporary driving position, the actual bending angle of the work is detected at that position, and then the driving die is further driven to the next temporary driving position. The mold is driven, and the actual bending angle of the workpiece is detected again at that position. When the actual bending angle of the work is detected at at least two temporary staking positions in this manner, the actual bending angle is determined based on the relationship between the amount of change in the squeezing amount corresponding to each of the temporary staking positions and the amount of change in the actual bending angles. Then, the springback angle of the workpiece is estimated using the data on the springback behavior under the bending condition stored in advance. According to the present invention, when the variation of the characteristic value between lots of the same material is taken into consideration, the above-described n-value (work hardening index), which is the characteristic value that has the greatest influence on the springback angle, is used as the substitute characteristic. The relationship between the amount of change in each amount of intrusion and the amount of change in each actual bending angle at at least two provisional intrusion positions is used. By using such a relationship, it is possible to accurately estimate the springback angle even if the material characteristic values vary between lots of the material.

Next, a bending method according to a second aspect of the present invention is a bending method in which a plate-shaped work is clamped by a driving die and a fixed die to perform a bending process. The actual bending angle of the workpiece is detected at at least two temporary driving positions of the mold, and the actual bending angle stored in advance is determined based on the relationship between the change in the driving amount and the change in the actual bending angle for each of the temporary driving positions. The present invention is characterized in that a springback angle of a work is estimated using data on a springback behavior under bending processing conditions, and a final drive-in position of the driving die is obtained based on the estimated value.

In the present invention, the springback angle of the workpiece is estimated based on the springback angle estimation method according to the first invention, and the final driving position of the driving die is obtained based on the estimated value. Therefore, since the final drive-in position is obtained based on the accurate estimated value of the springback angle, it is possible to realize extremely accurate bending.

Further, a bending apparatus according to a third aspect of the present invention for specifically realizing the bending method according to the second aspect of the present invention performs a bending process by pressing a plate-shaped work between a driving die and a fixed die. (A) The relationship between the amount of drive-in of the driving die with respect to the bending angle of the work and the ratio of the change in the drive-in amount to the change in the actual bending angle for each work condition of the work. (B) angle detecting means for detecting a bending angle during bending of a workpiece, and (c) detected by the angle detecting means at at least two temporary drive-in positions of the driving die. It is calculated from the relationship between the actual bending angle of the workpiece and the ratio of the springback angle to the ratio between the change in the driving amount and the change in the actual bending angle stored in the storage means. Calculating means for calculating a final driving position of the driving die from a springback angle at a target bending angle of the workpiece; and (d) a driving die for driving the driving die to the temporary driving position and then driving to the final driving position. It is characterized by having mold driving means.

In the present invention, the relationship between the bending amount of the driving die with respect to the bending angle of the workpiece and the relationship between the change amount of the driving amount and the change amount of the actual bending angle with respect to the springback angle is stored in advance in the storage means. It is remembered. When bending the work, first, the driving die is driven to the first temporary driving position by the die driving means, and the actual bending angle of the work is detected by the angle detecting means at that position, and thereafter, to the next temporary driving position. Further, the driving die is driven, and the actual bending angle of the work is detected again at that position. When the actual bending angle of the workpiece is detected at at least two temporary driving positions in this way, the springback with respect to the ratio between the change amount of the driving amount and the change amount of the actual bending angle stored in the storage means. The springback angle at the target bending angle of the workpiece is calculated from the angle relationship, and the final driving position of the driving die is calculated in consideration of the springback angle. Then, the driving die is driven to the calculated final drive-in position, and the bending is completed. In this way, the springback angle at the target bending angle of the workpiece is estimated based on the actual bending angles at at least two angle detection positions, so that the variation in the material characteristic value between lots of the material causes the variation in the springback angle. Even in some cases, the springback angle can be estimated with high accuracy, and thereby extremely accurate bending can be realized.

In the present invention, the at least two provisional driving positions are determined based on a relationship between a driving die driving amount with respect to a workpiece bending angle stored in the storage means and a relationship between a workpiece bending angle and a springback angle with respect to the workpiece bending angle. Can be computed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of a springback angle estimating method, a bending method and a bending apparatus using the same according to the present invention will be described with reference to the drawings.

FIG. 1 shows a system configuration diagram of a bending apparatus according to one embodiment of the present invention.

In the bending apparatus (press brake) of this embodiment, a die base 2 is fixed on a fixed table 1 and a lower die 3 is mounted on the die base 2 so as to face the lower die 3. An upper die 5 is attached to a lower portion of a ram 4 which is driven to move up and down so as to approach and separate from the lower die 3. The plate-shaped work W to be bent is inserted between the lower mold 3 and the upper mold 5, and the ram 4 is lowered while the end of the work W is abutted against the backstop device 6 to lower the work. The work W is bent by clamping the W between the lower mold 3 and the upper mold 5.

At the front of the fixed table 1, a work W
Is provided with an angle detection unit 7 for detecting a bending angle of the work W during the bending step. The angle detection unit 7 includes a light source 8 that projects slit light on the bent outer surface of the work W, and a CCD camera 9 that captures a linear projected image formed on the outer surface of the work W by the light source 8. The image captured by the CCD camera 9 is subjected to image processing to detect the bending angle of the work W. The angle detection unit 7 can be provided not only at the front part but also at the rear part of the fixed table 1, thereby improving the angle detection accuracy.

The image captured by the CCD camera 9 is displayed on a monitor television (not shown), and is processed as image data by a bending angle calculator 10. Then, the bending angle of the workpiece W is calculated by the calculation in the bending angle calculation unit 10, and the calculation result is input to the NC device 11. The NC device 11 includes a plurality of springback angles with respect to a ratio of a change amount of a drive-in amount to a change amount of an actual bending angle for each bending condition (machining condition) of the work W, and a plurality of metal members for a bending angle of the work W. A storage unit 12 is provided for storing the relationship between the die drive amounts and the like. The data stored in the storage unit 12 and the bending conditions (material, plate thickness, bending shape, mold shape, mechanical information, etc.) of the work W are provided. And a calculating means 13 for calculating the temporary driving position and the final driving position of the upper die 5 based on the above.

Incidentally, the springback (return due to elasticity) angle generated when bending the plate-shaped work W is determined by the tensile strength, longitudinal elastic modulus, work hardening index (n) of the material.
Value) and the like, but considering only the characteristic value variation between lots of the same material, the characteristic value that has the largest influence on this springback angle is n
Is considered a value. FIG. 2 shows the result of examining the correlation between the n value and the springback angle in the cold rolled steel sheet. On the other hand, as shown in FIG.
It has been found that there is a high correlation between the value and the bending radius of the material, and as shown in FIG. 4, when the bending radius of the workpiece W is different, the workpiece at the same bottom dead center (the upper die driving position) It has been found that a change occurs in the bending angle of W. That is, at a certain bottom dead center, a material having a small bending angle of the workpiece has a large bending radius, a large n value, and consequently a relationship that the springback angle increases. From this, it is possible to estimate the springback angle by detecting the bending angle of the work W at the predetermined position, and by controlling the amount of driving of the upper die 5 as the driving die based on the result,
Bending with high dimensional accuracy can be realized without depending on the variation of the material.

In this embodiment, as an alternative characteristic of the n value, which is the characteristic value that has the greatest influence on the springback angle, the change amount (ΔD) of each driving amount at at least two temporary driving positions and the actual bending The ratio (ΔD / Δθ) to the angle change (Δθ) is calculated, and this ratio (ΔD
/ Δθ) and the springback angle (Δθ), the springback angle at the target bending angle is calculated.

Next, the control flow of the die driving amount in the present embodiment will be sequentially described with reference to the flowchart shown in FIG.

S1: The bending conditions (material, plate thickness, bending shape, mold shape, mechanical information, etc.) of the work W which are inputted in advance and stored in the storage means 12 are read. S2: Die driving amount D with respect to bending angle θ of workpiece W
From the relationship (see FIG. 6) and the relationship between the springback angle and the target bending angle of the workpiece W (NC).
The relational expression (initial value of the apparatus) is selected, and the tentative run-in position when the upper and lower dies are moved close to each other, in other words, the angle detection position is calculated at n places (n ≧ 2). In addition, it is preferable that at least one of these temporary driving positions is a position as close as possible to the target bending angle as long as the workpiece W is not excessively bent.

S3 to S5: The work W is set by the operator and bending is started, and the upper die 5 is moved closer to the lower die 3 to the first temporary driving position among the n temporary driving positions. Then, when reaching the provisional driving position, the angle detection unit 7 detects the bending angle of the work W. S6: When the angle detection frequency N has not reached n (N <
In n), the upper die 5 is moved again to the second temporary driving position, and the bending angle of the work W is detected again at the second temporary driving position. This process is repeated until N = n.

S7: From the results of the angle detection at the above-mentioned n positions,
The ratio dD / dθ between the change amount dD of the drive-in amount and the change amount dθ of the actual bending angle is calculated. For example, when n = 2, 2
The ratio dD / dθ between the difference dD in the drive-in amount at the angle detection position of the point and the difference dθ in the detected angle is calculated. Then, the relationship between the ratio dD / dθ stored in advance and the springback angle Δθ, in other words, the dD / dθ-Δθ curve (FIG. 7)
) Is used to determine the springback angle Δθ corresponding to dD / dθ calculated as described above. Thus, the springback angle Δθ at the target bending angle is estimated. Here, when calculating the ratio dD / dθ, if the angle detection positions (temporary driving positions) are two (n = 2), the graph shows the relationship between the bending angle θ and the die driving amount D. , The ratio dD / dθ can be obtained by obtaining a straight line passing through the two points based on the two detected values. When the angle detection positions (temporary hunting positions) are three or more (n ≧ 3), the ratio dD / dθ can be obtained by using a method such as the least square method based on the three or more detection values. . FIG. 7 shows the relationship between the springback angle Δθ and the ratio dD / dθ, together with experimental value data.

S8-S9: The final driving position of the upper die 5 is calculated based on the estimated springback angle Δθ, and the upper die 5 is driven again to this position. S10: End the processing and end the flow.

The process shown in this flow may be performed for each bending process, but the operator can instruct a correction operation in an arbitrary process such as when a material lot is changed.

In the present embodiment, an angle detecting device using a light source for projecting slit light and a CCD camera for capturing a linear projected image has been described as angle detecting means for detecting a bending angle. However, as this angle detecting means, various types such as a capacitance type, a photoelectric type, and a contact type can be adopted.

In this embodiment, the lower die (die) is fixed, and the present invention is applied to a so-called overdrive type press brake for driving the upper die (punch). It is needless to say that the present invention can be applied to a so-called underdrive type press brake which drives a lower mold by a fixed type.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a bending apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing a correlation between an n value and a springback angle.

FIG. 3 is a graph showing a correlation between an n value and a bending radius of a material.

FIG. 4 is a diagram illustrating a relationship between a bending radius and a bending angle at the same bottom dead center.

FIG. 5 is a flowchart illustrating a control flow of a die driving amount.

FIG. 6 is a graph showing a relationship between a bending angle and a springback angle.

FIG. 7 is a graph showing the relationship between dD / dθ and the springback angle.

FIG. 8 is a graph showing a relationship between a work angle and a springback angle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed table 2 Die base 3 Lower mold 4 Ram 5 Upper mold 6 Backstop device 7 Angle detection unit 8 Light source 9 CCD camera 10 Bend angle calculator 11 NC device 12 Storage means 13 Calculation means W Work

Claims (4)

[Claims] 1. A method for estimating a springback angle of a work when a plate-shaped work is pressed by a driving die and a fixed die to perform a bending process, the method comprising: The actual bending angle of the workpiece is detected at at least two temporary drive-in positions, and the bending process stored in advance based on the relationship between the change amount of the drive-in amount and the change amount of the actual bending angle at each of the temporary drive-in positions. A springback angle estimating method characterized by estimating a springback angle of a workpiece using data on a springback behavior under the machining conditions. 2. A bending method in which a plate-shaped work is pressed by a driving die and a fixed die to perform bending, wherein at least two temporary drive-in positions of the driving die during bending of the work. The actual bending angle of the workpiece is detected, and based on the relationship between the change amount of the drive-in amount and the change amount of the actual bending angle for each of the temporary drive-in positions, the behavior of the springback in the previously stored processing condition of the bending process. A springback angle of a workpiece is estimated using data on the workpiece, and a final drive-in position of the driving die is obtained based on the estimated value. 3. A bending apparatus for performing bending by pressing a plate-shaped work by a driving die and a fixed die, wherein: (a) the driving die with respect to a bending angle of the work for each processing condition of the work; Storage means for storing the relationship between the drive-in amount and the relationship between the change amount of the drive-in amount and the change amount of the actual bending angle, and (b) an angle detecting means for detecting the bending angle during bending of the workpiece. (C) the actual bending angle of the workpiece detected by the angle detecting means at at least two temporary driving positions of the driving die, and the change amount of the driving amount and the actual bending stored in the storage means. The operation of calculating the final drive-in position of the driving die from the springback angle at the target bending angle of the work calculated from the relationship of the springback angle to the ratio of the angle change. A bending means comprising: a calculating means; and (d) a mold driving means for driving the driving mold to the temporary chasing position and then to the final chasing position. 4. The at least two provisional driving positions are calculated from a relationship between a driving die driving amount with respect to a workpiece bending angle and a springback angle with respect to a workpiece bending angle stored in the storage means. 4. The bending apparatus according to claim 3, wherein