JP3710268B2 - Bending method and bending apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bending method and a bending device for bending a plate-like workpiece by pressing it with a driving die and a fixed die.
[0002]
[Prior art]
In general, when V-bending a plate-shaped workpiece using a bending machine such as a press brake, the behavior related to the plastic deformation of the workpiece varies depending on the material property value. For this reason, even if the same material is used. However, it is known that the bending angle changes greatly due to variations in the characteristic values between lots. For this reason, it is extremely difficult to control the driving amount of the driving mold with high accuracy, and in actual bending, the actual situation is that it often depends on the intuition of a skilled operator.
[0003]
In order to deal with such problems, there are various press brakes that detect the bending angle of the workpiece during the bending process and control the final driving amount of the driving mold based on the detected bending angle. It has been proposed and put into practical use.
[0004]
For example, in the one proposed in Japanese Patent Laid-Open No. 6-328136, the upper and lower molds are once moved apart during the bending process to unload, and the bending angle of the workpiece is measured before and after the unloading. Thus, the spring back angle of the work is obtained, and the final driving amount is calculated from the obtained spring back angle and the bending angle of the work before moving the mold apart.
[0005]
For example, in what is proposed in Japanese Patent Application Laid-Open No. 7-265957, the bending angle of the workpiece is measured in a state where the die pressurizes the workpiece in the middle of bending, and the driving die is based on the measurement result. The final driving amount is calculated. In this case, the data of the springback angle is stored in advance for each material and thickness of the work, and the stored data is used to correct the relationship of the driving amount with respect to the bending angle of the work.
[0006]
[Problems to be solved by the invention]
However, in the former method (Japanese Patent Laid-Open No. 6-328136), the upper and lower molds are once moved relatively apart during the bending process to measure the springback angle. When the workpiece has an asymmetric shape, there is a possibility that the workpiece may fall during unloading and the contact point between the mold and the workpiece may be shifted. Therefore, it is necessary to prevent the workpiece from falling down by some means.
[0007]
On the other hand, according to the latter method (Japanese Patent Laid-Open No. 7-265957), since the bending angle of the workpiece is measured in a pressurized state, the above-mentioned problem of the workpiece falling can be solved. However, as shown in FIG. 9, the springback angle actually has a slight variation due to the variation in material property values between lots. Therefore, it is necessary to accurately estimate or detect the springback angle. FIG. 9 shows the springback angles at various bending angles in cold rolled steel sheets of the same type and different lots, and the springback angle is ±± due to variations in material property values between lots. It shows a variation of about 0.3 °.
[0008]
Further, since the method described in the latter publication only corrects the relationship of the driving amount with the bending angle of the workpiece stored in advance, the estimation accuracy of the final driving amount may be inferior. That is, as shown in FIG. 10, the relationship between the driving amount of the driving mold and the bending angle is a substitute characteristic of the mechanical properties of the workpiece material to be bent, and the bending accuracy is greatly affected by the change of the workpiece material. Will receive. Therefore, when bending a material that is close to the mechanical properties of the material stored in advance, this method can also bend the material with high accuracy. The relationship between the amount and the bending angle is greatly different, and the bending angle accuracy may be deteriorated.
[0009]
The present invention has been made to solve such problems, and accurately estimates the springback angle and the final drive-in position of the drive mold even if there are variations in material property values among lots of materials. Thus, an object of the present invention is to provide a bending method and a bending apparatus capable of realizing bending with extremely high angular accuracy.
[0010]
[Means for solving the problems and actions / effects]
In order to achieve the above-mentioned object, the bending method according to the first invention comprises:
In a bending method in which a plate-shaped workpiece is clamped by a driving mold and a fixed mold to perform bending,
During bending of the workpiece, the actual bending angle of the workpiece is detected at at least two temporary driving positions of the drive mold, and the relationship between the change in the driving amount and the change in the actual bending angle at each temporary driving position. Based on the above, the spring back angle of the workpiece is obtained using data relating to the behavior of the spring back under the bending processing conditions stored in advance, and the final drive position of the drive mold is obtained, and the obtained final drive position The drive mold is driven up to.
[0011]
In the present invention, when bending a workpiece, the driving mold is first driven to the first temporary driving position, and the actual bending angle of the workpiece is detected at that position, and then the driving mold is further moved to the next temporary driving position. When driven, the actual bending angle of the workpiece 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 manner, the relationship between the change amount of each driving amount corresponding to each temporary driving position and the change amount of each actual bending angle is used. Thus, the spring back angle of the workpiece is obtained using data relating to the behavior of the spring back under the bending processing conditions stored in advance, and the final driving position of the drive mold is obtained. According to the present invention, when the variation of the characteristic value between lots in the same material is taken into consideration, at least 2 as a substitute characteristic of the n value (work hardening index) that is the characteristic value that has the greatest influence on the springback angle. The relationship between the amount of change in each driving amount and the amount of change in each actual bending angle at the temporary driving position of the location is used, and the springback angle is obtained based on this relationship. Similarly, based on the relationship between the change in each drive amount and the change in each actual bending angle at the at least two temporary drive positions, in other words, the drive amount that is a substitute characteristic value of the mechanical properties of the material, In consideration of the relationship with the bending angle, the final driving position where the target bending angle is obtained is obtained by curve approximation or linear approximation. Therefore, for example, even if there are variations in material characteristic values between lots of materials, it is possible to accurately estimate the springback angle and the final driving position of the drive mold.
[0012]
Next, a bending apparatus according to the second invention for specifically realizing the bending method according to the first invention comprises:
In a bending apparatus that performs bending by pressing a plate-shaped workpiece between a driving mold and a fixed mold,
(A) A memory for storing the relationship of the drive-in amount of the driving mold with respect to the bending angle of the workpiece for each processing condition of the workpiece and the relationship of the springback angle with respect to the ratio between the change in the drive-in amount and the change in the actual bending angle. means,
(B) an angle detection means for detecting a bending angle during bending of the workpiece;
(C) Changes in the actual bending angle of the workpiece detected by the angle detection means at at least two temporary driving positions of the drive mold, and changes in the driving amount associated with each of the temporary driving positions, and the storage The spring back angle at the target bending angle of the workpiece is calculated from the relationship of the spring back angle with respect to the ratio of the change in the drive amount stored in the means and the change in the actual bending angle, and the final drive position of the drive mold And (d) mold driving means for driving the driving mold to the final driving position after driving the driving mold to the temporary driving position.
[0013]
In the present invention, the spring back is stored in advance in the storage means for the relationship between the amount of driving of the drive mold with respect to the bending angle of the workpiece for each processing condition of the workpiece and the ratio between the amount of change in the driving amount and the amount of change in the actual bending angle. The relationship between angles is stored. When bending a workpiece, first, the driving die is driven to the first temporary driving position by the mold driving means, and the actual bending angle of the workpiece is detected by the angle detecting means at that position, and then to the next temporary driving position. Further, the driving mold is driven, and the actual bending angle of the workpiece 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 manner, the spring back with respect to the ratio of the change in the driving amount and the change in 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 calculated springback angle and the change in each driving amount and the change in each actual bending angle corresponding to each temporary driving position are calculated. Based on the relationship, the final driving position of the drive mold is calculated. Then, the drive mold is driven to the calculated final driving position, and the bending process is completed. Thus, since the springback angle of the workpiece and the final drive-in position of the drive mold are estimated based on the actual bending angles detected at at least two angle detection positions, as in the first invention, between the lots of materials, Even if there are variations in the material property values at, the springback angle and the final driving position can be accurately estimated, and bending is performed based on this final driving position. It can be realized.
[0014]
In the present invention, the at least two temporary drive-in positions can be calculated from the relationship of the drive-in amount of the drive mold with respect to the bending angle of the workpiece stored in the storage means and the relationship of the springback angle with respect to the bending angle of the workpiece. .
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, specific embodiments of a bending method and a bending apparatus according to the present invention will be described with reference to the drawings.
[0016]
FIG. 1 shows a system configuration diagram of a bending apparatus according to an embodiment of the present invention.
[0017]
In the bending apparatus (press brake) of the present embodiment, a die base 2 is fixed on a fixed table 1, and a lower die 3 is mounted on the die base 2, and the lower die 3 is opposed to the lower die 3. An upper die 5 is attached to a lower portion of a ram 4 that is driven up and down so as to be spaced apart from and close to 3. A plate-like workpiece W to be bent is inserted between the lower die 3 and the upper die 5, and the ram 4 is lowered while the end of the workpiece W is abutted against the backstop device 6. The workpiece W is bent by sandwiching W between the lower mold 3 and the upper mold 5.
[0018]
An angle detection unit 7 for detecting the bending angle of the workpiece W during the bending process of the workpiece W is provided at the front portion of the fixed table 1. The angle detection unit 7 includes a light source 8 that projects slit light on the outer surface of the workpiece W that is bent, and a CCD camera 9 that captures a linear projection image formed on the outer surface of the workpiece W by the light source 8. The bending angle of the workpiece W is detected by performing image processing on the image captured by the CCD camera 9. The angle detection unit 7 can be provided not only in the front but also in the rear of the fixed table 1. Thus, the angle detection unit 7 is provided on both sides of the fixed table 1 and detects the bending angle of the two bending outer surfaces of the workpiece. The detection accuracy can be improved.
[0019]
The image captured by the CCD camera 9 is displayed on a monitor television (not shown) and processed by the bending angle calculation unit 10 as image data. 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 relationship between a plurality of springback angles with respect to a ratio between a change amount of the driving amount and a change amount of the actual bending angle for each bending condition (working condition) of the workpiece W, and a plurality of gold pieces corresponding to the bending angle of the workpiece. The storage means 12 for storing the relationship of the die driving amount and the like is provided, and the data stored in the storage means 12 and the bending condition of the workpiece W (material, plate thickness, bending shape, mold shape, machine information, etc.) And calculating means 13 for calculating the temporary driving position and the final driving position (bottom dead center) of the upper die 5 based on the above.
[0020]
By the way, it is said that the springback (return by elasticity) angle generated when bending the plate-like workpiece W is correlated with the tensile strength, longitudinal elastic modulus, work hardening index (n value), etc. of the material. However, considering only the variation in characteristic values between lots of the same material, it is considered that the characteristic value that has the greatest effect on the springback angle is the n 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. 3, it is known that there is a high correlation between the n value and the bending radius of the material, and when the bending radius of the workpiece W is different as shown in FIG. It has been found that the bending angle of the workpiece W changes at the same bottom dead center (upper position of the upper die). In other words, 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 a large spring back angle as a result. From this, it becomes possible to estimate the springback angle by detecting the bending angle of the workpiece W at a predetermined position, and by controlling the driving amount of the upper mold 5 which is a drive mold based on this result, Bending with high dimensional accuracy can be realized without depending on material variations.
[0021]
In this embodiment, as substitute characteristics of the n value, which is the characteristic value that has the greatest influence on the springback angle, the amount of change dD of each driving amount and the amount of change dθ of each actual bending angle at at least two temporary driving positions. calculating a ratio dD / d [theta] with, based on the relationship between the ratio dD / d [theta] and the spring back angle theta _s, it is adapted to calculate the spring-back angle in the target bending angle.
[0022]
Further, based on the springback angle at the target bending angle obtained as described above, and the relationship between the change amount dD of each driving amount and the change amount dθ of each actual bending angle at at least two temporary driving positions, The final driving position (bottom dead center) at which the target bending angle is obtained is calculated.
[0023]
Next, the control flow of the die drive-in amount in this embodiment will be described sequentially according to the flowchart shown in FIG.
[0024]
S1: Read the bending condition (material, plate thickness, bending shape, mold shape, machine information, etc.) of the workpiece W which is input in advance and stored in the storage means 12.
S2: Relational expression of default (initial value possessed by the NC device) from the relationship of the die drive amount D to the bending angle θ of the workpiece W (see FIG. 6) and the relationship of the springback angle to the target bending angle of the workpiece W When n is selected and the upper and lower molds are moved close to each other, the temporary driving position, in other words, the angle detection position is calculated at n positions (n ≧ 2). In addition, it is desirable that at least one of these temporary driving positions is as close as possible to the target bending angle within a range where the workpiece W is not excessively bent.
[0025]
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. When the temporary driving position is reached, the angle detection unit 7 detects the bending angle of the workpiece W.
S6: When the number of detected angles N has not reached n (N <n), the upper mold 5 is moved again to the second temporary driving position, and the workpiece W is bent again at the second temporary driving position. Detect the angle. This process is repeated until N = n.
[0026]
S7: A ratio between the change amount of the follow-up amount and the change amount of the actual bending angle is calculated from the above-described angle detection results at n places. For example, in the case of n = 2, the ratio dD / dθ between the difference dD in the driving amount at the two angle detection positions and the difference dθ in the detection angle is calculated. Then, using the relationship of the springback angle θ _s to the ratio dD / dθ stored in advance, in other words, the ratio dD / dθ calculated as described above, using the dD / dθ to θ _s curve (see FIG. 7). The corresponding springback angle θ _s is obtained. Thus, the springback angle θ _s at the target bending angle is estimated. Here, when the ratio dD / dθ is calculated, if there are two angle detection positions (temporary driving positions) (n = 2), the graph shows the relationship of the die driving amount D with respect to the bending angle θ. The ratio dD / dθ can be obtained by obtaining a straight line passing through these two points based on the two detected values. When the angle detection position (temporary driving position) is three or more (n ≧ 3), the ratio dD / dθ can be obtained using a method such as the least square method based on the three detection values. FIG. 7 shows the relationship of the springback angle θ _s to the ratio dD / dθ together with experimental value data.
[0027]
S8: The relationship between the change amount dD (= d ₁ −d ₂ ) of the follow-up amount obtained from the angle detection result at the above-mentioned n locations and the change amount dθ (θ ₁ −θ ₂ ) of the actual bending angle, and as described above. using springback angle theta _S to a target bending angle theta _T obtained Te, obtaining the final thrust position d _T of the target bending angle theta _T is obtained (see FIG. 8). Here, the graph showing this when calculating the final thrust position d _T, the angle detection position if (tentative thrust position) at two positions (n = 2), the bending relationship mold thrust amount D for the angle theta ( 8 refer) on, it is possible to obtain the final thrust position d _T by obtaining a straight line passing through those two points based on the two detection values. When the angle detection position (temporary driving position) is three or more (n ≧ 3), the final driving position d _T can be obtained using a method such as a least square method based on three or more detection values. it can.
[0028]
S9: Based on the estimated final driving position d _T , the upper mold 5 is driven again to that position.
S10: Finish processing and end the flow.
[0029]
The processing shown in this flow may be performed for each bending process, but the operator can instruct the correction operation in any process such as when the material lot is changed.
[0030]
In the present embodiment, as the angle detection means for detecting the bending angle, the one using an angle detection device including a light source that projects slit light and a CCD camera that captures a linear projection image has been described. Various other types of angle detection means such as a capacitance type, a photoelectric type, and a contact type can be adopted.
[0031]
In this embodiment, the lower die (die) is fixed and the upper die (punch) is applied to a so-called overdrive type press brake. However, in the present invention, the upper die is fixed. Needless to say, the present invention can be applied to a so-called underdrive type press brake for driving the lower die.
[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 showing a control flow of a mold drive-in amount.
FIG. 6 is a graph showing a relationship of a driving amount with respect to a bending angle.
FIG. 7 is a graph showing a relationship of a springback angle with respect to dD / dθ.
Figure 8 is a graph illustrating how to obtain a final thrust position d _T.
FIG. 9 is a graph showing a relationship between a workpiece angle and a springback angle.
FIG. 10 is a graph for explaining that the relationship between the amount of thrust and the bending angle varies depending on the material.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixed table 2 Die base 3 Lower mold | type 4 Ram 5 Upper mold | type 6 Back stop apparatus 7 Angle detection unit 8 Light source 9 CCD camera 10 Bending angle calculating part 11 NC apparatus 12 Memory | storage means 13 Calculation means W Workpiece

Claims (3)

In a bending method in which a plate-shaped workpiece is clamped by a driving mold and a fixed mold to perform bending,
During bending of the workpiece, the actual bending angle of the workpiece is detected at at least two temporary driving positions of the drive mold, and the relationship between the change in the driving amount and the change in the actual bending angle at each temporary driving position. Based on the above, the spring back angle of the workpiece is obtained using data relating to the behavior of the spring back under the bending processing conditions stored in advance, and the final drive position of the drive mold is obtained, and the obtained final drive position Bending method characterized by driving said driving mold. In a bending apparatus that performs bending by pressing a plate-shaped workpiece between a driving mold and a fixed mold,
(A) A memory for storing the relationship of the drive-in amount of the driving mold with respect to the bending angle of the workpiece for each processing condition of the workpiece and the relationship of the springback angle with respect to the ratio between the change in the drive-in amount and the change in the actual bending angle. means,
(B) an angle detection means for detecting a bending angle during bending of the workpiece;
(C) Changes in the actual bending angle of the workpiece detected by the angle detection means at at least two temporary driving positions of the drive mold, and changes in the driving amount related to the temporary driving positions, and the storage The spring back angle at the target bending angle of the workpiece is calculated from the relationship of the spring back angle to the ratio of the change in the drive amount stored in the means and the change in the actual bending angle, and the final drive position of the drive mold And (d) a bending apparatus that drives the driving mold to the final driving position and then drives the driving mold to the final driving position. The at least two temporary drive-in positions are calculated from the relationship of the drive-up amount of the drive mold with respect to the bending angle of the workpiece stored in the storage means and the relationship of the springback angle with respect to the bending angle of the workpiece. Item 3. A bending apparatus according to Item 2.

Images