JPH10128451A - Bending angle correcting method and press brake using above - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and correctly press over the whole length of a work and to obtain a highly precise bending angle with bending at one time without receiving the influence of the dispersion of a material. SOLUTION: When bending a plate like work W in co-operation with a driving die (punch 5) and a fixing die (die 4) driven with driving shafts of more than three shafts, on a way of bending, the bending angle of the work W is detected, the deviation between this detected bending angle and a target bending angle is obtained at three places, at least, of both ends of the work W and a central part except these both ends. Based on this obtained deviation, the correcting amount of the pressing amount of the driving die (punch 5) at the shaft position of each driving shaft is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention bends a plate-shaped work by cooperation of a driving die driven by three or more driving shafts and a fixed die disposed opposite to the driving die. The present invention relates to a bending angle correction method and a press brake capable of performing high-precision bending using the correction method.

[0002]

2. Description of the Related Art Conventionally, as a bending machine of this kind, FIG.
A press brake 51 as shown in FIG. In the press brake 51, the ram 52 and the fixed table 53 are opposed to each other, and a pair of side frames 54 and 55 are integrally provided at both ends of the fixed table 53. The hydraulic cylinders 56, 56 provided on the
Is configured to move up and down. And ram 5
An upper die (punch) 57 is provided at the lower end of the fixed table 5.
Lower dies (dies) 58 are arranged on the upper surface of the upper die 3, respectively, and a plate-like work is inserted between the upper dies 57 and the lower dies 58 to operate the hydraulic cylinders 56, 56 so that these upper dies 58 are moved. The work is pressed between the lower mold 57 and the lower mold 58 and bent at a required bending angle.

By the way, such a press brake 51
When the workpiece is bent using the method described above, there is a problem that an angle difference occurs between the center portion and both end portions of the workpiece due to the deflection of the ram 52 and the fixed table 53, that is, a so-called middle opening phenomenon occurs. For this reason, conventionally, a ram or a table is provided with a deflection compensating mechanism to correct the center opening phenomenon. A representative example of this deflection compensation mechanism is disclosed in, for example,
Patent No. 5622, a crowning mechanism using a wedge device, or, for example, JP-A-6-5
There is a crowning mechanism using a hydraulic cylinder as described in Japanese Patent No. 5218.

As a method for obtaining an accurate bent product by one bending process, there is a method described in Japanese Patent Application Laid-Open No. Hei 7-265957 proposed by the present applicant. According to the method described in this publication, an angle measurement is performed before a target bending angle (temporary drive-in position) during bending of a workpiece, and the measured value, springback amount data, and the workpiece bending angle−mold drive-in are performed. The final driving position is obtained based on the relationship between the amounts, and the die is driven to the final driving position so that the bending can be accurately performed without being affected by the variation in the material.

On the other hand, a press brake having three or more drive shafts is provided with a deflection detecting device for detecting deflection of a ram, and each drive shaft is controlled based on a detection value of the deflection detection device. 6-5441
No. 6 discloses this.

[0006]

However, in the case of using a wedge device as disclosed in Japanese Patent Application Laid-Open No. 2-55622, there is a problem that it is structurally difficult to change the crowning during pressurization of a work. Also, in the case of using a hydraulic cylinder as described in JP-A-6-55218, a change during pressurization is possible, but the driving amount by crowning is not directly controlled,
Since only the hydraulic pressure is managed, there is a problem that the amount of drive-in is an open loop and accurate drive-in cannot be performed.

In the case of using the method described in Japanese Patent Application Laid-Open No. Hei 7-265957, whether the correction can be accurately driven greatly affects the bending accuracy. Becomes important. But,
Even if this method is used to measure and feed back the amount of driving by crowning, since the pressurizing shaft and the crowning device have different mechanisms and control methods,
After calculating the correction run-in amount by measuring the bending angle, it is necessary to convert the control amount into separate control amounts for the pressurizing shaft and the crowning device, and to perform control in consideration of each operation delay, etc. There is a problem that becomes.

Further, in the apparatus disclosed in Japanese Utility Model Laid-Open Publication No. Hei 6-54416, it is possible to correct an angular error such as a center-opening phenomenon caused by bending of a machine in the middle of bending.
Angle difference due to variation in the longitudinal direction of the work, that is, even if it is possible to drive in evenly in the longitudinal direction of the work, even if the thickness and plastic characteristics of the work in the longitudinal direction gradually change, it will bend uniformly. No phenomena can not be solved.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and is simple and simple over the entire length of a work by combining a multi-point angle measurement during bending and a multi-axis drive mechanism. It is possible to drive exactly,
It is an object of the present invention to provide a bending angle correction method capable of obtaining a high-precision bending angle by a single bending process without being affected by variations in materials, and a press brake using the same.

[0010]

In order to achieve the above-mentioned object, a bending angle correcting method according to the present invention comprises a driving die driven by three or more driving shafts,
This is a bending angle correction method for bending a plate-shaped work in cooperation with a fixed die arranged opposite to the driving die, and detects a bending angle of the work during bending and detects this. The deviation between the bending angle and the target bending angle is determined at both ends of the work and at least three points in the center excluding the both ends, and the correction value of the drive-in amount of the driving die at the axial position of each driving shaft is determined based on the determined deviation. Is obtained.

In the bending angle correcting method according to the present invention, the bending angle of the workpiece is detected during the bending process, and the deviation between the detected bending angle and the target bending angle is determined at both ends of the workpiece and the central portion excluding the both ends. Are calculated at least at three points, and the obtained deviation is converted into a correction value for the drive-in amount of the driving die at the axial position of each driving shaft, thereby obtaining the correction value. In this way, even if a phenomenon in which the workpiece does not bend uniformly due to changes in the thickness or plastic properties in the longitudinal direction of the workpiece occurs, the correction value at each drive shaft position combining the crowning correction value and the tilt correction value is automatically adjusted. Therefore, the bending angle can be easily corrected, and a uniform and highly accurate bending angle can be obtained over the entire length of the work.

Also, the press brake according to the present invention has
A press brake for bending a plate-shaped work by cooperation of a drive mold driven by a drive shaft having a length equal to or more than a shaft, and a fixed mold disposed opposite to the drive mold; Storage means for storing a condition, a relationship between a springback angle with respect to a target bending angle of the workpiece, and a relationship between a drive mold driving amount and a workpiece bending angle, (b)
Bending angle detecting means for detecting a bending angle of the work at at least three positions along the longitudinal direction of the work during the bending, (c) a spring for the processing conditions of the work stored in the storage means and a target bending angle of the work. From the relationship of the back angle, a temporary drive-in position for each drive shaft of the drive die is calculated, and at this temporary drive-in position, the bending angle of the work detected by the bending angle detecting means and the storage means are stored. Calculating means for calculating the corrected driving amount of the driving die at the angle detection position from the stored relationship between the springback angle with respect to the target bending angle of the work and the relation between the driving die driving amount with respect to the bending angle of the work, (D) The final drive position at each drive shaft position is obtained by interpolation from the corrected drive amount calculated by the calculation means. Obtaining interpolation calculation means and (e)
The apparatus further comprises a mold driving means for driving the driving die to the temporary driving position and then driving to the final driving position.

In the press brake according to the present invention,
At the time of bending the work, the temporary working of the driving mold is determined based on the working conditions of the work stored in the storage means, the relationship between the springback angle with respect to the target bending angle of the work, and the relationship between the bending angle of the work and the driving amount of the driving mold. The driving position is calculated, and the driving die is driven by the die driving means to the provisional driving position, and the bending angle detecting means detects the bending angles of the work at at least three positions along the longitudinal direction of the work at that position. Is done. Next, based on the relationship between the detected bending angle and the springback angle with respect to the target bending angle of the work stored in the storage means in advance, and the relationship between the bending amount of the work and the driving amount of the driving die, the temporary bending position is determined. Is calculated, and the final driving position at each drive shaft position is obtained from the corrected driving amount by interpolation. Then, the driving die is driven to the obtained final position, and the bending is completed. Thus,
A single angle detection during the bending process enables accurate run-in at the longitudinal position of the work, even if the bending position is eccentric in the left-right direction, enabling high-precision bending in a short time Can be.

In the present invention, the interpolation calculating means includes a crowning correction value obtained from a difference in the amount of deflection of a fixed mold supporting table between a line connecting both ends of the work and a center portion, and the crowning correction value and the both ends of the work. It is preferable that the final drive position at each drive shaft position is calculated from the inclination amount correction value obtained from the table deflection amount difference.

The bending angle detecting means is preferably mounted movably in a longitudinal direction of the table along a rail provided on a front surface and / or a rear surface of the table supporting the fixed mold. This makes it possible to accurately detect the bending angle at an arbitrary position along the longitudinal direction of the work.

[0016]

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

FIG. 1 is a front view of a press brake according to an embodiment of the present invention, FIG. 2 is a side view of the press brake, and FIG.
FIG. 2 is a block diagram showing a control system configuration of the present embodiment.

The press brake of the present embodiment is provided with a fixed table 1 and a ram 2 which is driven to move up and down opposite to the table 1. A die (lower die) 4 having a V-shaped mold groove is held, and a punch (upper die) 5 is attached to a lower portion of the ram 2 so as to face the die 4 via a punch holding device 6. .

A pair of side frames 7 and 8 are integrally provided at both ends of the table 1, and a support frame 9 is provided so as to connect the upper ends of the side frames 7 and 8. A plurality of (four in this embodiment) ram driving devices 10a, 10b, 10c, 1
0d is attached, and these ram driving devices 10a
The ram 2 is swingably connected to the lower ends of 10 to 10d. Thus, the work W inserted between the punch 5 and the die 4 is bent by raising and lowering the ram 2 by the operation of the ram drive devices 10a to 10d.

Each of the ram driving devices 10a to 10d uses an AC servomotor 11a to 11d provided at the rear as a driving source and transmits the driving force via a timing belt 12 to the ram 2a.
Are transmitted to a ball screw 13 connected to the servo motors 11a to 11
The rotational driving force of d is converted into a moving force in the vertical direction, and the work W
Is configured to generate a pressing force with respect to

The vertical position of the ram 2 is determined by linear encoders (incremental encoders) 14a to 14d provided corresponding to the drive shaft positions of the ram drive devices 10a to 10d.
14d, and the detection data is
9a, the respective servo motors 11a to 11a through the servo amplifiers 15a to 15d in accordance with the respective axis positions.
11d is feedback-controlled, and brakes 16a to 16d attached to the motor shafts of the servomotors 11a to 11d are controlled by a machine control device (sequencer). Here, the linear encoders 14a to 14d are supported by a correction bracket 17 composed of two side plates provided along the side frames 7, 8 and a beam connecting the left and right side plates. I have. With such a configuration, the linear encoders 14a to 14d can measure the absolute position of each axis of the ram 2 without being affected by the deformation due to the load change of the side frames 7, 8. The servo motors 11a to 11d
The motor shafts are provided with encoders (absolute encoders) 18a to 18d for detecting the current positions of the servo motors 11a to 11d, and the servo amplifiers 15a to 15d are controlled by the data detected by the encoders 18a to 18d. It is supposed to be.

A control unit 20 including an NC unit 29 for controlling the above-described ram drive units 10a to 10d and a machine control unit (sequencer) is attached to the side of the main body frame of the press brake. An operation panel 21 including an input keyboard, a display for displaying various data, and various switches is suspended from the support frame 9 via a swingable arm 22. Further, a foot switch 23 for stepping operation is provided below the side of the body frame.

Each of the front and rear surfaces of the table 1 has three
A total of six angle measuring units 25 are provided movably along a linear guide 26 extending in the left-right direction. The angle measuring unit 25 includes a slit-shaped light source 26 that projects a linear projected image on the bent outer surface of the workpiece W.
And a CCD camera 27 that captures a linear projection image from the light source 26.
The bending angle of the workpiece W is calculated by processing the image captured by the bending angle calculation unit 28. The result of this operation is input to the NC unit 29.

In the NC unit 29, the specifications of the mold to be used (punch tip radius, punch height, die height, die V groove width, V groove angle, V groove shoulder radius, etc.), work specifications (material,
Bending strength (bending angle, bending length,
Bending position eccentricity etc.) is input, and the bending angle measurement during the bending process is performed before the target bending angle, and the measurement is performed from the both ends of the work in the left and right direction. A processing condition input unit 30 for inputting measurement conditions such as whether to perform is provided, and a left-right bending angle measurement position is calculated in a measurement position calculation unit 31 based on information input from the processing condition input unit 30. Each angle measurement unit 25 is moved to a required position according to the calculation result.

In the NC device 29, according to the processing conditions input from the processing condition input unit 30,
A measurement / pass / fail condition setting unit 32 for setting various conditions such as data such as an angle measurement position, a measurement process number, and a tolerance in bending, a sampling condition (number of times, an angle) for updating the database, and a pass / fail judgment condition of a bending angle; A bending angle-to-feed-in amount data section 33 in which data relating to the relationship between the bending angle and the driving amount of the ram 2 is registered, and a spring-back data section in which data relating to the spring-back angle to the target bending angle are registered. 34
And a pass / fail determination unit 35 for determining the bending accuracy of the workpiece that has been bent by the data from the bending angle calculation unit 28.
The final data at each angle measurement position of the ram 2 is obtained from the data from the bending angle to drive-in amount data unit 33 and the springback data unit 34, the data from the processing condition input unit 30, and the data from the bending angle calculation unit 28. A driving amount calculation unit 36 at each measurement position for calculating the driving amount;
Based on the data from the machining condition input unit 30, the tentative overrunning position (lower limit position) on each drive shaft of the ram 2 is calculated, and based on the data from the overrunning amount calculation unit 36 at each measurement position, the ram drive shaft is used. Calculate the final run-in amount of
A drive amount calculation unit (interpolation calculation unit) 37 at the ram drive shaft that outputs the calculation result to each of the ram drive devices 10a to 10d.
And temporarily stores data from the bending angle calculator 28 to register new data or updated data in the bending angle to drive-in amount data unit 33, and sets a calculation form and performs a coefficient calculation. Angle to drive amount data update processing unit 38 and bending angle calculation unit 2
A springback data update processing unit 39 is provided for temporarily storing data from No. 8 and registering new data or update data in the springback data unit 34, and also performs calculation form setting and coefficient calculation.

Next, the bending process of this embodiment will be described with reference to the flowchart shown in FIG.

AB: It is determined whether or not the mode is the bending angle measurement mode (step A). If the mode is not the measurement mode, the bending is executed in the normal mode (step B).
End the flow. On the other hand, when the mode is the measurement mode, the process proceeds to step C. Whether or not to perform the bending in the bending angle measurement mode is set by an operator using an external switch.

C to E: work information (material, bending line length, bending angle, etc.), mold information (mold height, V groove width, V angle, punch R, etc.), machine information from the processing condition input unit 30 (rigidity,
Processing conditions such as speed specification, stroke specification, etc.) are input (step C), and then the longitudinal position and setting state of the angle measuring unit 25, which are bending angle measurement conditions, are set (step D). Then, the longitudinal position of the angle measurement unit 25 is calculated according to the processing conditions and the measurement conditions (step E).

F: Calculate a temporary lower limit value for each mold drive shaft, in other words, a lower limit value at the time of measuring a bending angle. The details of this calculation will be described in detail with reference to the flowchart shown in FIG.

G to J: When the NC device 29 is started (step G), the angle measuring unit 25 moves to the calculated position. Next, the work W is set between the punch 5 and the die 4 (step H), and the mold driving shaft is driven to a temporary lower limit position to perform bending (step I). Next, the angle is measured by the angle measurement unit 25 at the provisional lower limit position, and the measurement result is displayed (step J).

KL: Whether all measured angles are smaller than target bending angle (WA) -springback angle (SB) + constant (where the constant is a value such as a tolerance), in other words, It is determined whether or not the ram 2 has reached the final lower limit. If the result of this determination is that the final lower limit has not been reached, the correction overrun amount at each angle measurement position is calculated. The correction drive-amount, as shown in Figure 5, the angle bend is registered with stratified by previously bending conditions - from the thrust amount curve, in FIG. When the measured angle between FA (D ₀ -D ₁ ) is required. It should be noted that the calculation of the corrected overrun amount is performed at each angle measurement position.

M: The final lower limit value for each mold drive shaft is obtained by interpolation from the corrected drive-in amount at each angle measurement position. The details of this calculation will be described in detail with reference to a flowchart shown in FIG.

N to P: When all the measured angles reach the target bending angle (WA) -springback angle (SB) + constant, the ram 2 is raised (step N), and then the bending accuracy is confirmed. It is determined whether or not to perform (Step O). If the accuracy is not checked, the flow is ended. If the accuracy is checked, the bending angle is measured and the measured value is displayed (Step P). In this case, in order to prevent the work W from falling due to the rise of the ram 2 and making the angle measurement impossible, it is desirable that the angle measurement be performed with the work W lightly clamped.

Q to S: It is checked whether or not the measured angle is within the allowable range (step Q), and if it is within the allowable range, the flow ends. On the other hand, if it is not within the allowable range, it means that the bending process has failed. Therefore, it is determined whether or not to perform the forced lower limit correction (step R), and if so, the final lower limit value is corrected (step R). S) End the flow, and if no correction is to be made, end the flow as it is. As a method of correcting the final lower limit value, the corrected drive amount may be obtained from the relationship between the bending angle and the drive amount shown in FIG. 5, and the final lower limit value of each drive shaft may be obtained by an interpolation operation described later.

Next, step F in the flowchart shown in FIG. 4, that is, a procedure for calculating a temporary lower limit value for each mold drive shaft will be described with reference to FIG.

F1: Bending data to be input
Work material MAT, plate thickness WT, product target bending angle WA,
Springback angle SB, inner bending radius F during molding
First, a punch tip biting amount GR is obtained based on data on formability factors such as R, punch tip radius PR, die V groove width DV, die V groove angle DA, and die V shoulder radius DR. This punch tip biting amount GR is the work material MA
T, plate thickness WT, product target bending angle WA, punch tip radius PR, and die V groove width DV are uniquely obtained by the following equation. GR = f (MAT, WT, WA, PR, DV) It is assumed that the function f has been determined in advance by experiment or simulation.

F2: Calculate the target bending angle FA 'at the time of angle measurement. This target bending angle FA 'is given by the following equation. FA ′ = WA−SB + AA Here, AA is a value indicating how many times before the target the angle measurement is performed.

F3: Drive-in amount PEI for bending only
(See FIG. 7) is obtained by the following equation. PEI = (gh) × tan (90 ° −FA ′ / 2) −
ij where g = DV / 2 + DR × tan (90 ° −DA / 2) / 2 h = (DR + WT) × sin (90 ° −FA ′ / 2) i = (DR + WT) × cos (90 ° − FA '/ 2)-
DR j = FR × (1 / cos (90 ° −FA ′ / 2) −1) Therefore, the drive-in amount PE due to the moldability factor
Is obtained by the following equation. PE = PEI + GR

F4 to F5: Next, in order to obtain the drive-in amount PE in consideration of the mechanical factors, the deformation state of each part is modeled as shown in FIG. 8, and the lower limit position in consideration of the mechanical deformation under load Is determined as follows. That is, in addition to the data on the above-described formability factors from the pressing condition input unit 30, the punch height PH, the die height DH, and the workpiece bending length W
L, the workpiece bending position WPP, and other data are input. Based on these data, the load displacement EUT of the ram 2, the load displacement EL of the table 1, and the amount of deflection DLi at each axis position of the table 1 (i = 1, 2, 2) 3, 4) are required. Here, one of the mechanical factors that is particularly problematic is the ram 2
And the load displacement of the table 1.

The table deflection DLi is obtained by multiplying the bending deflection YBi and the shear deflection YSi at each position when an evenly distributed load is applied to the beam supported at both ends by a difference coefficient DLCOR obtained from an experiment or the like. The bending deflection YBi and the shear deflection YSi are obtained as follows. As shown in FIG. 9, when the distance of the axis position from point A is AXP, when the axis position is between AC (when 0 ≦ AXP <LA), YB = − (RA / 6 × AXP ³ + C1 × AXP) / (E
× I) YS = K × RA × AXP / (G × A) When the axis position is between CDs (when LA ≦ AXP <LB) YB = − (RA / 6 × AXP ³ −WQ / 24 × (AXP
−LA) ⁴ + C1 × AXP) / (E × I) YS = (RA × AXP−WQ / 2 × (AXP−LA))
× K / (G × A) When the axis position is between DBs (when LB ≦ AXP <LL) YB = − (RA / 6 × AXP ³ −WBF / 6 × (AXP
−LE) ³ + C5 × AXP + C6) / (E × I) YS = (RA × AXP−WBF × (AXP−LE) ² ×
K / (G × A)

Therefore, the amount of deflection DLi at the axial position i obtained by an experiment or the like is represented by the following equation. DLi = (YB + YS) × DLCOR Here, YB: Bending amount A: Cross-sectional area YS: Shearing amount RA: Reaction force at point E E: Longitudinal elasticity coefficient WQ: Load per unit length G: Transverse elasticity coefficient WBF: Total load I: Secondary moment of area C1, C5, C6:
Constant K: Shear stress ratio The constants C1, C5 and C6 are given by the following equations. C5 = (WBF / 2 × (LB-LE) ² −WBF / 6 ×
(LB-LA) ² + ZZ / LB) × LB / LL C1 = (ZZ + C5 × (LB-LL)) / LB C6 = WBF / 6 × (LL-LE) ³ -RA / 6 × LL
³ −C5 × LL where ZZ = WBF / 24 × (LB−LA) ³ −WBF / 6 ×
(LB-LE) ³ + WBF / 6 × (LL-LE) ³ -R
A / 6 × LL ³

The load displacement EUT, EL of the ram 2 and the table 1 and the difference coefficient DLCO of the table deflection are also shown.
R can be obtained immediately by conducting an experiment or simulation in advance and obtaining an empirical formula that is uniquely determined when the processing conditions are given.

F6: In this way, the lower limit value DPTi of each axis is calculated. In the case of the example shown in FIG. 8, the target value DPT3 at the third axis position is represented by the following equation. DPT3 = PH + DH-PE-EUT-EL-DL3 Similarly, the lower limit value at each drive shaft position can be obtained by performing calculations on the first axis, the second axis, and the fourth axis.

Step M in the flowchart shown in FIG. 4 described above, that is, the procedure for obtaining the final lower limit value for each mold drive shaft by interpolation is shown in FIG.
This will be described with reference to FIG.

M1: The amount of table deflection at the measurement position is determined based on the bending load BF determined at the time of calculating the temporary lower limit (see FIG. 11). For example, the table deflection amount CWXC at the center of the work is calculated by the following formula: YB = − (RA / 6 × WPXC ³ + C1 × WPXC) /
Represented by (E × I _Z), the amount of deflection due to shear in the work center YS following equation YS = (RA × WPXC-WQ / 2 × (WPXC-L
A) Since it is expressed by ² ) × K / (G × A), it is given by the following equation. CWXC = YB + YS where WQ: bending load per unit length RA: reaction force at the left end of the table I _Z : second moment of area E: longitudinal elastic modulus G: transverse elastic modulus K, A, C1: other constants And the table deflection CWXL at the left end of the work
The table deflection amount CWXR at the right end of the work is also obtained. Here, the target bending angle FA 'at the temporary lower limit value and the target bending angle (WA-SB) at the time of the final run-in are very close values, and the difference in bending load between the two can be ignored. The measurement position, in other words, the position of both ends and the center of the work W from the left end of the table 1 is represented by the following equation, where LL is the distance between the table fulcrum, WPP is the eccentricity of the bending position, and WL is the bending length of the work. (See FIG. 12). Work center WPXC = LL / 2 + WPP Work left end WPXL = WPXC-WL / 2 Work right end WPXR = WPXC + WL / 2

M2: The difference CWPCH between the line connecting the corrected drive-in amounts HSTL and HSTR at the left and right end positions of the work and the correction amount HSTC at the center position is obtained from the corrected drive-in amount by the following equation (see FIG. 13). Here, HSTL, H
STR and HSTC are correction drive-in amounts at each angle measurement position. CWPCH = HSTC− (WPXC−WPXL) × (H
(STR-HSTL) / (WPXR-WPXL) -HST
L Similarly, from the table deflection at the measurement position obtained from the bending load, each table deflection CW at the left and right end positions of the work is similarly obtained.
The difference CWXCH between XL, CWXR and the center table deflection CWXC is determined by the following equation (see FIG. 11). CWXCH = CWXC- (WPXC-WPXL) × (C
(WXR-CWXL) / (WPXR-WPXL) -CWX
L

M3: Based on the amount of deflection of the table due to the bending load at the center of the table and at the position of each drive shaft calculated at the time of calculating the target position, C obtained in step M2 is obtained.
The ratio of WPCH and CWXCH is converted into a crowning correction amount at each drive shaft position (see FIG. 14). For example, the first
The crowning correction amount CWHH1 in the axis is the first
The table deflection amount due to the bending load at the shaft position is expressed as DL1 by the following equation. CWHH1 = DL1 × CWPCH / CWXCH-CWH
HL Here, CWHHL is a correction coefficient indicating that the value is determined based on the left end of the measurement position, and is calculated by the following equation. CWHHL = CWXL × CWPCH / CWXCH The same is obtained for other axes. The general formula is given by the following formula. CWHHi = DLi × CWPCH / CWXCH-CWH
HL (i = 1,2,3,4)

M4: The inclination amount including the crowning correction amount is obtained by obtaining the correction amount at both ends of the work after subtracting the crowning correction amount by the following equation (see FIG. 15). CWHTL = HSTL-CWXL × CWPCH / CWX
CH CWHTR = HDTR-CWXR × CWPCH / CWX
CH

M5: Based on the result of the calculation in the previous step M4, the amount of inclination CAKKi at each drive shaft position is obtained by the following equation (see FIG. 15). CAKKi = (APPi−APP1) × (CWHTR−
CWHTL) / (WPXR-WPXL) -CAKKL (i = 1, 2, 3, 4) Here, CAKKL is a correction coefficient indicating that the value is obtained based on the left end of the measurement position, and is calculated by the following equation. Can be CAKKL = (WPXL-APP1) × (CWHTR−
(CWHTL) / (WPXR-WPXL) -CAKKL In this manner, a tilt correction amount can be obtained at each axis position.

M6: In order to obtain the correction drive amount of each drive shaft position, the crowning correction amount obtained in step M3 and the inclination correction amount obtained in step M5 are added, and the correction amount HSTL at the left end of the work is added. Thus, the corrected drive-in amount DPSHi at each drive shaft position is obtained by the following equation (see FIG. 16). DPSHi = HSTL + CWHHi + CAKKi (i = 1, 2, 3, 4)

M7: The final lower limit value DP is obtained by subtracting the corrected drive-in amount from the temporary lower limit value of each drive shaft by the following equation.
Find TLi. Here, the reason why the subtraction process is performed is that the final lower limit value DPTLi is a value based on the lower end. DPTLi = DPTi-DPSHi (i = 1, 2, 2)
3,4)

In this embodiment, the interpolation of the final lower limit value is performed based on the deflection curve of the machine. However, the above-mentioned HSTL, HSTR, and HSTC are represented by quadratic curves as shown in FIG. Approximate interpolation may be performed. Approximate interpolation using a linear curve (linear line) is also possible.

In this embodiment, a description has been given of a case where a total of six angle measurement units are provided on each side of the table, three in total, but the angle measurement unit can be moved in the longitudinal direction of the work as in this embodiment. For example, by moving one or two angle measuring units on one side, measurement of three points on the workpiece may be performed. In addition, when only the bent outer surface on one side of the work can be measured under various conditions, the final bending angle may be obtained by doubling the angle measurement result of the outer surface that can be measured on the other side.

In this embodiment, the angle measuring unit is
Although a configuration including a slit-shaped light source and a CCD camera was used, various types of angle measurement units such as a contact type and a capacitance type can be used.

In the present embodiment, the correction is performed by measuring three points at the left and right ends and at the center of the work. However, by clarifying the measurement position, the bending angles at four or more points are measured and corrected. Embodiments are also possible. Again, in this case,
Again, the crowning correction amount is obtained from the difference between the line connecting them and the correction amount between them based on the correction amounts at both ends of the work, and the inclination correction amount is calculated from the correction amounts at both ends, and the total angle correction amount is calculated from the correction amount at the left end. It can be obtained in the same manner as in the case of the location.

In the present embodiment, a description has been given of the case where an AC servomotor and a ball screw are used as the drive source of the ram. However, as the drive source, a hydraulic unit and a cylinder may be used.

In this embodiment, the case where the number of drive shafts of the ram is four has been described. However, the number of drive shafts may be three, five or more.

[Brief description of the drawings]

FIG. 1 is a front view of a press brake according to one embodiment of the present invention.

FIG. 2 is a side view of the press brake of the present embodiment.

FIG. 3 is a block diagram illustrating a configuration of a control system of the press brake according to the present embodiment.

FIG. 4 is a flowchart showing a bending process of the present embodiment.

FIG. 5 is a graph showing a relationship between a bending angle and a drive-in amount.

FIG. 6 is a flowchart illustrating a procedure for calculating a temporary lower limit value in each mold drive shaft.

FIG. 7 is a diagram showing a geometric relationship among a die, a work, and a punch in air vent processing.

FIG. 8 is a diagram illustrating a deformed shape of each part.

FIG. 9 is a diagram for explaining a calculation formula of a table deflection;

FIG. 10 is a flowchart illustrating an interpolation calculation procedure of a final lower limit value in each mold drive shaft.

FIG. 11 is a diagram for explaining a calculation content of a table deflection amount;

FIG. 12 is a diagram for explaining calculation contents of a measurement position.

FIG. 13 is a diagram for explaining the calculation of a crowning amount based on a correction value.

FIG. 14 is a diagram for explaining calculation contents of a crowning correction amount at each drive shaft position.

FIG. 15 is a diagram illustrating the calculation contents of a tilt amount including a crowning correction amount and a tilt correction amount at each drive shaft position.

FIG. 16 is a diagram for explaining calculation contents of a correction value of each drive shaft position.

FIG. 17 is a diagram illustrating another example of the interpolation operation of the final lower limit value.

FIG. 18 is a view showing a conventional press brake.

[Explanation of symbols]

 Reference Signs List 1 table 2 ram 4 die (lower die) 5 punch (upper die) 10a to 10d ram drive device 11a to 11d servo motor 12 timing belt 13 ball screw 14a to 14d linear encoder 15a to 15d servo amplifier 16a to 16d brake 17 Correction brackets 18a to 18d Encoder 25 Angle measurement unit 28 Bending angle calculation unit 29 NC device 30 Processing condition input unit 31 Measurement position calculation unit 36 Drive-in amount calculation unit at each measurement position 37 Drive-in amount calculation unit in ram drive shaft

Claims (4)

[Claims] 1. A method of correcting a bending angle when a plate-shaped workpiece is bent by cooperation of a driving die driven by three or more driving shafts and a fixed die disposed to face the driving die. In addition to detecting the bending angle of the workpiece during the bending process,
The deviation between the detected bending angle and the target bending angle is determined at both ends of the work and at least three points in the center excluding the both ends, and the drive dies are driven into the axial positions of the respective drive shafts based on the determined deviation. A method for correcting a bending angle, wherein a correction value of an amount is obtained. 2. A press brake for bending a plate-like workpiece by cooperation of a driving die driven by three or more driving shafts and a fixed die opposed to the driving die, (A) storage means for storing the relationship between the working conditions of the workpiece, the springback angle with respect to the target bending angle of the workpiece, and the relationship between the amount of drive of the driving die with respect to the bending angle of the workpiece, and (b) the longitudinal direction of the workpiece during bending. Bending angle detecting means for detecting the bending angle of the work at at least three positions along the line, (c) the driving metal from the relationship between the processing conditions of the work stored in the storage means and the springback angle with respect to the target bending angle of the work. A temporary drive position for each drive shaft of the mold is calculated, and the bending angle of the workpiece detected by the bending angle detecting means at the temporary drive position. From the relationship between the degree and the springback angle with respect to the target bending angle of the work stored in the storage means and the relationship between the bending amount of the driving mold and the driving die drive amount, the correction driving of the driving die at the angle detection position is performed. Calculating means for calculating the amount; (d) interpolation calculating means for obtaining, by interpolation, the final driving position at each drive shaft position from the corrected driving amount calculated by this calculating means; and (e) the provisional driving of the driving die. A press brake comprising a mold driving means for driving to a final driving position after driving to a position. 3. A crowning correction value obtained from a difference in the amount of deflection of a table for supporting a fixed mold between a line connecting both ends of a work and a center portion, and a table of the crowning correction value and a table at both ends of the work. 3. The press brake according to claim 2, wherein a final drive-in position at each drive shaft position is calculated from a tilt amount correction value obtained from the deflection amount difference. 4. The table according to claim 2, wherein the bending angle detecting means is movably mounted in a longitudinal direction of the table along a rail provided on a front surface and / or a rear surface of the table supporting the fixed mold. Press brake as described in.