JP3452431B2 - Bending machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bending machine capable of obtaining an accurate bending angle. 2. Description of the Related Art Conventionally, as a method for obtaining a predetermined bending angle by bending in a bending machine such as a press brake, the following method is generally used. [0003] 1). Input various processing data such as work material, die V-groove width, shape, bending length, bending position, target angle, and calculate the magnitude and distribution of the load acting on the frame based on this data. Predict. The amount of deformation generated in the frame is predicted from this load, and the amount of bending of the frame in the reverse direction is determined in advance so as to offset the predicted amount of deformation. 2). The amount of protrusion of the mold is input, and the control device controls the amount of protrusion of the mold to perform processing so as to obtain a desired bending angle. 3). 2). The bending angle is directly input instead of the amount of the die inserted in the procedure described in (1). However, the above-mentioned 1). In the above procedure, it is difficult to obtain a desired angle at a time because the calculation is complicated and the accuracy of prediction is low.
That is, it is necessary to perform bending with the value obtained by the above-described procedure once, actually measure the bending angle, and perform the calculation again using the value to perform the bending. [0007] In addition, 2). In the above procedure, the plunging amount of the mold and the absolute bending angle are not uniform. In other words, when the magnitude of the bending reaction force acting on the press brake changes due to changes in the V width of the mold, the material of the work, the plate thickness, and the like, the amount of protrusion of the mold to obtain the required angle also changes. This depends on the intuition of the operator. Further, the above 3). In this case, the bending accuracy is poor. There are problems such as. SUMMARY OF THE INVENTION An object of the present invention is to pay attention to the above-described conventional technology, and it is possible to perform high-precision bending by correcting deformation occurring in a frame of a bending machine. An object of the present invention is to provide a bending machine . SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the problems described above.
The lower part of the upper table fixed to the
And a punch provided at the bottom of the left and right side plates.
The movable table is provided on the upper part of a lower table.
A die that bends a workpiece in cooperation with a punch
Left and right cylinders for moving the lower table up and down,
Detecting the load acting during bending of the work
A stress sensor provided on each of the intermediate plates for
Left and right upper limit valves to stop raising the left and right cylinders
The crowning cylinder provided on the lower table
The above-mentioned stress sensors are provided when bending the workpiece.
Of the left and right side plates based on the pressure detected by the sensor.
Calculate the amount of elongation and the amount of displacement of the left and right upper limit valves and calculate the left deflection
Determine the correction amount and the right-side deflection correction amount, and
Calculating the lining pressure, the theoretical value obtained in advance and the left and right
When calculating the left and right target feed amounts based on the deflection correction amount,
To the crowning cylinder and the optimal crowning pressure
When the force is applied, the left and right cylinders are
A control device for controlling until the right target feed amount is reached
It is equipped . Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows the entirety of a press brake 1 as a bending machine. The press brake 1 has side plates 3L, 3R standing upright on the left and right sides of the main body. Also,
An upper table 5 is fixedly provided on the upper front surface of the side plates 3L, 3R, and a lower table 7 is provided on the lower front surface of the side plates 3L, 3R so as to be able to move up and down. At the lower end of the upper table 5, a number of intermediate plates 9 as a connecting plate are mounted, and a punch P is mounted via the intermediate plate 9. This intermediate plate 9
, For example, a stress sensor 11 is attached as a sensor for calculating a load acting during bending. A die D is mounted on the upper end of the lower table 7. Cylinders 13L and 13R as main driving devices are provided on the lower left and right sides of the lower table 7, respectively, and the lower table 7 is moved up and down by the cylinders 13L and 13R to cooperate with the punch P on the die D Bending is performed on the positioned work W. The bending angle in the bending process depends on the amount by which the lower table 7 rises.
It is determined by stopping L, 13R. A pair of crowning cylinders 15 as an auxiliary driving device are provided at the center of the lower table 7, and a control panel 17 as a control device is mounted on the front surface of the upper table 5. This control panel 17
Cylinders 13L and 13R and crowning cylinder 1
5 is controlled. Next, the procedure of bending will be described with reference to FIG. After the start (step S1), processing data such as a bending plate thickness, a mold shape, a target bending angle θ0, and the like are input using a keyboard of the control panel 17 (step S2). Subsequently, a theoretical value D0 of the amount of movement of the lower table 7 with respect to the target bending angle is calculated (step S3). Referring to FIG. 3A, the calculation of the theoretical value D0 is performed as follows. Here, it is assumed that the upper table 5, the lower table 7, the punch P, the die D, and the like do not deform due to the reaction force during bending. Further, it is assumed that the bending angle is geometrically determined from the position of the tip of the punch P and the position of the die D. Further, the lowering of the lower table 7 after the processing causes the spring D to return when the die D is separated from the punch P is θSB. Referring to FIG. 3B, since the angle .theta. At the time of bending and pressing is .theta. =. Theta.0 -.theta.SB, the amount of elevation of the lower table 7 such that the angle at the time of bending and pressing becomes .theta. D0 is determined geometrically. Here, θ0 is the finished angle. Next, when the lower table 7 is raised by D0, the load acting on the intermediate plate 9 is obtained by the stress sensor 11 (step S4), and the optimum crowning pressure F is calculated (step S5). Referring to FIG. 4, the optimum crowning pressure F is the amount of deformation Y1 of the upper table 5 due to bending load.
The displacement of the distance between the punch P and the die D due to the deformation amount Y2 of the lower table 7 is changed by the deformation amount Y3 (Y
1 + Y2 = Y3) to make the blade interval between the punch P and the die D constant. That is, referring to FIG. 4A, the deformation amount Y1 at the point i in the upper table 5 is given by: Here, fj: load applied to the j-th intermediate plate. Kji: Coefficient of influence of the force fj on the position of the ith intermediate plate of the upper table. Referring to FIG. 4B, the amount of deformation Y2 at the point i in the lower table 7 is given by: Here, fj: load applied to the j-th intermediate plate. Lji: Influence coefficient of the force fj on the ith intermediate plate position of the lower table. Referring to FIG. 4C, the deformation amount Y3 of the lower table 7 due to crowning is as follows: Y3i = Mi · F where F: crowning pressure. Mi: coefficient of influence of pressure F on the position of the ith intermediate plate of the lower table. From the above results, since the change amount δi of the distance between the upper and lower tables 5 and 7 at the position of the ith intermediate plate 9 is δi = ABS (Y1i + Y2i−Y3i), the optimum crowning pressure is the bending load. The crowning pressure F at which the sum of the squares of the change amounts is minimized at the intermediate plate position (n1 to n2) in which it is acting may be obtained. [Equation 3] A more optimal crowning pressure F can be determined. Returning to FIG. 1, the left-side deflection correction amount δD
L and the right-side deflection correction amount δDR are calculated (step S6). That is, when the distribution of the bending load is not uniform with respect to the center of the machine, the elongation amounts of the left and right side plates 3L and 3R and the stop position of the upper limit valve are deviated. Will not be constant. For this reason, the automatic tilt at the time of offset bending is performed by calculating the amount of extension of the side plates 3L and 3R and the amount of displacement of the upper limit valve from the intermediate plate load and making corrections. The left-side deflection correction amount δDL and the right-side deflection correction amount δDR are given by the following equations. δDL = D1 L + D2 L (1) δDR = D1 R + D2 R (2) where D1 L: extension of left side plate 3L D1 R: extension of right side plate 3R D2 L: displacement of left upper limit valve D2 R: Forces RL and RR acting on the side plates 3L and 3R are expressed by loads f1 to fn acting on the respective intermediate plates 9 in order to obtain the elongation amounts D1L and D1R of the displacement side plates 3L and 3R of the right upper limit valve. RL = ΣKLn · fn, RR = ΣKRn · fn where KLn is a coefficient representing the ratio of the intermediate plate load fn acting on the left side plate 3L KRn is a coefficient representing the ratio of the intermediate plate load fn acting on the right side plate 3R. , The extension amounts D1L and D1R of the side plates 3L and 3R due to the load fn of the intermediate plate 9 are as shown in FIG.
Assuming that the spring constants of R are CL and CR, respectively, D1L = CL-RL = CL-ΣKLn-fn D1R = CR-RR = CR-ΣKRn-fn On the other hand, the upper limit valve generally has a load as shown in FIG. -Since it has displacement characteristics, it is necessary to correct the difference in displacement amount. This characteristic curve is represented by the following cubic expression. D 2 L = a L · RL ³ + ^b L · RL ² + c L · RL + d L = GL (RL), D 2 R = a R · RR ³ + b R · RR ² + c R · RR + d
From the above, the left-side deflection correction amount δDL and the right-side deflection correction amount δDR are obtained from the above-described equations (1) and (2). Returning to FIG. 1, the target feed amounts DL and DR of the lower table 7 from the origin position are determined by the following equation (step S7). DL = D0 + δDL, DR = D0 + δDR Next, the lowering table 7 is raised by setting the crowning pressure F to the previously determined value (step S8), and the actual feed amounts of the left and right cylinders 13L and 13R become the target feed amounts. If it has reached (step S9), the bending process ends. If both the actual feed amounts on the left and right have not reached the target feed amounts, the lower table 7 is further raised by the left and right cylinders 13L and 13R (step S1).
0). If only the left side does not reach the target feed amount, only the left cylinder 13L is used (step S11). If only the right side does not reach the target feed amount, the right cylinder 13L is used.
Only 3R is further operated (step S12). Then, the processes after the calculation of the intermediate plate load (Step S4) are repeated again, and the lower table 7
Keep rising. As described above, the actual load is obtained for each intermediate plate 9 and the deformation of the side plates 3L and 3R with respect to the actual load is calculated to correct the amount of rise of the lower table 7, so that the target bending angle can be accurately determined. Processing can be performed. In addition, the automatic tilt function for automatically adjusting the gap between the punch P and the die D eliminates the need to input a bending position even in the case of offset processing. As described above , according to the present invention,
Correct the extension of the left and right side plates and the displacement of the left and right upper limit valves.
Position of the punch and die off the center
In this case, appropriate bending can be performed .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart showing a procedure of a bending method in a bending machine according to the present invention. FIG. 2 is a perspective view showing the entirety of a general press brake as a bending machine. FIG. 3 is an explanatory diagram showing a relationship between a table movement amount and a bending angle when there is no deformation of a side plate or the like. FIG. 4 is an explanatory diagram of crowning correction. FIG. 5 is a graph showing spring constants of left and right side plates. FIG. 6 is a graph showing characteristics of an upper limit valve. [Description of Signs] 1 Press brake (bending machine) 3 Side plate 5 Upper table 7 Lower table 9 Intermediate plate (connecting plate) 11 Sensor 13 Cylinder (main drive unit) 15 Crowning cylinder (auxiliary drive unit) 17 Control panel ( Controller) P Punch D Die

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B21D 5/02

Claims (1)

(57) [Claims 1] On the left and right side plates (3L, 3R) which are erected.
At the lower part of the upper table (5) fixed to the
A punch (P) provided through a plate (9),
Vertically movable below the side plates (3L, 3R)
The punch (P) provided above the lower table (7)
Die (D) that bends the work (W) in cooperation with
And left and right for vertically moving the lower table (7).
Cylinder (13L, 13R) and folding of the work (W)
Each of the above to detect the load acting during bending
A stress sensor (11) provided on an intermediate plate (9);
Stop raising the left and right cylinders (13L, 13R)
Left and right upper limit valves and the lower table (7)
A crowning cylinder (15).
Stress sensor (11) at the time of bending the workpiece (W)
The left and right side plates (3
L, 3R) and the displacement of the left and right upper limit valves are calculated.
Deflection correction amount (δDL) and right deflection correction amount
(ΔDR) and calculate the optimal crowning pressure
And the previously determined theoretical value (D0) and the right and left deflection correction
The left and right target feed amounts (D) are determined by the amount (δDL, δDR).
L, DR) and the crowning cylinder
(15) with the optimum crowning pressure applied
The left and right cylinders (13L, 13R)
Control until the right target feed amount (DL, DR) is reached.
Characterized by having a control device for the bending
Machine .