JPH09327727A - Bending of shape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve working precision and productivity by calculating a curvature radius/bending direction at an arbitrary position of a shape and a length from a working start position to an arbitrary position of a shape and deciding an action quantity of a moving die. SOLUTION: In the method that a shape 1 is bent to a stereoscopic three dimensional shape by pushing through bending with using a fixed die 2 and moving die 3, the coordinate values for objective bending shape are grasped in a three dimensional orthogonal coordinate system. A curvature and bending direction at an arbitrary position of the shape 1 is calculated as well as a length along stereoscopic three dimensional shape from a working start position to the arbitrary position of shape 1. At the timing a pushing in quantity is along three dimensional shape is calculated, a theoretical moving quantity of the moving die 2 is decided based on calculated curvature radius/bending direction. A moving quantity of moving die 3 is decided by multiplying a theoretical moving quantity with a correction coefficient due to the inherent spring back to material and shape of the shape 1, bending is continuously executed from the bending start position of shape 1 to completing position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for pushing and bending a shaped material such as an aluminum alloy used for building materials, automobile parts, etc. between a fixed mold and a movable mold.

[0002]

2. Description of the Related Art In order to press and bend a shape material such as an aluminum alloy, a fixed mold having an insertion opening having a shape substantially the same as the cross-sectional shape of the shape material and a movable mold are provided at regular intervals. It is placed and placed, and the movable die is moved in such a positional relationship as to give a predetermined bending shape between these two dies, and the shape member is pushed between the two dies to bend it into a predetermined bending shape. I was working. FIG. 1 shows such a push-through bending device, a so-called multi-bender. Reference numeral 1 is an aluminum shape member, 2 is a fixed mold, 3 is a movable mold, and the movable mold is displaceable in a plane perpendicular to an axis passing through the fixed mold and further shaped in a bending direction. The angle θ can be changed at a displaced position in this plane so that the material can be easily pushed through. In the figure, the movable mold is such that the curve of the bending process that passes between the two molds has a radius of curvature R that is the effect of the target bending curvature and the springback specific to the material of the shape and shape. Is moved so as to be displaced by the operation amount M, and in the bending process, the bending process is performed while the profile is being pushed between these two molds and passing therethrough. It should be noted that the angle θ of the movable mold is for allowing the shape member to be inserted smoothly, and the bending process is not performed by giving the angle. In addition, in this type of push-through bending device, generally, the operation mechanism of the movable mold is as follows. In FIG. 1, when the horizontal direction (the direction in which the shape member is pushed into the fixed mold) is x, the vertical direction is y, and the direction perpendicular to the paper surface is z, the movable mold is in the y-axis direction and the z-axis direction. The mechanism is movable and capable of rotation control around the x-axis, y-axis, and z-axis. The movable die can be rotated around the x-axis so that the profile can be twisted around the axis of the profile. In such a bending process, the movable die must be displaced and moved in a plane perpendicular to the axis of the fixed die in accordance with the curvature of a predetermined bend, but a simple bend or a bend with a certain curvature is required. In the case of machining, it is sufficient to confirm the machining conditions experimentally and set the displacement position and the amount of movement, but in bending along a three-dimensional three-dimensional shape, it is possible to push the profile and bend it in a predetermined manner. It is necessary to apply a bend along the shape, and sequentially perform the processing by determining the operation amount of the movable mold according to the curvature of the bend along the predetermined bend shape as the bending process progresses. However, for such a three-dimensional solid shape, the amount of movement of the movable mold is calculated by grasping the bending curvature and the bending direction that differ depending on the processing position (position in the longitudinal direction of the profile). It is difficult to achieve accurate bending by automatic control of the movable mold.

[0003]

SUMMARY OF THE INVENTION The present invention has been devised to solve such a problem. Bending of a shape material such as aluminum alloy is performed by a fixed mold and a movable mold. It is an object of the method to enable accurate push-through bending by automatic control according to a preset three-dimensional three-dimensional bending shape.

[0004]

According to the first aspect of the present invention,
In order to achieve the above-mentioned object, in a method of bending a shape into a three-dimensional three-dimensional shape by push-through bending using a fixed mold and a movable mold, a method of
By grasping the coordinate values in the three-dimensional Cartesian coordinate system, calculate the radius of curvature and bending direction of the profile at an arbitrary position, and also calculate the length along the three-dimensional shape from the processing start position to the arbitrary position. Then, when the pushing amount is a length along the three-dimensional shape, the theoretical operation amount of the movable mold is determined by the calculated radius of curvature and bending direction, and the theoretical operation amount is determined by the material and shape of the shape member. It is characterized in that the amount of movement of the movable mold is determined by multiplying the correction coefficient by the unique springback, and bending is continuously performed from the bending start position of the profile to the bending completion position. Thereby, the bending radius and the bending direction are geometrically calculated by the coordinate values in the three-dimensional solid coordinate system, and the three-dimensional solid bending can be performed by the automatic control. Further, in the invention of claim 2, a specific step in the method of bending the profile into a three-dimensional three-dimensional shape by the push-through bending according to the method of the first aspect is defined, and the first step is defined. A step of grasping the target bending shape as coordinate values in a three-dimensional XYZ three-dimensional coordinate system with the longitudinal direction thereof as the X-axis direction, and as a second step, from the bending start position P ₁ of the long material to an arbitrary position P _n The step of obtaining the integrated value L _n along the target bending shape by the coordinate values from P ₁ to P _n , and the third step is the P _n position in the coordinates where the coordinate values of the first step are projected on the XY coordinate plane and the XZ coordinate plane. As a fourth step of _{obtaining the} bending radii R _XY and R _XZ in P from the coordinates of P _n-1 , P _n and P _{n + 1} , the pushing direction of the shape member with respect to the fixed mold is orthogonal to the x axis and the x axis. Direction y
The z-axis is the direction orthogonal to the x-axis and the x-axis and the y-axis, and the pushing amount L _n from the machining start position while pushing the shape member into the fixed mold.
At the point of time, the movable die is moved in the y-axis direction and is rotated about the z-axis to determine an operation amount in which the spring back corresponding to R _xy is corrected, and the movable die is also moved in the z-axis direction and the y-axis. The amount of movement corresponding to the spring back corresponding to R _xz is determined by the rotation of the circumference, and at the point of the pushing amount L _n from the machining start position, the bending of the profile is started while operating the movable mold with the above amount of movement. From the position to the bending complete position,
Bending is performed by a process of continuously performing bending. Further, according to the invention of claim 3,
In order to correct the springback caused by the actual bending work, the correction coefficient C is calculated by the following equation to control the moving amount of the movable mold. C = {A × (Z × σ _0.2 ) +0.3} × 10 ⁻³ × R +
B where A is a coefficient in the range of (8 to 11) × 10 ⁻⁶ B is a constant in the range of 3.0 to 3.6 Z is an average value of the cross-section coefficients of the tension side and the compression side in the cross section of the shape member (Mm ³ ) σ _0.2 : 0.2% proof stress in tensile test (kgf / m
m ² ) R: radius of curvature of bending (mm) With this, it is possible to accurately obtain a correction coefficient when correcting springback, and it is possible to improve processing accuracy. Still further, according to the invention of claim 4, in the inventions of claims 1, 2 and 3, the theoretical rotation angle θ calculated geometrically according to the radius of curvature of the bending.
By setting the rotation amount of the movable mold to 45 to 55% of _t , it is possible to prevent wrinkles and buckling of the profile during bending. Note that here, the theoretical rotation angle θ _t is θ _t = 2 × tan ⁻¹ (M /
At the angle given by L), the profile is x from the exit of the fixed mold.
It is assumed that the movable mold and the tangential direction of the shape member passing through the movable mold are orthogonal to each other, assuming that they are drawn in the axial direction and draw an arc of a radius R toward the entrance of the movable mold and pass through the movable mold. The angle of rotation of the mold. According to the present invention, with such a configuration, it is possible to accurately and promptly perform displacement operation control of a movable mold for bending a three-dimensional three-dimensional shape.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the drawings. FIG. 3 shows a three-dimensional bent shape of the aluminum profile 1 which is the workpiece, which is set as a target in advance. FIG.
In, the longitudinal direction of the bent shape of the profile is approximately aligned with the X axis. The directions perpendicular to this are the Y and Z axes, respectively. 4 and 5 show the three-dimensional shape of the profile 1 to be processed as X.
The shape projected on the -Y and X-Z planes is shown by the central axis of the profile. The three-dimensional bending shape of the work material is these X,
It is given by the coordinate value P (x, y, z) in the Cartesian coordinate system of the Y and Z axes. In this case, if the movable die is given a movement amount (M), ignoring springback, etc., in FIG. 1, the profile is pushed in the x-direction, and when it exits the fixed die, it is in the x-direction. Immediately after that, it is bent by drawing an arc with a constant radius toward the movable mold. In addition,
In this specification, the movement amount (M) of the movable mold means the amount of movement from the position on the axis of the movable mold on a plane orthogonal to the axis (x) of the fixed mold. When the profile passes through the movable mold, the amount of movement of the movable mold at that time (M)
It is processed into an arc that fits in and comes out of the movable mold. This means that when the movable die moves through the movable die even if the movable die movement amount (M) changes after leaving the fixed die at an arbitrary position on the shape material and before leaving the movable die. It means that the bent shape after processing depends on the operation amount (M) of the movable mold at the time of exit from the movable mold, depending on the operation amount (M) of the movable mold. From the above, the amount of movement of the movable mold corresponding to the amount of pushing can be obtained, but the amount of pushing does not change the longitudinal length of the profile before and after bending, and follows the three-dimensional bending shape. It can be calculated from the length from the machining start position. By this, if the bending radius and bending direction of the shape at a predetermined position are known, the amount of movement of the movable mold with respect to the amount of pushing of the shape into the device is obtained, and the amount of movement corresponding to the predetermined amount of pushing can be moved. Just move the mold. In addition, the movement amount (M) of the movable mold is the X-shape of the three-dimensional solid coordinate system.
Calculated curvature radius at the predetermined position by the shape obtained by projecting the -Y and X-Z plane, the operation amount of the movable die in the y-axis direction (M _y)
And the z-axis movable die movement amount (M _z ) may be moved in both directions by the respective movement amounts. It should be noted that the amount of pushing and the amount of movement (M) of the movable mold corresponding thereto may be calculated continuously, but this calculation operation is performed at appropriate intervals to push the shape and move the movable mold. If this is done smoothly at this interval, bending can be performed with a minimum error.

That is, when viewed at arbitrary positions P (x, y, z) in the bending process, as shown in FIG. 3, subdivisions at these positions P ₁ , P ₂ , P ₃ ,. for each location, performs bending by controlling the relative operation amount of the fixed mold of the movable mold in accordance with the radius of curvature, sequentially P _2, P _3, and · · · P _n By advancing the processing, it is possible to perform bending processing into a preset three-dimensional shape. Therefore, when the length L between the adjacent positions P ₁ and P ₂ of the profile in the bending process is determined by the position on the X, Y, Z coordinates, the position P ₁ (P _1X , P _{1Y on the} XY coordinates is obtained. ) To the position P ₂ (P _2X , P _2Y ), the length L _XY is approximated by a straight line, and from these coordinates, L _XY = [(P _2X −P _1X ) ² + (P _2Y −P _1Y ). ² ] ^1/2 (1) Similarly, in XZ coordinates, the length L _XZ from the position P ₁ to the position P ₂ is L _xz = [(P _2X −P _1X ) ² + (P _2Z −P _1Z ) ² ] ^1/2 (2), the length L of the section P ₁ P ₂ of the profile in the three-dimensional solid shape of the X, Y, and Z axes can be obtained from the following formula. L = [(L _XY ) ² + (L _XZ ) ² ] ^1/2 (3) Therefore, the length from the processing start position in the three-dimensional bending shape at any bending processing position P _n of the profile is Is determined as the integrated value L _n .

Next, the radius of curvature R of bending at the position P ₂
Ask for. FIG. 6 shows a partially enlarged view in which a line segment passing between _three points P ₁ , P ₂ , and P ₃ on the curve representing the shape of the profile shown in FIGS. 3 to 5 is projected on the XY plane. The line segment between these points is point Q
Approximating an arc centered at (Q _X , Q _Y ) as a straight line P
The coordinates A (A _X , A _Y ) of the midpoint of ₁ P ₂ are the points P ₁ , P ₂
From the coordinates P ₁ (P _1X , P _1Y ) and P ₂ (P _2X , P _2Y ) of A _X = (P _1X + P _2X ) / 2 (4) A _Y = (P _1Y + P _2Y ) / 2 (5 ) Similarly, the coordinates B (B _X , B) of the midpoint of the straight line P ₂ P _3
Y ) is B _X = (P _2X + P _3X ) / 2 (6) B _Y = (P _2Y + P _3Y ) / 2 (7). The slope of the straight line P ₁ P ₂ is (P _2y −P _1y ).
/ (P _2x −P _1x ), and the slope of the straight line P ₂ P ₃ is (P _3y
−P _2y ) / (P _3x −P _2x ), and the gradient α of the straight line QA
, Since the straight line P ₁ P ₂ and QA are orthogonal, α = −1 × (P _2x −P _1x ) / (P _2y −P _1y ) (8) The slope β of the straight line QB is also the straight line P ₂ P _{Since 3} and QB are orthogonal to each other, β = −1 × (P _3x −P _2x ) / (P _3y −P _2y ) (9) In addition, two straight lines QA and QB passing through the point Q have a gradient α = Q _Y −A _Y / Q _X −A _X (10) Gradient β = Q _Y −B _Y / Q _X −B _X (11) Q _Y −A _Y = α (Q _X −A _X ) (12) ) Q _Y −B _Y = β (Q _X −B _X ) (13) Eliminating the unknown Q _Y , α (Q _X −A _X ) + A _Y = β (Q _X −B _X ) + B _Y (14) _{these, α · Q X -α · A} X + A Y = β · Q X -β · B X + B Y (15) Q X = (- β · B X + B Y + α · A X -A Y) / ( α-β) (16) Therefore, the x coordinate Q _X of the Q point is determined, and similarly, Q _Y
Is determined. Therefore, the radius of curvature R is as follows. _{R = [(Q X -A X} ) 2 + (Q Y -A Y) 2] 1/2 (17) Thus, (16) alpha in the equation, the beta (8), by substituting equation (9), By substituting this equation into equation (17), P
_The radius of curvature R at the P ₂ position can be obtained from the coordinate values of ₁ , P ₂ , and P ₃ . Also, these points P ₁ , P ₂ and P ₃ were calculated, but the two points P ₂ and P ₃ after these points were sequentially overlapped, and at the P ₃ position by P ₂ , P ₃ and P _4. By calculating the radius of curvature R, appropriate bending can always be performed.

Next, the theoretical operation amount M _y (movement amount in the y direction) of the movable mold with respect to the radius of curvature R when viewed on the XY plane is calculated as follows with reference to FIG. Immediately after exiting the fixed mold, the extruded profile exits in the x-direction, draws an arc of radius R until it enters the movable mold, is bent by the movable mold with radius R, and is continuously ejected. It is approximated as going. In this case, the center of this radius R is in the y-axis direction of the fixed mold outlet. The distance between the outlet a of the fixed mold and the center c of this radius R is R. Here, when the foot of a perpendicular line drawn from the center b of the movable mold in the theoretical motion amount M _y to the x direction, that is, the straight line ac is d, cbd is a right triangle, and ca = R and bd = L. ^{, cd = (R 2 -L 2} ) 1/2 M y = ad = R- (R 2 -L 2) becomes ^1/2. Since the above relationship holds in the X-Z coordinate system as well, the theoretical operation amount M _{z of} the movable mold in the Z-axis direction can be obtained. Using the movable die movement amounts in the Y-axis direction and the Z-axis direction calculated in this way, respectively, the radius of curvature on the XY coordinate plane and the curvature on the XZ coordinate plane at the integrated value L _n of the pushing amount. By calculating the theoretical operation amount of the movable die in the y direction and the theoretical operation amount of the z direction from the radius, it is possible to perform a three-dimensional three-dimensional shape bending process. These numerical processes are easily calculated automatically if a numerical value of a three-dimensional solid shape is given, which facilitates the operation amount of the movable mold for continuously and accurately performing bending. Can be obtained. still,
In the above description, the control method in which the target bending shape is decomposed into the XY coordinates and the XZ coordinates so as to perform the motion amount control of the movable mold in the y direction and the z direction and processed, is shown. The movable die may be directly operated in the bending direction after obtaining the bending direction.

The above-mentioned amount of movement of the movable die is a theoretical amount of movement derived from the geometrical three-dimensional shape of the shape material, but in actual bending, a springback peculiar to the material and the cross-sectional shape is applied. Therefore, it is necessary to correct these springbacks in order to accurately perform bending work on a target shape. That is, the present inventors previously proposed a correction method in the application of Japanese Patent Application No. 7-184793 by clarifying the relationship of the correction coefficient with respect to these springbacks. In FIG. 8, as shown by the relationship between the radius of curvature of bending and the amount of movement of the die, the amount of movement of the movable die for bending, that is, the theoretical amount of movement M _t , calculated by the above-described method to obtain the target shape Indeed there is a difference in movement amount between the mold operation amount M _a conducted to the bending shape the target for this difference corresponds to a so-called spring-back.

From the relationship shown in FIG. 8, the ratio of operation amount M _a / M
_When the relationship between _t and R is shown in the figure for each shape of various materials,
As shown in FIG. 9, it is represented by a straight line having an inclination peculiar to the material and shape of the shape member, and as shown in the drawing, each straight line passes through substantially one point B. From this, the theoretical operation amount M of the movable mold
the relationship between the radius of curvature of the bending ratio M _a / M _t execution operation amount M _a for _t experimentally obtained, it calculates the correction coefficient C by the equation shown below. C = α · R + B (18) where C: correction coefficient α: slope of straight line for each shape (b / a): see FIG. 9 R: radius of curvature (mm) B: horizontal axis obtained by experiment Intersection. 3.0 from the figure
A constant in the range of up to 3.6 By the way, although the slope of the straight line differs for each of these samples, the factors that influence the amount of springback are:
It can be seen as the 0.2% proof stress (σ _0.2 ) of the material, the section modulus (Z) and the bending radius R. When the relationship between the slope of the straight line and Z × σ _0.2 was obtained for these samples, the results shown in FIG. 10 were obtained. These relationships are also linear relationships and can be approximated by a linear function.
Is α = {A × (Z × σ _0.2 ) + D} × 10 ⁻³ (19) where A is the slope (x / y) of the straight line in FIG. 10, and 9.5 × 1
It is in the range of (8 to 11) × 10 ⁻⁶ with 0 ⁻³ as the midpoint. Z: Section modulus Z is represented by the average value on the tensile side and the compression side in the section of the profile (mm ³ ) σ _0.2 : 0.2% proof stress (kgf / mm ² ) D: The intersection of the straight line and the horizontal axis ( = 0.3) Therefore, from equations (16) and (17), C = {A × (Z × σ _0.2 ) +0.3} × 10 ⁻³ × R + B (20) Therefore, this correction coefficient is estimated. The operation amount M _t of the movable mold for bending is as follows. M _a = C · M _t By using the movable die movement amount obtained in this way, highly accurate bending can be performed.

Further, during the push-through bending as described above, at the operating position where the movable mold is displaced with respect to the solid mold, the rotation angle θ is centered on the intersection of the shape member central axis and the movable mold center line. Although the generation of wrinkles and buckling of the profile due to bending is prevented, the inventors of the present invention previously described that, at this rotation angle θ, the shape is formed by push-through bending using a fixed mold and a movable mold. When bending a material, 45 to 5 against the theoretical rotation angle calculated geometrically according to the bending radius
It has been found that setting the rotation amount of the movable mold to 5% makes it possible to bend an extruded shape member having good shape accuracy, and filed an application for Japanese Patent Application Laid-Open No. 7-353511. Therefore, also in the method of bending a three-dimensional shape of the present invention, the rotation angle θ of the movable mold is 45 to 45 with respect to the theoretical rotation angle geometrically calculated according to the bending radius.
By setting the rotation amount of the movable mold to 55%, it is possible to obtain a bent product having good shape accuracy by preventing buckling and wrinkling during bending.

(Embodiment) An embodiment is shown in FIGS.
It will be described below based on. FIG. 11 shows the X-Z coordinate plane projection coordinates of the target three-dimensionally bent profile, and FIG. 12 shows the XY plane projection coordinates. Table 1 shows movement amounts M _z and M _{y in} the z and y axis directions of the movable die in consideration of the correction coefficient calculated according to FIGS. 11 and 12, and the movable die rotation amount R around the y axis or the z axis. _z and R _y are shown. x _L is the pushing amount. As a result, the results of bending the ten shape members were measured, and the results were compared on the same coordinate plane as those of FIGS. 11 and 12. As a result, each sample had an error of several meters in each position coordinate.
m or less, and even the largest error is 8.5.
mm.

Table 1

[0014]

As described above, according to the present invention, it is possible to easily and accurately perform a bending process even on a three-dimensional complex shape. Since it is numerically represented, it becomes possible to automatically control the movable die, and it is possible to improve the processing accuracy and the productivity significantly.

[Brief description of drawings]

FIG. 1 Conceptual diagram of pushing and bending a shape member by a fixed mold and a movable mold

[Figure 2] Cross section of fixed mold

[Fig. 3] Three-dimensional shape of a frame in a three-dimensional coordinate system

FIG. 4 is a projection view of the three-dimensional shape of FIG. 3 on the XY plane.

5 is a projection view of the three-dimensional shape of FIG. 3 on the XZ plane.

6 is a partially enlarged view of FIG.

FIG. 7: Relationship between bending radius of curvature and amount of movement of movable mold

FIG. 8 shows the relationship between the radius of curvature of bending and the movement amount of the movable mold (execution movement amount / theoretical movement amount).

FIG. 9: Relationship between bending radius of curvature and movable die movement amount

FIG. 10 Relationship between slope α and z × σ _0.2

FIG. 11 is a projected coordinate position of the processed shape of the embodiment on the XZ plane.

FIG. 12 is a projected coordinate position of the processed shape of the embodiment on the XY plane.

[Explanation of symbols]

 1: Shape material 2: Fixed mold 3: Movable mold

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Sasamoto 1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Prefecture Nippon Light Metal Co., Ltd., Group Technology Center (72) Inventor Hino, Hinohara Kambara-machi, Anbara-gun, Shizuoka Prefecture 1-34-1 Nippon Light Metal Co., Ltd. Group Technology Center (72) Inventor Keiichi Sugiyama 2-22-20 Higashishinagawa, Shinagawa-ku, Tokyo Within Japan Light Metal Co., Ltd.

Claims (4)

[Claims] 1. A method of bending a shape into a three-dimensional three-dimensional shape by push-through bending using a fixed die and a movable die, wherein a coordinate value in a three-dimensional orthogonal coordinate system is set with respect to a target bend shape. Grasp and calculate the radius of curvature and bending direction of the profile at an arbitrary position, and also calculate the length along the three-dimensional three-dimensional shape from the processing start position to the arbitrary position, and the pushing amount is the three-dimensional shape. At the time of the length along the shape, the theoretical operation amount of the movable mold is determined by the calculated radius of curvature and bending direction, and the correction amount by the springback peculiar to the material and shape of the profile is added to the theoretical operation amount. A method for bending a profile, which comprises multiplying the amount of movement of the movable mold by multiplying and performing bending continuously from the bending start position of the profile to the bending completion position. 2. A method for bending a shape into a three-dimensional three-dimensional shape by push-through bending using a fixed die and a movable die, wherein the first bending step is a target bending shape whose longitudinal direction is the X-axis direction. the step of grasping the coordinate values in three-dimensional XYZ three-dimensional coordinate system in the, as a second step, the integrated value L _n along the intended bending shape from the bending start position P ₁ of the profile to the desired position P _n from P ₁ The step of obtaining the coordinate values up to P _n , and the third step is the coordinate values of the first step as the third step.
A step of obtaining bending radii R _XY , R _XZ at the P _n position in the coordinates projected on the Z coordinate plane from the coordinates of P _{n -1} , P _n and P _{n + 1.} The pressing direction of is the x-axis, the direction orthogonal to the x-axis is the y-axis, and the direction orthogonal to the x-axis and the y-axis is the z-axis, and the pushing amount L _n from the processing start position while pushing the profile into the fixed mold Move the movable mold to y
The movement amount in which the spring back corresponding to R _xy is corrected by the movement in the axial direction and the rotation about the z axis is determined, and the movable die is also set to R _xz by the movement in the z axis direction and the rotation about the y axis. A corresponding motion amount with the corrected springback is determined, and thus, at the time of the pushing amount L _n from the machining start position, the movable mold is operated with the above motion amount while continuously moving from the bending start position of the profile to the bending completion position. And a bending step, and a bending method for a profile, comprising: 3. The method for bending a profile according to claim 1, wherein a correction coefficient C for correcting the springback is calculated by the following equation to control the operation amount of the movable mold. C = {A × (Z × σ _0.2 ) +0.3} × 10 ⁻³ × R +
B where A is a coefficient in the range of (8 to 11) × 10 ⁻⁶ B is a constant in the range of 3.0 to 3.6 Z is an average value of cross-sectional coefficients of the tensile side and the compression side in the cross section of the shape (Mm ³ ) σ _0.2 : 0.2% proof stress in tensile test (kgf / m
m ² ) R: Curvature radius of bending (mm) 4. The rotation amount of the movable mold is set to 45 to 55% of the theoretical rotation angle θ geometrically calculated according to the radius of curvature of the bending. Bending method of the section shape.