JPH0688083B2 - Split mold for bending and knitting method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a mold used for bending a plate and a knitting method thereof. More specifically, the present invention is a split mold in which the mold width can be changed according to the bending width of a plate material, and particularly a split mold effective for use in folding machines such as folding machines, bending machines, and press brakes. And a method of organizing the same.

(Prior Art) For a cabinet, a showcase, a vending machine, a refrigerator / freezer, a panel, a sink, a switchboard, etc., a metal plate whose edge is bent into a U shape or a Z shape is used. In order to fold a plate material in this way, usually, after bending the short edge side edge of the work cut into a predetermined size shape, the work (hereinafter referred to as blank) is turned in a plane and aligned with the inside of the short side bend. It is made by fitting the upper mold to the folding width and bending the long side edges. When bending the long side by, for example, the wing method, there is a rise due to the bending of the short side that has already been bent, so the clamp type (upper type) has a length obtained by subtracting two blank plate thicknesses from the long side length. Therefore, it is necessary to prepare a large number of upper molds having different mold widths, and to replace the upper molds each time the blank width changes, which requires time and effort. Moreover, much of this work relies on manual work, which prevents automation of folding machines, eg NC, CNC control. Therefore, a split type and its exchanging device suitable for automatic control have been desired.

As a folding split type that meets this demand, for example, the type shown in Japanese Utility Model Laid-Open No. 59-44616 is known. As shown in FIG. 4, this mold exchanging device includes an upper mold body 101 attached to the lower end of a ram, a split upper mold 102 that is slidable in the lower part of the upper mold body 101 in the mold width direction, and is reversible. Of a large number of thin upper mold 103, a select claw drive mechanism 104 provided in the front part of the upper mold main body, and a reversing mechanism 105 for reversing a predetermined number of thin thin upper molds 103, of a portion exceeding the working width. The split upper die 102 is moved by the select claw 106 from the processing position, that is, moved outward along the upper die body 101,
In addition, a series of upper molds are formed in the center by the width of the inverted thin upper mold 103 so that the molds can be automatically and easily replaced.

(Problems to be Solved by the Invention) However, this mold exchanging device has one split upper die 10
When pulling out a desired number of thin wall upper molds 103 from a group of thin wall upper molds 103 prepared for the purpose of adjusting a value that cannot be divided by 2, a predetermined number of thin wall upper molds 103 are used as a reference. Since the mold 103 is picked up and inverted by the spline shaft 107, the divided molds cannot be distributed symmetrically with respect to a certain reference plane, for example, the machine center.

That is, since the center of the mold is not always constant and moves depending on the selected number of the thin upper molds 103, it is necessary to align the blank center, that is, the machine center with the mold center each time, which is very inconvenient.

Also, if such a center position correcting means is not provided,
The gap between the split upper mold 102 located at both ends and the blank material becomes large to the width of the thin upper mold (usually around 5 mm), which causes "edge blurring" during bending of the blank material. There is fear.

Therefore, an object of the present invention is to provide a splitting die for bending and a knitting method thereof, which can prevent the occurrence of ridge line blurring of a workpiece by automatically allocating the workpiece symmetrically with respect to the center of the processing machine. .

[Structure of the Invention] (Means for Solving the Problems) In order to achieve such an object, the splitting die for bending according to the present invention is a splitting die incorporated in a bending apparatus, and is a width direction of the die. Having a pair of block bodies screwed into a screw rod along the, along with the rotation of the screw rod from the reference surface of the bending device movable in the opposite directions along the width direction in the same amount, and, A pair of block molds having variable mold widths, a large number of segment molds composed of thin plates divided in the width direction, and a number of the segment molds corresponding to the distance between the block molds are extracted to obtain the block And a reversing mechanism for reversing and inserting between the molds, wherein the reversing mechanism supports each of the segment molds and is connected to the extracted segment molds to extract the segment molds. And a reversing shaft for reversing only one, and holding the whole group of segment molds connected to the one block mold along a direction toward the other block mold, and interlocking with the movement of the one block mold. A segment holder that moves the entire group of segment dies along the inversion axis, and a segment holder that is provided between the inversion axis and the group of segment dies and has a quantity corresponding to the distance from the reference surface to each of the block dies. A segmenting die for connecting a segmenting die, which has a segmenting die selecting and connecting means for selecting the same number of the segmenting die from the reference surface in the opposite direction along the width direction and connecting to the reversing shaft. Is.

Further, in the group of segment dies as a whole, when each of the block dies is located on the reference plane, one end of both ends of the group of segment dies corresponding to the one block die side is located on the reference plane. Is held by the segment holder, the segment type selective connecting means is attached to the reversing shaft, and the segment type that moves beyond the reference plane with the movement of the segment holder is moved with respect to the reversing shaft. The fixed key to be connected and the segment type of the same number as the segment type that is attached to the reversing shaft so as to move back and forth so as to move in the opposite direction to the moving direction of the segment holder at the same time And a movable key for connecting to the inversion axis.

Further, the method for knitting the splitting dies for bending according to the present invention is such that, when a bending die having a desired width is formed by combining a pair of block dies and a segment die made of a thin plate, the block dies are simultaneously moved in opposite directions. While moving the same amount to the position from the center of the mold to an integer multiple of the plate thickness of the segment mold, an integer number of segment molds between them are extracted from the same number of segment mold groups in opposite directions from the mold center. Then, it is thrown in and it is made to constitute a bending die.

(Operation) In the present invention having such a configuration, when the die width is changed, the reversing mechanism is operated to invert the segment die, and then the changed dimension of the die width is set to the left and right from the die center. The pair of blocks are moved so as to be divided into units, and then the segment type corresponding to the distance between the two block types is selected and the segment type is inverted again by the inversion mechanism so as to be inserted between the blocks. As a result, the center position of the die is always constant even if the die width is changed, and the gap between the die and the work is evenly distributed on both sides, so that the occurrence of ridge blur can be prevented.

(Embodiment) The configuration of the present invention will be described in detail below based on an embodiment shown in the drawings. The present embodiment is applied to the upper die of a folding machine (folding machine).

1 (A) and 1 (B) are front views showing the principle of a split mold for bending according to an embodiment of the present invention, and FIG.
Shows the state before the segment inversion insertion at the maximum die width, and FIG. 1 (B) shows the state with the minimum die width. Figure 2 shows
FIG. 3 is a vertical cross-sectional view showing the folding split die according to the embodiment, and FIG. 3 is a vertical cross-sectional view showing the principle of a folding machine to which the split split die according to the embodiment is applied.

First, as shown in FIG. 3, the folding machine is a blank consisting of an upper die 31 attached to a ram 34 and moving up and down, and a lower die 32 fixed to a frame 35 constituting the body of the folding machine. A holder 33, a rocker arm 37 having a blade 36 for bending the protruding tip edge W ₁ of the blank W held by the holder 33 in the vertical direction at the tip, and a drive for swinging or horizontally moving the arm 37. It is mainly composed of actuators 38, 39, 40 and a main body frame supporting them.

Of the blank holders 33, either one of the molds, usually the upper mold 31, can be moved up and down in order to move the blank W in and out, and the mold width can be changed to correspond to the blank width. As the upper die 31, the bending split die of the present invention can be applied.

1 (A) and 1 (B) show a principle view of a splitting die for bending according to the present invention as seen from the front. This bending split mold (hereinafter simply referred to as split mold) is a group of segment molds 1 composed of thin plates finely divided in the width direction, and a pair of block molds 2A, 2B and segments located at both ends of the segment mold 1. A predetermined amount of mold 1 is extracted and the block molds 2A, 2
And a reversing mechanism 3 inserted between B. The reversing mechanism 3 includes a reversing shaft 4 that supports the segment mold, a segment holder 9 that moves the segment mold 1 along the reversing shaft 4, and a set that selectively connects the reversing shaft 4 and the segment mold 1. Selection keys 5A, 5B (corresponding to segment type selection connecting means) and segment type 1 deviated from the selection keys 5A, 5B
It is composed of stoppers 6 and 7 for fixing.

The segment mold 1 is composed of a thin plate obtained by finely dividing a bending mold having a desired shape in the width direction (hereinafter simply referred to as width direction or mold width direction), for example, a thin plate having a wall thickness of about 5 mm, and collecting a large number in a stack in the width direction. Thereby, the main part of the bending split mold is formed. This segment mold 1 is attached to a reversing shaft 4 of a reversing mechanism 3 which is rotatably supported by an upper mold body 8 mounted on a processing machine body, for example, a ram 34,
It is supported so as to swing in a plane orthogonal to the mold width direction. The group of segment types 1 and the above-described reversing shaft 4 are selectively connected by a pair of selection keys 5A and 5B, and have a relation in which an arbitrary quantity is interlocked. The group of segment dies 1 is held by a segment holder 9 that constitutes the reversing mechanism 3, and is provided so as to be movable in the width direction along the reversing shaft 4.

The segment holder 9 is attached to the upper die body 8 with a sliding gib 10 and is provided slidably in the die width direction. The segment holder 9 is connected to one of the block molds 2A, and holds the entire group of segment molds 1 along the direction toward the other block mold 2B. Therefore, the segment holder 9 is driven by the block mold 2A in association with the movement of the one block mold 2A, and moves the entire group of segment molds 1 along the reversing shaft 4.

A feed shaft that holds a movable key (one of selection keys) 5B that penetrates the reversing shaft 4 and feeds it in the width direction inside the reversing shaft 4.
11 built-in. The feed shaft 11 is supported by a cylindrical bearing 12 interposed between the feed shaft 11 and the reversing shaft 4 and is provided so as to be movable only in the axial direction by a slide key 13 mounted between them. A first screw rod 15 is screwed into the hollow portion 14 at the tip of the feed shaft 11, and is provided so as to be movable in the width direction by the rotation of the screw 15. In order to allow the movable key 5B to move in the axial direction, the reversing shaft 4 is provided with a long groove 16 in the axial direction, and the movable key 5B is accurately moved in the width direction, that is, the axial direction of the reversing shaft 4 by using this as a guide. It is provided to do. Also,
A gear 17 is fixed to one end of the reversing shaft 4 and meshes with a rack rod 18 driven by a hydraulic cylinder (not shown). Therefore, the reversing shaft 4 is rotated by a predetermined angle, for example, 180 ° by the linear drive of the hydraulic cylinder.

The pair of block molds 2A and 2B located at both ends of the segment mold 1 are rotatably supported by the upper mold body 8
By being respectively supported by the screw rods 19 and slidably fitted to the segment holders 9 via the sliding gibs 27, along with the rotation of the second screw rods 19, the die center O is moved in the width direction. At the same time, they are provided so that they can move linearly in the opposite directions by the same amount. The block molds 2A and 2B are composed of a block body 20 and a movable piece 21 that is attached to the block body 20 so as to be swingable in the mold width direction.
By making the movable piece 21 the outer edge portion of the block molds 2A, 2B, the mold width is made variable. That is, the movable piece 21 is attached to the block main body 20 so as to be swingable in the width direction by the pin 22, and is normally biased downward by the compression coil spring 23, that is, directed downward in the vertical direction. Therefore, when closing the mold, the movable piece
The width of the block molds 2A and 2B is different between when the mold is closed and when the mold is opened, because the block 21 contacts the blank W and rotates so as to be expanded outward. Only restored to its original size. Here, the movable piece 21 is provided so that the upper surface 21a of the front and side, 21b forms the inclined surface, does not interfere with the blank leading edge W ₁ and the side edge W ₂ which is folded. Further, the movable piece 21 is attached such that the bottom surface is flush with the block body 20 when the mold is closed, and the front inclined surface 21a and the side inclined surface 21b portions project from the block body 20, respectively.

Second screw rod 19 supporting the block type 2A, 2B
The left and right are threaded with the same pitch, and their rotations give the left and right block types 2A and 2B a movement toward or away from each other. The second screw rod 19 and the first screw rod 15 are timing belts.
They are connected by 24 and rotate synchronously by the rotation of the drive motor 25. Therefore, the screws of the first screw rod 15 and the second screw rod 19 in the reversing shaft 4 in the left side region in the figure are cut in the same direction at the same pitch, and the movable key 5B and the block type 2B on the left side in the diagram are in the same direction at the same time. It is provided to move the same amount to.

Further, the upper die body 8 is provided with a stopper 6 for preventing the segment die 1 released from the selection keys 5A, 5B from freely rotating and rotating toward the block dies 2A, 2B. The stopper 6 is a sliding key that fits into the notch 26 formed on the back surface of the segment mold 1, and is the maximum width at which all the segment molds 1 can be inverted and inserted between the block molds 2A and 2B. In a state where the segment molds 1 are arranged in equal amounts to the left and right from the mold center O (see FIG. 1A), the segment molds 1 extend to the position closest to the leftmost segment mold 1. Therefore, the stopper 6 is in a relationship of slipping into the notch 26 and restraining the segment die 1 at the same time when the leftmost segment die 1 is disengaged from the selection keys 5A and 5B. A stopper 7 is also provided on the block mold 2B. The stopper 7
Is to prevent the segment die 1 from freely rotating when it is disengaged from the selection keys 5A and 5B between the tip of the stopper 7 and the machine center O, and is a quarter-circle formed integrally with the block die 2B. It is a receiver. Although these stoppers 6 and 7 are effective for reversing and inserting only the desired number of segment molds 1, they can be replaced by means such as increasing the reversing angle to prevent rotation due to their own weight.

As shown in FIG. 1B, when the block molds 2A and 2B are respectively located at the mold center O, one of the both ends of the group of segment molds 1 is one of the segment molds 1 as a whole. It is held by the segment holder 9 so that one end corresponding to the block mold 2A side is positioned at the mold center O.

The selection keys 5A and 5B as the segment type selection connecting means are
The segment dies 1 provided between the reversing shaft 4 and the group of segment dies 1 and having a quantity corresponding to the distance from the die center O to each block die 2A, 2B are reversed from each other along the width direction from the die center O. The same number is selected in the direction and connected to the reversing shaft 4.

More specifically, the selection keys 5A and 5B are a kind of slide keys that can slide relatively smoothly with respect to the segment mold 1, and in FIG. And a fixed key 5A located on the right side, and a movable key 5B located on the left side when facing. The fixed key 5A is fixed to the reversing shaft 4, and moves along the segment holder 9 beyond the mold center O to the right side in the drawing.
Are connected to the inversion axis 4. On the other hand, the movable key 5B is attached to the reversing shaft 4 so that when the group of segment holders 9 moves in the width direction in conjunction with the block mold 2A, the segment keys 9 simultaneously move in the opposite direction to the moving direction by the same amount. It is mounted so that it can move back and forth. Also, this movable key 5B
Moves in the opposite direction by the same amount as the movement of the segment holder 9, so that the same number of segment dies 1 as the segment dies 1 that have moved to the right side in the drawing beyond the die center O are connected to the reversing shaft 4. It will be.

Therefore, the group of segment holders 9 is a block type 2A.
When moving in the width direction in conjunction with, by the fixed key 5A,
Segment mold 1 moving to the right in the figure from the mold center O
Is connected to the reversing shaft 4 and moved by the same amount in the direction opposite to the moving direction of the segment mold 1 by the movable key 5B, which is located on the left side of the mold center O in the drawing and is connected by the fixed key 5A. The same number of segment type 1 as the inversion axis 4
Connected to. In this way, the segment molds 1 of the same amount are extracted from the machine center O in the horizontal direction in the drawing.

The above-described embodiment is merely an example, and can be modified as appropriate without departing from the scope of the present invention. For example, the selection keys 5A and 5B of the reversing mechanism 3 may be plural, and may be replaced with a spline shaft or the like. Further, the segment type selective connecting means of the reversing mechanism 3 is constituted by a member which has a selection key of the same width as the segment type 1 which arbitrarily projects in the radial direction and which projects leftward and rightward from the center of the die toward the end by the same amount. Alternatively, the segment mold 1 may be selectively connected to the reversing shaft 4. Further, in the present embodiment, the segment mold 1 is inverted and inserted into the block molds 2A and 2B, but the segment mold arbitrarily extracted may be moved up and down and thrown in between the block molds 2A and 2B. good. Further, in the present embodiment, the variable width type having the movable pieces 21 is adopted as the block types 2A and 2B at both ends, but the width adjustment type (illustrated in the figure is movable between the block type and the segment type). It is also possible to make the block type into a fixed width type in which the movable piece 21 is not provided by interposing (omitted).

Although the above embodiment is an example applied to a folding machine, it can be adopted as a split type for other bending machines such as a press brake and a bending machine.

Next, the operation of this embodiment will be described.

According to the split mold configured as described above, the bending work of the plate-shaped work W can be performed by a simple operation as follows.

For example, width 700mm with both edges already bent, thickness 0.5mm
Explaining the case of bending the leading edge of the plate blank W of No. 1, the mold width l of the upper mold is: l = L−2t−2α where L: outer width of blank t: plate thickness α: gap (equal distribution on both sides) Therefore, l + 2α = 700− (2 × 0.5) = 699 mm. In this case, block type 2
The maximum width of A and 2B is 200 mm. So block type on both ends
Subtracting the maximum width 200 mm x 2 for 2A and 2B, the maximum width for segment mold 1 is 299 mm. If the width of one segment mold is 5 mm, the desired number of segment molds is 299/5.
= 59.8, but if you round off the fractional 0.8 to make 59, α = 1/2 {700- (2 x 200)-(2 x 0.5)-(59 x
5)} = 2mm, but a gap of about 2mm is acceptable for practical bending work. The die width l is cut off at a pitch of 5 mm for one segment die.

This extraction of the segment mold 1 moves the entire segment mold 1 to the left side in the figure by rotating the first and second screw rods 15 and 19 according to a program in advance, and at the same time moves the movable key 5B to the right side in the figure. Move by the same amount, pick up 147.5 mm each from the center O of the processing machine, that is, 59 segment dies 1. The segment type group 1 on the left side, which is out of the selection keys 5A and 5B, is the upper die body 8 or the block type 2B.
Immediately engages with the stoppers 6 and 7 attached to the shaft to prevent free rotation.

After a predetermined number of segment molds 1 are selectively extracted from the group of segment molds 1, the drive cylinder at one end of the reversing shaft 4 is operated, and the reversing shaft 4 is normally rotated by a predetermined angle by 180 ° to extract the segment molds. Invert the group of 1. At this time,
Since the block dies 2A and 2B at both ends are also moved in the opposite directions by the same amount by the action of the second screw rod 19 which is synchronously rotated by the timing belt 24, a gap of the same amount as the die width of the extraction segment die 1 is formed. It is provided. Therefore, the extracted segment mold 1 is inverted and inserted between the block molds 2A and 2B to form an upper mold of a predetermined width. At this time, the inverted segment mold 1 contacts the sliding gib 27 attached to the segment holder 9 for positioning.

Then, when the upper die 31 is lowered by the operation of the ram 34, the die is closed and the plate-shaped blank W placed at a predetermined position is pinched. At that time, the block mold on both ends of the upper mold 31 descending
Since the movable piece 21 of 2A, 2B is pushed down to the lower die 32 side by the action of the spring 23 to reduce the die width, the lateral bending edge W ₂ of the blank W interferes with the both-end block die 2A, 2B. The mold can be inserted without The block dies 2A and 2B avoiding the side bent portion W ₂ of the blank W are automatically expanded to the original die width because the movable piece 21 abuts on the blank W and is relatively expanded upward. Spread it out and hold the blank W. Therefore, the upper mold can be obtained by extracting a desired number of segment molds 1, reversing and inserting between the block molds 2A and 2B, and then merely lowering the molds without interfering with the side edge W ₂ of the bent blank W. It is possible to construct an upper mold which is closed and has a predetermined width. Moreover, in the present apparatus, the upper die length is always distributed by the same amount to the left and right of the machine center O, so that it is not necessary to perform alignment with the mounted blank W.

After closing the mold, the bending arm 37 is swung to bend the tip of the blank into a predetermined shape. After the desired bending process, the ram 34 is lifted to raise the entire upper die 31 slightly, and then the blank W is extruded forward so that the front inclined surface 21a of the block dies 2A, 2B is bent when the blank front end edge is bent. W
Make sure that it does not interfere with _1, and then raise it again to the rising end. Then, prepare for the next processing.

When the operation of the cylinder, the drive motor 25, etc. is performed by NC control or CNC control, this kind of work can be automated.

[Effects of the Invention] As is clear from the above description, according to the folding split mold and the knitting method thereof of the present invention, the center of the processing machine and the center of the mold are automatically matched regardless of the mold width. It is possible,
Therefore, if the blank is preliminarily positioned in the center of the machine and fed, the bending work can be performed without performing the centering operation at the same time when the blank is put in, and thereby the occurrence of the ridge blur can be prevented.

For this reason, it is necessary to store various information about blanks, such as dimensions, shape, bending conditions, work procedure, etc.
With NC control and CNC control, it is possible to knit the mold to the desired width and proceed to the next bending process immediately after one bending operation is completed, and it is possible to realize efficient production of various small quantities. .

Moreover, since the movement of the mold is reversed and the movement in the width direction is simple and there are few moving parts, the number of actuators required is small and the cost can be reduced, and automation by NC, CNC control, etc. is facilitated.

[Brief description of drawings]

FIG. 1 is a principle view showing an embodiment of a splitting die for bending according to the present invention when viewed from the front. (A) shows a state before segment reversal insertion at the maximum die width, and (B) shows a minimum die width. The states are shown respectively. FIG. 2 is a transverse sectional view of the same split type. FIG. 3 is a principle view showing the outline of a plate bending machine to which the split mold of the present invention is applied, and FIG. 4 is a front view showing the outline of the conventional split mold. 1 …… Segment type, 2A, 2B …… Block type, 3 …… Inversion mechanism, 4 …… Inversion axis, 5A, 5B …… Selection key (Segment type selection connecting means, 5A …… Selection key fixed key, 5B ...... Movement key of selection key), 9 ... Segment holder, 15,19 ... Screw rod, 20 ... Block body, 21 ... Movable piece, 23 ... Spring, O ... Machine center, Mold center (reference) surface).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigemi Ono 3-27-3, Kanda Sakumacho, Chiyoda-ku, Tokyo SJ Yapan Co., Ltd. (72) Inventor Akiri Suzuki 5-36, Shimomeguro, Meguro-ku, Tokyo No. 42 (56) Reference JP 57-149026 (JP, A) JP 58-148021 (JP, A) JP 59-225827 (JP, A) JP 59-44616 (JP, A) A) JP-A-55-136517 (JP, A) JP-A-61-206526 (JP, A) Nikkan Kogyo Shimbun "Press Technology" June 1983 Extra number Vol. 21 No. 7 P. 131-136 "FMS of sheet metal line" (Toshio Hongo)

Claims (3)

[Claims] 1. A split mold incorporated in a bending apparatus, comprising a pair of block bodies (20, 20) screwed to a screw rod (19) along the width direction of the mold, the screw rod Along with the rotation of (19), a pair of block dies (which can move the same amount in opposite directions along the width direction from the reference plane (0) of the folding device and have a variable die width ( 2
A, 2B), a number of segment molds (1) made of thin plates divided in the width direction, and a number of the segment molds (1) corresponding to the distance between the block molds (2A, 2B) are extracted. , The block type (2
And a reversing mechanism (3) for reversing and inserting between A and 2B). The reversing mechanism (3) supports each of the segment molds (1) and is connected to the extracted segment mold (1). And an inversion axis (4) that inverts only the extracted segment type (1), and the entire group of segment types (1) connected to the one block type (2A) to the other block type (1). 2B) is held along a direction toward the block holder (2A), and the group of segment dies (1) is moved along the reversal axis (4) in conjunction with the movement of the one block die (2A). 9) and between the reversal axis (4) and the group of segment molds (1), the number of which corresponds to the distance from the reference surface (0) to each of the block molds (2A, 2B). Use the segment type (1) with the reference plane ( 0) and segment type selective connecting means (5A, 5B) for selecting the same number in opposite directions along the width direction and connecting to the reversing shaft (4). Split type. 2. In the group of segment types (1) as a whole, each of the block types (2A, 2B) is the reference plane (0).
The segment holder (9) so that one end corresponding to the one block mold (2A) side of both ends of the group of segment molds (1) is positioned on the reference plane (0) when positioned. The segment type selective connecting means (5A, 5B), which is held, is attached to the reversing shaft (4) and moves beyond the reference plane (0) as the segment holder (9) moves. The fixed key (5A) connecting (1) to the reversing shaft (4) and the reversing shaft (4) so as to simultaneously move the same amount in the opposite direction to the moving direction of the segment holder (9). A movable key (5B) that is attached so as to move back and forth, and connects the same number of segment dies (1) as the segment dies (1) that have moved beyond the reference plane (0) to the reversing shaft (4). Claim scope characterized by having Bending for split according to paragraph 1. 3. When a bending die having a desired width is formed by combining a pair of block die (2A, 2B) and a segment die (1) made of a thin plate, the block die (2A, 2B) is simultaneously formed. While moving the same amount in mutually opposite directions to transfer from the mold center (0) to a position of an integral multiple of the plate thickness of the segment mold (1), an integer number of segment molds (1) are placed between these mold centers. A method of knitting split dies for bending, which comprises extracting a same number from (0) in the opposite direction from a group of segment dies and putting them in to form a fold.