JP2001137954A - Bending method and bending machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bending method and a bending machine capable of preventing a die from breaking and an overload from applying to a machine. SOLUTION: When an upper frame 3U is moved up/down and a work W is clamped with a press die 11 of the upper frame 3U and a support die 15 of a lower frame 3L, at the state the work W does not exist, the pres die 11 is abutted on the support die 15, the distance between the press die 11 and the support die 15 is measured by a measuring means 31 and is set as zero. The distance between the press die 11 and the support die 15, when the work W is actually clamped, is measured by a measuring means 31, a comparison/ discrimination part 61 of a NC device 51 compares the measured distance and the reference value for a plate thickness of the work W which is inputted into a memory 59 of the NC device 51, when discriminating the measured distance is larger than the reference value, working is immediately stopped as discriminating the work W is not carried in by one sheet in a normal way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bending method and a bending machine.

[0002]

2. Description of the Related Art Conventionally known bending machines include those shown in FIGS. 9 and 10. FIG.

Referring to FIG. 9, in this bending machine 101, a rotating shaft 107 is provided on a bracket 105 projecting upward above a rear end (left end in FIG. 9) of a lower frame 103L. An upper frame 103U as a holding ram is provided on the rotating shaft 107 so as to be vertically swingable.

A plate holding plate 109 is provided at the front end of the upper frame 103U, and a holding die 111 is attached to a lower end of the plate holding plate 109. A front plate 113 is provided at a front end of the lower frame 103L, and a receiving mold 115 is attached to an upper end of the front plate 113. The hydraulic cylinder 17 for clamping is provided rotatably by a pin 120 at the lower end.

[0005] A hydraulic cylinder 117 for clamping is provided on the lower frame 103L facing upward, and the tip of a piston rod 119 is attached to the upper frame 103U.

[0006] In a space 121 between the lower frame 103L and the upper frame 103U, a bending die 123 having a generally U-shape is provided. A piston rod 12 of a hydraulic cylinder for bending 125 attached upward to the lower frame 103L is provided on the lower surface of the bending die 123.
7 tips are attached. Also, the bending mold 123
A bending die moving mechanism 129 for swinging the bending die 123 back and forth is provided on the rear surface.

The above-mentioned dies 111, 115, 123
Has a strength and a shape that can correspond to the maximum thickness of the work W to be bent.

Accordingly, the upper frame 103U is vertically rotated about the rotating shaft 107 by the clamping hydraulic cylinder 117, and the receiving mold 115 and the presser mold 111 are rotated.
The work W is clamped in cooperation with. The bending hydraulic cylinder 125 and the die moving mechanism 129 cooperate with each other to move the bending die 123 along a desired trajectory so that the work W
Is bent into a desired shape.

As another bending machine 131, FIG.
There is something like that shown in The folding machine 131 includes a lower frame 133L that supports the whole, and a front block 135 is provided at the front (right side in FIG. 10) of the lower frame 133L. At the upper end of the front block 135, a receiving mold 13 is provided.
7 are provided.

At a position above the lower frame 133,
Hinge pin 13 provided rearward (left side in FIG. 10)
Upper frame 13 rotatable up and down around 9 as a fulcrum
3U are provided. A plate holding block 141 is integrally provided at a front portion of the upper frame 133U, and a holding die 143 opposed to the receiving die 137 is provided at a lower end of the plate holding block 141.

A clamp motor 145 is provided above the upper frame 133U, and rotates the eccentric shaft 147 to swing the upper frame 133U up and down about the hinge pin 139. The eccentric shaft 1
The 47 connecting pin 1 has a bow-shaped connecting arm 1
The upper end of the connecting block 151 is rotatably mounted, and the lower end of the connecting arm 151 is connected to the front block 1.
35 is rotatably mounted via a pin 153.

A space 155 between the lower frame 133L and the upper frame 133U is provided with a generally U-shaped bending mold 157, which is moved along a desired locus by a bending mold moving mechanism (not shown). Then, the clamped work W is bent. In addition, each said mold 13
7, 143 and 157 have strengths and shapes that can correspond to the maximum plate thickness of the work W to be bent.

Therefore, when the eccentric shaft 147 is rotationally driven by rotating the clamping motor 145, the connecting arm 151 swings with the pin 153 as a fulcrum. As a result, the upper frame 133U moves vertically with the hinge pin 139 as a fulcrum. The work W is clamped by the presser die 143 and the receiving die 137 by swinging. At this time, the extension of the connecting arm 151 generates a clamping force. Then, the bending die 157 is moved to perform the bending of the work W.

[0014]

However, in such a conventional technique, when the workpieces W (semi-finished products before bending) are supplied on an automatic line, the workpieces W are supplied one by one to a workpiece carrying-in device. If the single-piece detector is not attached, or if the single-piece detector is attached but a detection error occurs due to a deviation of the workpiece W, the bending machine 10
There is a possibility that a plurality of works W may be carried in to the members 1 and 131. In addition, since the automatic bending machine can detect whether or not there are a plurality of workpieces when the workpiece W is clamped and carried in, the detection may not be performed when the workpiece W is displaced. There is a problem that there is a risk of damage or overloading of the machine.

The most suitable place for detecting the thickness of the work is the place where the work W is gripped during the bending work. The upper frames 103U and 133U on which the presser dies 111 and 143 are mounted, are used. In the clamping hydraulic cylinder 117 and the clamping motor 145 as a driving source for driving,
The gripped plate thickness cannot be detected, and cannot be determined even when a plurality of workpieces W are gripped.

Therefore, there is a problem that even if a plurality of works W are clamped, bending work is performed, and there is a possibility that a mold is damaged or an overload is applied to a machine. In particular, in the case of the bending machine 131 using the eccentric shaft 147 described above,
Clamping near the bottom dead center of the eccentricity causes an extremely large clamping force. If a plate thicker than the specification is clamped, the connecting arm 151 may be damaged.

From the above, it is conceivable to provide a plurality of thickness measuring devices and measure the actual thickness before loading the work W into the bending machines 101 and 131. In this case, However, it is not efficient because a new measurement step is added. Further, since the place where the thickness of the work W is actually measured is not limited to the bent portion, the above-described problem cannot be completely solved.

SUMMARY OF THE INVENTION An object of the present invention is to pay attention to the above-mentioned problems of the prior art, and it is possible to prevent a mold from being broken or an overload from acting on a machine. It is to provide a processing method and a bending machine.

[0019]

To achieve the above object, a bending method according to the first aspect of the present invention comprises a presser foot provided swingably with respect to a lower frame having a receiving die. The upper frame provided with the mold is swung up and down by a vertical movement mechanism to clamp the work in cooperation with the receiving mold and the holding mold, and the work is performed by a bending mold movably provided in various trajectories. In the bending method for bending a workpiece, a length measuring means for measuring the distance between the presser die and the receiving die by bringing the presser die into contact with the receiving die in the absence of a work during the bending process. After zeroing
The work is carried in by swinging the upper frame upward to separate the presser die and the receiving die, and the work is clamped by the presser die and the receiving die, and the presser die and the receiving die at this time are clamped. The distance between the molds is measured by the length measuring means and compared with the thickness of the work. If the measured distance is equal to or greater than a reference value for the thickness of the work, the processing is immediately stopped. It is assumed that.

Therefore, when the upper frame is moved up and down by the up-down moving mechanism and the work is clamped by the presser die provided on the upper frame and the receiving die provided on the lower frame, there is no work first. In this state, hold the presser die against the receiving die, set the distance between the presser die and the receiving die at this time to zero, and set the presser die and the receiving die when the workpiece is actually clamped. Is measured by the length measuring means, and if the measured distance is larger than the previously input reference value for the thickness of the work, processing is stopped immediately because it is determined that only one work has not been properly loaded. I do.

According to a second aspect of the present invention, there is provided a bending method.
2. The method according to claim 1, wherein the reference value for the thickness of the work is 1.5 times the thickness of the work.

Therefore, when the distance between the presser die and the receiving die measured at the time of clamping the workpiece is 1.5 times or more the thickness of the workpiece to be bent, a plurality of workpieces are carried in. And stop machining.

According to a third aspect of the present invention, there is provided a bending method comprising:
The upper frame is swung up and down through an eccentric shaft provided at one end of a connecting arm that connects the lower frame with the receiving mold and the upper frame with the presser die, and In a bending method using a bending machine for clamping a work in cooperation with a receiving die and bending the work by a bending die provided movably along various trajectories, the upper frame is swung upward. After the work was carried in with the holding mold and the receiving mold separated from each other, the work was clamped by the holding mold and the receiving mold, and the stress generated in the connecting arm by the clamp was measured. If the stress is equal to or greater than the stress set in advance with respect to the thickness of the work, the processing is immediately stopped.

Therefore, by rotating the eccentric shaft provided between the connecting arm and the upper frame or the lower frame, the upper frame is swung up and down, and the presser die provided on the upper frame and the lower When clamping the work in cooperation with the receiving mold provided on the frame, the stress generated in the connecting arm by this clamping is measured, and the measured stress is set in advance with respect to the thickness of the work. If the stress is equal to or greater than the set stress, the processing is immediately stopped.

According to a fourth aspect of the present invention, there is provided a bending machine for clamping a work with a presser die and a receiving die and bending the work with a bending die. A control device for controlling the movement of the die and the bending die; and a length measuring means for measuring a distance between the presser die and the receiving die. A memory for storing a reference value and the like for a condition and a plate thickness of a work, and a reference value preset in the memory for an interval between the presser die and the receiving die measured by the length measuring means. A comparison / judgment unit for judging to immediately stop the bending when the measured interval exceeds the reference value.

Therefore, by moving the upper frame up and down,
When clamping the work with the presser die provided on the upper frame and the receiving die provided on the lower frame, first press the presser die into contact with the The distance between the presser die and the receiving die is measured by length measuring means and set to zero. Then, the distance between the presser die and the receiving die when the work is actually clamped is measured by the length measuring means, and the comparison / judgment unit of the control device inputs the measured distance to the memory of the NC device in advance. If it is determined that the measured distance is larger than the reference value by comparing the reference value with respect to the thickness of the work being processed, it is determined that only one work has not been normally carried in and processing is immediately stopped.

According to a fifth aspect of the present invention, in the bending machine according to the fourth aspect, the reference value is 1.5 times the plate thickness of the work. It is.

Therefore, the comparison / judgment section of the control device determines that the distance between the presser die and the receiving die measured at the time of clamping the workpiece is at least 1.5 times the plate thickness of the workpiece to be bent. When it is determined, it is determined that a plurality of works are being carried in, and the processing is stopped.

According to a sixth aspect of the present invention, in the bending machine, the eccentric shaft provided at one end of a connecting arm for connecting the lower frame provided with the receiving die and the upper frame provided with the presser die. A bending machine that swings the upper frame up and down to clamp the work in cooperation with the presser die and the receiving die, and bends the work with a bending die movably provided in various trajectories. And a control device for controlling the movement of the presser die, the receiving die, and the bending die, and a stress measuring means for measuring a stress of the connecting arm. A memory for storing a reference stress and the like of the connecting arm with respect to bending conditions and each plate thickness, and a stress of the connecting arm measured by the stress measuring unit is stored in the memory in advance. A comparison / judgment unit for judging to immediately stop bending when the measured stress exceeds the reference stress compared with the reference stress being moistened, Is what you do.

Therefore, by rotating the eccentric shaft provided between the connecting arm and the upper frame or the lower frame, the upper frame is swung up and down, and the presser die provided on the upper frame and the lower When clamping the work in cooperation with the receiving mold provided on the frame, the stress generated in the connecting arm by this clamping is measured by the stress measuring means, and the comparison / judgment section of the control device is measured. If the stress generated in the connecting arm is determined to be greater than the reference stress stored in the memory of the control device which is set in advance for the thickness of the workpiece and stored in the memory of the control device, the machining is immediately performed. Stop.

[0031]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a bending machine 1 according to the present invention. In this bending machine 1, a rotating shaft 7 is provided on a bracket 5 projecting upward at the rear end (the left end in FIG. 1) of the lower frame 3L. The frame 3U is provided so as to be able to swing up and down.

At the front end of the upper frame 3U, a plate holding plate 9 is provided, and at the lower end of the plate holding plate 9, a holding die 11 is attached. A front plate 13 is provided at a front end of the lower frame 3L, and a receiving die 15 is attached to an upper end of the front plate 13.

The lower frame 3L is provided with a clamping hydraulic cylinder 17 as an up-down moving mechanism facing upward.
It is attached to U. Hydraulic cylinder for clamping 17
Is rotatably provided at the lower end by a pin 20.

The lower frame 3L and the upper frame 3
A U-shaped bending die 23 is provided in a space 21 between the U and the U. The distal end of the piston rod 27 of the hydraulic cylinder for bending 25 attached upward to the lower frame 3L is attached to the lower surface of the bending die 23. A bending die moving mechanism 29 for moving the bending die 25 is provided on the rear surface of the bending die 25.

Referring also to FIG. 2, the upper frame 3
A length measuring means 31 is provided across the U and the lower frame 3L, and measures the distance between the upper frame 3U and the lower frame.

As the length measuring means 31, for example, as shown in FIG. 3, a block 33 is attached to the lower end surface of the upper frame 3U, and a rack 35 is provided to protrude downward from the block 33. A block 39 having a rotatable pinion 37 meshing with the rack 35.
Is attached to the lower frame 3L, and the pinion 3
An encoder 41 is attached to 7.

Therefore, the rack 35 moves up and down with the up and down movement of the upper frame 3U to rotate the pinion 37, and the amount of rotation is detected by the encoder 41 to measure the distance between the upper and lower frames 3U and 3U. Lengthen.
Although the rack 35 is attached to the upper frame 3U and the pinion 37 is attached to the lower frame 3L here, the rack 35 may be attached to the lower frame 3L and the pinion 37 may be attached to the upper frame 3U.

Alternatively, for example, as shown in FIG. 4, a block 45 having a linear scale 43 attached to one of the upper frame 3U or the lower frame 3L, and a detection head 47 attached to the other side. 49 may be provided to measure the distance between the upper frame 3U and the lower frame 3L.

Alternatively, although not shown, a potentiometer, an operation transformer, a laser displacement sensor, or the like may be provided to measure the distance between the upper frame 3U and the lower frame 3.

The above-described clamping hydraulic cylinder 1
7, an NC device 51 as a control device to which the bending hydraulic cylinder 25, the bending die moving mechanism 29, the length measuring means 31, and the like are connected is provided in proximity to each other as shown in FIG. .

Referring to FIG. 5, the NC unit 51 has a CPU 53 as a central processing unit, and input means 55 such as a keyboard for inputting various data.
Output means 57 such as a CRT for outputting various data is provided. Further, the CPU 53 is connected to a memory 59 for storing a machining program, machining conditions, and the like, and a comparing / judging unit 61 for judging whether or not the work W is carried in from the length measurement result described later. Further, the length measuring means 31 is connected, and the distance between the presser die 11 and the receiving die 15 whose length has been measured is sent to the NC device 51.

Each of the dies 11, 15, 25 has a strength and a shape which can correspond to the maximum thickness of the work W to be bent.

Next, the operation in the bending process will be described. First, a machining program such as a bending shape, a bending length, and a thickness of a workpiece W is registered in a memory 59 of the NC device 51, and when the machining is started, the machining program is called from the memory 59. Here, prior to machining, the upper frame 3U is lowered by the hydraulic cylinder for clamping 17 to receive the presser die 11 without the work W, and the die 15 is received.
And zero setting of the length measuring means 31 is performed.

When the bending operation is started, the upper frame 3U is lifted by the hydraulic cylinder 17 for clamping so as to leave a space between the presser die 11 and the receiving die 15, and the work W is carried in. When the work W is carried into the predetermined position, the upper frame 3U is lowered by the hydraulic cylinder 17 for clamping, and the work W is clamped by the presser die 11 and the receiving die 15.

At this time, the presser die 11 is
Then, the distance between the receiving die 15 is measured and transmitted to the NC device 51, and the comparing / determining unit 61 compares it with the thickness data of the work W of the machining program stored in the memory 59. For example, assuming that the measured value is D and the thickness data is T,
When D> 1.5T with 5T as a reference value, it is determined that a plurality of works W have been carried in, and processing is immediately stopped. On the other hand, if D <1.5T, it is determined that the bending is normal and the processing is continued, and the bending die 25 is moved along a desired locus by cooperation of the bending hydraulic cylinder 25 and the bending die moving mechanism 29. The work W is bent into a desired shape.

From the above results, the distance between the presser die 11 and the receiving die 15 when the work W is clamped can be measured, and the length measurement result is input to the NC device 51. By comparing with the reference value for the thickness of the workpiece W, it can be determined whether or not the clamped work W is one. As a result, when it is determined that there are a plurality of sheets, the processing is immediately stopped, so that it is possible to prevent the mold from being damaged and the machine from being overloaded.

FIG. 6 shows another embodiment. The folding machine 63 includes a lower frame 65L for supporting the entirety.
A front block 67 is provided at the front (right side in FIG. 6). At the upper end of the front block 67,
A receiving mold 69 is provided.

At a position above the lower frame 65L,
An upper frame 65U that is swingable in the vertical direction with a hinge pin 71 provided at the rear (left side in FIG. 6) as a fulcrum is provided. A plate holding block 73 is integrally provided at a front portion of the upper frame 65L, and a holding die 75 facing the receiving die 69 is provided at a lower end of the plate holding block 73.

A clamp motor 77 is provided above the upper frame 65U, and an eccentric shaft 79 is connected to the clamp motor 77. This eccentric shaft 7
9 is an arc-shaped connecting arm 83 with a pin 81.
Is rotatably attached to one end of the eccentric shaft 79. When the eccentric shaft 79 is rotated, the eccentric shaft 79 rotates around the pin 81.
The upper frame 65U swings up and down around the hinge pin 71. The lower end of the connecting arm 83 is rotatably attached to the front block 67 via a pin 85.

In a space 87 between the lower frame 65L and the upper frame 65U, a bending die 8 having a substantially U-shape is provided.
9 is provided, and is moved along a desired locus by a bending die moving mechanism (not shown) to be clamped.
Is bent. In addition, the length measuring means 91 of the above-described mechanism is provided across the upper frame 65U and the lower frame 65L, and measures the distance between the upper frame 65U and the lower frame 65L.
Each of the dies 69, 75, 89 has a strength and a shape that can correspond to the maximum thickness of the work W to be bent.

With the above configuration, when the clamp motor 77 is rotated from the state shown in FIG. 7A, the eccentric shaft 79 is driven to rotate, and as shown in FIG. Swings about the pin 85 as a fulcrum. As a result, the upper frame 65U is connected to the hinge pin 71.
Is swung upward with the fulcrum as the fulcrum, and the presser die 75 is
Leave 9

Then, when the workpiece W is carried into the receiving mold 69 and the clamping motor 77 is rotated, the
As shown in (C), the presser die 75 and the receiving die 6
9 clamps the workpiece W. In this state, the connecting arm 83 has not yet been extended.

When the clamping motor 77 is further rotated, as shown in FIG. 7D, the connecting arm 83 is extended by the thickness of the plate to generate a clamping force. Then, the bending die 89 is moved to bend the work W.

In this bending machine 63, similarly to the above-described bending machine 63, the length measuring means 91 is provided over the upper frame 65U and the lower frame 65L, and the length measuring means 91 is provided between the upper frame 65U and the lower frame. The distance between them is measured. As the length measuring means 91, there is one as shown in FIG. 3 or FIG.

The NC device 51 to which the above-described clamping motor 77, bending mold moving mechanism, length measuring means 91, and the like are connected is provided in close proximity. Clamping motor 77
Except for what has changed, the description is omitted because it is exactly the same as that described above. Also, the operation of bending by the bending machine 63 is exactly the same as that of the above-described bending machine 1, and the description is omitted.

From the above results, the distance between the presser die 75 and the receiving die 69 when the work W is clamped can be measured, and the length measurement result is input to the NC device 51. By comparing with the reference value for the thickness of the workpiece W, it can be determined whether or not the clamped work W is one. As a result, when it is determined that there are a plurality of sheets, the processing is immediately stopped, so that it is possible to prevent the mold from being damaged and the machine from being overloaded.

It should be noted that the present invention is not limited to the above-described embodiment of the present invention, and by making appropriate changes,
It can be implemented in other aspects. That is, in the embodiment of the invention described above, the length measuring means 91 is provided between the upper frame 65U and the lower frame 65L.
Instead, the connecting arm 83 may be provided with a stress measuring means such as a strain gauge 93 (in parentheses in FIG. 6).

Then, as shown in FIG. 8, the stress generated in the connecting arm 83 at the time of clamping for each plate thickness of the work W is obtained as a reference stress, and the NC device 51 is used.
In the actual processing, the comparison / judgment unit 61 detects the stress generated in the connecting arm 83 when the workpiece W is clamped, compares it with the reference stress, and compares the stress with the reference stress. If it exceeds the reference value, the machining is stopped. Even in this case, the same operation and effect as those described above can be obtained.

[0060]

As described above, in the bending method according to the first aspect of the present invention, the upper frame is moved up and down by the up-and-down moving mechanism, and is provided on the presser die provided on the upper frame and the lower frame. When clamping the work with the receiving die, first press the holding die into contact with the receiving die with no work, and set the gap between the pressing die and the receiving die at this time to zero. In advance, measure the distance between the presser die and the receiving die when actually clamping the work,
If the measured distance is larger than the previously input reference value for the thickness of the work, it can be determined that a plurality of works are being clamped. As a result, when it is determined that there are a plurality of sheets, the processing is immediately stopped, so that it is possible to prevent the mold from being damaged and the machine from being overloaded.

In the bending method according to the second aspect of the present invention, the distance between the presser die and the receiving die measured at the time of work clamping is 1.5 times the thickness of the work to be bent, which is the reference value. If the number is more than twice, it is determined that a plurality of works are being carried in, and the processing is stopped. Therefore, it is possible to prevent the mold from being damaged and the machine from being overloaded.

In the bending method according to the third aspect of the invention, the upper frame is swung up and down by rotating an eccentric shaft provided between the connecting arm and the upper frame or the lower frame. When the work is clamped in cooperation with the presser die provided on the lower frame and the receiving die provided on the lower frame, the stress generated in the connecting arm by the clamping is measured, and the measured stress is measured. Is greater than or equal to the reference stress preset for the workpiece thickness,
Since it can be determined that a plurality of works are being clamped and the machining is immediately stopped, it is possible to prevent the mold from being damaged and the machine from being overloaded.

In the bending machine according to the fourth aspect of the present invention, when the upper frame is moved up and down to clamp the workpiece with the presser die provided on the upper frame and the receiving die provided on the lower frame. First, in a state where there is no work, the presser die is brought into contact with the receiving die, and the distance between the presser die and the receiving die at this time is measured by a length measuring means and set to zero. Then, the distance between the presser die and the receiving die when the work is actually clamped is measured by the length measuring means, and NC
When the comparing / determining unit of the apparatus compares the measured distance with a reference value for the thickness of the work previously input to the memory of the NC apparatus and determines that the measured distance is larger than the reference value. Can determine that a plurality of works are being clamped. As a result, when it is determined that there are a plurality of sheets, the processing is immediately stopped, so that it is possible to prevent the mold from being damaged and the machine from being overloaded.

In the bending machine according to the fifth aspect of the present invention, the comparison / judgment section of the control device determines that the distance between the presser die and the receiving die measured at the time of work clamping is the thickness of the work to be bent. If it is determined that it is 1.5 times or more, it is determined that a plurality of workpieces have been loaded and processing is stopped, so that damage to the mold and overloading of the machine are prevented. Can be.

In the bending machine according to the sixth aspect of the present invention, the upper frame is swung up and down by rotating an eccentric shaft provided between the connecting arm and the upper frame or the lower frame, so that the upper frame is attached to the upper frame. When the work is clamped in cooperation with the presser die provided and the receiving die provided on the lower frame, the stress generated in the connecting arm by the clamping is measured by the stress measuring means and controlled. The comparing / judging unit of the device compares the measured stress with a reference stress preset for the thickness of the workpiece and stored in the memory of the NC device, and the stress generated in the connecting arm is larger. When it is determined that the number of clamped works is two or more. As a result, when it is determined that there are a plurality of sheets, the processing is immediately stopped, so that it is possible to prevent the mold from being damaged and the machine from being overloaded.

[Brief description of the drawings]

FIG. 1 is a side view showing an entire bending machine according to the present invention.

FIG. 2 is a schematic front view as viewed from a direction II in FIG.

FIG. 3 is a front view showing a specific example of a length measuring means.

FIG. 4 is a front view showing another specific example of the length measuring means.

FIG. 5 is a block diagram illustrating a configuration of an NC device.

FIG. 6 is a side view showing the entirety of another bending machine according to the present invention.

FIGS. 7A to 7D are operation diagrams showing a clamping operation by the bending machine of FIG. 6;

FIG. 8 is a table showing a plate thickness and a reference stress of a connecting arm stored in an NC device in advance.

FIG. 9 is a side view showing a conventional bending machine.

FIG. 10 is a side view showing another bending machine that is more common than the conventional one.

[Explanation of symbols]

 1, 63 Bending machine 5L, 65L Lower frame 5U, 65U Upper frame 11, 75 Presser die 15, 69 Receiving die 25, 89 Bending die 43 Linear scale (measuring means) 51 NC device (control device) 59 Memory 61 Comparison / judgment unit 79 Eccentric shaft 83 Connecting arm 93 Strain gauge (stress measuring means) W Work

Claims (6)

[Claims] 1. An upper frame provided with a holding die and swingable with respect to a lower frame provided with a receiving die and vertically moved by an up / down moving mechanism so as to swing the receiving die and the holding die. In the bending method of clamping the work in cooperation with and bending the work by a bending mold provided so as to be movable in various trajectories, in the bending process, the work is performed with the presser die without the work. After the length measuring means for measuring the distance between the presser die and the receiving die by abutting the receiving die is set to zero, the upper frame is swung upward to separate the presser die and the receiving die. At the very least, the work is carried in, the work is clamped by the presser die and the receiving die, and the distance between the presser die and the receiving die at this time is measured by the length measuring means to determine the thickness of the work. Compared and measured length is the work thickness A bending method comprising: immediately stopping the processing when the value is equal to or more than a reference value. 2. The method according to claim 1, wherein the reference value for the thickness of the work is 1.5 times the thickness of the work. 3. The upper frame is swung up and down via an eccentric shaft provided at one end of a connecting arm connecting a lower frame having a receiving mold and an upper frame having a holding mold. In a bending method in which a work is clamped in cooperation with the presser die and the receiving die and the work is bent by a bending die movably provided in various trajectories, the upper frame is swung upward. After the work is carried in by moving the presser die and the receiving die away from each other, the work is clamped by the presser die and the receiving die, and the stress generated in the connecting arm by the clamp is measured. If the applied stress is equal to or greater than a reference stress set in advance with respect to the thickness of the work, the machining is immediately stopped. 4. A bending machine for clamping a work by a presser die and a receiving die and bending the work by a bending die, wherein the presser die, the receiving die and the bending die are moved. A control device for controlling, and a length measuring means for measuring a distance between the presser die and the receiving die, wherein the control device is configured to control a work thickness, a bending condition, and a reference value for the work thickness. The distance between the presser die and the receiving die measured by the length measuring means is compared with the reference value preset in the memory, and the length is measured. And a comparing / judging unit for judging to immediately stop the bending when the interval exceeds the reference value. 5. The method according to claim 1, wherein the reference value is 1.
The bending machine according to claim 4, wherein the value is five times. 6. The upper frame is pivoted up and down via an eccentric shaft provided at one end of a connecting arm connecting a lower frame provided with a receiving mold and an upper frame provided with a holding mold. A bending machine for clamping a work in cooperation with the presser die and the receiving die and bending the work by a bending die movably provided in various trajectories, wherein the presser die, the receiving die A control device for controlling the movement of the die and the bending die; and a stress measuring means for measuring the stress of the connecting arm, wherein the control device is configured to control the thickness of the work, the bending conditions, and the connection for each thickness. A memory for storing a reference stress and the like of the arm; and a ratio of the stress of the connecting arm measured by the stress measuring means to the reference stress stored in the memory in advance. And a comparison / judgment unit for judging to immediately stop the bending when the measured stress exceeds the reference stress.