Springback prediction method, bending method for deformed steel bars

Abstract

To provide a prediction method that easily and accurately predicts a spring back quantity at the time of bending a deformed reinforcing bar, and a deformed reinforcing bar bending method.SOLUTION: A spring back quantity prediction method comprises: a reinforcing bar supply step S1 of supplying a deformed reinforcing bar 30 to a reinforcing bar bending device 1; a first bending angle measuring step S2 of measuring a bending angle, while releasing bending force to the deformed reinforcing bar, after bending the supplied deformed reinforcing bar; a second bending angle measuring step S3 of measuring the bending angle, while releasing the bending force again, after further bending the reinforcing bar having the bending force removed therefrom; and a spring back predicting step S4 of predicting a relation between the bending angle and the spring back quantity, utilizing measured results by the first bending angle measuring step and the second bending angle measuring step, after executing the second bending angle measuring step one or plural times, where the bending angle is set to gradually become larger as progressing to the later step. A deformed reinforcing bar bending method uses the predicted result.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for predicting the amount of springback during bending of a deformed bar, and a method for bending a deformed bar. [Background technology]

[0002] It is known that springback occurs during bending of metal members, and it is necessary to carry out bending while taking the amount of springback into consideration.

[0003] Patent Documents 1 and 2 describe techniques for predicting the amount of springback during bending of long metal members such as pipes.

[0004] Patent Document 1 describes that in order to calculate the springback parameters of a long member such as a pipe, a test pipe is subjected to a pair of bending processes and the resulting bending angles are measured.

[0005] Patent Document 2 describes how, when bending a tube, the amount of springback is predicted based on the results of two different test bending operations. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2011-508674 [Patent Document 2] Japanese Unexamined Patent Publication No. 48-103067 Summary of the Invention [Problem to be solved by the invention]

[0007] The prediction techniques of Patent Documents 1 and 2 are both based on the assumption that the bending target is a uniform member, and predict the springback amount based on the results of bending different test pipes or bending different parts of a calibration pipe. However, when applied to predicting the springback amount of a member whose axial and circumferential cross sections are not uniform, such as a deformed bar, the error becomes large. That is, when bending a member whose axial and circumferential cross sections are not uniform, such as a deformed bar, the behavior of the bending process changes depending on the installation mode on the bending device, the bending position, etc., so that when bending results of different members or different parts are used, the error becomes large.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a prediction method for easily and accurately predicting the amount of springback during bending of a deformed bar, and a bending method for a deformed bar using the prediction results. [Means for solving the problem]

[0009] The above object can be achieved by the following means. [1] A springback amount prediction method for predicting a springback amount during bending of a deformed reinforcing bar using a reinforcing bar bending device having a fulcrum member that constitutes a fulcrum for bending and a force point member that rotates around the fulcrum member, A reinforcing bar supplying step of supplying the deformed reinforcing bar to the reinforcing bar bending device; a first bending angle measurement step of bending the supplied deformed bar to a predetermined bending angle by rotating the force application member, and then measuring the bending angle of the deformed bar in a state where the bending force of the force application member against the deformed bar is released; A second bending angle measurement step of bending the reinforcing bar from which the bending force of the force point member has been released to another bending angle, and then measuring the bending angle of the deformed reinforcing bar in a state in which the bending force of the force point member against the deformed reinforcing bar is released; A springback prediction step of predicting a relationship between the bending angle and a springback amount using a measurement result of the first bending angle measurement step and a measurement result of the second bending angle measurement step after performing the second bending angle measurement step once or a plurality of times. Equipped with The method for predicting a springback amount, wherein the different bending angle in the second bending angle measurement step is an angle greater than the predetermined bending angle in the first bending angle measurement step performed immediately before, or the different bending angle in the second bending angle measurement step performed immediately before.

[0010] [2] The springback prediction method according to [1], A springback amount prediction method in which the specified bending angle in the first bending angle measurement step and the different bending angle in the second bending angle measurement step are determined based on a target bending angle when bending a deformed bar using the prediction result.

[0011] [3] A bending method for a deformed steel bar utilizing the springback prediction method according to [1] or [2], A method for bending a deformed reinforcing bar, in which the reinforcing bar bending device used for predicting the amount of springback is used to bend a supplied deformed reinforcing bar to a set bending angle determined based on the target bending angle and the predicted results of the amount of springback.

[0012] [4] A method for bending a deformed steel bar according to [3], A method for bending a deformed bar, comprising further bending the deformed bar used to predict the amount of springback to the set bending angle. Effect of the Invention

[0013] According to the springback prediction method of [1], it is possible to provide a method for easily and accurately predicting the springback amount during bending of a deformed steel bar.

[0014] According to the springback prediction method of [2], in predicting the springback amount, the bending angle in the bending angle measurement step can be set based on the target bending angle, so that the bending angle is allocated to a predetermined angle interval suitable for the target bending angle, making it possible to select the optimal bending angle for predicting the springback amount.

[0015] According to the bending method of deformed bars in [3], by using the springback amount prediction results, a bending method of deformed bars with less error can be provided. In other words, by using the actual bending machine as the rebar bending device used to predict the amount of springback, the error in the predicted numerical value can be reduced. As a result, the amount of springback can be predicted extremely accurately, so that the deformed rebar can be bent to the target bending angle with extremely high accuracy.

[0016] According to the bending method of deformed bars described in [4], when bending deformed bars, the amount of springback at the target bending angle is determined based on data obtained by measuring the springback amount of the bar itself to be bent. This allows the set bending angle to be determined with extremely accurate prediction, making it possible to perform bending with extremely high accuracy. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a perspective view of a main portion of an example of a reinforcing bar bending device used in the springback prediction method of the present invention. [Diagram 2] FIG. 2 is a block diagram showing a control system of the reinforcing bar bending device. [Diagram 3] FIG. 1 is an enlarged view showing an example of a deformed steel bar that is the subject of processing in the present invention, where (a) is a partial cross-sectional view showing the outer surface and axial cross-section of the deformed steel bar, and (b) is a cross-sectional view taken along line AA in (a). [Figure 4] 1 is a flowchart of a method for predicting a springback amount. [Diagram 5] FIG. 2 is a schematic plan view of a reinforcing bar bending device showing the bending state of a reinforcing bar at each step in a springback amount prediction method. [Figure 6] 13 is a graph showing the relationship between the rotation angle of the force application member and the amount of springback (angle). [Figure 7] 1 is a flowchart of an example of a method for bending a reinforcing bar using a springback prediction method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, the method for predicting the amount of springback and the method for bending a deformed bar according to the present invention will be described with reference to Figs.

[0019] FIG. 1 shows a perspective view of a main part of an example of a reinforcing bar bending device used in the springback prediction method of the present invention. The reinforcing bar bending device 1 shown in FIG. Reinforcement This is a device for bending. The example in FIG. 1 shows a case where a deformed reinforcing bar 30 (hereinafter simply referred to as "reinforcing bar 30") is bent. The rebar bending apparatus 1 comprises a flat reference surface portion 5 which forms a reference plane that specifies the bending direction during bending, a fulcrum member 10 which forms the fulcrum for the bending process on the reference surface portion 5, a force point member 20 which rotates around the fulcrum member 10 along the reference surface portion 5, an end holding portion 6 which holds one end of the rebar 30 immobile on the reference surface portion 5, a photographing device 15 which can photograph the bending state of the rebar, and a control portion 2 which controls the entire apparatus.

[0020] The force application member 20 is composed of a roller member rotatably mounted on a revolving drive shaft 20a extending in the direction of an axis VL perpendicular to the reference surface portion 5, and the outer circumferential surface of this roller member abuts against the reinforcing bar 30 to apply a bending force to the reinforcing bar 30. The revolving drive shaft 20a is driven by a drive system using a stepping motor, and is configured so that the revolving angle can be accurately controlled via the control unit 2.

[0021] The camera 15 is for detecting the bending angle of the reinforcing bar 30. For example, the angle is measured by a digital image correlation method based on a video captured by the camera 15. Then, using this reinforcing bar bending device 1, the amount by which the reinforcing bar 30 returns to its original angle when bent at a specified angle, that is, the so-called springback amount (Δθ), can be measured as described below.

[0022] FIG. 2 shows a block diagram of a control system of the reinforcing bar bending device 1. The reinforcing bar bending device 1 is not particularly limited in terms of its control, but can be configured, for example, as shown in Fig. 2. The control unit 2 is supplied with image (video) data taken by a photographing device 15 equipped with a camera or the like, and this image data is used to measure the amount of springback. The memory unit 4 stores various data required for bending, measurement data, etc., and uses them to control the device. The operation unit 18 inputs various data required for bending, inputs information required for device operation, and issues operation instructions. The swivel drive unit 8 controls the swivel position of a swivel drive shaft 20a that swivels a force application member 20 controlled by the control unit 2, and accurately controls the swivel angle.

[0023] FIG. 3 is an enlarged view showing an example of a reinforcing bar 30 that is the subject of processing in the present invention, where (a) is a partial cross-sectional view showing the outer surface and axial cross-section of the reinforcing bar 30, and (b) is an AA cross-sectional view in (a). The reinforcing bar 30 used in the bending process in this embodiment has a shape in which two ribs 31 formed in the longitudinal direction of the reinforcing bar and a number of knots 32 formed between the ribs 31 in the circumferential direction of the reinforcing bar form unevenness on the reinforcing bar surface 30s, as shown in FIG. 3(a), for example. The two ribs 31 are provided 180 degrees apart in the circumferential direction of the reinforcing bar, as shown in FIG. 3(b). The knots 32 are provided so as to be slightly inclined in the circumferential direction of the reinforcing bar, and are provided at positions alternately shifted in the axial direction with the rib 31 in between. The ribs 31 are formed higher than the knots 32 in the example of FIG. 3, but they may be the same height, and the portion of the ribs 31 constitutes the outermost diameter D of the reinforcing bar 30.

[0024] Hereinafter, a method for predicting the amount of springback of the reinforcing bar 30 will be described with reference to Fig. 4 and Fig. 5. Fig. 4 shows a flowchart of the method for predicting the amount of springback, and Fig. 5 shows a schematic plan view of a reinforcing bar bending device showing the bending state of the reinforcing bar at each step in the method for predicting the amount of springback.

[0025] Note that the rotation angle of the force application member 20 (the rotation angle of the reinforcing bar 30 in the clockwise direction in the figure) is the rotation angle (θ) formed by the reference line DL when the reinforcing bar 30 is in a straight state (as shown in the figure) and the straight line BL of the bent part, as shown in FIG.

[0026] Here, the camera of the photographing device 15 photographs from a direction perpendicular to the reference surface portion 5. In other words, the photographing device 15 is positioned so that the reference line DL of the reinforcing bar 30 and the straight line BL of the bent portion of the reinforcing bar 30 can be accurately measured.

[0027] First, the springback amount prediction method will be outlined. The springback prediction method, as shown in FIG. 4, includes a rebar supply step S1 in which a rebar 30 is set in a rebar bending device 1, a first bending angle measurement step S2 in which the springback amount at the angle at which the rebar 30 is first bent is measured, a second bending angle measurement step S3 in which the springback amount at the angle position at which the rebar is bent to a larger angle is measured, and a springback prediction step S4 in which the relationship between the bending angle and the springback amount is predicted using the measurement results of the first and second bending angle measurement steps (S2, S3).

[0028] Each step of the method for predicting the amount of springback will be described in more detail with reference to FIG. First, a reinforcing bar supplying step S1 is carried out. In this reinforcing bar supplying step S1, as shown in Fig. 5, the reinforcing bar 30 is set at a predetermined position of the reinforcing bar bending device 1. This is done so that the side of the reinforcing bar 30 is in contact (or substantially in contact) with the fulcrum member 10, and the end holder 6 positions and fixes the reinforcing bar 30 on the reference surface portion 5.

[0029] The setting direction of the reinforcing bar 30, particularly in the shape shown in Fig. 3, is set in a direction in which the ribs 31 are aligned in a direction perpendicular to the reference surface portion 5. This is because, when the outermost diameter D of the reinforcing bar 30 is relatively large compared to the portion of the reinforcing bar surface 30s, twisting of the reinforcing bar 30 is avoided by bending the reinforcing bar 30 in a direction intersecting the portion of the outermost diameter D (see Fig. 3). Therefore, in the case of a reinforcing bar 30 that does not have a portion such as a rib 31, there is no particular restriction on the setting direction.

[0030] Next, a first bending angle measuring step S2 is carried out. In this first bending angle measuring step S2, as shown in Fig. 5, the force application member 20 is rotated and the reinforcing bar 30 is bent to a predetermined bending angle (θ1 = 90 degrees). After that, the force application member 20 is rotated slightly in the reverse direction (counterclockwise direction) and the bending force of the force application member 20 on the reinforcing bar 30 is released. With this bending force released, the bending angle of the reinforcing bar 30 is measured and the springback amount (Δθ1) by which the bending angle returns from the state of θ1 is measured. Note that the amount of rotation in the reverse direction is not particularly specified, and it is sufficient if it is to the extent that the springback amount can be measured.

[0031] Next, a second bending angle measuring step S3 is carried out. In this second bending angle measuring step S3, the force application member 20 is rotated again in a clockwise direction as shown in Fig. 5 with respect to the reinforcing bar 30 from which the bending force of the force application member 20 has been released, and is bent to the next bending angle (θ2 = 120 degrees). After that, the force application member 20 is rotated slightly in the opposite direction to release the bending force of the force application member 20 on the reinforcing bar 30 again. With the bending force released, the bending angle of the reinforcing bar 30 is measured, and the amount of springback (Δθ2) by which the bending angle returns from the state of θ2 is measured.

[0032] Next, the second bending angle measuring step S3 is carried out for the second time. This second bending angle measuring step S3 is carried out at a larger angle than the first time. In this case, too, with respect to the reinforcing bar 30 from which the bending force of the force application member 20 has been released, the force application member 20 is rotated again in the clockwise direction to the bending angle (θ3 = 150 degrees), and then the force application member 20 is rotated in the opposite direction to release the bending force of the force application member 20 against the reinforcing bar 30 again. With the bending force released, the bending angle of the reinforcing bar 30 is measured, and the springback amount (Δθ3) by which the bending angle returns from the state of θ3 is measured.

[0033] Next, the third second bending angle measuring step S3 is performed. This third second bending angle measuring step S3 is performed at an even larger angle. In this case, the force application member 20 is rotated again in the clockwise direction to the bending angle (θ4 = 180 degrees) with respect to the reinforcing bar 30 from which the bending force of the force application member 20 has been released, and then the force application member 20 is rotated in the opposite direction to release the bending force of the force application member 20 on the reinforcing bar 30 again. With the bending force released, the bending angle of the reinforcing bar 30 is measured, and the springback amount (Δθ4) by which the bending angle returns from the state of θ4 is measured.

[0034] Next, a springback prediction step S4 is carried out. This springback prediction step S4 is a process that utilizes the measurement results of the springback amount (Δθ) at each bending angle of 90 degrees (θ1), 120 degrees (θ2), 150 degrees (θ3), and 180 degrees (θ4) described above. In other words, the springback amount (Δθ) at a predetermined angle can be predicted based on the measurement results.

[0035] Here, the prediction of the springback amount (Δθ) will be explained based on experimental data. Note that Fig. 6 is a graph showing the relationship between the rotation angle of the force application member and the springback amount (angle).

[0036] The data obtained by the measurements in the first bending angle measuring step S2 and the second bending angle measuring step S3 described above is expressed, for example, as shown in the graph in FIG. 6. In this graph, the vertical axis indicates the springback amount (Δθ) and the horizontal axis indicates the rotation angle of the force application member 20 (the bending angle θ of the reinforcing bar 30). As can be seen from this graph, the relationship between the springback amount (Δθ) and the bending angle θ can be defined as a relational expression θ=f(θ). If this relational expression is a linear expression as in the case of using the bending results of different specimens of a uniform member or different parts of the same specimen as shown in the prior art, it can be expressed as Δθ=aθ+b. Note that when the thickness or shape of the reinforcing bar 30 is different, the inclination angle (coefficient a) and constant b of the graph are expressed as different functions.

[0037] In the example shown in Fig. 6, the second bending angle measuring step S3 was performed three times, but it is sufficient to perform it at least once. In addition, the relationship between the bending angle and the springback amount was predicted based on the measurement results when the predetermined bending angle in the first bending angle measuring step was 90 degrees (θ1) and the other bending angles in the second bending angle measuring step were 120 degrees (θ2), 150 degrees (θ3), and 180 degrees (θ4), but the predetermined bending angle and the other bending angle are not limited to the above values. For example, they can be appropriately selected depending on the target bending angle θs in the bending process described later.

[0038] For example, when the target bending angle θs, which is the final bending angle, is 90 degrees, it is not necessary to perform the prediction by bending up to 180 degrees as in the example shown in Fig. 6, but it is sufficient to measure the springback amount during bending at a plurality of appropriate angles between 0 and 90 degrees. That is, following the prediction of the springback amount, the predetermined bending angle in the first bending angle measurement step and another bending angle in the second bending angle measurement step may be determined based on the target bending angle when bending the same type of rebar as the rebar used for the prediction. In addition, when determining the predetermined bending angle in the first bending angle measurement step and the other bending angle in the second bending angle measurement step, it is preferable to set them to angles that are appropriately distributed.

[0039] A bending method for a reinforcing bar 30 using the above-mentioned springback prediction method will be described below. Fig. 7 shows a flowchart of an example of a bending method for a reinforcing bar using the springback prediction method. The bending shown in Fig. 7 is an example of bending a bending portion used in the prediction method shown in Fig. 4 to a target bending angle θs.

[0040] 7, in carrying out the bending method for the reinforcing bar 30, the reinforcing bar 30 is set in the reinforcing bar bending device 1, and the steps from the reinforcing bar supply step S1 to the springback prediction step S4 are carried out. After carrying out the steps up to the springback prediction step S4, the same reinforcing bar bending device 1 uses the predicted data to move to the actual processing step S5.

[0041] 6, when further bending is performed to a specified angle, for example 200 degrees, the force application member 20 is rotated and bent to an angle θt where θt-△θt=200 using the linear function found from the above measurement results. In other words, when the force application member is rotated to θt=(200+b) / (1-a), it returns by the amount of springback (Δθt), and the final bending angle (target bending angle θs) becomes 200 degrees.

[0042] 7, the reinforcing bar 30 to be actually bent is set in the reinforcing bar bending device 1, both angle measurement steps S2 and S3 for predicting the amount of springback are performed to acquire data, and a calculation (step S4) is performed in the short time until the final bending angle is reached to process the reinforcing bar to the set bending angle. In other words, the final turning angle of the force application member 20 is turned to the bending angle calculated based on the predicted amount of springback to obtain a product with a target bending angle θs.

[0043] When bending a reinforcing bar used to predict the springback amount at a different location, or bending a reinforcing bar of the same type that is made of the same material, size, and shape as the reinforcing bar used to predict the springback amount, if the reproducibility of the bending state is maintained, it is possible not to predict the springback amount for each bending location. That is, the process up to the springback prediction step S4 is performed with the reinforcing bar set initially, and the relationship between the bending angle and the springback amount is stored in the reinforcing bar bending device 1. Then, based on this stored data, subsequent bending operations are performed. In this case, if the reinforcing bar manufacturer and manufacturing lot are the same, bending with less error can be performed for the same type of reinforcing bar based on the initial prediction result. On the other hand, if the manufacturing lot or the reinforcing bar manufacturer is changed, it is preferable to predict the springback.

[0044] In this way, in the springback prediction method of this embodiment, when the reinforcing bar 30 is supplied to the reinforcing bar bending device 1 and bent by the force point member 20 around the bending fulcrum member 10, the bending force by the force point member 20 is released during bending of the reinforcing bar 30, and the bending angle measurement step of measuring the springback amount (Δθ) of the reinforcing bar 30 at that time is performed multiple times at different bending angles at the same part. Based on the results of these multiple springback measurements, the springback amount (Δθ) of the reinforcing bar 30 at a specific bending angle is predicted, making the measurement easy, and the springback amount at a specific bending angle can be predicted quickly and accurately. As a result, no work consideration time is required to predict the springback amount in bending of the reinforcing bar, and the reinforcing bar can be bent quickly and quickly.

[0045] In addition, when predicting the amount of springback (Δθ), the measurement angle in the bending angle measurement step, i.e., the bending processing angle, can be set based on the target bending angle θs, so that it can be allocated to an angle that is suitable for the target bending angle θs, making it possible to select the optimal angle for accurately predicting the amount of springback.

[0046] In the springback prediction method of this embodiment, the bending angle of the reinforcing bar 30 is measured using an image taken from a direction perpendicular to the bending reference surface 5, so that angle data (position displacement data) can be obtained as a two-dimensional image, making calculations easier and enabling the springback prediction process to be performed at high speed.

[0047] Furthermore, in the springback prediction method of this embodiment, the number of times the second bending angle measurement step S3 is performed is not specified, but by performing it two or more times, the springback amount is measured three or more times, which enables accurate prediction based on more measurement data.

[0048] In addition, in the bending method of this embodiment, the reinforcing bar bending device 1 used for predicting the amount of springback is the same as the reinforcing bar bending device 1 used in actual production, so the error in the predicted value can be reduced. As a result, the amount of springback can be predicted very accurately, and the reinforcing bar 30 can be bent to a very accurate target bending angle θs. Also, there is no need for a test device in addition to the actual device used for bending, which saves on facilities.

[0049] Furthermore, in the bending method of this embodiment, when bending the reinforcing bar 30, the amount of springback is predicted based on the measured value of the springback amount of the reinforcing bar itself to be bent, thereby enabling extremely accurate bending.

[0050] Although one embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate within the scope of the present invention.

[0051] In the above embodiment, the reinforcing bar 30 has the shape shown in FIG. 3, but the uneven shape of the ribs 31, the joints 32, etc. may be of another shape. [Explanation of symbols]

[0052] 1 Rebar bending device 5 Reference plane section (reference plane) 10 Support member 15 Imaging Equipment 20 Force point member 30 Reinforcement bars (deformed bars)

Claims

1. A springback amount prediction method for predicting a springback amount during bending of a deformed reinforcing bar using a reinforcing bar bending device having a fulcrum member that constitutes a fulcrum for bending and a force point member that rotates around the fulcrum member, A reinforcing bar supplying step of supplying the deformed reinforcing bar to the reinforcing bar bending device; a first bending angle measurement step of bending the supplied deformed bar to a predetermined bending angle by rotating the force application member, and then measuring the bending angle of the deformed bar in a state in which the bending force of the force application member against the deformed bar is released; a second bending angle measurement step of bending the reinforcing bar from which the bending force of the force point member has been released to another bending angle, and then measuring the bending angle of the deformed reinforcing bar in a state in which the bending force of the force point member against the deformed reinforcing bar is released; A springback prediction step of predicting a relationship between the bending angle and a springback amount using a measurement result of the first bending angle measurement step and a measurement result of the second bending angle measurement step after performing the second bending angle measurement step once or a plurality of times. Equipped with The different bending angle in the second bending angle measurement step is an angle larger than the predetermined bending angle in the immediately preceding first bending angle measurement step or the different bending angle in the immediately preceding second bending angle measurement step. A method for predicting springback amount.

2. The springback prediction method according to claim 1, The predetermined bending angle in the first bending angle measurement step and the other bending angle in the second bending angle measurement step are determined based on a target bending angle when bending the deformed bar using the prediction result. A method for predicting springback amount.

3. A bending method for a deformed reinforcing bar utilizing the springback prediction method according to claim 1 or 2, Using the rebar bending device used to predict the amount of springback, the supplied deformed rebar is bent to a set bending angle determined based on the target bending angle and the predicted result of the amount of springback. How to bend deformed steel bars.

4. The bending method for the deformed steel bar according to claim 3, The deformed steel bar used to predict the amount of springback is further bent to the set bending angle. How to bend deformed steel bars.

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