JP3591066B2 - Form bending method - Google Patents

Description

【０００８】
各曲率半径ごとに金型動作量（図１参照）との関係を調査したところ、図２に黒丸で示す金型動作量Ｍ_ａ が必要であった。なお、図２の白丸は、スプリングバックのないことを前提にして算出した可動金型の理論動作量Ｍ_ｔ であり、理論動作量Ｍ_ｔ に対する実効金型動作量Ｍ_ａ の比Ｍ_ａ ／Ｍ_ｔ が補正係数Ｃとなる。なお、可動金型の回転角θは、可動金型の動作位置において形材の軸線と直交する角度に設定して加工を行う。また、図２では、試料１についての調査結果を表したが、他の試料２〜４も同様な関係を示した。
そこで、図２の結果に基づき各試料について曲率半径Ｒと補正係数Ｃとの関係を調査したところ、両者の間に図３に示す関係が成立していた。すなわち、補正係数Ｃは、次式（１）の一次関数で曲率半径Ｒから求められることが判った。
Ｃ＝α×Ｒ＋Ｂ ・・・・（１）
ただし、α：図３の各試料ごとの直線の傾き
Ｒ：曲率半径
Ｂ：直線と横軸との交点であり、３．２８を中間点とし３〜３．６の範囲にある。
【０００９】
図３にみられるように、各試料ごとに直線の傾きαが異なる。その理由としては、形材の断面係数Ｚ及び０．２％耐力σ_０．２ が掲げられる。断面係数Ｚは、形材断面における引張り側と圧縮側の断面係数の平均値で表される。そこで、試料１〜４について、直線の傾きαとＺ×σ_０．２ との関係を求めたところ、図４に示す結果が得られた。
図４も直線関係であることから、直線の傾きαは、次式（２）の一次関数で表されることが判った。
α＝｛Ａ×（Ｚ×σ_０．２ ）＋Ｄ｝×１０^−３ ・・・・（２）
ただし、Ａ：図４の直線の傾きを示し、９．５×１０^−６を中間点とし（８〜１１）×１０^−６の範囲にある。
Ｚ：断面係数
σ_０．２ ：０．２％耐力（ｋｇｆ／ｍｍ^２ ）
Ｄ：直線と横軸との交点（＝０．３）
式（２）を式（１）に代入すると、式（３）が得られる。
Ｃ＝｛Ａ×（Ｚ×σ_０．２ ）＋０．３｝×１０^−３×Ｒ＋Ｂ ・・・・（３）
このようにして求められた補正係数Ｃを使用し、目標曲率半径Ｒを得るために必要な可動金型の実行動作量Ｍ_ａ を決定する。この実行動作量Ｍ_ａ で形材を曲げ加工すると、後述する実施例に示されているように高精度の曲げ加工が可能となる。
【００１０】
実施例２：（角筒状形材の曲げ加工）
表１に掲げた試料１〜４から図５に示すサイズ及び形状をもつ角筒状形材を作製し、各種目標曲げ半径で曲げ加工した。このときのＡ値，Ｂ値及び補正係数Ｃを表２に示す。なお、表２以降では、×１０^−６を省略してＡ値を表現した。また、表２に示した試料番号において、ハイフンの前の数値は表１に掲げた試料番号を、ハイフンの後の数値は各試料に関する個々の条件ごとの番号を示す。
【００１１】

【００１２】
各試料１−１〜４〜３について、それぞれ１０本の形材を曲げ加工したあと、曲げ部の曲率を測定した。測定結果を、各１０本の試験片中目標値に対して最大の誤差を生じたものを最大曲率半径Ｒ_ｍａｘ ，最少曲率半径Ｒ_ｍｉｎ として表３に示した。また、目標曲げ半径とＲ_ｍａｘ ，Ｒ_ｍｉｎ との差の目標曲げ半径に対する百分率（％）で誤差を表した。
【００１３】

【００１４】
表２及び表３から明らかなように、補正係数を取り込んで曲げ加工するとき、加工後の形材形状を目標形状に誤差１４％以内の高精度で一致させることができた。特に、Ａ値，Ｂ値，補正係数Ｃとして中間値を採用して曲げ加工の条件を設定したものでは、目標形状に対して数％の誤差，具体的には６．５％程度の誤差で曲げ加工することが可能になった。
【００１５】
実施例３：（円筒状形材の曲げ加工）
引張り強さσ_Ｂ ＝１７．５ｋｇｆ／ｍｍ^２ 及び０．２％耐力σ_０．２ ＝８．５ｋｇｆ／ｍｍ^２ のアルミ合金ＪＩＳ Ａ６Ｎ０１で図６にサイズ及び形状を示す円筒状の形材を作製し、表４の条件下で曲げ加工した。なお、曲げ加工では、各条件ごとに１０本を試験した。
【００１６】

【００１７】
曲げ加工後の形状を実施例２と同様に測定した結果を、表５に示す。曲げ加工後の形材は、表５にみられるように極めて高い寸法精度をもつものであった。
【００１８】

【００１９】
実施例４：（チャンネル材の曲げ加工）
引張り強さσ_Ｂ ＝１７．５ｋｇｆ／ｍｍ^２ 及び０．２％耐力σ_０．２ ＝８．５ｋｇｆ／ｍｍ^２ のアルミ合金ＪＩＳ Ａ６Ｎｏ１で図７にサイズ及び形状を示すチャンネル材を作製し、表６の条件下で曲げ加工した。なお、曲げ加工では、各条件ごとに１０本を試験した。
【００２０】

【００２１】
曲げ加工後の形状を実施例２と同様に測定した結果を示す表７にみられるように、曲げ加工後の形材は、曲げ半径方向に関して断面積が大きく変化する形状であるにも拘らず、高い寸法精度をもつものであった。
【００２２】

【００２３】
実施例５：（角筒状形材の二点曲げ）
試料１の材料で図８に示すサイズ及び形状の角筒状形材を作製し、表８に示すＡ，Ｂ及びＣの各条件下でＲ_１ 部及びＲ_２ 部の曲げ方向及び曲率半径が異なる加工を連続して行った。この場合も、各条件ごとに１０本の試験片を曲げ加工した。
【００２４】

【００２５】
曲げ加工された形材の形状は、実施例２の場合と同様にして求めた結果を示した表９にみられるように寸法精度が高いものであった。
【００２６】

【００２７】
【発明の効果】
以上に説明したように、本発明に従った曲げ加工においては、本発明者等が実験結果から求めた補正係数及び定数を取り込んで加工条件を設定し、固定金型に対する可動金型の変位量を定めることにより、回転引き曲げ等に比較して曲げ半径が大きな曲げ半径で加工する押し通し曲げにおいても、スプリングバックに起因した誤差要因を解消し、寸法精度よく曲げ加工することが可能になる。このようにして得られた曲げ加工製品は、自動車用スペースフレーム，車両用フレーム，建築用部材等として広範囲な分野で使用される。
【図面の簡単な説明】
【図１】通し曲げ加工の説明図
【図２】曲率半径と可動金型動作量との関係を示すグラフ
【図３】曲率半径と補正係数Ｃとの関係を示すグラフ
【図４】図３の直線の傾きαとＺ×σ_０．２ との関係を示すグラフ
【図５】実施例２で曲げ加工した角筒状形材の斜視図
【図６】実施例３で曲げ加工した円筒状形材の斜視図
【図７】実施例４で曲げ加工したチャンネル材の斜視図
【図８】実施例５で二点曲げ加工した角筒状形材の斜視図[0001]
[Industrial applications]
The present invention relates to a method for two-dimensionally or three-dimensionally bending a material such as an extruded aluminum alloy used as a frame material or a building member of an automobile or a vehicle by a push-through bending method.
[0002]
[Prior art]
Examples of a method of bending a long shape material such as an extruded aluminum material include rotary pull bending and push-through bending using a mold. In the push-through bending, as shown in FIG. 1, a movable mold is used which is arranged to be vertically and horizontally movable and rotatable with respect to a fixed mold. If the profile is pushed through the fixed mold, and the projection of the profile protruding from the fixed mold is constrained by the movable mold and the profile is continuously pushed through the fixed mold, the position of the movable mold with respect to the fixed mold is increased. The profile is bent at a curvature determined from the relationship.
[0003]
[Problems to be solved by the invention]
This push-through bending has a larger bending radius R as compared with general pulling bending and the like. Therefore, the degree of processing is small, and a large amount of elastic strain is generated inside the processed profile. The elastic strain causes a springback in which the profile after passing through the movable mold tries to restore the original shape. In addition, the springback changes complicatedly depending on various processing conditions, and cannot be quantitatively grasped. For this reason, it is difficult to form a shape into a target shape, and in fact, the target shape is obtained by repeating a number of trial and error.
The present invention has been devised to solve such a problem, and predicts a springback amount for obtaining a target bending shape, and incorporates the predicted value to bend the moving amount of the movable mold. It is an object of the present invention to significantly reduce the number of trial and error by giving the data as input data to an apparatus, and to perform bending processing efficiently and with high accuracy.
[0004]
[Means for Solving the Problems]
In order to achieve the object, the bending method of the present invention sets a movable mold at a position displaced with respect to a fixed mold, and performs bending by pushing a shape material through the fixed mold and the movable mold. when the movable metal based on the correction coefficient of the correction coefficient C that is represented by the ratio M _{a /} M _t is calculated by the following equation was calculated execution operation amount M _a with respect to the theoretical operation amount M _t of the movable mold The operation amount of the mold is determined. This method is applied to two-dimensional or three-dimensional bending of a profile.
C = {A × (Z × σ _0.2 ) +0.3} × 10 ⁻³ × R + B
A: Coefficient in the range of (8 to 11) × 10 ⁻⁶ B: Constant in the range of 3.0 to 3.6 Z: Average value of the cross-sectional modulus on the tensile side and the compressive side in the cross section of the shaped material ( mm ³ )
σ _0.2 : 0.2% proof stress in tensile test (kgf / mm ² )
R: radius of curvature (mm)
[0005]
Factors that affect the amount of springback include the 0.2% proof stress (σ _0.2 ), section modulus (Z), and bending radius (R) of the material. The present inventors clarified the relationship between each factor and springback by experiments, and derived the above-described relationship from which the springback can be quantitatively predicted. According to this relational expression, it is possible to perform processing within the error range in about two tests without having to repeat many trial and errors.
[0006]
【Example】
Embodiment 1: (Derivation process of springback amount prediction formula)
Using the extruded aluminum material having the material properties shown in Table 1, the material was bent at various radii of curvature, and the amount of springback was measured.
[0007]

[0008]
When checking the relationship between the mold operation amount for each radius of curvature (see FIG. 1), die operation amount M _a indicated by a black circle was required in FIG. Incidentally, the white circles in FIG. 2 is a movable mold of the theoretical operation amount M _t which is calculated by assuming that there is no spring-back, the ratio M _{a /} M of the effective mold operation amount M _a with respect to the theoretical operation amount M _{t t} becomes the correction coefficient C. The processing is performed with the rotation angle θ of the movable mold set at an angle orthogonal to the axis of the profile at the operating position of the movable mold. In addition, FIG. 2 shows the results of the investigation on Sample 1, but the other Samples 2 to 4 also showed the same relationship.
Then, when the relationship between the radius of curvature R and the correction coefficient C was examined for each sample based on the results of FIG. 2, the relationship shown in FIG. 3 was established between the two. That is, it was found that the correction coefficient C was obtained from the radius of curvature R by a linear function of the following equation (1).
C = α × R + B (1)
Here, α: slope of a straight line for each sample in FIG. 3 R: radius of curvature B: intersection of the straight line and the horizontal axis, and is in the range of 3 to 3.6 with 3.28 as an intermediate point.
[0009]
As shown in FIG. 3, the slope α of the straight line differs for each sample. The reasons include the section modulus Z of the profile and the 0.2% proof stress σ _0.2 . The section modulus Z is represented by the average value of the section modulus on the tension side and the compression side in the section of the profile. Then, when the relationship between the slope α of the straight line and Z × σ _0.2 was determined for Samples 1 to 4, the results shown in FIG. 4 were obtained.
Since FIG. 4 also has a linear relationship, it was found that the gradient α of the straight line was represented by a linear function of the following equation (2).
α = {A × (Z × σ _0.2 ) + D} × 10 ⁻³ (2)
However, A: indicates the inclination of the straight line in FIG. 4 and is in the range of (8 to 11) × 10 ⁻⁶ with 9.5 × 10 ⁻⁶ as the middle point.
Z: Section modulus σ _0.2 : 0.2% proof stress (kgf / mm ² )
D: Intersection point between straight line and horizontal axis (= 0.3)
By substituting equation (2) into equation (1), equation (3) is obtained.
C = {A × (Z × σ _0.2 ) +0.3} × 10 ⁻³ × R + B (3)
Thus using the correction coefficient C obtained by, it determines the execution operation amount M _a of the movable mold required to obtain the target radius of curvature R. If the execution operation amount M _a bent profile in the processing that, it is possible to highly accurate bending as shown in the examples below.
[0010]
Example 2: (Bending of rectangular tubular material)
From the samples 1 to 4 listed in Table 1, rectangular tubular members having the size and shape shown in FIG. 5 were prepared and bent at various target bending radii. Table 2 shows the A value, B value and correction coefficient C at this time. In Table 2 and subsequent figures, the A value is expressed by omitting × 10 ⁻⁶ . In the sample numbers shown in Table 2, the numerical value before the hyphen indicates the sample number listed in Table 1, and the numerical value after the hyphen indicates the number of each sample for each condition.
[0011]

[0012]
For each of the samples 1-1 to 4-3, after bending each of ten shaped members, the curvature of the bent portion was measured. The results of the measurement are shown in Table 3 as the maximum radius of curvature R _max and the minimum radius of curvature R _min for each of the ten test pieces that produced the maximum error with respect to the target value. In addition, the error was expressed as a percentage (%) of the difference between the target bending radius and _Rmax , _Rmin with respect to the target bending radius.
[0013]

[0014]
As is clear from Tables 2 and 3, when bending was performed by taking in the correction coefficient, the shape of the processed material could be matched with the target shape with high accuracy within 14% of the error. In particular, when the bending conditions are set by using intermediate values as the A value, the B value, and the correction coefficient C, an error of several%, specifically, an error of about 6.5% with respect to the target shape is obtained. It is now possible to bend.
[0015]
Example 3: (Bending of cylindrical shaped material)
A cylindrical member having the size and shape shown in FIG. 6 is manufactured using an aluminum alloy JIS A6N01 having a tensile strength σ _B = 17.5 kgf / mm ² and a 0.2% proof stress σ _0.2 = 8.5 kgf / mm ² . Then, bending was performed under the conditions shown in Table 4. In the bending, ten pieces were tested for each condition.
[0016]

[0017]
Table 5 shows the results of measuring the shape after bending in the same manner as in Example 2. As shown in Table 5, the profile after bending had extremely high dimensional accuracy.
[0018]

[0019]
Example 4: (Bending of channel material)
A channel material having the size and shape shown in FIG. 7 was prepared using an aluminum alloy JIS A6No1 having a tensile strength σ _B = 17.5 kgf / mm ² and a 0.2% proof stress σ _0.2 = 8.5 kgf / mm ² . Bending was performed under the conditions of No. 6. In the bending, ten pieces were tested for each condition.
[0020]

[0021]
As can be seen from Table 7 showing the results of measuring the shape after bending in the same manner as in Example 2, the shape after bending has a shape whose cross-sectional area changes greatly in the bending radial direction. Had high dimensional accuracy.
[0022]

[0023]
Example 5: (Two-point bending of rectangular tubular material)
A rectangular tube-shaped material having the size and shape shown in FIG. 8 was prepared from the material of sample 1, and the bending directions and the radii of curvature of R ₁ and R ₂ under the conditions A, B and C shown in Table 8 were obtained. Different processing was performed in succession. Also in this case, ten test pieces were bent for each condition.
[0024]

[0025]
The shape of the bent shape member had high dimensional accuracy as shown in Table 9 showing the results obtained in the same manner as in Example 2.
[0026]

[0027]
【The invention's effect】
As described above, in the bending according to the present invention, the present inventors take in the correction coefficients and constants obtained from the experimental results, set the processing conditions, and set the amount of displacement of the movable mold with respect to the fixed mold. In the case of press-through bending in which a bending radius is larger than that in rotary pull bending or the like, error factors caused by springback can be eliminated, and bending can be performed with high dimensional accuracy. The thus obtained bent product is used in a wide range of fields as a space frame for a vehicle, a frame for a vehicle, a member for a building, and the like.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of through bending. FIG. 2 is a graph showing a relationship between a radius of curvature and a movable mold operation amount. FIG. 3 is a graph showing a relationship between a radius of curvature and a correction coefficient C. FIG. 5 is a graph showing the relationship between the inclination α of the straight line and Z × σ _0.2 . FIG. 5 is a perspective view of a rectangular tubular material bent in Example 2. FIG. 6 is a cylindrical shape bent in Example 3. FIG. 7 is a perspective view of a channel material bent in Example 4; FIG. 8 is a perspective view of a rectangular cylindrical shape material bent in two points in Example 5;

Claims (3)

Was set at a position displaced a movable mold with respect to the fixed die, the the stationary mold and the movable mold bending forced through the frame members when processing, perform operations relative to the theoretical movement amount M _t of the movable mold the correction factor C which is represented by the ratio M _{a /} M _t amount M _a is calculated by the following equation, based on the calculated correction coefficient profile, characterized by determining an operation amount of the movable mold Bending method.
C = {A × (Z × σ _0.2 ) +0.3} × 10 ⁻³ × R + B
A: Coefficient in the range of (8 to 11) × 10 ⁻⁶ B: Constant in the range of 3.0 to 3.6 Z: Average value of the cross-sectional modulus on the tensile side and the compressive side in the cross section of the shaped material ( mm ³ )
σ _0.2 : 0.2% proof stress in tensile test (kgf / mm ² )
R: radius of curvature (mm) A method for bending a profile, wherein the profile is bent two-dimensionally or three-dimensionally using the correction coefficient C according to claim 1. A shaped member bent by the method according to claim 1.

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