矩形材淺抽成形之眼模半角選定與其變形不均分析

Selection of Semi-angle and Analysis of Inhomogeneous Deformation for Skin-pass Drawing of Rectangular Shapes

曾竹毅(Chi-Yi Tseng)

指導教授 ： 林恆勝

共同指導教授 ： 許源泉(Yuan-Chuan Hsu)

國立虎尾科技大學/工程學院/機械與機電工程研究所/碩士(2008年)

https://doi.org/10.6827/NFU.2008.00007

摘要

現今精密機械所使用之傳動元件，如線性滑軌與滑塊等，皆需要很高的真直度和形狀精度，此類傳動元件之尺寸精度會影響平台操控的精度，並影響後續加工以及儀器量測的精度，其機械加工的前製程為輥軋或抽拉成形加工。而冷間精抽通常實施於多道次輥軋預成形後，或於多道次抽拉為預成形後，再以預成形進行最終小面縮率的抽拉，此類形材截面可視為多塊矩形組成，而對於矩形材的抽拉成形而言，其寬度與厚度方向可能有不同縮率，以及不同的眼模半角的組合，若嘗試以田口法來尋求最佳眼模半角值，往往需要相當大的模擬量。

本研究先將形材抽拉製程簡化為矩形材之抽拉，首先藉由有限元素套裝軟體DEFORM-3D來模擬方形材的表面精抽製程，探討不同眼模半角、面積縮率的組合對成形負荷之影響，並定義平均應變差，以計算工件抽拉後的變形不均度，再藉由此方形材之表面精抽製程的學理基礎，本研究提出矩形材精抽為方形材之最佳眼模半角選用準則，並以DEFORM-3D軟體模擬，進行抽拉成形負荷的驗證，以及估算工件變形的均勻度。

由模擬結果驗證，當矩形工件進行寬度縮率與厚度縮率不等之抽拉，且工件出口截面為正方形時，其在寬度與厚度方向之最佳眼模半角值範圍，將分別介於方形材在相同寬度與相同厚度抽拉時之最佳眼模半角，與寬度及厚度縮率之總合面縮率進行抽拉時之最佳眼模半角之間；矩形材抽拉之最佳眼模半角所對應之平均應變差，亦落在準則所預測之區間內。

關鍵字

金屬成形 ； 冷間精抽 ； 變形不均

並列摘要

Transmission components used in precision machines like rails or sliders for linear motion guide demand high straightness and shape precision. The precision of these components affect the precision of machine movement and subsequent machining or measuring precision. Prior to machining, workpiece for the rails or sliders has to be rolled or drawn. Cold skin-pass drawing is usually applied on the preform, which may be produced by multiple shape rolling or drawing, with light reduction of cross-section. The cross-section of the shaped workpiece can be considered to be comprised of rectangles. As for drawing with rectangles, there can be possible combinations of different thickness and die semi-angle along both the width and thickness directions. It would require tremendous amount of case simulation in searching of the optimum die semi-angle by Taguchi method.

In order to verify the guideline in selecting the optimum die semi-angles, this work first computed the drawing load of square bar by finite element simulation with DEFORM-3D under various combinations of die semi-angles and reduction of cross-section. Optimum angle can be obtained which yielded lowest drawing load for the same reduction. “Mean variation of effective strain” was defined in order to quantify the level of deformation inhomogeneity under the choice of various parameter combinations. The result of square drawing was further applied to the selection of optimum die semi-angles for drawing from rectangle to square, and corresponding deformation inhomogeneity was also verified with finite element simulation.

The finite element simulations verified that when drawing square to rectangle with different width and thickness reductions, the range of optimum die semi-angle in the width direction fell between the optimum angles in drawing square with the same width reduction and with same area reduction. While the range of optimum die semi-angle in the thickness direction fell between the optimum angles in drawing square with the same area reduction and with the same thickness reduction. The corresponding deformation inhomogeneity also fell in the range as predicted by this guideline.

並列關鍵字

metal forming ； cold skin-pass drawing ； inhomogeneous deformation

參考文獻

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