熱鍛模具設計之有限元素法分析

Abstract

由於國內外鍛品市場之蓬勃發展，鍛造業者面臨到鍛品品質之要求，以及在納期縮短方面均較以往嚴苛，所以利用電腦輔助工程分析（Computer-Aided Engineering，CAE）已是刻不容緩的課題。本研究選用DEFORM軟體做為分析軟體，輔以實驗室自行開發之中文化介面，選擇目前國內熱鍛產品之一的汽車交流發電機之磁座作為載具進行模具設計之分析。 在研究方法上，首先選擇一具有代表性之磁座產品，從產品之尺寸來設計預成形鍛及成形鍛模具，利用初步電腦模擬分析，從不同的胚料高度中，選擇最適合之鍛粗高度，然後分析剪摩擦係數對熱鍛過程中胚料爪部生長的影響，最後從材料流動模式來變更原始預成形模具設計方式，由分析結果來決定最適合磁座爪部生長之製程參數，建立一套CAE分析流程。建立磁座產品之CAE模擬模式之後，本研究針對產品生產時爪部未填滿之問題，探討可能發生之原因，然後利用CAE分析出解決問題之方法。 此外，由於鋼料價格不斷上漲，材料成本已經大幅壓縮到產品的利潤，本研究藉由CAE軟體開發熱鍛模具之閉模鍛造技術，利用所分析之磁座產品，將其原本開放式的鍛造模具設計方式變更為閉模設計之樣式。研究過程中以閉模之基本概念來設計第一套閉模鍛造模具，然後將閉模設計之模具圖檔匯入CAE軟體中，分析其胚料成形結果，若不如預期則再回頭修改模具圖檔，然後進行分析，直到滿意為止。模擬分析結果顯示胚料可以由原本的1.5公斤減少到1.1公斤，而產品之得料率也從60%提升到81%，此CAE技術輔助之開發流程可成為開發各種鍛造模具之方法。

Due to keen competition in the forging products market, the forging companies are forced to respond to the market requirements by delivering a new product in a lead-time much shorter than that before. In order to cope with this dilemma, using CAE software to help the die design becomes a must for the forging industry. In the present study, the finite element software DEFORM with the Chinese graphic user interface was employed to analyze the hot forging process of manufacturing an automobile generator component, which is used as a holder of the coil. Since the coil holder bears a complex geometry with six claws extruded from the base, it cannot be produced by a single forging process, and in consequence, a preform is required to help the material flow in the subsequent forming process. In the present study, the finite element analysis was first performed to examine the effect of the process parameters, such as blank dimension and friction condition, on the material flow in the performing process. The friction condition and the material flow in different performing processes were discussed, and an optimum blank height and die design were then determined from different strokes of upsetting forging based on the finite element simulation results. The production process with the proposed die design was also implemented. The sound product obtained in the production process validated the finite element analysis. Due to the arising price of the steel, the material cost has been the major concern in the forging industry. In order to reduce the material cost, a closed-die forging process for producing a nearly net shape of the coil holder was proposed. According to the simulation results, the blank weight could be reduced from 1.5kg to 1.1kg, and the yield rate of the product increased from 60% to 81%. The methodology of computer-aided die design for the hot forging process developed in the present study could be applied to other forging products. The received results of this study could also be the reference resources for related academic research and be used to develop related products for the factory manufacturing.