發泡光反射罩材料PET熱壓成形製程參數研究

Investigations on the Process Parameters of Hot Stamping for PET Reflector

溫志強(Chih-Chiang Wen)

指導教授 ： 蔡哲雄

國立臺北科技大學/機電學院/製造科技研究所/碩士(2009年)

摘要

以PET材料製作成一定形狀的反射罩通常使用熱壓成形法(Hot stamping process)。然而針對PET材料熱壓成形技術之報告則是相當少見，本文主要係應用田口實驗設計及有限元素分析來探討PET薄板材料熱壓成形製程的最佳參數組合。本文以熱壓一厚度0.70mm，斷面為U型形狀之PET反射罩之理想製程參數為探討對象。衝床衝頭設計有一通水孔用來加熱或冷卻衝頭控制衝頭溫度，而母模則未施加溫度控制。
由文獻資料及若干本文實際熱壓測試，擬定熱壓程序規劃如下：(1)熱水(以設定的熱水溫度)加熱衝頭達一段時間後，(2)衝頭將PET料片壓入母模，並保持若干時間(成形時間)，(3)切換冷卻水冷卻衝頭若干時間(冷卻時間)，(4)關閉冷卻水保持靜止若干時間(定形時間)，之後拉回衝頭完成熱壓成形。歸納影響產品品質的重要參數中以設定的熱水溫度、成形時間、冷卻時間及定形時間等為四個影響因子，並各挑選三個適當的水準，導入田口實驗設計法，且建立L9(34)三水準四因子之直交配置表，分析各個控制因子對成品影響的程度，實驗設計共執行9次實驗找出最佳的組合，之後再參照最佳組合熱壓程序進行有限元素法熱壓模擬分析。最終獲得連續熱壓生產下之理想的程序為：通熱水溫度86℃加熱衝頭65秒，之後衝頭將PET料片壓入模穴熱成形維持35秒，之後關閉熱水改通以冷卻水(25℃)冷卻衝頭10秒，之後關閉冷卻水並保持靜止時間10秒後拉回衝頭，完成熱壓成形。經使用本文上述程序進行實作驗證結果顯示成品尺寸可控制在合格範圍內。

關鍵字

PET材料 ； 熱壓成形 ； 背光板 ； 田口實驗 ； 有限元素分析

並列摘要

In this paper, the optimization of hot stamping procedures for an U-shape cross-sectional backlight plate with 0.7 mm thickness of PET (polyethylene terephthalate) sheet material was been investigated by using Taguchi method and finite element analysis. One water tunnel designed in the punch of the press for heating the punch by circulating hot water or cooling the punch after heating stage by circulating cold water (25℃) in it. As for the die body, there is no temperature control.
According to the references in the literature and some present preliminary hot stamping testing, we plan the stamping procedures as follows: (1) Switch on the hot water (a designated water temperature) to heat the punch for some time (heating time), (2) Punch the PET sheet into the die and then keep heating for some time (forming time), (3) Shut the hot water and switch on the cooling water immediately to cool down the punch (and the PET workpiece) for some time (cooling time), (4) Switch off the cooling water and keep motionless for some time (form-fixed time), and then pull open the punch to complete the stamping process. In our investigations, we select four process parameters that influence the product quality very much as control factors in Taguchi’s experiment design, they are the designated temperature of hot water, forming time, cooling time, and form-fixed time, and adopt three appropriate levels for each factor to construct the L9(34) matrix experiment. By analyzing the S/N ratios of the quality characteristics for these nine experiments, the optimum process conditions can be obtained for only one cycle of hot stamping process. And then we use finite element method to simulate the hot stamping process for the situation of continuous production based on the optimum process conditions obtained from Taguchi’s method and use the analyzed data to modify the hot stamping parameters for producing continuously. The results of our investigations show that the optimum procedures of the hot stamping process for PET sheet material in continuous production are as follows: (1) Set the hot water at 86℃ to heat the punch lasting 65 seconds. (2) The punch presses the PET sheet into die cavity and keeps 35 seconds for forming time. (3) Shut the hot water and switch on the cooling water simultaneously to cool down the punch (and PET workpiece) for 10 seconds. (4) Switch off the cooling water and keep motionless for 10 seconds then pull open the punch to complete the stamping process. By using present developed process parameters for the hot stamping process experiments, the geometric accuracy of the products reveal steady and acceptable.

並列關鍵字

PET (polyethylene terephthalate) ； Hot stamping process ； Backlight plate ； Taguchi method ； Finite element analysis

參考文獻

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