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標題: | 鈹銅模仁用於非球面鏡片射出成型研究 Study on the Use of Be-Cu Alloy Mold Inserts in Plastic Injection Molds for Aspheric Optic Lens |
作者: | YEN-HAO CHEN 陳彥豪 |
指導教授: | 楊申語 |
關鍵字: | 鈹銅模仁,非球面鏡片射出成型, Be-Cu Alloy Mold Inserts,Aspheric Optic Lens,Injection Molding, |
出版年 : | 2006 |
學位: | 碩士 |
摘要: | 非球面鏡片模仁一般以無電解鎳鍍層為主,但是成本昂貴且製程時間長;在產品設計初期,快速模仁開發具相當優勢,鈹銅材料與無電解鎳有類似加工特性,是暫用模仁的好選擇。
本研究探討鈹銅材料用於射出成型模仁的適用性評估及非球面鏡片射出成型製程技術。第一部份探討製程參數對鈹銅表面氧化速率的影響,比較不同塑料(PS、PMMA、COC)與不同製程條件(模具溫度、融膠溫度、射出速度)對鈹銅模仁表面氧化程度影響。進一步探討射模次數對模仁氧化層生成影響,固定製程參數而增加射模次數,分析其表面情況作為模仁壽命評估基準;另於實驗中加入氮氣系統使模仁與氧氣隔離,評估氧化改善程度;最後將鈹銅披覆鎳磷鐵氟龍鍍層,進行射出實驗,比較鍍膜前後差異性。第二部份探討製程參數對非球面鏡片品質影響,導入田口實驗設計,探討模具溫度、融膠溫度、保壓壓力及射出速度等製程因子對非球面鏡片形狀精度影響,利用光彈系統觀察射出件殘留應力分佈狀況。 鈹銅氧化實驗結果顯示,射出條件對模仁表面氧化影響,以融膠溫度最顯著,射出速度、模溫次之;相同製程參數下,使用不同塑料影響不大。相較於提高料溫,模溫改變對氧化程度影響不大。模擬鏡片射出參數1000模次實驗結果顯示,隨射模次數增加,模仁表面氧原子濃度呈線性成長趨勢,表面粗糙度亦隨之增加,欲使成品具較佳表面粗糙度,模仁壽命建議在250模次,此時粗糙度值與初始模仁相差僅7~8nm;當射出模次超過1000次,模仁表面出現微刮痕,射出鏡片因表面缺陷而無法使用。在開合模過程中,增加氮氣系統延緩模仁表面氧化效果並不顯著,氧化層成份經ESCA化學組態分析為Cu2O,並且沒有發現BeO存在。為解決氧化問題,本研究嘗試在鈹銅模仁鍍層,經1000模次射出成型實驗,表面無氧化物形成,且表面性質良好與初始狀況幾無差異。 非球面鏡片射出實驗結果以母模面輪廓形狀精度誤差值為品質特性望小為目標,量測數據經變異數分析所得結果顯示,影響表面形狀精度因子以模具溫度最為重要,其次為保壓壓力,高模溫及高保壓壓力可得較佳形狀精度。輔以光彈實驗觀察分子定向及殘留應力,使用扇型澆口模具溫度影響最明顯,隨模溫升高,光彈條紋逐漸減少;使用方型澆口,提升融膠溫度,可有效降低光彈條紋。而射出速度設定必須適中,過低射速造成零件靠近澆口處嚴重雙折射差值;射速過高,則使零件中心產生殘留應力。過大保壓壓力,會使光彈條紋明顯增加,顯示成品件殘留應力過大。 For the molds of optical lenses, ultra-precision machined mold inserts are required. Most of the mold inserts are machined by a single-point diamond (SPD) turning of electroless nickel deposit on tooling material. Since the preparation procedure makes the nickel deposit expensive and time-consuming, other materials for rapid tooling during development are demanded. In this study, Be-Cu alloy which can be SPD machined is explored. This study is devoted to investigating the use of the Be-Cu alloy mold insert in plastic injection molds for aspheric optic lens. In the first part of this study, the effects of the molding conditions on the oxidation of mold inserts are experimentally investigated. The parameters include mold temperature, melt temperature and injection speed; the materials include PS, PMMA and COC. The oxidation degree and surface roughness of the Be-Cu inserts as function of injection counts are measured and analyzed. To reduce the oxidation, blowing nitrogen into mold cavity and depositing Ni-P-PTFE on the insert surface are attempted. In the second part of this study the effects of the conditions on the molding quality of aspheric optic lens using a Be-Cu insert in the injection mold. Taguchi’s method is employed to evaluate the significance of different processing condition on the quality of molded parts. Form errors of molded parts measured by the surface profiler and residual stresses measured by photo-elasticity are used to evaluate the molding quality. The results indicate that melt temperature is the major factor to influence mold oxidation rate, and injection speed and mold temperature are next in importance. There is no obvious change of the oxidation behavior in Be-Cu mold insert when using different material in the same molding conditions. The differences in the change of surface roughness in the first 250 injection counts are less than 7~8 nm. When the injection counts exceeds 1000, micro crack can be observed in the mold surface. Thus the molded optic lens can not be used. The XPS analysis show that Cu2O is the primary constituent on the surface of the mold insert. Blowing nitrogen onto cavity surface has no significant effect on reducing oxidation. On the other hand, Ni-P-PTFE deposit can prevent the oxidation perfectly. The differences between the profiles in mold insert and molded parts are used to evaluate the molding precision. Mold temperature and packing pressure are found to be the principle factors affecting the molding precision. Higher mold temperature and packing pressure result in better dimensional precision. The molecular orientation and residual stress are compared with aid of birefringence observed with polariscope. Molded in a fan-gated mold, it is found that the lenses molded with higher mold temperature yield less orientation and residual stress. Molded in a rectangular-gated, lenses molded with higher meet temperature yield less residual stress. Over-packing causes drastic disturbance to molecular orientation and results in poor molding quality. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/33679 |
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顯示於系所單位: | 機械工程學系 |
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