精密薄殼組件的模流分析與射出成型參數最佳化

Abstract

DVD光碟的發明在資料保存上有著極大的貢獻，為了提高光碟生產效率，降低生產成本，因此本研究目的為應用田口法輔助分析影響翹曲在射出成型製程技術中的有效因子，並歸納與建立薄殼射出成型最佳參數系統化流程。至於縮短射出件製造週期時間會導致產品翹曲量增加，特別對薄殼件而言容易影響品質，反而使生產效率降低；因此本研究也兼顧以製程週期與品質條件，做為探討最佳射出成型參數的分析目標，達到既能縮短週期時間並能保持產品品質的參數數據的建立。 本研究利用田口式實驗計畫法找到射出成型條件中重要影響因子，並利用模流分析軟體Moldex3D模擬射出成型加工過程，應用田口方法得到薄殼塑膠件的成型參數以減少因體積收縮所產生的翹曲。為了到達目標所以採用Moldex3D軟體分析且利用有五水準的田口直交表 進行實驗設計。使用射出時間、塑料溫度、模具溫度、保壓時間、保壓壓力及冷卻時間等六個參數進行實驗得到各組的翹曲量和收縮率，接著利用信號雜訊比得到參數的最佳水準以及各參數在翹曲的影響。 應用田口式實驗設計法去找出射出成型的優化條件，是一個相當有效率的方法，可以找出射出成型中有效因子的最佳設定，並得到產品成型後的最小翹曲。在本研究中，將光碟生產週期時間縮短至5秒，而翹曲值只有0.063mm達到目前相關產業可接受製程效率的生產標準。 在實驗過程中得知使用不同設計的水路對產品品質具有很大的改善，選擇適當的水路在相同成型參數條件下翹曲量差了三倍之多。將簡單薄殼件的實驗結果應用在複雜曲面薄殼，發現保壓壓力是影響總翹曲最重要的因子。本研究另外使用較複雜的機殼模型分別以三種不同材料進行測試實驗，結果發現利用本研究所建議的最佳製程參數系統化分析法加上田口實驗法的輔助，能使產品品質提昇7%~18%，可提供為相關研究或實務的應用參考。

The invention of DVD was a great contribution to data storage. In order to improve DVD manufacturing efficiency and decrease the production cost, so the purpose of this research aims to analyze the effective factors of warpage of DVD and find optimal parameters in injection-molded process applying the Taguchi method. As to reduce injection-molded product cycle time will increse the warpage of products, especially for thin-wall injection parts, will reduce the quality, and decrease production efficiency. So we expect to find the optimal set of injection molding process parameters that can reach the goal of both reducing production cycle time and keeping the quality of products. This research used the experimental design of Taguchi method to determine the injection molding conditions, and the injection processes were simulated using the commercial software Moldex3D. The application of Taguchi optimization technique to reduce warpage problem related to the shrinkage variation with critical process parameters was studied. For this purpose, several cases about Moldex3D analysis are carried out by utilizing the combination of process parameters based on five-level of L25 Taguchi orthogonal array design. In most of the cases, six critical injection parameters were used.These parameters are injection time, melt temperature, mold temperature, packing time, packing pressure and cooling time.The signal-to-noise (S/N) are used to find the optimum levels and to indicate the impact of the process parameters on warpage. In addition, applying the experimental design of Taguchi method is a quite effective method to deduce the optimum set of effective factors in injection molding to produce plastic parts with minimum warpage. Based on the resolved data suggested by the current research, the product efficiency has been improved. DVD production cycle time can be reduced to 5 second, in the case that the warpage of discs were keet in the region of 0.063mm attain to production standard. The experimental results indicate that the quality of products are improved greatly while using another layout of the cooling chanels designed by our Lab(NCTU CIDM Lab). In this experiment, selecting suitable cooling chanels and keeping the other parameters the same can reduce the critical warpage value more than three times. Applying the concluded regulation from the study of the simple thin-shell plastic parts to the model of general 3D surface thin-shell parts, the results showed that the factor of packing pressure was aslo the critical factor to the warpage issue. In addition, this research proposed three different kind of material to the simulation tasks of complicated phone cover, the results showed that the quality of the tested phone cover are improved, that the warpage was reduced from 7% to 18% by using the proposed method of modified Taguchi optimization method.