雷射科技已被發展出來數十年，從原先的軍事運用取向到轉運用到民生工業中，以及現在大舉投入工業中成為新興的工業生產的核心技術。雷射加工應用一直是這十幾年來，科技業與工業中快速蓬勃發展的主要技術之一。相較於傳統工業技術，雷射具有的高能量密度、可加工對象廣泛、不需真空環境或輻射防護、非接觸式加工等等優點使其成為工業發展的核心關鍵。雷射也發展出許多不同的類型，使其能夠更廣泛的適應各種工業需求。依照加工對象的不同可以選擇不同雷射，如使用Nd: YAG雷射加工金屬、使用CO2雷射加工玻璃或高分子材料。而本文研究的對象是使用CO2雷射切割偏光板，在光電產業中原先都使用刀輪這類傳統接觸式加工來進行切割。本研究中希望透過探討雷射切割過程中所使用的輔助氣體在雷射加工頭中的流道設計，來分析輔助氣體與雷射切割過後熱效應區之間的關係。透過改善熱效應區大小，來提升雷射切割偏光板的產能與良率。
為了透過有限元素模擬了解氣體在雷射切割的過程中對偏光板的影響，首先需要具備有限元素分析軟體的操作能力，也同時需要有流體力學等基礎觀念。並且還需要透過文獻探討，以及有效率的實驗設計法來讓研究更快取得結果與並讓研究方向更貼近目標。除了透過模擬了解氣體的流場狀態，更需要透過切割實驗來找尋模擬與實際狀況的關聯。透過田口方法的實驗規劃可以讓實驗更有效率，還能同時能夠分析各因子對切割品質的影響。
經由有限元素模擬與田口實驗法的使用，本文提出了對於偏光板被雷射切割後產生的熱效應區邊框問題的觀察。並透過模擬提出了經由改變雷射切割加工頭的構造與流道設計的建議，來改變輔助氣體流場達到改善熱效應區問題。經由田口實驗法，來比較並提出雷射功率、加工速度、脈衝頻率與氣體流量對於熱效應區大小的影響力。

Laser technology was widely used in modern industry. The main study of this thesis was about the relation between the flow field of laser cutting nozzle and the width of the heat affected zone on polarizers. By using computer-aided engineering software (FLUENT) to simulate the flow field of clean dry air (CDA) in the nozzle. The laser cutting nozzle was combined with a barrel and a mouthpiece. After analyzing the flow field of the CDA in laser cutting nozzle with original design, we designed a new laser cutting nozzle with two gas runner to create swirl flow in the nozzle. To compare the results of simulations, we started to have experiments to find the relation between the heat affected zone (HAZ). Five control factors were selected as follows: (1) power of the laser source, (2) velocity of cutting, (3) frequency of the pulsed laser, (4) volume flow rate of CDA, and (5) the pressure of CDA. By using one-factor-at-a-time experiments, we find out the relations for each factor with the width of HAZ. And using Taguchi method to find the optimal parameters for each factor with two different designs of nozzles. By using variation analysis, we can decide which factor is the most significant factor in controlling the width of HAZ.

From simulations and experiments, we have several conclusions: (1) With higher power the bigger width of HAZ will get, and when the power over 16% the position of the pulsed spot will have scorch marks like splash in both sides. (2) The width of HAZ will decrease with the increasing cutting speed. Because of the laser source with a PSO system which can control the distance between every two pulsed spots, and when the cutting speed increased, the energy on the polarizers for per unit area is decreasing. So the residual heat is getting lower and the width of HAZ is also smaller. (3) With bigger of the flow rate, the width of HAZ is bigger too. We found that when the flow rate up to 50 L/min, the width of HAZ will substantially increase. Because of the expansion effect will stronger than the cooling effect on that situation, so the softening polarizers will be expanded before being solidified. (4) But the frequency of pulsed laser and the pressure of CDA, the reaction of the width of HAZ has no clear trend. (5) According to the variation analysis of the Taguchi methods, we found that the most significant factor is the power of the laser, the second one is the cutting speed, and the most insignificant one is the flow rate of the CDA. (6) With simulations to analyze the flow field of CDA in the nozzle, we found that the swirl flow can be created by simply modified the gas runners’ position. The nozzle with two gas runners is much easier to make and has better benefits than it with three gas runners. And when the gas runners with 7O of the inclination, the greatest swirl flow will get.

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