微球接頭組裝技術之研究

Abstract

微球接頭是由圓球與球殼兩個元件所組裝構成的，其能夠提供多角度和多方向的自由度，不但能改變運動方向，還能承受一定量的負荷，有相當大的發展潛力。然而在微米尺寸等級時，由於生產與製作不易限制了其應用的範圍，對此本研究設計其以機上微組裝技術來製作微球接頭，首先加工製作出微圓球與微球殼，接著藉由微球殼材料自身的彈性變形，直接在生產製作微圓球與微球殼的機台進行組裝。此方法可省略物件的夾持交換，減少夾持誤差，相對位置準確。 為了瞭解此機上微組裝方法之組裝情形，本研究先採用可靠度工程中常用之失效模式、影響與關鍵性分析(Failure Mode, Effect and Criticality Analysis, FMECA)來判斷微球接頭可能的失效情形，發現倘若微圓球和微球殼之幾何形狀設計不良，除了會造成組裝過程中微元件的損壞，導致組裝失敗，也會使裝配後的微球接頭間隙不適當而造成效能不佳。對此本研究利用有限元素法配合電腦數值軟體ANSYS來解決這個問題，針對組裝過程中微元件的變形情況做模擬分析探討。藉由模擬所獲得的資訊，可改善組裝的品質，確保此組裝方法之可行性與實用性。 由研究結果顯示，由於微球殼是薄殼時之徑向變形量比厚殼時來的大，且在開口角度170度時有最大的可容許徑向變形量；若當微球殼的半徑大小固定時，組裝後預得到適當餘隙配合之微球接頭，則與之配合之微圓球以選擇開口角度170度較佳，半徑大小則依間隙和微球殼的變形量來決定。

關鍵字：機上微組裝、微球殼、變形模擬、失效分析、間隙配合。

The micro spherical joint assembled by precision a micro spherical ball and shell has great potential for application to the micro robots and machines. It can not only deliver the force and moment but also supply high freedom of movement. It is very simple and easy to operate on the machine using the elasticity deflection for the assembly of the micro ball and shell. In order to know the reliability of the micro spherical joint, reliability analytical tools such as failure mode effect and criticality analysis (FMECA) and fault tree analysis (FTA) are used. According to FMECA and FTA, the dimensional mistakes and assembly load were the main factors making the micro joint failure. In order to overcome the problem, deflection of micro spherical shell were simulated under the various conditions of shell angles, radius, and thickness for some materials by means of the finite element method and computer-assisted numerical program ANSYS. The simulated results based on deflection would be helpful for designing the dimension of the micro assembly parts and handling the correct clearance of joints. Keyword: micro assembly, micro spherical shell, deflection simulation, FEMCA, gap analysis.