四軸快速成型系統之研製

A Study of Four-axis Rapid Prototyping System

胡雅慧(Ya-Hui Hu) ； 林高輝(Kao-Hui Lin) ； 吳元升(Yuan-Sheng Wu)

《南亞學報》 30期 (2010/12) Pp. 103-126

https://doi.org/10.6989/JN.201012.0103

摘要

由於快速成型技術係採用分層加工及逐層堆疊之原理建構模型，因此可快速且直接製程複雜之幾何模型，提供工件進行詳細評估與分析，而消失模具有生產成本低、重量輕及環保等特性，相當適合作為快速成型之加工材料，以降低昂貴的研發設計費，故快速成型技術已成為一廣泛應用之成型方式。然而在傳統的快速成型加工中，多以雷射光進行單層垂直面之輪廓加工動作，為了降低階梯誤差，則藉由減小切層厚度以提升加工精度，但卻因切層數的增加而延長加工時間，不易應用於大尺寸工件之製作。本研究以快速成型之分層堆疊原理及消失模鑄造之概念，配合輪廓佈點演算法、座標空間轉換及四軸切割機構，發展一套四軸快速成型系統，進行各層輪廓之斜面切割，以有效改善階梯效應所產生之誤差，並於設定成型誤差範圍內，可採用較厚之加工層以減少切層數，有效提高成型速度，達到提升加工精度與加工速度之目的。利用本研究發展的四軸快速成型技術及機構進行220 mm x 120 mm x 50 mm範圍內之不規則外型實心瓶加工實驗得知，當層厚為10 mm時，斜面加工與階梯加工之工件誤差分別為0.87 %及2.89 %，加工時間分別為53分鐘及44分鐘，而控制階梯誤差在1 %以下，加工時間則需145分鐘。另由500 mm × 250 mm × 500 mm甜甜圈外型之加工件，進行大尺寸消失模製程流程之說明與成品誤差分析探討，結果顯示，整體理論體積誤差量ET值約為0.35 %。由實驗結果顯示，本研究所發展之大尺寸消失模之四軸快速成型系統，在相同誤差量之範圍設定下，所提出之斜面加工技術在速度上約為傳統階梯加工技術之2.8倍，且可實際應用於大尺寸消失模之快速成型製程上，可有效達成提升傳統快速成型之加工精度與加工速度等效能。

關鍵字

消失模 ； 快速成型 ； 四軸切割機構 ； 斜面加工 ； 階梯加工

並列摘要

By applying the principles of layer-by-layer cutting and layer-by-layer stacking, RP can not only construct a complicated geometrical model rapidly and directly but also offer detailed evaluation and analysis of the result of each workpiece. Yet, in order to lower the cost in research and development, the lost foam, which uses much lighter material and can greatly reduce the cost of production and the damage onto the environment at the same time, is a better alternative for prototyping. All these attribute to the popularity of RP, which has already become a commonly-used prototyping method. However, in traditional RP, single layers are generally processed with laser on a vertical plane. In order to reduce stair errors, the thickness of each single layer has to be reduced to gain better precision, which inevitably prolongs its machining time and makes it difficult for large scale machining. Based on the principle of layered stack and the concept of lost foam casting and coupled with the methods of Contour Distribution, Spatial Coordinate Transformation and Four-axis Cutting Mechanism, a Four-axis Rapid Prototyping system is developed to process bevel plane cutting and reduce the stair errors. When the error is controlled within a certain range, this system can perform thicker layer machining and reduce the number of layers, so as to achieve better precision and higher forming speed. By using the Four-axis RP System of this study, the workpiece - a solid bottle of irregular shape whose size is within 220 mm x 120 mm x 50 mm-is processed to compare the bevel error and the stair error. The result shows that, when the slice is as thick as 10 mm, the bevel error and the stair error are respectively 0.87% and 2.89%, with their machining spans 53 minutes and 44 minutes; yet, the Stairs processing is obtained under 1%, with its procession span as long as 145 minutes. Another workpiece shaped like a doughnut of 500 mm x 250 mm x 500 mm is also processed to illustrate the steps of the large-scale lost foam prototyping system and offer discussion about the error analysis. The result shows that the total volume error ET of the prototyped workpiece is around 0.35 %. Therefore, it is concluded in this study that, within the same range in error, the bevel machining speed is greatly improved, which is about 2.8 times as fast as that of the traditional machining. The large scale lost foam Four-axis Rapid Prototyping system indeed helps to raise the precision and speed of the traditional rapid prototyping.

並列關鍵字

Lost Foam ； Rapid prototyping(RP) ； Four-axis Cutting Mechanism ； Bevel machining ； Stair machining