基於 Open CASCADE 開發機械手臂 CAM 技術和軟體

Development of CAM Technology and Software for Industrial Manipulator based on Open CASCADE

徐顯舜(Hsien-Shun Hsu)

指導教授 ： 蔡孟勳

國立臺灣大學/工學院/機械工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202201577

摘要

近年來自動化生產蓬勃發展，機械手臂系統除了傳統搬運外，也取代人力進行許多加工應用，例如：去毛邊、焊接以及曲面拋光等各式加工。而這些加工應用所需的路徑需透過CAM(Computer-Aided Manufacturing)軟體產生，目前市面上也推出多款商用機械手臂加工CAM軟體。商用CAM軟體需支付高額授權費用以及功能眾多不易上手，對於中小企業難以負擔以及缺少專業人員去做使用。因此本研究透過幾何核心開源函式庫Open CASCADE(OCC)開發CAM軟體及技術，設計一套符合中小企業需求之客製化軟體，不僅操作易上手，也降低生產成本協助中小企業實現更高的自動化水準。
本論文以電腦圖學中常見的數學模型NURBS(Non-Uniform Rational B-Spline)為基礎，實現三種曲線規劃方式，分別為公差規劃、步長規劃和點數規劃。公差規劃為以使用者所設定公差和最大步長為參數進行計算，使曲線誤差符合設定之公差，線段以不超過最大步長為原則；步長規劃則以不考慮公差情況下以步長為參數進行計算，使規劃出的每一路徑長接近設定之步長；點數規劃則以加工點數量為參數進行計算，主要用於長線段加工，因為長線段只需數個路徑點即可表示。在加工應用過程中，因刀具半徑不同須將規劃出的路徑進行刀具補正，因此本論文也應用路徑偏置演算法進行路徑偏置。
本研究圖形化介面透過WinForms進行開發，提供1.加工線段選擇；2.刀具向量方向選擇和正反向切換；3.路徑規劃方式及參數設定；4.路徑偏置/深度設定；5.前側傾角設定和進退刀參數設定。路徑規劃完後輸出NC碼供機械手臂加工，並將加工參數和相關資訊存入XML(Extensive Markup Language)檔，未來在相同但參數不同之路徑可進行編輯操作，以上實現完整的CAM功能。

關鍵字

機械手臂 ； NURBS曲線 ； 刀具路徑規劃 ； 路徑偏置 ； OCC ； 軟體開發

並列摘要

In recent years, automated production has flourished. Industrial manipulators systems not only handle traditional handling, but also replace manpower for many manufacturing applications like：deburring, welding and surface polishing. These tool paths need to be generated by CAM (Computer-Aided Manufacturing) software and a variety of commercial CAM software for industrial manipulators has been launched on the market nowadays. However, these commercial software needs to pay high licensing fees and the functions are too complicated to use. It’s unaffordable for SMEs (Small and Medium Enterprises) and lack of professionals to use. Consequently, this research develops CAM software and technology through the geometric modelling core open source library Open CASCADE(OCC). It aims to develop a customized software that meets the needs of SMEs as well as easy to operate. It reduces production costs to help SMEs achieve a higher level of automation.
Based on the common mathematical model – NURBS (Non-Uniform Rational B-Spline) in computer graphics, this thesis implements three tool path planning methods, namely tolerance planning, step length planning, and point number planning. Tolerance planning is to use the tolerance and maximum step length as the parameters to make the calculation, so that the chord error conforms to the setting tolerance, and the line segments not exceed the maximum step length. The step length planning is to calculate with the step length as the parameter without considering the tolerance, so that each planned line segment is close to the setting step length. The point number planning is to calculate with number of tool path points as the parameter. It’s mainly used for long straight lines because the long line segment can be represented by only a few path points. In the process of machining, the planning path would be shifted due to the different radius of the tool, so this thesis also applies the curve offset algorithm to offset the path.
The graphical user interface of this thesis is developed through WinForms, which provides: 1. the selection of tool path, 2. the selection of tool axis direction and direction switching, 3. the different path planning method and its parameters setting, 4. path offset, depth, 5. front / side rake angle setting and the cutting and retraction parameters. After the tool paths are planned, the NC code is output for the robotic arm to process. The processing parameters and related information are stored in the XML (Extensive Markup Language) file which users can edit in the future. After the functions mentioned above are implemented, the robotics CAM software will be realized.

並列關鍵字

Industrial manipulator ； Tool path planning ； NURBS curve ； Tool path offset ； OCC ； Software development

參考文獻

[ 1 ] M. Shpitalni, Y. Koren, C.C. Lo, Realtime curve interpolators, Computer-Aided Design, vol. 26, pp. 832-838, 1994.

[ 2 ] D. C.H. Yang, T. Kong, Parametric interpolator versus linear interpolator for

precision CNC machining, Computer-Aided Design, vol. 26, pp. 225-234, 1994.

[ 3 ] S.S. Yeh, P.L. Hsu, The speed-controlled interpolator for machining parametric curves, Computer-Aided Design, vol. 31, pp. 349-357, 1999

[ 4 ] R. T. Farouki, Y.F. Tsai, Exact Taylor series coefficients for variable-feedrate CNC curve interpolators, Computer-Aided Design, vol. 33, pp. 155-165, 2001.