Development of CNC Interpolator with Short Block Fitting and Look-Ahead Functions

• Main Authors: Chih-Yu Tseng, 曾旨煜
• Other Authors: Meng-Shiun Tsai
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/65840769034610842525

碩士 === 國立中正大學 === 機械工程所 === 96 === A computer numerical controller (CNC) plays an important role in machine tools. In traditional manufacturing system, a free-form curve or surface are designed with computer-aided design (CAD) systems. Then computer-aided manufacturing (CAM) system uses continuous short block (CSB) or small circular blocks to approximate the free-form curve and send the codes into CNC machine tools. However, this approach has some problems such as large volume data transmission which might cause the loading of the CNC; feedrate fluctuation and velocity discontinuous. It is difficult to achieve high-speed and high-precision under the CSB approach. To overcome the problems, the parametric interpolation is used as the substitute for the conventional interpolation. In this thesis, the CSB fitting scheme with Bezier curve is proposed. By using a look-ahead technique, the sensitivity curvature of curves can be detected and the acceleration/deceleration motion planning is applied for feedrate profiles. Finally, the proposed interpolation is compared with the traditional interpolation. The simulation results show that the proposed interpolation scheme can achieve better tracking and contour accuracies than the conventional interpolation approach. Keywords: CNC, Bezier Curve, Look-Ahead, interpolation .