Lookahead and Acceleration/Deceleration Algorithms for Micro-Line Blocks Machining

In micro-line blocks machining with real-time curve reconstruction, the original contour of workpieces usually can not be reconstructed accurately, and the contour errors of the reconstructed curves exceeds the allowable limit of contour error.Curve reconstruction conditions, including corner angle condition which depends on allowable feedrate of the corner angle, chord length condition which is based on correlated change of the corner angles and chord lengths of successive micro-line blocks are given.A feedrate profile planning algorithm across the knots of the reconstructed curve with S-shape acceleration/deceleration (acc/dec) is presented in lookahead and acc/dec algorithm.Simulations and experiments using these new methods show that the maximum contour error between the reconstructed curve and the micro-lines is less than the permissible contour error set in CAM software for segmenting the original curve into the micro-line blocks, and the machining speed is 1.5~3.3 times the speed of traditional machining process.The results indicate that by using the new algorithms, geometry elements of original contour of workpieces can be distinguished from NC code effectively, and the base points can be found, so the original contour of workpieces can be reconstructed accurately, and the interpolation points pass every knot of the reconstructed curve precisely.The method discussed has application in complex contour machining and designing middle or high grade CNC.