G codes for the specification of Pythagorean-hodograph tool paths and associated feedrate functions on open-architecture CNC machines
نویسندگان
چکیده
A new class of machine codes for the specification of Pythagorean-hodograph (PH) curve tool paths, and associated feedrate functions, is proposed. The PH curves are a special family of free-form curves, compatible with the Bézier/B-spline representations of CAD systems, that are amenable to real-time interpolation at constant or variable feedrate directly from their exact analytic descriptions. The proposed codes are compatible with ‘ordinary’ (linear/circular) G codes, and may be regarded as extensions thereof. Compared to the customary approach of using piecewise-linear/circular approximations, they offer significant improvements in the accuracy, efficiency, data volume, and flexibility of part programs for free-form shapes. Experimental results from an implementation of these real-time PH curve interpolators on an ‘open-architecture’ CNC milling machine are also described. 1998 Elsevier Science Ltd. All rights reserved.
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