A feedrate optimization method for CNC machining based on chord error revaluation and contour error reduction
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ORIGINAL ARTICLE
A feedrate optimization method for CNC machining based on chord error revaluation and contour error reduction Baoquan Liu1 · Mengjie Xu1
· Jianping Fang2 · Yong Shi1
Received: 25 June 2020 / Accepted: 19 October 2020 © Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract Interpolation of parametric curves is one of the most effective methods in high-performance computer numerical control (CNC) machining. Its precision highly depends on chord errors from feedrate scheduling and contour errors from real-time machining. In order to improve machining precision, a novel feedrate optimization method is proposed in this paper. The osculating circle (OC) method can effectively estimate the chord errors, but its precision degrades if the trajectory curvature changes dramatically. Therefore, an iterative algorithm based on OC method is developed to reevaluate the chord errors, which can upgrade the estimation precision and further improve the feedrate constraints. To reduce the contour error, feature zones on the trajectory are firstly selected according to the kinestates and a specified zone length. In each feature zone, the projection of tracking error onto the zone chord-line is calculated as a new vector, based on which an indirect contour error compensation method is proposed through refining the feedrate profile. To ensure that the contour error can be reduced, the compensation performance is pre-estimated before implementation. Finally, simulation results in different scenarios are presented to validate the high precision of the proposed method. Keywords Feedrate optimization · CNC Machining · Chord error revaluation · Contour error reduction
1 Introduction Along with the fast development of industrial productivity, computer numerical control (CNC) machining has become more and more important in various automation fields [1]. Conventional machining method is based on curve fitting using fundamental lines and circular arcs. When the trajectory becomes more complicated, the data amount as well as the computation and transmission burden increase dramatically. Then, the system efficiency will decrease sharply and the existing mechanical vibrations will be enlarged [2]. Interpolation of parametric curves is an effective solution in CNC machining. Complex trajectories can be constructed and expressed by parametric equations; then, through feedrate scheduling, the interpolation points can be determined
Mengjie Xu
[email protected] 1
School of Electrical & Control Engineering, Shaanxi University of Science & Technology, Xi’an, China
2
TOLL Microelectronics Co., Ltd, Xi’an, China
in sequence during real-time machining, which makes the machining process simpler and more intuitive [3–6]. In parametric curve interpolation, if the feedrate profile is scheduled, in every interpolation period Ts , the chord-line connected by adjacent interpolation points is calculated and utilized as the toolpath instead of the real curve segment [7]. Then, chord errors, which describe the deviations bet
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