Abstract
From the machining center (MC) user’s point of view, the author proposes a practical approach to estimating the trajectory errors of a circular arc interpolation cutter path produced by the NC servo characteristics for a target MC in this paper. Firstly, a simple and convenient acceleration/deceleration procedure model is given for describing the behavior of the servo axes in an interpolation motion of circular arc segments. This model contains two parameters whose value is necessary to be identified by experiments. The first is the time constant of the servo axes and its value can be easily determined from the radius reduction in circular motion trajectories corresponding to different radius and feed rate. The second is a timing parameter to define the time interval of the acceleration and the deceleration procedures between two interpolation segments, and its value can be readily identified from a measured trajectory of two circular arc cutter path. Based on the model and an assumption, in which the motion of each segment is independently performed, a concise and efficient simulation algorithm to calculate a cutter path trajectory composed of many circular arc segments in detail is developed. Comparison results of the simulated cutter path trajectories with the measured ones and the contours of work pieces machined under the same motion condition sufficiently demonstrate the effectiveness and reliability of the proposed approach. Therefore, as a useful tool, the approach is applicable to beforehand estimating the influence of the NC acceleration/deceleration motions on cutter path accuracy or judging the motion conditions for the machining purpose without performing an actual machining test with the machining center.
