NC直線加減速処理によるマシニングセンタの直線補間工具経路の運動誤差推定

Abstract

From the machining center (MC) user’s point of view, the authors propose a practical approach to estimate the trajectory error of a linear interpolation cutter path produced by the linear acceleration/deceleration (Acc/Dec) processing for a target MC in this paper. Firstly, a simple and convenient motion model is established for describing the behavior of the servo axes corresponding to the linear Acc/Dec procession of a linear segment, which can be applied to any linear segment regardless of length. Based on the model and a linearity assumption on the dynamics of servo system, a simulation method is developed to precisely calculate the cutter path trajectory in detail together with the servo axis speed from the motion parameters commanded in NC program. The algorithm not only has a very simple structure but also demonstrates high efficiency in actual calculation. In order to confirm the effect of the approach, verification experiments have been performed on the target MC, in which specially designed cutter paths were inspected by a cross grid measuring device with high resolution in non-contact state. These measured trajectories are compared and discussed with the ones simulated under the same motion parameters, from different perspectives. The examination results sufficiently demonstrate the effectiveness of the proposed model and simulation method. Therefore, as a useful tool, the approach provides a potential application possibility, i.e. beforehand estimating the influence of the NC Acc/Dec processing on cutter path accuracy or judging the motion conditions for the machining purpose without performing an actual machining with the target MC.