Feed Rate Planning And Software Development For Complex Surfaces Machining Based On Kinematics Constraint Analysis

It is of great significance to obtain the actual feed rate which affects the machining efficiency and accuracy in five-axis machining of complex surface.Due to the time-varying tool orientation and the physical constraints of each movement axis,the actual feed rate at cutter location point(CLP)with respect to the workpiece is rather different from the expected feed rate given in the NC code.This phenomenon will make process planning such as feed rate scheduling invalid.To this end,a real-time acquisition and analysis software of feed rate based on Remotools for Heidenhain CNC is developed to collect the real-time data of the machine tool.Then,speed distribution mode on each axis of the machining center with given feed rate as well as the speed limit of each axis are identified.Moreover,methods for calculation of the actual speed of each axis and estimation of machining time based on the acceleration/deceleration model are further established with considering the constraints of turning points.Through kinematic analysis of the machine tool,the CLP feed rate with respect to the workpiece in machining process can be calculated.To keep the actual CLP feed rate equal to the expected one,an optimization method is proposed for scheduling of the feed rate in NC code.The method is validate by a group of simulations.Finally,an impeller hub machining experiment is carried out on the Mikron UCP800 Duro five-axis machine center equipped with HEIDENHAIN ITNC530 M CNC,to verify the effectiveness of the proposed methods.The results indicate that the offline speed calculated by the method in this paper is basically consistent with the measured speed for each axis in machining process,which verified the effectiveness of speed distribution mode.Meanwhile,the maximum deviation between the CLP feed rate and the expected feed rate exceeds 90%,which means the CLP feed rate with respect to the workpiece in the actual machining process depends on feed rate distribution mode of CNC.The traditional method which assigns the expected feed rate to the F code of NC file is unacceptable.The effectiveness of the proposed method for scheduling of the feed rate in NC code,making the actual CLP feed rate equal to the expected one,is verified by the experiment where the deviation of processing time between the estimated one and the actual one is only 6.3%.