Calculation method for step length based on the kinematics model of machine tools

To improve the precision and cutting efficiency of the tool path generation in five-axis NC machining of sculptured surfaces, through kinematic modeling of the special machine tools, a new calculation method for step length is presented. Aiming at five-axis NC machines with non-orthogonal structure of tool swinging and table rotation type, the kinematic model including the establishment of the motion transmission and the decomposition of the motion coordinate is constructed. And then, it is shown that the cutting error depends on the structures of the machine tools as well as the surface geometry. Moreover, a new algorithm is developed to estimate the cutting error and calculate the maximum allowable step length. Examples show that the maximum error of the new algorithm is reduced by 37.01% comparing with the conventional method of variable step, and the average step length is improved by 8.91% comparing with the equal step at the same cutting tolerance. It suggests that the cutting error can be controlled effectively and the proposed method is an effective means for improving machining efficiency and quality of five-axis machining of sculptured surfaces.