A novel approach to determination of wheel position and orientation for five-axis CNC flute grinding of end mills

Abstract

In practice, the flutes of end mills are ground using CNC grinding machines via controlling the grinding wheel’s position and orientation to guarantee the designed flute parameters including rake angle, flute angle, helix angle, and core radius. However, for the previous researches, the designed flute profile was ground via building a specific grinding wheel with a free-form profile using two-axis CNC grinder. And, the free-form grinding wheel will greatly increase the manufacturing cost, which is too complicated to implement in practice. In this research, the flute-grinding processes were developed with a standard grinding wheel via five-axis CNC grinding operations. The mathematical representation of machined flute parameters was deduced in terms of the grinding wheel’s position and orientation. The geometrical constraints to avoid interference and abnormal flute profile for the five-axis CNC fluting were first developed in this work. Finally, the difference between the designed flute parameters and the machined flute parameters were formulated as a constrained optimization problem so as to determine the wheel’s position and orientation. The set of effective initial points for this optimization model was found mainly distributed the first quadrant of the contact area. The fminsearch function in Matlab toolbox was recommended to solve the optimization model due to its capability of handling discontinuity problem. The solution obtained in optimization model and the corresponding machined flute parameter were verified and compared with Boolean simulation in CATIA to confirm the validity and efficiency of the proposed approach. The results showed that the accuracy of machined flute parameters could achieve 1e-3 mm and 1e-2°, which satisfied the machining tolerance. This study provides a general solution for the CNC fluting operations and could be extended to grind complex surface of end mills in the future study.