Abstract: From the spatial kinematic point of view, in order to keep the relative position between the cutter and work piece un-changed, the kinematic transformation from traditional machine tools to free-form ones can be simply realized by two times of vector revolution. However, available CNC system cannot per-form the transformation for each data point during the machining process at real time, nor being it necessary in practice. Therefore, a simple algorism put forward is, it is only necessary to perform the transformation at the reference point, and by means of analyzing the higher order spatial acceleration, all the setting parameters for free-form machine tools can be determined. Accurate formulas for transformation are deduced. In comparison with other methods, this algorism has the advantages of clear in principle, less calculative amount, simpler and more accurate. An example is also given to verify the algorism, and from the reference point is reliable.

Key words: Cradle, Free-form milling machine, Machinesetting parameters, Spatial kinematics