Stiffness increasing device for the moving elements of the CNC milling machines

This work presents a new concept of automatic compensation of the ram deformation during its in-cantilever horizontal motion of the milling machines that feature a ram slide (headstock) on the column side. During the ram horizontal motion that is a CNC controlled axis of the machine, there is a permanent modification of the ram gravity center that makes the reaction forces in the guideways to permanently change their rates as well. Thus, an elastic variable deformation occurs on the ram supports along with the elastic deformation of the guideways and the elastic deformation of the ram slide. The new concept of automatic compensation of the elastic deformation presented in this work takes its compensation force from the feed kinematic linkage of the ram, having interdependence between the ram motion length and the rate of the compensation force. The rate of the compensation force taken over from the kinematical linkage is very low, then it is mechanically multiplied (>100 times), until the value needed for the quasi-total compensation of the elastic deformations is reached. The experimental application of this new concept has been done on a milling machine model BFK 1000 CNC, where an increase by 90% of the ram geometrical accuracy while going out in cantilever has been obtained, compared to the case when such a compensation device would be missing.