MATHEMATICAL MODELS OF CUTTING FORCES IN TURNING OPERATIONS

Abstract

The paper considers a variant of the predictive determination of the cutting force components for non-free cutting when turning. It is established that both the process of plastic deformation and the process of friction on back surfaces adjacent to main and auxiliary cutting edges of the tool influence the magnitude and direction of a cutting force component. The resulting force is defined as the vector sum of the forces that occur on the main and auxiliary cutting edges. We propose to determine the cutting force direction in non-free cutting as a vector in the direction of chip flow relative to the main cutting edge. The cutting process photography fixes the inclination angle of the chip flow. It is confirmed that in free cutting, the direction of chip flow is perpendicular to the main cutting edge. Contour turning on CNC lathes is accompanied by a change in the direction of feed motion resulting in a change in the main and auxiliary kinematic angles of the cutting tool. An increase in the active length of the main cutting edge in this situation leads to an increase in the contact area of the back surface of the main cutting edge with the workpiece surface, and, consequently, to an increase in the friction component of force, acting on the main cutting edge. Experimental measurement of the cutting force components makes it possible to determine the degree of influence of the force components associated with both the process of plastic deformation of the work material and the process of friction on the back surfaces adjacent to the main and auxiliary cutting edges of the tool. The obtained analytical dependences express the functional relationship between the elements of the cutting modes, the geometric parameters of the cutters, the degree of wear, the shape of the workpiece surface, and physical and mechanical properties of the work material. A large set of parameters included in the formulas for determining the components of the cutting force allows adequate monitoring the nature of the force interaction of the elements in the technological system when processing parts.