The geometric characteristics of NC machined surface include surface roughness, surface waviness and surface texture. Surface roughness is the basic unit that constitutes the geometric characteristics of the machined surface. When metal cutting tools are used to process workpiece surface, surface roughness is mainly affected by geometric factors, physical factors and numerical control processing factors.
(1) Geometric factors
From the geometric point of view, the shape and geometric angle of the tool, especially the radius of the tool tip arc, the principal deflection angle, the secondary deflection angle and the feed in the cutting parameters, have a great influence on the surface roughness.
(2) Physical factors
Considering the physical essence of the cutting process, the plastic deformation of metal materials occurs due to the rounded edge of the cutting tool and the extrusion and friction behind it, which seriously deteriorates the surface roughness. When strip chips are formed by processing plastic materials on NC lathe, it is easy to form chips with high hardness on the rake face. It can replace the rake face and cutting edge for cutting, so that the geometric angle of the tool and the amount of back cutting tool change. The outline of the chip tumors is very irregular, so that the tool marks of varying depth and width appear on the surface of the workpiece. Some debris tumors are embedded in the workpiece surface, which increases the surface roughness. The vibration during cutting increases the surface roughness parameters of workpiece.
(3) Process factors
From the point of view of technology, the influence on the surface roughness of metal parts is mainly related to cutting tools, workpiece material and NC processing conditions.