With the progress of science and technology and the development of society, people have put forward higher and higher requirements for the performance and quality of precision machined products. The performance and quality of the product is determined by the product design and is guaranteed by the quality of the manufacturing and assembly of precision hardware machining, which includes both machining accuracy and surface quality. The surface quality of precision mechanical parts is one of the most important indicators, especially for the reliability of the parts at high speeds, high temperatures and high pressures.

Machining surface is through precision machining or other methods to change the size, shape and performance of the blank surface, so that it meets the requirements of the design drawings. But the external surface formed by precision machining of mechanical parts after turning is not a completely ideal surface. A very thin surface layer is formed on the surface of the part after machining, and its characteristics are very different from those of the internal substrate. Precision hardware processing, the surface in the entire cutting process in the wedge, extrusion, fracture and friction of the complex state of force, elastic and plastic deformation, in the cutting force, cutting heat and the common action of the surrounding media, changing the original geometric characteristics of the workpiece surface and physical and mechanical properties. Therefore, the use of "surface quality" to evaluate the geometric, physical, chemical or other engineering properties of the surface layer of the machined parts and the degree of compliance with the technical requirements of the parts, the main content of the expression is divided into the following aspects.

Surface roughness: precision hardware processing surface with a smaller spacing of the peaks and valleys of the micro-geometric shape characteristics, it is mainly precision machining in the cutting tool trajectory formed by the wave height and wavelength ratio is generally greater than 1:50.

Surface waviness: intermediate geometric shape error between the macro geometric shape error and surface roughness, it is mainly caused by the cutting tool offset and vibration, its wave height to wavelength ratio is generally 1:50 to 1:1000.

Surface finish texture: the main direction of the surface microstructure, which depends on the precision machining method used for surface formation, i.e. the relationship between the main and feed movements.

Scars: defects that appear in some individual positions on the surface of a precision hardware machining, they are mostly randomly distributed. Examples are burrs, cracks and scratches.

The physical and mechanical properties of the surface layer: in the process of machining precision mechanical parts, in the surface of the part occurs in a variety of complex physical and chemical changes, caused by the physical and mechanical properties of the surface layer changes. Mainly includes the following three aspects: surface layer hardening, surface layer changes in metallurgical organization, surface layer residual stress.

The impact of surface quality on the performance of the part.

Surface quality reflects a number of geometric features and physical and mechanical properties of the surface layer. It has a great influence on the wear resistance, fit quality, fatigue strength, corrosion resistance and contact stiffness of precision hardware processing and other aspects of the use of performance. The service life of precision hardware depends to a large extent on the wear resistance of the parts, the wear resistance of the parts and the friction of the material, the working environment lubrication conditions and the surface quality of the parts and other factors, in other conditions to determine the case, the surface quality of the parts plays a very important role.

With the progress of science and technology and the development of society, people have put forward higher and higher requirements for the performance and quality of precision machined products. The performance and quality of the product is determined by the product design and is guaranteed by the quality of the manufacturing and assembly of precision hardware machining, which includes both machining accuracy and surface quality. The surface quality of precision mechanical parts is one of the most important indicators, especially for the reliability of the parts at high speeds, high temperatures and high pressures.

Machining surface is through precision machining or other methods to change the size, shape and performance of the blank surface, so that it meets the requirements of the design drawings. But the external surface formed by precision machining of mechanical parts after turning is not a completely ideal surface. A very thin surface layer is formed on the surface of the part after machining, and its characteristics are very different from those of the internal substrate. Precision hardware processing, the surface in the entire cutting process in the wedge, extrusion, fracture and friction of the complex state of force, elastic and plastic deformation, in the cutting force, cutting heat and the common action of the surrounding media, changing the original geometric characteristics of the workpiece surface and physical and mechanical properties. Therefore, the use of "surface quality" to evaluate the geometric, physical, chemical or other engineering properties of the surface layer of the machined parts and the degree of compliance with the technical requirements of the parts, the main content of the expression is divided into the following aspects.

Surface roughness: precision hardware processing surface with a smaller spacing of the peaks and valleys of the micro-geometric shape characteristics, it is mainly precision machining in the cutting tool trajectory formed by the wave height and wavelength ratio is generally greater than 1:50.

Surface waviness: intermediate geometric shape error between the macro geometric shape error and surface roughness, it is mainly caused by the cutting tool offset and vibration, its wave height to wavelength ratio is generally 1:50 to 1:1000.

Surface finish texture: the main direction of the surface microstructure, which depends on the precision machining method used for surface formation, i.e. the relationship between the main and feed movements.

Scars: defects that appear in some individual positions on the surface of a precision hardware machining, they are mostly randomly distributed. Examples are burrs, cracks and scratches.

The physical and mechanical properties of the surface layer: in the process of machining precision mechanical parts, in the surface of the part occurs in a variety of complex physical and chemical changes, caused by the physical and mechanical properties of the surface layer changes. Mainly includes the following three aspects: surface layer hardening, surface layer changes in metallurgical organization, surface layer residual stress.

The impact of surface quality on the performance of the part.

Surface quality reflects a number of geometric features and physical and mechanical properties of the surface layer. It has a great influence on the wear resistance, fit quality, fatigue strength, corrosion resistance and contact stiffness of precision hardware processing and other aspects of the use of performance. The service life of precision hardware depends to a large extent on the wear resistance of the parts, the wear resistance of the parts and the friction of the material, the working environment lubrication conditions and the surface quality of the parts and other factors, in other conditions to determine the case, the surface quality of the parts plays a very important role.