Surface roughness refers to the micro-geometric features composed of small spacing and tiny peaks and valleys on the surface of processed parts. It is generally formed by the processing method adopted or other factors. There will be corresponding surface quality requirements in the mechanical drawings, generally represented by three codes: Ra, Rz, Ry plus numbers.

The arithmetic mean deviation of the contour Ra, the ten-point height of the microscopic unevenness Rz, the maximum height of the contour Ry

The main reasons for the formation of surface roughness are:

1) Surface roughness caused by tool marks between the tool and the machined surface during processing;

2) Surface roughness caused by plastic deformation when the cutting tool is separated from the machined surface;

3) Surface roughness caused by friction between the tool and the machined surface;

4) Surface roughness caused by high-frequency vibration between the tool and the machined surface.

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