Surface Roughness is the surface roughness we call in our daily measurement. This also means that the unevenness of fine pitch and tiny peaks and valleys in the process of processing products. 

Usually, it refers to the small distance between two peaks or two valley fingers (wave distance). In general, the wave distance is within 1mm or less. It can also refer to the measurement of the microscopic profile, commonly known as a microscopic error value. 

We generally have a baseline for evaluating roughness. The highest point above the baseline we name it as the crest point, and the lowest point below the baseline is the trough point. Then the height between the wave crest and the wave trough is represented by Z, and the micro-texture distance of the processed product is represented by S.

Under normal circumstances, the size of the S value in the national verification standards is:

S＜1mm is the surface roughness
1≤S≤10mm is the surface waviness

China's national metrological verification standard stipulates that the three parameters of VDA3400, Ra, Rmax to evaluate the surface roughness of the verification, and the unit of measurement is μm.

Parameter relationship

Wear resistance of workpiece
Coordination stability
Fatigue strength
Corrosion resistance
Tightness
Contact stiffness
measurement accuracy
...

Coating, thermal conductivity and contact resistance, reflectivity and radiation performance, resistance to liquid and gas flow, and current flow on the surface of conductors will all have varying degrees of influence.