Roughness of machining surface and its influencing factors

Surface roughness is one of the important marks to measure the quality of machined surface, wnich has a great influence on the wear reistance,corrosion 
resistance and fatigue strength of parts.However,there are many factors affecting the surface roughness in the procgssing, in order to be high to good.

Factors affecting surface roughness

一.Causes of rough machined surface
1.Residual area: The residual area is the uncut area left on the machined surface after cuttig by the main and auxiliary cutting edges of the tool.

2.Scales: When cutting plastic metal mnaterials with high-speed steel tools at low or mediumn speed,such as low carbon steel, medium carbon steel, stainless steel.Aluminum alloys, etc, often produce finsh- scale 
burrs on the machined surface, which are called scaly burrs.
The appearance of scales increases the surface roughness of the machined surface.

3.Built-up edge: During the cutting process, when the built-up edge is generated, its protruding part can, replace the cutting edge to cut into the workpiece and 
draw grooves of different depths on the machined surface; when the built-up edge fragment adhere to the machined surface,
causing fine burrs and increasing the roughness.surface,

4.Vibration in the cutting process, because the process system produces periodic vibration, so that the machined surface appears atriation or ripple marks, so 
that the surface roughness value is significantly. 

When cutting plastic metal, when the cuting speed is very low or very high, the surface roughness value is small.

It is because the built-up edge is not easy to produce at low speed; when the cutting speed is high,the plastic deformation is reduceded, and 

the scale can be eliminated. When cutting brittie materiais, the infuefice of cutting speed is small, because the materia deformation is small, so the surface roughness value is also reduced.

2.Geometric parameters of the tool: the radius ot the tool nose arc, the main cutting edge angle and the auxiliary cutting edge angle have a great influence on the 
residual area and vibration. Getterally, when the tool nose arc radius increases and the main deflection angle and the auxiliary deflection angle decrease,the surface 
roughness value is small. If the machine tool stiffness is low, the tool nose arc radius is too large or the main deflection angle is too small. Vibration will be produced
due to the increase of cuttingg force, which will increase the surface roughness value.

3.Cutting tool material: The cutting too material is different, the size of the arc radius of the cutting edge and the time to maintain shafpness are different. High.
speed steel knives can be sharpened vefy sharp, but the retention time is shorter, so the surface roughness value is smaller when cutting at low speed. The radius of the 
cutting edge of the cemented carbide tool is very large after grinding, and the cutting surface roughness is small at high speed.

4.Workpiece material: when processing plastic materials, the lower the hardness of the vonkpiece material, the less the appeargance of hard hemp, debris,
scales and cold hardness, and the smalle the surface roughness value.Therefore, the surface roughness of high carbon steel, medium carbon steel and quenched and tempered
steel after processing is smaller than that of low carbon steel. When processing cast iron steel,When processing cast iron, because the chips are
 broken, the surface roughness of cutting cast iron is large than workpiece processing.larger than that of north stee under the conditon of workpiece procession.