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Precision workpiece roughness

Precision workpiece roughness is in line with international standards (ISO), and the term surface roughness should be used for formal and rigorous expressions.



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Surface roughness refers to the small spacing and small peaks and valleys of the machined surface. The distance (wave distance) between its two crests or two troughs is very small (below 1mm), which is a microscopic geometric shape error.fWwYoYike manufacturer company

Specifically, it refers to the level of the tiny peaks and valleys Z and the distance S. Generally divided by S:fWwYoYike manufacturer company

S<1mm is the surface roughnessfWwYoYike manufacturer company

1≤S≤10mm is the wavinessfWwYoYike manufacturer company

S>10mm is f shapefWwYoYike manufacturer company
 fWwYoYike manufacturer company

02. Factors forming surface roughnessfWwYoYike manufacturer company
 fWwYoYike manufacturer company

Surface roughness is generally formed by the machining method used and other factors, such as the friction between the tool and the surface of the part during the machining, the plastic deformation of the surface layer metal when the chips are separated, and the high-frequency vibration in the process system, electrical machining The discharge pits and so on. Due to the difference in machining methods and workpiece materials, the depth, density, shape and texture of the traces left on the processed surface are different.fWwYoYike manufacturer company
 fWwYoYike manufacturer company

03. Evaluation basis for surface roughnessfWwYoYike manufacturer company
 fWwYoYike manufacturer company

1) Sampling lengthfWwYoYike manufacturer company
 fWwYoYike manufacturer company

The unit length of each parameter, the sampling length is the length of a reference line for evaluating the surface roughness. Generally use 0.08mm, 0.25mm, 0.8mm, 2.5mm, 8mm as the reference length under the ISO1997 standard.fWwYoYike manufacturer company

Selection of sampling length L and evaluation length Ln of Ra, Rz, RyfWwYoYike manufacturer company
 fWwYoYike manufacturer company

2) Evaluation lengthfWwYoYike manufacturer company
 fWwYoYike manufacturer company

Consists of N reference lengths. The surface roughness of each part of the component surface cannot truly reflect the true roughness parameters on a reference length, but N sampling lengths are needed to evaluate the surface roughness. Under the ISO1997 standard, the evaluation length is generally N equal to 5.fWwYoYike manufacturer company
 fWwYoYike manufacturer company

3) BaselinefWwYoYike manufacturer company
 fWwYoYike manufacturer company

The baseline is the contour centerline used to evaluate the surface roughness parameters.fWwYoYike manufacturer company
 fWwYoYike manufacturer company

04. Surface roughness evaluation parametersfWwYoYike manufacturer company
 fWwYoYike manufacturer company

1) Height characteristic parametersfWwYoYike manufacturer company
 fWwYoYike manufacturer company

Ra contour arithmetic mean deviation: the arithmetic mean of the absolute value of the contour deviation within the sampling length (lr). In actual measurement, the more the number of measurement points, the more accurate Ra is.fWwYoYike manufacturer company

Rz Maximum profile height: the distance between the top line of the profile peak and the bottom line of the valley.fWwYoYike manufacturer company

In the commonly used range of amplitude parameters, Ra is preferred. Before 2006, there was also an evaluation parameter in the national standard, which was "the ten-point height of micro-roughness" represented by Rz, and the maximum height of the contour was represented by Ry. After 2006, the national standard canceled the ten-point height of micro-roughness and adopted Rz. Indicates the maximum height of the contour.fWwYoYike manufacturer company
 fWwYoYike manufacturer company

2) Spacing feature parametersfWwYoYike manufacturer company
 fWwYoYike manufacturer company

Rsm The average width of the contour element. Within the sampling length, the average value of the microscopic unevenness of the contour. The microscopic unevenness distance refers to the length of the contour peak and the adjacent contour valley on the midline. In the case of the same Ra value, the Rsm value is not necessarily the same, so the reflected texture will also be different. Surfaces that value texture usually pay attention to the two indicators of Ra and Rsm.fWwYoYike manufacturer company

The Rmr shape characteristic parameter is expressed by the contour support length ratio, which is the ratio of the contour support length to the sampling length. The profile support length is the sum of the length of each section of the profile obtained by intercepting a straight line parallel to the center line and a distance of c from the top line of the profile within the sampling length.fWwYoYike manufacturer company
 fWwYoYike manufacturer company

05, VDI3400, Ra, Rmax comparison tablefWwYoYike manufacturer company
 fWwYoYike manufacturer company

The Ra indicator is often used in actual domestic production; the Rmax indicator is commonly used in Japan, which is equivalent to the Rz indicator; the European and American countries often use the VDI3400 standard to indicate surface roughness. When doing European mold orders, the VDI indicator is often used, such as often heard from customers. "The surface of this product is made according to VDI30."fWwYoYike manufacturer company





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