What are the commonly used methods for measuring surface roughness?

There are many kinds of roughness testers, and the specific selection should be determined according to the size, material, and roughness value of your workpiece.

Generally speaking, the roughness tester is divided into two types: contact type and non-contact type, and there are two types of contact type: desktop and handheld, and the contact profilometer is the most common application in the machinery manufacturing industry; The non-contact type is mainly white light interferometer, which has the highest accuracy and can reach nanometers, and is mainly used for ultra-precision surface roughness measurement, which is widely used in the semiconductor industry, 3C industry, optics and colleges and universities.

<> the current roughness tester is automatically measured, the operation is relatively simple, and the specific steps refer to the manufacturer's manual.

The following can tell you the operation steps of SuperView W1 Optical 3D White Light Interferometer roughness analysis:

Place the sample on the fixture to ensure that the sample is stable;

Place the fixture on the stage;

Check the motor connection and environmental noise to confirm the status of the instrument;

Use the joystick to adjust the triaxial position, move the sample under the lens and locate the interference fringes on the surface of the sample;

Complete operations such as scan settings and naming;

Click Start Measurement (enter the 3D view window to rotate and adjust for a while);

Enter the data processing interface, click "Remove Shape", use the default parameters, and click Apply to obtain the surface roughness profile of the sample;

Enter the analysis tool module, click Parameter Analysis, directly obtain the surface roughness data, click the parameter standard on the right to replace the parameter standard, and add or delete the parameter type;

If you want to get line roughness data, you need to extract the hatching;

Enter the data processing interface, click the "Extract Profile" icon, and select the appropriate direction profile line for profile extraction;

Enter the analysis tool interface, click the "Parameter Analysis" icon, click the parameter standard on the right, and check the required line roughness related parameters to obtain the line roughness RA data.

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Roughness refers to the degree to which the machined surface of the work is not smooth. In the cutting process, the cutting marks caused by the feed appear in the form of crests and troughs, and the peak-to-trough height is very small, generally more than a few tenths of a micron, so the surface roughness belongs to the microscopic shape error of the surface of the part. Its measurement method:

1) Direct measurement method: use optical and electric instruments to directly measure the relevant parameters on the surface of the part to determine the roughness grade.

Direct measurement is further divided into contact measurement and non-contact measurement.

2) Comparative measurement method: compare the measured surface with the standard roughness sample to evaluate the roughness grade. The roughness template (also known as the roughness standard block) is a group of metal blocks made by different processing methods (turning, planing, flat milling, end milling, grinding, etc.).

3) impression method: this method is mostly used for the inner surface that can not be directly measured by the instrument, the impression can be made into a block with plastic materials, and it is attached to the measured surface, and the contour of the measured surface is copied on the laminating surface after being removed, and then the impression is measured to determine its roughness grade.

4) Comprehensive measurement method: it uses a certain characteristic of the measured surface to indirectly evaluate the level of surface roughness, but cannot measure the specific value of the uneven height of the peak and valley.

1) Direct measurement method, direct measurement is divided into contact measurement and non-contact measurement.

2) Comparative measurement method.

3) Impression method.

4) Comprehensive measurement method.

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There are many ways to represent surface roughness, but here are three of the most common surface roughness representations, as well as their definitions and formulas.

Common surface roughness notations:

ra = centerline average roughness.

Set the length l on the surface profile curve, take the center of the length as the x-axis, and divide the sum of the areas of all oblique lines in the length by the value obtained by measuring the length l. That is, RA.

Formula: ra=|f(x)|dx / l

ry = maximum roughness.

The maximum roughness value rmax ry is the vertical distance from the highest peak to the lowest valley of the curve in the length l. (The Rmax and Ry algorithms have the same concept, but the peaks and valleys of sampling are different.) In recent years, RY has almost replaced RMAX).

Formula: rmax=ry=rp+rv

rz = 10 point average roughness.

The length L is extracted on the surface profile curve, and the distance between the height and the fifth peak and the fifth trough is measured at the center of the curve, i.e., Rz.

Formula: rz=|y1+y2+y3+y4+y5|+|y1+y2+y3+y4+y5| / 5

The relationship between the three is about 4ra ry rz, and the unit is um.

Face roughness traps.

The same surface roughness value, but the peak-to-valley pattern is different.

ConclusionAlthough the surface roughness value is the result of quantifying the surface state, so that the processor has a reference basis and standard, but the same value, the actual surface type may still be different!

In the pursuit of more precise and detailed surfaces, it is necessary to realize that the distance is the same, but it is more challenging to reach than to reach. (Represents peak-to-valley distances that are closer and more even.) There may be differences in the concept of selecting tools and setting grinding conditions, not just in terms of wheel grit.

If we can have this cognitive foundation, we will not fall into the myth of numbers.

1. Comparative method: The comparative method is simple to measure, and is used for on-site measurement in the workshop, and is often used for the measurement of medium or rough surfaces. The method is a method of comparing the measured surface with a roughness sample marked with a certain value to determine the value of the surface roughness to be measured.

When comparing, the processing method, processing texture, processing direction, and material of the sample are required to be the same as the surface of the measured part.

2. Light section method: the surface roughness is measured by a double-tube microscope, which can be used as a parameter evaluation for Ry and Rz, and the measurement range is up to 50.

3. Interferometry: The shape error of the measured surface is displayed in an interference fringe pattern by using the principle of light wave interference interference (see flat crystal and laser length measurement technology), and the microscopic part of these interference fringes is magnified and measured by using a microscope with high magnification to obtain the measured surface roughness. The tool for measuring surface roughness using this method is called an interference microscope.

This method is suitable for measuring the surface roughness of Rz and Ry down to microns.

Surface roughness, roughness meter test method, using calibration test will be.