Roughness Ra detection

The core testing capabilities of You'er Hongxin Testing Laboratory cover: 3D micro surface image (sub nanometer level)Roughness Ra detectionShaft shape and position tolerance (full parameter detection), gear radial accuracy. The instrument has high precision, such as a resolution of 1nm, and the spindle error of the roundness meter is extremely small. It is widely used and can detect everything from light guide plates to microelectronic components. With the support of technological strength, it provides reliable measurement support for precision manufacturing.

Surface roughness refers to the micro geometric shape error composed of tiny peak valley spacing on the machined surface, with adjacent peaks and valleys typically spaced less than 1 millimeter apart. It is a technique for evaluating the micro geometric characteristics of an object's surface, mainly used to detect the degree of fluctuation of small peaks and valleys on the processed surface.

Simply put, surface roughness is an indicator of the smoothness of a surface, which describes the degree of unevenness of the surface at the microscopic scale. Common parameters include contour arithmetic mean deviation (Ra), contour maximum height (Rz, Ry), etc.

The practical use and significance of surface roughness

Surface roughness has a significant impact on the performance of mechanical parts, mainly manifested in the following aspects:

Impact on wear resistance: The rougher the surface, the smaller the effective contact area, the greater the pressure, the greater the frictional resistance, and the faster the wear

Affects the stability of fit: rough surfaces are prone to wear, causing an increase in gap fit and a decrease in actual effective interference fit

Affects fatigue strength: rough surfaces have valleys, which are sensitive to stress concentration like sharp notches

Impact on corrosion resistance: Rough surfaces can easily allow corrosive substances to penetrate into the inner layer of the metal through microscopic valleys

Impact on sealing: rough surfaces cannot fit tightly, resulting in gas or liquid leakage

Influence on contact stiffness: The ability of the joint surface of the component to resist deformation is closely related to the surface roughness

Impact on measurement accuracy: Surface roughness directly affects the accuracy of measurement

In addition, surface roughness also affects the coating, thermal conductivity, contact resistance, reflection performance, fluid resistance, etc. of the parts.

Roughness Ra detectionmethod

The measurement methods for surface roughness are divided into two categories: contact and non-contact:

1. Contact measurement method

Touching method (commonly used):

Using a diamond stylus with a curvature radius of about 2 microns to slowly slide along the surface

Convert displacement into electrical signals through an electrical length sensor

Automatically calculate parameters such as Ra, Rz, Ry, etc

Suitable for roughness measurement of 0.025-6.3 microns

Advantages: High precision and wide application; Disadvantage: There is some wear on the surface (very slight)

2. Non contact measurement methods

Interference method:

Using the principle of light wave interference, surface shape is displayed through interference fringe patterns

Suitable for fine surface measurement ranging from 0.025 to 0.8 micrometers

Advantages: No damage, high precision, white light interferometry can accurately measure nanoscale roughness

Impression method:

Copy the surface contour using plastic materials such as paraffin wax

Suitable for surfaces such as deep holes, blind holes, grooves, etc. that cannot be directly measured