Method for the detection of surface roughness

Surface roughness measurement methods are compared with measurement, non-contact measurement, contact measurement and die method:

Comparison method is to compare the measured surface with the known value of the roughness of the value of the roughness model, such as the surface of the measured surface is smooth, can be compared to the magnifying glass, comparative microscope, in order to improve the accuracy of detection. The choice of the model should make the material, the shape and the method to be the same as the measured work piece. The comparison method is simple and practical, and is suitable for the surface of medium and low precision in the condition of the workshop. The accuracy of the comparison method is largely related to the technical proficiency of the inspectors.

The non contact measurement method includes the light cut method, the interference method, the laser reflection method and the laser holography method. Light cutting microscope is a method of measuring surface roughness using the principle of light cut. Interference method is used to measure the interference fringes on the measured surface by means of the principle of light wave interference. Laser reflection method is to illuminate the measured surface through a laser beam at a certain angle, and the surface roughness can be measured by observing the reflection intensity. The basic principle of laser holography is based on the measured surface by laser irradiation, coherent radiation, interference pattern of shooting the measured hologram surface a surface profile is obtained, then the distribution of silicon photocell measurements of black and white striped black and white stripes measured intensity, contrast ratio, degree of roughness and evaluation of surface to be measured.

The method of contact measurement is usually used. The needle scanning method is to use the instrument's stylus to gently across the surface of the measured surface, the micro uneven profile of the measured surface will enable the stylus to make the vertical displacement. Then the change of displacement is converted into electricity by the sensor, and the evaluation parameters of the measured surface roughness are shown on the display after the signal amplification and the integral calculation. Can also be drawn by the recorder of the measured surface micro profile. The surface roughness measuring instrument designed and manufactured according to the principle of the needle trace method is usually called the contour instrument. According to the difference of the principle of conversion, can have the inductance type outline instrument, the capacitance type contour instrument, the electric contour instrument and so on. Contour can be measured Ra, Rz, Ry, S, Sm and TP, and other parameters.

Impression method is to use plastic materials will be measured surface copy made impression, indirect methods to measure the impression again. Common impression materials Sichuan wax, paraffin wax, celluloid, low melting point alloy etc.. The impression material may not completely fill the surface bottom, remove the impression and make the crest has been decreased, so the height parameter value is usually higher than the impression height parameters of the surface to be measured the actual value is small, therefore should be revised according to the experimental results. The general impression method applied to the inner surface roughness detection.