Introduction of several surface defect detection methods for automatic product appearance detection

Date：2021-12-23 11:12:03Views：1918

As we all know, in the process of industrial manufacturing, there will always be various production defects, which is inevitable. In the past, most product inspection was carried out with the naked eye. With the development of machine vision technology, using machine instead of human eye inspection has become the development trend in the future. In industrial production, using machine vision detection equipment, the system has measurement function and can automatically measure the appearance dimensions of products, such as outline, aperture, height, area and so on.

Introduction to product surface defect detection:

The detection of product surface defects belongs to a machine vision technology, that is, computer vision is used to simulate the function of human vision, image acquisition, processing, calculation, and finally the actual detection, control and application of specific objects. Defect detection usually refers to the detection of defects on the surface of articles, such as spots, dents, scratches, color difference, defects, scratches, less materials and more materials.

Product surface defect detection includes:

1. Surface inspection:Stains, scratches, shallow pits, shallow tumors, edge defects, pattern defects, etc.

2. Dimension measurement:Inner ring diameter, outer ring diameter, eccentricity, height, thickness, etc. On the basis of rapid, accurate and effective analysis of defect types, it also overcomes the shortcomings of human eye fatigue, low accuracy and low efficiency, improves production efficiency and ensures product quality.

Surface defect detection methods are described as follows:

1. Laser detection method

This measurement method is an on-line non-contact detection equipment. The contour measuring instrument is suitable for the detection of long materials in rolling, such as round steel, square steel, deformed steel, T-shaped steel, etc. general surface defects, scratches, folds, bulges, pits, etc. it is composed of four laser two-dimensional sensors evenly distributed around the center, which can detect all directions, Realize all-round inspection and measurement without blind area. It can immediately identify the defects of rolled products and support the operator to decisively identify the defective products, so as to improve the profitability of the production line. The profiler monitors the cross section and then forms a high-resolution display of the complete surface, which allows the detection of local and periodic surface defects and dimensional changes of rolled products. There are no requirements for the material and temperature of rolled products, and the surface defects of 0.5mm and above can be detected.

2. Magnetic flux leakage detection

Magnetic flux leakage testing technology is widely used in nondestructive testing of iron and steel products. The detection principle is to use the magnetic source to locally magnetize the tested material. If there are defects such as cracks or pits on the material surface, the permeability of the local area will be reduced, the magnetic resistance will be increased, and part of the magnetization field will leak out from this area, so as to form a verifiable magnetic flux leakage signal.

3. Infrared detection

Infrared detection is to generate induced current on the surface of continuous casting slab through high-frequency induction coil. Under the skin effect of high-frequency induction, its penetration depth is less than 1 mm, and the induced current in the surface defect area will lead to more power consumption on the surface per unit length, causing the temperature rise of local surface of continuous casting slab.

4. Ultrasonic flaw detection

Ultrasonic testing is based on the principle that the characteristics of sound pulse change at the defect. The reflection condition of sound wave in the workpiece will be displayed on the fluorescent screen. It is a method to judge the internal defects and material properties of the workpiece according to the time and shape of the reflected wave. Ultrasonic flaw detection technology is often used to detect the internal defects of metal pipes.

5. Optical machine vision intelligent detection

The basic principle is that a certain light source shines on the metal surface to be tested, the surface image of continuous casting slab is obtained by high-speed CCD camera, the image feature vector is extracted by image processing, and the surface defects are detected and classified by classifier.

In summary, among many surface defect detection systems, the laser detection method is suitable for on-line detection of various types of long materials, and it is a non-contact nondestructive detection method. It can detect and locate defects without being affected by external factors (such as material, temperature, etc.) and meet the on-line quality detection and monitoring of various production lines. The company's testing services cover: electronic component testing and verification, IC authenticity identification, product design and material selection, failure analysis, function testing, factory incoming material inspection, tape braiding and other testing items. Welcome to call Chuangxin testing, we will serve you wholeheartedly.