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Grinding wheel surface topography detection method (3)

Non-contact detection

The non-contact detection method mainly obtains the surface morphology of thehigh performance cutting disc in two ways: one is the microscope type detection method, and the surface topography information of the grinding wheel is obtained by microscope imaging, measurement or scanning; the other is the optical detection method, Optical measurement technology is combined with information processing technology to detect based on optical scattering or interference principles.

1.Microscopic detection

(1) Microscope quasi-focus method

The basic principle of the detection method is to focus on the apex of the abrasive grain on the surface of the grinding wheel and the lowest point of the surrounding metal bond by using a reflective microscope, and record the change value of the scale of the focus knob, which is different from the focus knob. The product of the representative dimensions is the blade height of the abrasive particles. The smaller the size represented by each of the focus knobs, the higher the accuracy of the microscope quasi-focus method. The microscope quasi-focus method has a small investment and simple operation, and can directly detect the height of the blade of the abrasive grain; and the shape of the abrasive grain can be obtained by multiple focusing of the abrasive grain by the reflection microscope. However, the calculation of the distribution density of the abrasive particles is cumbersome, and the discrimination of the focusing condition is too subjective and the detection accuracy is low.

(2) Binocular vision

The binocular vision method is to capture the binocular stereo image of the surface of the grinding wheel by using a stereo microscope by imitating the human visual system. Through the analysis and processing of the image, the depth information of each point on the surface of the grinding wheel is accurately obtained, and then the surface morphology of the grinding wheel is reconstructed by modeling. The schematic diagram is shown in Fig. 5. When constructing the actual binocular vision detection system and collecting binocular stereo images, a fixed CCD camera is used to move the grinding wheel through the translation device. The method realizes the detection of the characteristic information such as the abrasive grain height, the abrasive grain spacing and the abrasive wear amount on the surface of the grinding wheel. The direct detection method has the advantages of high detection precision, intuitive detection result, high calculation efficiency, strong adaptability, and simple operation.

2. Optical detection

According to the different detection principles used, the optical detection method is divided into optical scattering principle detection technology and optical interference principle detection technology.

(1) Photoelectric detection method

The principle of photoelectric detection method is to use the light beam to project onto the surface of the grinding wheel. The edges of the abrasive cutting edge of the grinding wheel are reflected by the light, and the reflected light is injected into the photomultiplier tube through the rectangular grating, thereby obtaining the corresponding photoelectric waveform, and then amplified and limited. The amplitude and shaping get the square wave to be tested, and the computer receives the square wave signal and analyzes and processes it. The spacing and width of the square wave correspond to the abrasive grain spacing and the abrasive grain wear surface length, respectively, so that parameters such as the average abrasive grain spacing and the average abrasive grain wear surface length can be obtained. Comparing the rectangular waves detected at different stages of the grinding process, the variation of the abrasive grains (such as wear, passivation, crushing, and shedding) can be obtained, and the surface of the grinding wheel can be monitored in real time.
This method can detect the abrasive grain spacing, density and degree of wear, but can not detect the blade height of the abrasive particles.

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(2) Light interception method

The light interception method is also called the light cut method. The detecting device is mainly composed of an optical indexing head, a projection mirror, a microscope and the like. The principle of the optical intercept method is to rotate the indexing handle to read the spatial position of the abrasive grains on the circumference of the grinding wheel, and then use the light source in the projection mirror to illuminate the surface of the grinding wheel with a rectangular beam through the lens and the grating to form a rectangular measuring belt. The long axis is parallel to the axis of the grinding wheel. The microscope lens is tangent to the circumferential direction of the grinding wheel, and the length and axial position of the abrasive cutting edge can be measured by the graduated eyepiece in the microscope.

This method can detect the height of the abrasive blade, but it is very cumbersome to detect the distribution density of the abrasive particles. Since the light is irradiated on the transparent object, most of the transmission and refraction occur, resulting in inconspicuous reflection effect, blurred imaging, plus the measurement field of view is a slit, the field of view is dark, it is difficult to identify the measured point, and sometimes the surface of the grinding wheel is The scratches or the pits from which the abrasive grains fall off are also misjudged as the height of the blade, so the effect of detecting the diamond grain with high transparency is not satisfactory.

The abrasive grain density, spacing and edge height can be obtained by measuring the points on the surface of the grinding wheel. The detection method has high detection precision, but it is not suitable for surface topography detection of fine-grained grinding wheels, and the laser probe is expensive, and it is not suitable for industrial use.

(3) Laser focusing method

Laser focusing is also called laser interferometry. At present, the most typical one is the laser probe interferometry method, which uses a very thin focused optical probe to project the surface of the grinding wheel. A reference mirror is placed near the surface of the grinding wheel. The reference light and the measuring light adopt the same path, wherein the reference light can pass through the piezoelectric actuator on the shaft. The position is slightly moved, the interference fringes are observed and stored, and the change in height on the surface causes a change in the optical path difference between the reference light and the measuring light, thereby causing a change in the signal on the photodetector; phase analysis of the interference fringe image can be performed. The actual height of the sampling point on the surface of the grinding wheel is obtained, thereby obtaining the surface profile of the grinding wheel.

This method can detect the edge height, spacing and density of abrasive grains on the surface of the grinding wheel. This technology is highly sensitive but susceptible to vibration.
At present, the method for detecting the surface topography of the grinding wheel is not mature enough. All kinds of testing methods can only measure one element or several elements of the grinding wheel shape. If the surface features of the grinding wheel are to be described from different angles, each testing method needs to cooperate with each other. , take advantage of each other.

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