Call Now
3nh
2024-12-24
When the paint on the car surface ages, peels off or is damaged, the car needs to be repainted. In the process of repainting, the influence of various factors can easily lead to inconsistent colors after paint application. In order to detect the consistency of the color of car paint, a multi-angle colorimeter can be used. This article introduces the method of measuring the color difference of car paint with a multi-angle colorimeter.
Car paint
1. Impact of repeated spraying
The vehicles are old, and some of them have been repeatedly painted, including repairs and spraying, because they have expired and are aging. The superposition and integration of a large number of coatings and materials has led to a unique solidified color pattern on the vehicle body, that is, a composite color pattern, which is difficult to mix.
2. The influence of paint color matching
In the process of color matching for their vehicles, they lacked work experience and scientific methods, which resulted in a large error between the actual vehicle color and the standard vehicle color, which in turn caused a large contrast between the adjusted color and their operating vehicles.
3. Human Operation Impact
Problems caused by human operation. Due to incorrect operation and non-standardization in manual work, the masterbatch selection is wrong or the masterbatch is filled incorrectly, resulting in a serious discrepancy between the mixed color and the original color of the car body.
4. Environmental factors
Problems caused by environmental factors. Many problems arise in the color adjustment process due to environmental influences, such as dim light, colored light sources contained in the light, different angles of the car body and color matching, etc. These factors will cause color difference.
5. Influence of spraying process
Selection issues in spraying operations. When spraying colors, the master needs to design and select the air pressure, spray width, spray volume, etc. In addition, different profiling during the actual spraying process will also cause color difference. In addition, failure to scientifically and reasonably fill in the auxiliary materials during the spraying operation will also cause paint surface problems, mainly color difference caused by leveling problems.
6. Influence of spraying equipment
The color difference may also be caused by the failure of spraying equipment, tools, etc. In addition, if the repair process fails to follow the standard procedures and work is not carried out, it is very easy to cause color differences.
Multi-angle colorimeter to measure the color difference of car paint
Traditionally, the color difference detection of automobile paint coating mainly adopts the visual method. Since the visual method is affected by the light source environment, observation angle and the subjective psychology of the observer, it is easy to lead to unstable evaluation results. Therefore, in order to improve the accuracy of the evaluation results of automobile paint coating color difference, a colorimeter can be used.
When measuring the color of automobile paint, the colorimeter uses the internationally accepted CIELab color space. In this chromaticity space, the color difference △E between two chromaticity values in the CIELab color space (L* sample, a* sample: b* sample) and (L* standard, a* standard, b* standard) *ab decides: △E*ab=[(△L*)2 + (△a*)2+ (△b*)2]1/2. Among them: △L*=L*sample-L*standard (brightness difference), △a*=a*sample-a*standard (red/green difference), △b*=b*Xiangpin-b*standard (yellow /blue difference). If △L* is a positive value, it means the sample is lighter in color; if △L* is a negative value, the sample is darker. If △a* is a positive value, the sample is reddish; if △a* is a negative value, the sample is green. If △b* is a positive value, the sample is yellowish; if △b* is a negative value, the sample is blue. Generally, △E*ab can be used to evaluate color difference. The smaller the △E*ab value, the smaller the color difference.
When using a colorimeter to measure the color difference of car paint, first measure the spectral distribution of the light to be measured or the spectral reflectance of the sample, and then calculate the chromaticity value. However, the color of the car body paint varies greatly with different observation angles. Advanced colorimeter uses D65 light source (standard daylight, color temperature of 6500K) single direction (45°) lighting, which can measure the color of car paint from 5 angles at the same time.
The 15° viewing angle is a high gloss color. This observation direction is close to specular reflection, and the color is greatly affected by the metal flakes in the paint. When measuring at a 110° viewing angle, it is far away from specular reflection and most of the influence of metal flakes can be excluded. The measurement result shows the diffuse reflection color of the sample, that is, the color of the pigment itself.
The color difference measurement results of 15° and 25° mainly reflect the brightness difference, that is, the difference in the size and arrangement of the metal flakes; the color difference measurement results of 75° and 110° mainly reflect the hue deviation; since 45° is the best angle for the human eye to see colors, the measurement result of 45° better reflects the visual effect of the human eye.
Usually, the color difference measurement results of 25°, 45° and 75° are used as the color difference measurement index. First, the color value of the color standard sample is input into the colorimeter, and then the measurement is performed based on this value. The measurement result is the color difference value between a certain point on the car body and the color standard sample.
