Call Now
3nh
2024-12-16
With the continuous development of urban rail transit and the improvement of people's aesthetic level, people have higher and higher requirements for the appearance of urban rail trains, especially the appearance and color of urban rail train doors. This has led to the main engine factory to strictly control the color quality, especially the color difference, during the production process of train door product modeling and appearance. So, how to solve the color difference of urban rail train doors? What is the color difference range?
1. Influence of paint materials
In the paint production process, the paint color is mainly configured according to the standard color palette. Paint can be divided into two types: monochrome paint and glitter paint. Among them, glitter paint can be divided into metallic paint and pearlescent paint; monochrome paint mainly relies on the reflection effect of pigment particles. Since scattered light is mainly the main body, no angular color effect will be produced, so it is necessary to control the color difference by controlling the film thickness of the paint. Glitter paint will have an angular color effect. Therefore, when the paint formula is fixed, the adjustment of different construction parameters will also change the aluminum powder, resulting in different color change effects.
2. Influence of paint spraying method
Under the condition of the same paint material, different spraying methods and spraying equipment will lead to paint color difference. Spraying methods can be divided into manual spraying and automatic spraying, and these two spraying methods have different effects on the color difference of paint. There are obvious differences in hue and color between the two. The reasons for the inconsistent spraying effects of these two automatic spraying equipment are mainly reflected in the following aspects: first, the aluminum powder content inside the paint is different; second, the distribution of aluminum powder in the spray paint is different; third, the surface coverage of the aluminum plate is different; fourth, the directional arrangement of the paint film inside the aluminum powder is different.
3. Influence of paint supply system
The paint supply system also has a great influence on the color difference of the glitter paint, mainly due to the following two aspects: (1) The circulation time in the air supply circulation system can also directly affect the paint color, especially the high-powder aluminum paint. In the case of a large amount of aluminum powder, if it is left for a long time, aluminum powder precipitation will occur, which will have a great impact on the color of the aluminum powder. (2) When the paint supply system is in a clean state, the color will increase with the type of paint, and the paint supply system needs to be cleaned and changed frequently. If the paint supply system is not clean enough and there is residual paint mixed in, the old paint will definitely have a great impact on the color of the new paint.
The traditional method of controlling the color difference of paint on urban rail train doors mainly adopts the visual method, which is to compare with the color plate under a specific light source by human eyes. This method is highly subjective and has many influencing factors, and it cannot quantify the color difference value. Therefore, in order to accurately and objectively measure the color difference of urban rail train door paint, professional color measurement instruments can be used.
At present, the color difference of paint on urban rail train doors is generally measured by multi-angle colorimeter. The Sanen MS3005 multi-angle colorimeter is a commonly used colorimeter. The light source in the colorimeter is generally set to D65 daylight light source, and the observation angles are 15°, 25°, 45°, 75°, and 110°. The quantitative measurement of paint color generally adopts the CIE color system of the International Commission on Illumination. The principle of measurement is that the monochromator irradiates the sample to be measured, and the reflected light passes through the phototube to convert the light signal into an electrical signal, which is amplified by the amplifier and measured by the ammeter. The current intensity, thus realizing the measurement of the absolute value of the color of the reflected light of the sample to be measured, that is, the CIELab color space. The L* of the color represents the lightness value; a* represents the red/green value; and b* represents the yellow/blue value. △L* is "+" for lighter colors, and "-" for darker colors. △a* is "+" for redder colors or less green, and "-" for greener colors or less red. △b* "+" indicates that the color is more yellow or less blue, and "-" indicates that the color is more blue or less yellow.
When using a multi-angle colorimeter to measure the color difference of the paint film, first measure the spectral distribution of the light to be measured or the spectral reflectance of the sample, and then calculate the chromaticity value. The color difference △E between two chromaticity values (L* sample, a* sample, b* sample) and (L* standard, a* standard, b* standard) in the CIEL*a*b* color space is expressed by the following formula. At present, there is no unified standard for the evaluation of automotive paint film color difference, and automobile manufacturers generally control it based on their own experience. For example, some automobile manufacturers evaluate color difference with △E*ab: the paint film color should be consistent with the standard color plate specified in the contract, and the △EE*ab of a single angle (such as 45°): △L*=(-2.0, 2.0), △a*=(-1.0, 1.0), △b*=(-1.0, 1.0), △E*ab≤2.2; the average value of △E*ab at 5 angles <1.5 means the color is qualified, otherwise it is unqualified.
