In the early stage of powder coating development, it was mainly used for metal corrosion protection. With the continuous advancement of powder coating production and application technology, and the strengthening of environmental awareness and regulations in various countries around the world, the application range of powder coatings continues to expand, and the decorative beautification of powder coatings is also increasingly caused. People pay attention to it, and the assembly line assembly of modern enterprises (such as refrigerators, air conditioners, instrumentation, metal doors and windows, aluminum profiles, electromechanical equipment, etc.) requires that the quality of the interior and exterior of the coated products is highly stable, and the color of the coating between batches is uniform. The important requirements of the customer.
Figure 1, powder coating
GB/T9761-98 “Visual color and paint varnish visual colorimetric” and other effects are based on the ISO3668-1976 standard, the specification of the color of the coating color comparison method, can be used in natural light, color box artificial standard light source Under the test, the commonly used light source is D65, A. Visual colorimetry requires higher observers. The observer responsible for colorimetric examination should pass the color blind inspection lens. The lens with glasses must have a uniform spectral transmittance throughout the visible spectrum; Ages vary widely, and observers over the age of 40 are also subject to color blind examinations. Continuous operation of the observer reduces the colorimetric quality. Visual inspection is the most direct and sensitive detection method. Instrument measurement in color matching is an important auxiliary means of quality control.
The color measuring instruments mainly include two types of color difference meter and spectrophotometer. The color difference meter is cheap and easy to carry, and can be used for convenient and quick color measurement comparison. It can also provide data reference for color matching personnel, but the error is large, and the color matching operation cannot be directly performed. There are two types of spectrophotometers, one is portable, like a colorimeter, but the measurement is more accurate, and the reflectance spectrum curve can be measured, and the system data output can be performed, which can be used together with the color matching software; another type of desktop spectrophotometer The price is high and the volume is large, which is only suitable for laboratory use. At present, color difference meter and portable spectrophotometer are widely used, but currently the color matching software is expensive, and only a small number of powder coating enterprises are applied.
Figure 2, CS-660 Portable Spectrocolorimeter
Step 1: Take the spectrophotometer CS-660 as an example to make the following measurements, prepare the sample of the powder coating to be tested (as shown in Figure 3), and press the surface to a uniform level with a powder former;
Figure 3. Powder sample to be tested
Figure 4. Powder pressed into a cake
Step 2: Turn on the instrument, set various parameters and formulas according to the instructions, and perform black and white calibration;
Figure 5, black and white calibration
Step 3: After the black and white calibration is completed, press the “Print” button to first position the measurement area, and align the standard to be tested with the test hole. Be careful not to leak light to avoid affecting the test result. Press “Test” button and “drop” sound. After completing the measurement, view the test results;
Figure 6: Standard test results
Step 4: After the above standard measurement is completed and saved, press the “Menu” button to enter the “Sample Measurement” interface under the standard. Align the sample with the test hole according to the standard measurement method. The “Test” button is used for measurement, and the “drip” sound is used to complete the color difference measurement, and the measurement result can be obtained (Fig. 4).
Figure 7. Sample measurement results
According to the measurement results, the customer can perform color matching, which greatly reduces the time cost and labor cost.
Color matching and quality control are the most basic and important technical tasks in the production of powder coatings. At present, many companies are still using low-efficiency pure manual operations, and some have begun to use the aid of colorimeter, while the main domestic powder coating companies The color matching technology is only in the hands of a few key technicians, and the quality inspection personnel in the production line only use the visual inspection to fine-tune the color of the product. However, with the continuous development of powder coating, many managers have gradually realized the efficiency and quality assurance brought by the spectrophotometer. The use of spectrophotometer will gradually become popular, and the technicians only have to measure the instrument. The combination of technology and visual judgment, practical experience, etc., can truly do the color measurement and control of powder coating products.