Analysis of the causes of color difference in production control

　　1. The quality of raw materials for incoming billets fluctuates

　　After various raw materials enter the factory, they are ball milled, spray dried, and made into powder. Under the condition that a certain amount of pigment is added, the decorative effect of porcelain bricks has a great relationship with the whiteness of the white material. Under normal circumstances, the whiter the basic white material, the whiter the color of the porcelain brick, and the color of the brick is brighter and brighter. On the contrary, the color is relatively dull, giving people a feeling of old age. The fluctuation of ceramic raw materials, especially the change of fo2o3 and tio2 content, is bound to affect the whiteness of the basic white material, resulting in chromatic aberration between batch products.

　　Solution:

　　In order to eliminate or reduce the resulting color difference defects, it is necessary to stabilize the source of raw materials and strictly control the quality of incoming raw materials. At the same time, set up an iron removal process in the production process to reduce the iron oxide content in the billet.

　　2. The amount of pigment added to the micro-powder polishing tile is not allowed

　　The accuracy of the amount of pigment added, the impact on the color difference of the product is obvious. The more the amount is added within a certain range, the darker the color. The less the amount is added, the lighter the color.

　　Solution:

　　The purchased colorant must be re-weighed at the time of batching. It is not possible to fully believe the weight specified by the colorant manufacturer on the package. It is best to add it in a bag or in a barrel. It is best to weigh it with a small scale with higher precision.

　　3. Change of ball milling fineness

　　The fineness of ball milling generally only stipulates the upper limit, and the lower limit is not determined. However, if the fineness of the two balls is good, and they are at the upper limit and the lower limit respectively, the color difference is easy to be caused by inconsistent particle sizes.

　　4. Changes in particle size and gradation of colored materials

　　After the plain white material and the colored material are mixed evenly in a certain proportion, they are processed and formed by a certain production process. When the proportion of the plain white material and the colored material changes, the color depth of the porcelain brick also changes accordingly. To effectively control the resulting color difference defects, the gradation of the pigment particles during spray drying must be formulated and strictly controlled. In addition, during spray drying, changes or fluctuations of many factors will cause changes in the particle size and gradation of the powder, such as mud moisture, viscosity, pump pressure, spray blade aperture, etc. Therefore, it is necessary to control the relevant factors to ensure the stability of powder particle size and particle gradation.

　　5. The proportion of colored materials changes

　　In the ratio of powder, the color difference is caused by the uneven moisture of various colored powders, the blockage of the silo mouth, the mechanical failure of the electronic batching scale and other factors.

　　6, forming pressure changes

　　The forming pressure of the press, especially the change of the maximum pressure, will affect the density of the green body. The maximum pressure is large, the density is high, the green body has a good finish, and the color is uniform after firing. The maximum pressure is small, the density is low, and the surface of the green body is rough and has a color difference. Therefore, changes in forming pressure can easily lead to color difference between the two batches of products. Changes in the thickness of the green body will also cause color difference, the thickness is small, the firing is easy, and the porcelain degree is good. The thickness is too large, it is difficult to fire, and the degree of porcelain is low, but the color of the two batches is different, resulting in color difference between the two batches of products.

　　7. The pressing parameters formulated by multiple presses are inconsistent, resulting in color difference.

　　8, firing system

　　The change of firing conditions will have a significant impact on the color difference of porcelain bricks. If the air pressure changes, the firing temperature and atmosphere will change abnormally, resulting in the color difference of the product:

　　① A large change in firing temperature will affect the whiteness of the body after firing.

　　② If the air supply volume of the combustion-supporting air and the air extraction volume of the kiln fan change, it may cause a reduction atmosphere, and the brick surface will be blue or dark, resulting in color difference.

　　③ The fluctuation of kiln pressure will change the original firing system, so that the length of preheating belt, firing belt and cooling belt will change and affect the firing, resulting in color difference.

　　(4) The firing cycle is also an important factor. In the case of a determined formula, the firing cycle cannot be adjusted at will, otherwise it will affect the color of the brick.

　　⑤ There is always a temperature difference between the middle and both sides of the kiln. When the temperature difference exceeds a certain level, the color of the products in the middle and the products on both sides will be different, resulting in color difference.

　　The current kiln design length, width and output of a single kiln have broken through the original production thinking, the kiln control is more difficult, if the control is not legal, there will often be empty kiln, sparse kiln situation occurs, empty kiln, sparse kiln before and after the production of products appear color difference.

　　Second, the color difference caused by polishing

　　1. Scraping flat thickness: Due to factors such as product deformation, the polishing workshop adopts different scraping flat thickness. Due to the different surface depth during the firing process, the color of the pigment is inconsistent, so the different scraping flat thickness will affect the color of the product.

　　2. Factors such as the quality of the module (the amount of grinding of the module, the density of the module) and the change of the module arrangement cause the uneven smoothness of the surface of the brick to form a color difference between different products.

　　3. During the polishing process, the amount of water applied by the polishing machine is not enough, and the color difference is caused by the inconsistent surface processing of the brick.

　　4. When adjusting the surface smoothness and flatness of the brick, the swing adjustment of the polishing machine is inconsistent, resulting in the color difference of the same batch of products.

　　5. The super clean and bright grinding disc is improperly adjusted and the uneven amount of wax water drops causes color difference.

　　Color difference caused by uneven fabric of micro-powder bricks

　　1. The blockage of the blanking pipe leads to the change of the powder ratio, which causes the instability of the surface pattern between the brick and the brick to cause the color difference.

　　2. Due to the inconsistent fluidity of the powder, the powder with good fluidity in the fabric moves smoothly with the distributor, and the powder agglomeration with poor fluidity causes the accumulation of powder, resulting in unstable cloth effect and color difference.

　　3. The uneven grid surface causes the powder to be dragged inconsistently to form a color difference.

　　4. Uneven mixing causes color difference.

　　5. The operating parameters of different presses and different feed trucks for micro-powder bricks are inconsistent, resulting in color differences between the same batch of products.

　　6. The inconsistency of the filling depth of the mold cavity between different presses causes the color difference of the same batch of products.