Deformation is a major problem commonly found in ceramic water cup products, which has a greater impact on the quality of ceramic products. Therefore, reducing deformation failure is a main direction of ceramic production. Here we discuss the factors that affect the deformation of ceramic water cups in more detail in Tangshan Win-Win Ceramics:
(1) Influence of plaster model on deformation
The plaster model is an important tool in the molding process. The model is not standard, not only involves the shape and specification of the device, but also directly affects the deformation of the product.
Practice has proved that the quality of the plaster model is not good, and the model is too dry, which will produce serious polygonal lotus leaf-like deformation. Even if the blank is flattened during demolding, it will still be deformed after firing. Secondly, the water absorption rate of the model is not uniform due to uneven water mixing and drying during the manufacturing process of the plaster model. After the win-win multi-mud cake is put into the plaster mold, the green body will be deformed due to uneven water content on the mold. The uneven wetness of the plaster model, resulting in uneven water absorption and uneven mold release, is one of the factors that cause warping.
The mold seat of the molding machine is not centered, and the plaster model does not fit well with the mold seat, and there is a loose phenomenon, which makes the unscrewed body thick and thin, which is easy to deform.
(2) Influence of forming pressure and mud moisture on deformation
Generally, it can be considered that the greater the pressure of the mud, the longer the pressure time, the higher the density of the green body, the lower the porosity, and the less the deformation rate of the product. The high moisture content of mud will increase drying shrinkage. If the shrinkage is inconsistent, it will lead to deformation of the green body.
Therefore, the purpose of increasing the molding pressure and reducing the molding moisture is to improve the density and strength of the green body and reduce its drying shrinkage, which is beneficial to the reduction of deformation.
(3) Influence of forming method on deformation
It is generally believed that roll forming has a smaller deformation rate of the blank than knife pressing. This is because the contact surface between the rolling head and the mud is large, which increases the pressure on the mud. At the same time, the calendering effect given to the mud is a relative motion of both rolling and sliding, so that the particles in the mud can maintain the original non-directional arrangement, so the rolling-formed green body has a more uniform and dense structure, high strength, and can reduce deformation. . The effect of the knife press forming blade on the mud is only relative sliding, the green body is less compressed and the density is poor, so the deformation rate of the green body is larger than that of rolling.
The deformation rate of the male mold is smaller than that of the female mold. At present, for the roll forming of plate products, in the south, taking Jingdezhen as an example, the female mold is commonly used, and in the north, taking Liaoning as an example, the male mold is used for forming. Generally speaking, it can be considered that male mold forming can reduce the deformation of the green body. Because the formed body shrinks as the moisture decreases during the drying process. If the shrinkage is uneven, deformation will occur. In fact, it is very unlikely to achieve a completely uniform mold release, so it is impossible for the dried green body to be completely deformed. If the blank has a uniform object in the mold release process, there is a constraint on the edge of the product, so as to force it to be uniformly released from the mold, which is beneficial to reduce deformation. However, when the male mold is formed, the green body is just buckled on the plaster mold, which invisibly provides a uniform binding force to the green body shrinkage, which reduces the free surface of deformation caused by shrinkage, which is beneficial to prevent deformation. A ceramic research institute pointed out in the research on the deformation of disc products: using a male mold to form, the flexural strength of the bottom of the disc is higher, and the mold can be released after the green body is completely dry and released, which greatly reduces the drying process of the green body. deformation. In this way, the flat plate is formed, the rim is less uneven, the bottom of the plate is flat, and the surface of the finished porcelain is smooth and free of pinholes. However, the poor plasticity and strong viscous mud are difficult to be demolded by the male mold, because the green body is easy to crack before it is released from the mold.
(4) Influence of mud throwing, demoulding and improper drying on deformation
Improper operation of mud throwing, demoulding and drying during molding is also an important factor affecting deformation.
Improper mud casting means that the mud cake is not placed in the center of the quasi-gypsum model, and the distribution and compaction degree of the mud particles are not the same, which will cause the different parts of the green body to shrink and deform.
Premature demoulding or even forced demoulding directly damages the local green body. Even if it is smoothed by hand, the damaged part is still deformed after firing. Because the green body does not leave the model, the plasticity of the mud material is still very high. Under the action of external force, the particles will move in the direction of the external force together with the water film surrounding it, so that structural tension and pressure appear on the product. local unevenness. This unbalanced phenomenon is usually not easy to find when drying, until after firing, it is deformed due to the difference in shrinkage caused by no density.
If the blank plate is not flat, the blank will also deform during the drying process. If the temperature of the drying room is too high, not only the model is easily damaged, but also the edge of the green body is prone to warping and cracking due to the rapid drying of the green body and the rapid evaporation of water.
Post time: Oct-31-2022