The hollow brick has strict requirements for the forming operation. If there is any negligence in the production preparation and operation process, it will bring many problems to the forming. Therefore, special attention should be paid to the following points during the molding operation:
In summer, with the change of climate, the moisture content in raw materials fluctuates, so pay close attention to the change of moisture content in production. When the moisture content is low, it is necessary to add water to the raw material in time to make it reach the moisture required for molding. When the moisture content in the raw material is too high, it is necessary to properly reduce the moisture content in the raw material. It can be reduced by adding some dry materials to the raw material, such as dry fly ash, coal gangue, slag, tailings of other mines and other industrial waste slag. When adding these components into the raw material, it is necessary to select the right time and specify the adding position. It must be added at the crushing position of the raw material. In this way, the added components can form a good mixture with the main components of the raw material to make the performance of the raw material uniform. If the adding time is too late, and then add after the raw material is broken, then the performance of the raw material is not uniform because several materials cannot be fully mixed, The molding work cannot be carried out smoothly. That is, the forming can be carried out, but the quality of the formed green body is also extremely unstable. When adding water to raw materials, it is also necessary to pay attention to the time of adding water. It is necessary to add 98%~100% of the water required for raw material molding when raw materials are broken and crushed, so that the water content of raw materials can meet the requirements of molding water. Don't wait until the raw material enters the extruder to add water, which is too late to ensure that the added water is evenly dispersed in the raw material, and the water content on the surface and inside of the particles will also be greatly different, which is not conducive to the consistency of the raw material performance, and will cause certain harm to the molding and green body performance.
In terms of lubricating water at the machine mouth, attention should also be paid to the amount of water added. Under the condition of ensuring normal molding, water should be added as little as possible. Although molding can also be carried out with more water, this will make the surface of the green body absorb too much water, which will have a certain impact on the drying process of the green body and the uniformity of the green body performance. It is inevitable to form delamination phenomenon in the forming body by using the screw extruder, which is generally called spiral striation. This texture (layering) is formed by the uneven extrusion of mud from the machine mouth section through the spiral blade. When raw materials are formed into mud strips, we hope to increase the density of the green body by the close combination of particles, rather than by the effect of lubricants. According to the principle of the densest packing of raw materials, when the proportion of each component in the coarse, medium and fine particles of raw materials is distributed according to "big at both ends and small in the middle", the density of the green body is the largest, that is, the particles can reach the densest packing. All particles with one particle size can not achieve good forming effect, and when the proportion of each component is out of balance, it can not achieve good forming effect, and it is easy to produce delamination during forming.