What Is Roll Forming?

Roll forming is developed from spinning blank forming. It is to change the knife to a rolling head. The rolling head and the model are respectively rotated around a fixed axis, and the plastic mud put into the model is stretched and pressed into a green body, and the shape and size of the green body completely depend on the "cavity" formed by the rolling head and the mold surface.

Roll forming is evolved from the spin forming method. The difference between rolling and spinning is that the flat sample knife is changed to a rotary rolling head. During molding, the model containing the mud and the roller are rotated around their own axis at a certain speed and in the same direction, while the roller is rotating while gradually approaching the model containing the mud, and "rolling" and "pressing" the mud. forming. During the rolling, the sludge is uniformly spread out, and the force from small to large is relatively gentle and uniform. It is less likely to damage the original arrangement of the billet particles and cause inter-particle stress, and the structure of the billet is uniform. Secondly, the

Roll forming is the same as spinning forming, which can use male die rolling and female die rolling. The male die rolling uses a roller to determine the shape of the male face (appearance) of the green body. It is suitable for forming flat, wide-mouth utensils and products with a pattern on the inner surface of the blank. The female die rolling system uses a roller to form the inner surface of the body. It is suitable for molding products with small caliber and deep concave. When the male die rolls,

Roll forming is based on the force of the rolling head. Therefore, whether the design of the rolling head is appropriate or not is a key issue for rolling forming. General requirements for rolling heads:

The shape and size required for molding products are not easy to produce defects.

It is beneficial for the extension of mud and the discharge of residual mud during rolling.

Long service life with proper surface hardness and smoothness.

Easy to manufacture, repair, adjust, and disassemble.

The material of the roller is easy and the price is cheap. ^[1]

Roll-forming mud is subject to calendering force, larger forming pressure and faster forming speed, which requires the mud to have better plasticity, higher yield value, larger extension deformation, and smaller water content. The extension deformation of plastic mud increases with the increase of water content. If the plasticity of the mud is too poor, the extension deformation is also small due to the small amount of water. It is easy to crack during rolling and the model is easily damaged. If a strong plastic material is used, its yield value is correspondingly low due to its high moisture content when it is suitable for roll forming, and it is easy to stick to the roller during rolling, and the green body is also easy to deform. Therefore, the roll forming requires the mud to have proper plasticity and to control the water content. After the porcelain factory determines the composition of the raw material during production, the plasticity of the mud is generally adjusted by controlling the water content to meet the needs of rolling. Therefore, the moisture content of the mud should be strictly controlled during roll forming.

The requirements of rolling molding for mud are also related to the use of male or female rolling, hot rolling or cold rolling. When the male mold is rolled, the mud is outside the model, so the moisture in the mud is less than that of the model. At the same time, the male mold is required to have better ductility (that is, a larger amount of deformation) to adapt to the male mold Roll forming features. Therefore, the mud suitable for male mold rolling should have better plasticity and less moisture. When the female mold is rolled, the moisture can be slightly more, and the plasticity of the mud can be slightly worse. During cold rolling, the moisture of the mud should be less and its plasticity is better; during hot rolling, the plasticity and moisture of the mud are not strict. In addition, the molding moisture is also related to the shape and size of the product. When molding large products, the moisture is lower, and when molding small products, the moisture is higher. The moisture of the mud is also related to the rotation speed. If the rotation speed of the roller is small, the moisture of the mud can be higher. The speed of the roller is fast, so the moisture of the mud should not be too much, otherwise the roller is easy to stick, even flying mud. The water content is also related to the origin of the mud and the processing method. Generally, the moisture of the roll-formed mud ranges from 19% to 26%. ^[2]