Advantages and weaknesses of pulp molding products

The molding process of paper molding products mainly includes vacuum adsorption molding method and grouting molding method. Vacuum adsorption molding method is the most commonly used molding method in the production of paper pulp molding products. In this process, the final paper pulp molding products can become qualified products after many times entering and leaving the mold. The molds used in pulp molding include adsorption molding molds, finishing molds and die-cutting molds.

1. Adsorption molding mold The structure of adsorption molding mold is composed of punch, concave die, mesh die, mold base, mold back cavity and gas chamber, etc. The mesh mold is the main body of the mold. Because the mesh mold is woven from a diameter of 0.15mm wire mesh (metal or plastic), the mesh number is generally between 40 and 65 mesh. It cannot be independent of the molding mold and must be attached to the surface of the mold to form. The mold back cavity is a mold that maintains a certain thickness with the mold working face and is completely synchronized with the shape of the mold working face. The cavity formed between the back part and the mold seat, that is, the convex and concave die, is a shell with a certain wall thickness. The working face of the die and the back cavity are connected by a uniform small hole. The die is mounted on the formwork of the forming machine by the die holder. The other side of the template is equipped with an air chamber, which is communicated with the back chamber, and the wall of the air chamber is provided with two channels for compressed air or vacuum extraction.

The pulp is formed after the pulp is broken through the molding mold to adsorb the pulp on the convex mold, and the thickness of the product is mainly controlled by adjusting the adsorption time. The thickness is usually 2 ~ 5mm, and the thickness is determined according to the size and strength requirements of the paper mold product.

① The size of the adsorption molding mold to determine the reserved amount of the adsorption molding mold is the key to mold design. Molded products from the wet paper blank to the finished product, due to the elimination of water shrinkage, and the same product at different locations of the shrinkage rate is not the same, and there is no law, resulting in the product in the molding process of multi-directional, changeable shrinkage changes, to the mold design to determine the reservation caused by difficult, this is mainly through experience. The size of the hot pressing die is mainly determined by the size of the integral die.

The adsorption molding mold is currently made of atomic ash, curing agent, resin and aluminum alloy. When it is used for industrial internal packaging products with low precision requirements, it can be directly manufactured by casting method, and those with high precision requirements must be manufactured by mechanical cutting processing. The lower convex mold of the molding mold is mainly made of aluminum alloy after processing, and the upper concave mold can be directly poured out from the corresponding lower convex mold using resin to ensure its manufacturing accuracy.

2. Mold mold structure includes punch die, concave die, mesh die and heating element. The punch or concave die with a mesh mold is provided with a drainage vent. When working, the wet paper blank is first squeezed in the forming mold, and 20% of the water is squeezed out. At this time, the moisture content in the wet paper blank is 50% ~ 55%, and then the wet paper blank is heated in the mold, and the remaining water is heated and vaporized.

In the process of pressing and drying the wet paper blank with the molding mold, the mesh mold in the molding mold will cause the surface of the product to produce mesh marks and the mesh mold will be deformed or even damaged quickly in frequent extrusion. In order to solve this problem, a new type of netless mold has been developed. The life of the non-mesh mold is 10 times that of the general mesh mold, and the cost is reduced by 50%. The paper mold products made with it are of high precision, and the internal and external surfaces are smooth and without mesh marks.

3. The wet paper blank will be deformed to different degrees after drying. When the outer surface shape of the paper mold products requires high precision, the paper mold products should go through an integral process. The mold used in the integral process is called the integral mold.

The size of the punch under the mold is obtained according to the outline size of the packaged product, the size of the punch under the mold is the outline size of the product, and the size of the concave mold is the sum of the size of the lower punch mold and the thickness of the paper and plastic product.

The mold is generally made of brass, aluminum alloy and stainless steel.

4. Die cutting mold according to the needs of enterprises and products to decide whether to die cutting, die cutting tool with alloy steel material, die specific use of ordinary carbon steel material.

Due to the deviation of mold design and manufacturing accuracy, mold wear after use and other reasons, the edges of paper mold products are often uneven. In order to make the products clean and beautiful, the paper mold products with higher appearance requirements are equipped with a cutting process. Die cutting die is used to trim the rough edges of paper mold products. However, the cutting process of paper molding products is unreasonable, it wastes resources, increases the cost of products, and destroys the edge fiber structure of products. At present, high-precision molds have been developed, and products produced using such molds do not need cutting processes.