The design of pulp molded products is not only the design of structural equipment, many of the properties of its products from the raw materials, additives, fillers and production processes to decide. Therefore, the design of pulp molded products is a comprehensive technology and structure technology.
Some basic requirements
In addition to the general physical strength of paper products and other requirements, but also should be based on the different uses of products, from the process and structure design, pay attention to the following properties to meet the specific requirements.
(1) Adsorption: The liquid repellent properties of pulp molded articles, including the absorption properties of liquids such as water, oil and ink, are particularly important for paper tableware.
(2) appearance of the product quality: the appearance of the naked eye can be observed with the appearance of defects, these defects include dust, holes, wrinkles, tendons, screen printing, spots, pulp pimples, plaques, cracks, curling, depression, inconsistent color Not beautiful appearance.
(3) product accuracy: refers to the size of the product, shape and location of the error between the design requirements. The accuracy of pulp molding products according to the current manufacturing method, can only reach below the national standard level.
2. Structural design points
Pulp molded articles in addition to paper products, strength and toughness, but also can be made according to the use of functional requirements of a variety of complex shapes. Used as disposable disposable utensils, the shape is relatively simple, the strength requirements are not too high. For industrial packaging, its shape is very complex, it must meet the industrial packaging of the three major requirements: First, positioning requirements. Packaging products must be able to ensure that the packaging has a fixed position in the packaging, packing and packaging items required synchronization between the shape, contact appropriate, accurate size. Second, the buffer requirements. The product as a whole should have certain toughness and flexibility, and the surface should be somewhat soft. When it is in contact with the packed articles, it can not damage the surface gloss of the packaged articles and can eliminate the impact when the packaged articles are impacted and vibrated during handling. Third, bearing. Requirements products have a certain strength and rigidity to support the packaging and withstand external pressure. In order to meet the above functional requirements of products, in addition to selecting the appropriate raw materials, additives and production processes, the more important is the structural design.
(1) functional structure: the characteristics of pulp molding process determines the formation of the same product can only have a thickness, in order to meet functional requirements, adjust the strength and cushioning can be used when the shape of the cavity and standing ribs, the cavity can increase the product The overall flexibility and flexibility, uplift can increase product strength and rigidity. In the larger plane, high carrying capacity, you can design here as a corrugated or honeycomb.
(2) Technological structure: Since the early stage of forming the pulp molded product is a wet paper blank, the water should be gradually precipitated in the production process. The shape, location and size of the product will be greatly changed. In the same plane and the same Different positions in the direction of contraction of the total product is different, then warping or torsion deformation of the product. In order to adjust this deformation, only take the shape of the structure to balance. The shape of the structure used to adjust the shrinkage is called the structure of the product.
(3) Structure-related parameters to determine the principle:
Stripping slope. During the forming process of the pulp molded article, the wet paper blank is fastened on the mold, and the pulp fibers are embedded in the meshes of the mesh mold. In order to facilitate the transfer of the wet paper blank, the surface of the article parallel to the mold releasing direction should be There is a reasonable stripping slope. If the inclination is too small, the mold release will be difficult, which will cause the product surface to be scratched or cracked. Too large a slope will reduce the dimensional accuracy of the product and affect the packaging function.
Product wall thickness. According to the conditions of use and the type of slurry to determine the product wall thickness, wall thickness is an important factor affecting product strength. Increasing the thickness of the product is not simply to increase the consumption of raw materials, but also in the adsorption molding determines the wall thickness of the production efficiency, increase the wall thickness will increase the drying energy consumption and make products have depression, shrinkage and sandwich quality defects. So in the case of products to meet the strength of the wall thickness should be minimized. Wall thickness in the use of adsorption molding in the range of 0.5-6mm, in the use of pressure forming the wall thickness of 3-20mm.
Transition fillet. Pulp molded articles at the inner and outer surface corners, uprising and the main body of the junction and the vertical bar of the terminal must be rounded corners, to avoid the right angle. Fillet transition is conducive to the manufacture of molds and attached to the screen, which is conducive to the release of wet paperboard blank release, is conducive to the slurry flow in the adsorption forming, help to reduce stress concentration.