How To Design Reinforcement Ribs For Rotomolded Products
Reinforcement ribs are a method often used in roto-molded products to increase strength. They not only make the wall thickness of the product uniform, but also save materials, improve strength, and avoid appearance defects of the product. Since some roto-molded products are large flat thin-walled products, the surface of the product is more prone to warping and deformation, and the strength is not high. Therefore, in order to increase the rigidity and strength of the large plane and the stress-bearing part of the product, it is necessary to consider designing reinforcement ribs on the corresponding surface of the roto-molded product. Moreover, products designed with reinforcement ribs can also use less raw materials and molding time to achieve the same strength, which makes the wall thickness, strength and cost better coordinated.
As for the size of the reinforcement rib, there are three elements: length, width and height. The height here refers to the size of the reinforcement rib protruding from the wall. The strength of the reinforcement rib is mainly determined by this height. Generally speaking, the design height of the reinforcement rib should be at least 4 times greater than the average wall thickness of the product to greatly enhance the strength of the product. The width of the reinforcement rib should be designed to be at least 5 times the average wall thickness of the product to provide enough space for the powder or liquid to flow into the cavity. If the space is too narrow, the raw material cannot flow into this part of the mold cavity evenly, resulting in bridging, internal porosity and increased shrinkage of the product.
When hollow ribs cannot be used, solid ribs with shorter height can also be used. However, the problem with solid ribs is that the raw material is easy to bridge and cannot completely fill the mold cavity where the ribs are located. If the solid ribs are completely filled, it will cause the local wall thickness to increase, increase the cooling time, and shrink more than the thin-walled parts around the ribs, causing the surrounding wall surface to deform. Therefore, solid ribs should be used with caution in general.