See How Rotational Molding Manufacturers Deal With Product Warping And Deformation
1. Analysis of the causes of warping and deformation
Although roto-molded products are non-pressurized, they are less prone to warping and deformation than other pressurized molding methods.
However, roto-molded products are generally complex in shape, uneven in wall thickness, and not completely symmetrical.
This causes the cooling rate and shrinkage rate between different parts of the product to be inconsistent, and warping and deformation occurs in large planes and parts with large wall thickness differences.
PE products have a relatively large shrinkage rate after roto-molding, generally 2% to 3%, or even as high as 3% to 5%.
The dimensional accuracy is poor, and the shrinkage rate is even higher in parts with large local linear dimensions.
The shrinkage of the product is also related to factors such as the heating temperature, cooling and shaping temperature, cooling rate, and product demolding temperature during product molding.
These factors are not easy to accurately control during the roto-molding process.
Especially in the process of product demolding, many roto-molding manufacturers start demolding when the product temperature is 70 to 80°C or even higher in order to pursue production efficiency.
Then the product shape is controlled by post-molding treatment. Since the factors of human control in the demolding process are too strong, the shrinkage of the product is more difficult to control.
For products with strict requirements on the product's external dimensions and deformation.
In addition to taking targeted measures in the rotational molding process, the post-molding process is also important.
In order to produce higher quality products, emphasizing the stability and uniformity of the production process should be an important concept throughout the entire manufacturing process.
2. Solutions for warping and deformation
When designing rotational molded products, try to avoid large planes.
Structural forms such as reinforcing ribs, steps, overlaps (bridges) or surface groove decorations can be used to reduce the plane area, thereby controlling warping.
Adjust the position of the mold on the mold frame to eliminate factors that increase the wall thickness difference and affect the uniformity of heating and cooling.
According to the structural characteristics of the product, make a shaping tool or a fixed tool with a movable part to shape the product in the post-cooling and sectioning stage.
For products with special shapes, you can also combine a simple shaping tool to pass compressed air into the product to force the product to shape and shape, which has a better effect.
Take reasonable cooling measures to try to make the cooling rate of each part of the product consistent.