How to Improve Wall Thickness Uniformity in Rotational Molding

The following methods can be used to improve wall thickness uniformity in rotational molding and to control local wall thickness in specific areas of the product.

1. Position the mold correctly.
Secure the rotomolding mold in the proper position on the mold frame and adjust the balance of the rotating arm or mold support to ensure stable rotation during the entire molding cycle.

2. Keep the main and secondary shaft speeds stable.
The rotational speeds of both the main shaft and the auxiliary shaft should remain balanced and consistent. Stable rotation helps the material distribute more evenly over the mold surface and reduces irregular wall thickness.

3. Ensure even heating in the oven.
The heating oven should be able to heat the mold evenly from all directions. Uneven heating can cause the resin to melt and adhere at different rates, resulting in wall thickness variation.

4. Reverse rotation during both heating and cooling.
During both the heating and cooling stages, the mold should reverse direction once. The direction change should be quick, and in most cases the forward and reverse rotation times should be kept equal.

5. Increase thickness where needed.
In areas where greater wall thickness is required, the corresponding section of the mold can be preheated or the local heat insulation effect can be reduced so that more material can melt and adhere in that area.

6. Reduce thickness where needed.
In areas where reduced wall thickness is required, the corresponding part of the mold can be insulated so that the molten material is less likely to adhere to the mold surface or continue building up in that section. This helps reduce the thickness of the targeted area.

This insulation method can also be used to create local non-adhering areas on the mold surface so that resin does not bond to certain sections, which may help form openings or special features. However, openings produced in this way are generally not highly regular in shape.