In fact, plastic products with sudden change of wall thickness are not easy to be processed in the process of rotational molding. The average wall thickness of products mainly depends on the amount of feeding, and its uniformity is greatly related to the structure of the mold itself and the rotational molding process. If the uneven wall thickness occurs in the process of rotational molding, it is very likely that there are problems in structure, temperature and speed.

In terms of the structure of rotational molding products and rotational molding molds, generally, the thickness of the concave corner of the rotational molding products (the outer convex of the mold) is small, while the thickness of the convex corner of the products (the inner concave of the mold) is large. However, if the angle of the convex part of the products is too small, it is easy to cause defects such as materials can not fill the mold and bring corresponding holes, so the products should not have sharp corners, Usually use large smooth arc transition.

The melting and adhesion ability of plastics is mainly related to the mold temperature. Where the mold temperature is high, the plastic is easy to melt first and coat layer by layer with the rotation of the mold, so there will be more adhesive resin, while there is relatively less adhesive resin in the parts with low temperature, resulting in uneven product wall thickness.

The wall thickness of the product is also related to the rotation speed. The uneven rotation speed is easy to cause uneven wall thickness and irregularity. Therefore, the motor with constant torque or constant speed that can be automatically controlled is generally used to ensure the uniform rotation of the main and auxiliary shafts. When the wall thickness of one part of the product is greatly different from that of other parts, and the mold cannot be modified, it is necessary to find a solution from the perspective of process.

Solution

Fix the rotational molding die in a proper position on the mold base, and adjust the balance of the mold base.

The rotation speed of the main and auxiliary shafts shall be kept proportional and uniform.

The heating furnace can ensure that the mold is heated evenly in all directions.

In the process of heating and cooling, change direction once, and change direction quickly. Generally, the forward rotation and reverse rotation time are the same.

Where the thickness of the product needs to be increased, the corresponding part of the die shall be preheated or the influence of thermal insulation factors shall be reduced.

At the part where the thickness of the product needs to be reduced, the corresponding part of the mold shall be insulated with tetrafluoroethylene plate or asbestos pad, so that the molten material is not easy to adhere to the mold or accumulate continuously, so as to reduce the thickness of this part. This method is also used to lining the thermal insulation layer on the mold so that the resin cannot be adhered to the inner surface of the mold to obtain the opening part, but the opening made by this method is generally not regular.