Causes
In the rotomolding process, it is not easy to process products with sudden wall thickness. The average wall thickness of the product depends on the amount of material to be fed. The uniformity is related to the structure of the mold itself and the rotational molding process.
From the rotomolding product and the rotomolding mold structure, generally, the thickness of the concave corner of the rotomolded product (the convexity of the mold) is small, and the thickness of the convex portion of the product (the concave of the mold) is large, but if the product is large The angle of the convex part is too small, which may cause the material to be unable to fill the mold and bring corresponding holes and other defects, so the product should not have sharp corners, usually with a 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 is coated with the rotating layer of the mold, and there are more adhesive resins, and the resin adhered to the lower temperature portion. Relatively small, resulting in uneven wall thickness.
The wall thickness of the product is also related to the rotation speed. The rotation speed is not uniform, it is easy to cause uneven wall thickness, and there is no regularity. Therefore, the motor with constant torque or constant rotation speed can be automatically controlled to ensure the constant rotation of the main and auxiliary shafts. When the wall thickness of a certain part of the product is different from other parts, if the mold cannot be modified, it is necessary to seek a solution from the technical point of view.
solution
Fix the rotomolding mold to the appropriate position on the mold base and adjust the balance of the mold base.
Main, the secondary shaft rotation speed is balanced and the speed is even.
The furnace can ensure that the mold is heated evenly in all directions.
Both the heating and cooling processes are reversed once, and the commutation is quick, generally forward, and the reverse time is the same.
In the part where the thickness of the product is required to be increased, the corresponding part of the mold should be preheated or the influence of heat insulation factor should be reduced.
In the part where the thickness of the product is required to be reduced, the corresponding part of the mold is filled with a tetrafluoroethylene plate or an asbestos pad to prevent the molten material from being attached to the mold or continuously stacked to reduce the thickness of the portion. This method is also used to separate the portion. The hot layer is lined on the mold so that the inner surface of the mold cannot adhere to the resin to obtain the opening portion, but the opening made by this method is generally not regular.