What is rotomolding technology

Roto-molding technology, also known as rotational molding, rotational molding, rotational molding, etc., is expressed in English as rotational moulding. The following is a detailed introduction to roto-molding technology:

Process principle
Plastic raw materials are added to the mold, and then the mold is continuously rotated along two vertical axes and heated. Under the action of gravity and heat energy, the plastic raw materials in the mold are gradually and evenly coated, melted and adhered to the entire surface of the mold cavity, forming into the required shape, and then cooled and shaped into products.

Process flow
Material pretreatment: Select suitable plastic raw materials, clean them, remove impurities, and then dry them to ensure the purity of the raw materials.
Material delivery: Put the pretreated plastic raw materials into the cylinder of the roto-molding machine.
Heating and melting: Start the roto-molding machine, the cylinder starts to rotate, and the heating system heats the raw materials to melt them.
Roto-molding: The melted plastic raw materials are subjected to centrifugal force in the cylinder and evenly adhere to the inner wall of the cylinder to form a uniform plastic film. As the cylinder continues to rotate and heat, the plastic film will gradually thicken until it reaches the preset thickness.
Cooling and solidification: When the product melt reaches the preset thickness, stop heating and start the cooling system to cool the product in the barrel to harden it.
Demolding: When the product is completely cooled and hardened, it can be demolded from the barrel to obtain the final rotational molding product.
Features
Advantages
Low mold cost: For products of the same size, the cost of rotational molding molds is about 1/3 to 1/4 of the cost of blow molding and injection molding molds.
Good product edge strength: The thickness of the product edge can exceed 5 mm, which completely solves the problem of thin edges of hollow products.
Various inlays can be placed: Various components can be easily embedded in the product.
Complex shape and adjustable wall thickness: Products with very complex shapes and thickness exceeding 5 mm can be produced without adjusting the mold, and the wall thickness of the product can be adjusted freely.
Fully enclosed products can be produced: fully enclosed plastic products can be produced.
Fillable foaming material: The product can be filled with foaming material to achieve insulation function.
Diverse surface treatments: Various surface pattern treatments can be provided, and various color products can be produced. Anti-ultraviolet and anti-aging treatments can be applied, and various stone and wood simulation effects can be applied.
Disadvantages
High energy consumption: In each rotational molding cycle, the mold and mold frame must repeatedly undergo alternating high and low temperatures, resulting in large energy losses.
Long molding cycle: During the rotational molding process, the material is not subjected to strong external forces. It only relies on it to gradually melt and adhere to the surface of the mold cavity during contact with the mold cavity surface. The heating time is quite long, usually more than 10 minutes, and sometimes even more than 20 minutes.
High labor intensity: During the rotational molding process, loading, demolding and other processes are not easy to mechanize and automate, and are usually operated manually.
Poor product size accuracy: In addition to being affected by the type of plastic, the size of the rotational molded product is also restricted by many factors such as cooling speed, type and amount of release agent, so the size accuracy of the rotational molded product is difficult to control.
Application areas
Containers: Widely used in water storage tanks, storage tanks for various liquid chemicals, gasoline containers, battery shells, etc.
Automobile: polyethylene and polyvinyl chloride resins are used to roto-mold various pipes, such as air conditioning elbows, backrests, armrests, etc.
Sports equipment and substitutes: such as water balls, floats, bicycle seats, boats, and buffer shock absorbers between ships and docks.
Toys, models, and handicrafts: Since rotational molding molds can be manufactured using precision casting, electroforming and other processes, the surface of the roto-molded parts has a good "copy" effect on the fine structure of the mold cavity surface, and is often used to make products with greater ornamental value.
Others: There are also various boxes, shells, large pipes and other parts, such as turnover boxes, trash cans, machine shells, protective covers, lampshades, bathrooms, toilets, telephone rooms, yachts, etc.