Technology Frontier: Rotomolding

Technology Frontier: Rotomolding

-01-Introduction to Roto-molding Process

There are many processing and molding processes for plastics and their composite materials. In addition to the common extrusion molding, injection molding, blow molding and other processes, roto-molding is also a processing method for plastic products. Roto-molding, also known as rotational molding or rotational casting, is a plastic molding process.

Rotomolding is also known as rotational molding, rotational molding, rotational molding, rotational casting, rotational molding, etc., and is expressed in English as RotationalMoulding.

The rotomolding process is to first add the plastic raw material into 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 material in the mold is 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 a product.

At present, the foreign rotomolding industry is developing rapidly, while the domestic rotomolding industry is developing slower than other plastic molding processing industries due to various factors, such as slower processing cycles and limitations on the materials used.

It should be noted that the production efficiency of rotomolded products is very low. Generally, a product needs to be produced in 30-60 minutes, including forming, cooling, and disassembly of the mold. Therefore, the quantity of the product is determined by the number of molds, and multiple molds can be rotated on the machine at the same time.

-02-Characteristics of rotomolding process

1. Low cost of rotomolding molds: For products of the same size, the cost of rotomolding molds is about 1/3 to 1/4 of the cost of blow molding and injection molding molds;

2. The edge strength of rotomolded products is good. Rotomolding can achieve a thickness of more than 5 mm on the edge of the product, which completely solves the problem of thin edges of hollow products

3. Rotomolding can be used to place various inlays

4. The shape of rotomolded products can be very complex and the thickness can exceed 5 mm

5. Rotomolding can produce fully enclosed products

6. Rotomolded products can be filled with foaming materials to achieve thermal insulation

7. The wall thickness of rotomolded products can be freely adjusted without adjusting the mold

8. The product is hollow and seamless, with uniform wall thickness, and the wall thickness can be adjusted to make the product high-strength

9. It can provide a variety of surface pattern treatments, produce products of various colors, can be treated with UV protection and anti-aging, and can be used for a variety of stone and wood simulation effects

-03-Application of roto-molding technology

At present, roto-molded products can be used in transportation, traffic safety facilities, entertainment industry, river channel dredging, construction industry, water treatment, medicine and food, electronics, chemical industry, aquaculture, textile printing and dyeing and other industries.

1. Container-type rotational molding parts. This type of plastic parts are widely used in water storage tanks, storage tanks for various liquid chemicals (such as acids, alkalis, salts, chemical fertilizers, pesticides, etc.), gasoline containers (gasoline storage tanks and fuel tanks for cars and airplanes), battery shells, etc.

2. Rotational molding parts for automobiles, mainly using polyethylene and polyvinyl chloride resins, roto-molding various pipes, such as air conditioning elbows, backrests, armrests, etc.

3. Sports equipment and various substitutes. There are mainly various roto-molded parts of polyvinyl chloride, such as water balls, floats, bicycle seat cushions, boats, and buffer shock absorbers between boats and docks. Surfboards, boats, etc. are also roto-molded parts.

4. Toys, models, handicrafts, etc. Since rotational molding molds can be manufactured using precision casting, electroforming and other processes; the surface of the rotationally molded part has a good "copy" effect on the fine structure of the mold cavity surface, so the rotational molding method can make the product quite delicate and beautiful, so it is often used to make products with great ornamental value, especially toys, models, handicrafts, etc.

In addition to the above, rotational molding products are widely used in various boxes, shells, large pipes and other parts, such as turnover boxes, garbage bins, machine shells, protective covers, lampshades, bathrooms, toilets, telephone rooms, yachts, etc. Rotational molding products have been widely used in the storage and transportation of liquid chemicals, washing tanks and reaction tanks in chemical companies, industrial coatings, rare earth production, as well as river and sea buoys, domestic water tanks and other fields.