Rotomoulding

Rotomolding or rotational molding is an industrial thermoplastics processing for the manufacturing of hollow plastic products.

In the rotational molding process we can obtain pieces made of polyethylene, EVA (ethylene vinyl acetate), PVC, plastisol or other thermoplastic resin.

The principle of thermoplastics transformation by rotational molding is simple. The process consists of introducing a specific quantity of resin into a cavity mold. The mold is placed in biaxial rotation at low speeds, as it is heated inside an oven to melt the resin contained. The resin melted during the rotation process acquires the shape of the internal walls of the mold as it solidifies.

The mold for rotomoulding may be aluminum, copper, nickel, steel, resins, gypsum or ceramics, which must be in the form of the desired product.

 
The four main phases of the rotational molding process:

• Load a specific amount of polymeric resin powder into the mold.
• Heat the mold inside an oven, while it keeps a constant rotation, causing the resin to melt and acquiring the form of the walls of the mold. The rotation of the mold must be carried out in two or more axes to ensure a good distribution of the molten polymer resin.
• Extract the mold from the oven and cooling the mold to solidify the resin therein, allowing handling of the formed piece by an operator.
• Remove the piece from the mold.

 
Rotomolding – Carousel System

Representing the rotational molding process:

• Carousel System – The 4 stages.

 

Phase 1:

• Beginning the sequence of rotational molding process.
• Filling the mold with a dosage of polymeric resin.
• Closing the mold and place it on the automated basket.

 

Phase 2:

• Introduction of the mold in the oven.
• The mold is kept constant quotation.
• Beginning of the resin melting into contact with the mold walls.

 

Phase 3:

• Move the mold to an air cooling station.

 

Phase 4:

• Extraction of the final product from the mold.

 

Rotational molding offers advantages compared to other industrial processing of thermoplastic (injection blow molding, vacuum). In this process we obtain parts with low or high level of complexity, completely airtight and hollow parts or with dimensions that can go up to 25,000 liters as tanks or silos.

• A hollow product can be manufactured in one piece without joints or joint lines.
• The final product is not subject to tensions.
• The molds are relatively inexpensive in production cost.
• The runtime of a mold is short.
• The production of small parts is economically feasible.
• Very low material waste in production.
• Ability to create multilayer products.
• Resistant to cracking and corrosion.
• Possibility of inclusion of metallic elements in accordance with the product specifications.
• Possibility to insert high-quality graphics.

The application possibilities for rotomolding products are endless:

• Food Industry
• Pharmaceutical and therapeutic
• Security
• Toys
• Playgrounds
• Automobile
• Displays and Advertising
• Outdoors
• Industry

There is an infinity of products that can be obtained by rotational molding with large shape diversity, different sizes, different colors, strength and security:

• Tanks and reservoirs
• Toolboxes
• Paddling pools
• Playgrounds
• Product displays
• Toys
• Floating Products (boats, rafts, etc.)
• Merchandising
• Ornamental
• Covers for electrical and electronic household