All about Rotational Moulding

All about Rotational Moulding

Categories: news

"Rotational molding," also known as "rotomolding," is a plastic casting process for producing hollow, seamless, and double-walled parts. By heating thermoplastic powdered resin in an open mold tool and rotating it, it solidifies by cooling. The molded parts generated by this process are usually highly durable and robust.

Rotational molding does not involve pressure, which makes tooling less expensive than other types of molding. It is ideal for producing extensive parts since you can use the tooling in any size. There are few restrictions in terms of part design, allowing the designer to integrate complicated details.

Hundreds of years ago, ancient Egyptians created ceramics using rotational molding. In 1855 and 1910, the Swiss began producing artillery shells and hollow chocolate eggs using a rotational molding process that was more advanced than what the Egyptians used to create uniform wall thickness and density. Several patents documented the nature of this casting process during these periods. The process was criticized as slow, and it encountered several challenges, preventing its wide adoption.

During the 1940s, nickel-copper plastic was electroformed onto polyvinyl chloride plastisol resin to make doll heads. It used cold water to quench the parts during the molding process after being molded. There were only electric motors and gas burners in the set-up. In addition to road cones, marine buoys, and armrests made with the method, it had attracted many industries to adopt it in their production processes.

Nowadays, rotational molding is used to produce large and complex parts in various applications. Processes are better understood, and equipment designs have improved dramatically. Some manufacturers continue to struggle with prolonged heating and cooling cycles. To accommodate the growing demand, developers have modified rotational molding equipment.

It may seem simple to understand rotational molding, but in reality, some manufacturers find it challenging to achieve a good product through the process. Compared to other molding methods, rotational molding has several advantages. Manufacturers and end-users can obtain the following benefits through proper design and settings:

• The durability of a part is increased by a consistent wall thickness on all sides, edges, and corners. Uniform wall thickness can be achieved with the right rotational speed and cooling cycles, even on thick-walled parts. Rotational molding produces thicker corners and edges than blow molding, stretching the molten material at those points.

• Parts with double walls can fabricate without secondary processing, like welding and joint fabrication. As a result of the seamless edges, the pieces produced have increased durability.

• A low-cost material such as aluminum can manufacture the mold since it doesn't have to withstand high pressures. Only short production runs require less investment in tooling.

• Flexible production: Multiple parts can be molded simultaneously in a single machine. It is possible to schedule maintenance activities on one mold while the other is used when rotational molding equipment has independent arms.

• Rotational molding can produce more significant parts: Parts with a hollow interior can be made using rotational molding. Heat chambers and cooling chambers are the only limitations.

• A single part is manufactured in rotational molding, so fewer downstream processes are required, and minimal waste is required. As a result, trimming and stripping steps are not necessary. Runners, sprues, and cut-offs generated by rotational molding are less wasteful.

• You can easily incorporate design features such as textures and symbols into the surface of a tool by adding such details.

This process has some disadvantages:

• It may not be feasible to produce high volumes with rotational molding because of its long cycle times and high cost. As the part and the entire mold are slowly heated to the molten state and gradually cooled to room temperature after molding, it consumes a lot of time during the molding process. A cooling system may be employed to remove the heat, but it requires an additional cost.

• Due to the limited availability of automation features, manual steps (e.g., demolding) are still involved. Consequently, the operation is more expensive.

• Materials limited: This method requires powdered polymers as the raw material since you must convert it into powdered form to be successful. Materials other than polyethylene are expensive and hard to grind. The polymer also needs to be thermally stable, limiting the types of resin used.

• The tool's shorter service life can be attributed to the thin and soft metal used in it can only be used for a few cycles before it must be replaced to ensure the quality of the parts made with it.

• Molding specific details and designs are challenging: Making a large flat surface uniform in thickness is difficult due to the flow of the resin. In addition, rotational molding machines cannot create parts with high tolerances and sharp edges; high-pressure molding may be an option.

Conclusion

In Rotational Molding Design Firm China, while rotational molding, the powdered resin is heated in a hollow mold tool while slowly being rotated and cooled to form an open, seamless, and double-walled part that sets. It began hundreds of years ago, became popular in the mid-20th century, and continues today. You can find various applications in this process.

Molds, furnaces, and cooling chambers are associated with rotational molding equipment. Depending on the process sequence, rotary molding machines are distinguished by the direction in which the mold travels.

NEXT ARTICLE

BACK TO ALL