Rotomolding

Rotomolding Process

Hollow object production is done via rotational molding. A preweighted amount of polymer, either in liquid or powder form, is first added to one-half of a cold mold to start the process. Next, the mold is sealed and put inside an oven biaxially rotated. At first, the polymer rotates inside the mold as it spins. Most of the polymer mass remains at the bottom of the mold, forming a pool because of the low rotational speed, which ranges from 2 to 20 rpm.

The polymer starts to melt, or react in the case of thermosets, as soon as the inside surface of the mold reaches a sufficient temperature, coating the mold. As the mold turns, additional polymer layers cover the mold's inner surface until the entire polymer pool disappears. The mold is moved into a chilly area, and the molding is removed once it has cooled to the proper temperature so that a fresh batch of polymer can be charged to start the next cycle.

Rotomolding Products

The industrial potential for items made using rotational molding is practically infinite. The transformation of products composed of less resilient materials into rotomolded products is an increasing trend in manufacturing. Because of the method and the properties of the materials, rotomolding offers a wide range of advantages. Some examples of rotomolding product conversions include pallets, agricultural tanks, drainage piping, laundry carts, Department of Defense items, air cargo containers, burial urns, cemetery products, and even tornado shelters.

Types of Rotomolding Machines

• Rock and roll machine
• Clamshell producer
• Up and over rotational machine
• Material jetting machine
• Shuttle machine
• Swing arm machine
• Carousel machine

The rock and roll machine mostly produces long, narrow pieces. The clamshell machine occupies less area than the shuttle and swing arm machines while still heating and cooling in the same chambers. Due to their modest heating and cooling chambers, vertical rotational machines are small-to-medium in size and energy-efficient compared to the other rotomolding machines.

In addition, although there is a single-arm shuttle machine, most shuttle machines have two arms that alternate the molds between the cooling station and the heating chamber. The arms revolve the molds in a biaxial motion and are independent of one another. Finally, the swing-arm machine is advantageous for businesses with extensive cooling cycles or significant demolding durations. It has a biaxial movement and up to four arms.

Areas Where Rotomolding Can Be Used

Food Sector

Temperature-sensitive food items or dry ice pellets and blocks can be transported and stored in the food business using rotomolded packaging. This is possible, for instance, with an insulated polar container. Rotomolded using foam insulation and FDA-approved polyethylene, polar containers are perfect for the food distribution, fish, and wine industries.

Military Sector

The military sector needs to use high-quality cases to transport its robust equipment. Rotomolded packaging and cases are ideal for handling materials where delicate equipment needs to be transported or stored safely.

Medical Sector

In the medical industry, it is typical to transport and store fragile equipment. Therefore, packaging for medical and pharmaceutical products must adhere to strict standards and rules that often require rotomolded cases.

Advantages of Rotomolding

• Rotational molding has several benefits, including homogeneous wall thickness, minimal tooling costs, and design flexibility. Molds can be made in a wide variety of sizes and shapes. Additionally, there are several choices for textures, colors, and materials using rotomolding. They are economical and environmentally friendly because extra material is frequently reused.
• Rotational molding is superior to other molding techniques in terms of design. With the right design, items that are put together from numerous pieces can be molded as one part, reducing the need for expensive fabrication.
• Other inherent design advantages of rotomolding include constant wall thickness and robust exterior corners that are almost stress-free. Reinforcing ribs can be built into the part to increase strength. These ribs can either be introduced or designed into the component.

Drawbacks of rotomolding

• Slower production time
• Rotomolding uses more plastic, so products are heavier
• The process has a low thermal efficiency, resulting in longer cycles