by Multi7Adm Multi7Adm

Rotational Molding what is it

Rotational Molding what is it?

They often ask us for more information about the technique of Rotational Molding and its differences with other plastic forming techniques. We will try to cover the basic questions and the basic points concerning the production of plastic objects by rotomolding, as is often called.

Rotational Molding (BrE casting) includes a heated hollow mold filled with powdered polymer, a material that you can obtain from our company.
It then rotates slowly (usually around two vertical axes), causing the softened material to disperse and stick to the mold walls. In order to maintain a uniform thickness throughout the section, the mold continues to rotate continuously during the heating phase. This continuous rotation in combination with the correct temperature control serves and aims at avoiding deformations of the product during the cooling phase.

The process was applied to plastics in the 1940s, but in the early years it was not used much. The reason was because it was a process that was limited mainly to special bulky objects. But in the last two decades the machines have evolved considerably. Also, improvements in process control and plastic powder developments have led to a significant increase in use in many areas.

Production process

The process of rotary casting is a process of high temperature and low pressure plastics. It uses heat and biaxial rotation (ie, rotation in two axes) for the production of hollow objects. Critics of the process discuss the long cycle times, as only one or two cycles per hour can typically be made. This is unlike other processes, where parts can be built in a few seconds. The process of Rotational Molding has some very distinct advantages.

Rotational Molding ADVANTAGES

1. Making large hollow components, such as water, oil tanks, is much easier
2. Can not accept competition from abroad (eg China, Turkey, etc.) due to the high cost of transportation, if it concerns rolling objects.
3. Rotary molds are significantly cheaper than other types of molds.
4. Very little material is lost using this procedure.
5. Surplus material can often be reused, thus making a very cost-effective and environmentally sustainable manufacturing process.

Rotational Molding – The 4 stages of production

Rotary casting process
The rotary casting process consists of four distinct phases:

1. Placing a measured amount of polymer

(usually in powder form) in the mold. Material you can buy from our company that produces polyethylene powder and not just sells.

2. Heat the mold in an oven while rotating until all the polymer melts and adheres to the die wall

The hollow section must be rotated by two or more axes. Axes rotating at different speeds to avoid the accumulation of polymer powder. The length of time that the mold spends in the oven is critical. Long time and the polymer will be degraded, reducing impact resistance. A short period of time and the polymer melt may be incomplete. The polymer will not have time to melt and completely adhere to the mold wall. Therefore, it is likely that bubbles will occur in the polymer. This has an adverse effect on the mechanical properties of the finished product.

3. Cooling the mold with controlled cooling

This stage of the cycle can be quite large. The polymer must be cooled so that it can be solidified and can be handled safely by the operator. This usually takes a few minutes. The section will shrink on cooling so that it can be separated and facilitate easy removal of the article from the mold. The cooling rate must be maintained within a certain range. Very fast cooling (for example, water spraying) will result in cooling and shrinkage at an uncontrolled rate, creating a warped section.

4. Remove the object from the mold

by Multi7Adm Multi7Adm

Rotational Molding main differences and advantages over other techniques

Rotational Molding main differences and advantages over other techniques

Rotational Molding main differences and advantages over other techniques. Rotomoldin offers great advantages when compared to other techniques.

The main differences between Rotational Molding and other plastics production techniques such as blow molding or injection molding machines are the following:

• powdered material instead of granules is used
• material melts in the molds rather than being molded under pressure in molds in melting mode.
• the die has biaxial rotation.
• molds are considerably more economical than other molds, e.g. injection molds due to their simplicity
• operating pressures are relatively low, allowing molds to be made of less expensive materials.
• wall thickness is controlled by the amount of powder placed in the mold.
• uniformity of the wall thickness can be maintained within ± 10 percent, which is better than what is usually feasible with the blow molding process.

Advantages of Rotational Molding

• the costs for molds and tools are relatively low.
• The rotomolding technique easily adapts to the production of many different products
• hollow, completely enclosed objects as well as open-ended pieces can easily be produced
• there is little or no waste.
• Wall thickness and piece weight can be easily controlled.
• uniform wall thickness.
• Deviations can be controlled within a maximum tolerance of ± 10 percent.
• Pieces with complex shapes and embossed patterns (eg logo, motif, etc.)
• Any size of a track can be easily created
• there is little or no shrinkage or distortion.
• Excellent surface detail and finish.
• Similar objects or different parts of a product or in different colors are produced simultaneously.
• Plastic or metal inserts may already be embedded as an integral part of the manufactured article
• double wall constructions, color mixing and special effects creation are feasible.

by Multi7Adm Multi7Adm

Rotational Molding Applications

Rotational Molding Applications

Rotational Molding Applications are mainly in the following areas:

  • Automotive industry
  • Agricultural industry
  • Furniture industry
  • General industry
  • Packaging industry such as containers, pallets and tanks
  • Sports and recreation
  • Water treatment industry
  • Marine equipments
  • Construction industry

Rotational Molding Applications in details


There is a varied number of containers available for handling and transporting materials. These include cooling boxes, barrels, containers, etc.


Tanks produced by rotary casting can be used to store water, chemicals, waste, fuel and other liquids. They can also hold up to 50,000 liters. Some types of tanks produced by this process include fuel and oil tanks, septic tanks, water treatment tanks and transport tanks.

Toys and leisure products

Playground equipment, balls and many popular toys can be made using Rotational Molding techniques. In addition, outdoor furniture, garden planters, rain barrels and other necessary to enjoy outdoor spaces can also be created with Rotomolding procedures.

Industrial products

Recycling bins, water filtration systems are some of the industrial applications of rotary casting. The durable character of the products produced through rotomolding makes it an ideal mechanical process for products used in industrial sectors.


Potential is enormous and involves the construction of larger objects such as: diesel fuel tanks, tractor dashboard, wheel arches, instrument panels and ducts. It is also ideal for the construction of trolleys for supermarkets and mobility devices for people with disabilities. As well as plastic cones, road signs and other road products.

Material Handling

When it comes to shipping and material handling, Rotomolding can create a solution for almost any scenario – no matter how big the job is. Some of the popular products created with these methods include: crates, pallets, refrigerated boxes, transport containers, garbage containers, aid strollers and packaging supplies.

Medical products

Special products with durability are essential in the medical field. Fortunately, rotary casting can create many of the widely used products in hospitals, clinics and laboratories, including medical specimen covers, oxygen face masks and paramedics.

Marine Industry

In marine environments, resistant and lightweight materials are critical. Therefore, the rotomolding process creates ideal floats, buoys, dock floats and pool linings, even pleasure craft such as canoes, kayaks, sub & surf boards.


As noted earlier, uses for Rotational Molding are extremely flexible and adaptable, hence the need for a diverse class. Some of the items that fall into this category include:

dental chairs,
storage cabinets,
agricultural equipment,
storage of cleaning equipment and manhole covers
And much more
In recent years, rotational moldingtechniques have also been used in artistic design areas such as lighting, decorative products and art.

Rotational Molding Applications – Product Photos


Rotational Molding – main differences and advantages over other techniques

List of Rotational Molding Materials

Back to Home Page