Rotational molding, also known as rotomolding, is a production process to form hollow parts of limitless sizes. It is a cost-effective method for the production of large-plastic parts.

Here, the heated hollow parts are filled with either a charge or a short weight of the material. Afterward, it usually rotates slowly around two perpendicular axes. This makes the softened material disperse and stick to the wall of the mold.

The mold keeps rotating during the heating phase to maintain the thickness throughout the part. The rotation also prevents deformation or sapping during the cooling phase.

At the end of this read, you will have a deep-rooted understanding of why Rotational Molding is essential.

How Does Rotational Molding Work?

Here, the plastic material, in powdered form is placed into the hollow mold. Often, the material is usually from either cast aluminum or fabricated sheet steel form.

The hollow is closed up and rotates slowly in two axes. It is essential to note that the mold is heated in the oven as it rotates. Besides, the polymer eventually melts and the inside of the mold lays up.

After the process of melting the polymer, and powder has been completed, the mold is moved to the cooling phase. The cooling is done with air or a fine mist of water.

When the mold is done cooling, the hollow parts solidify. Also, when the material has sufficiently cooled to release away from the mold surface, the process is stopped and the product is taken out of the mold. The process is also known as (de-molding).

That’s it.

Although the idea of rotomolding is hassle-free, anyone that has been involved will tell you otherwise.

Rotomolding involves a casting process with no pressure in play. What that means is that the material cannot be controlled in the way you will in a high-pressure process like injection molding.

What Are the Materials Involved in Rotomolding?

Back in 1961, the first-ever polyolefin powder which is a low-density polyethylene was demonstrated to the rotation industry. Today, polyethylenes have become one of the most popular materials for rotational molding. And that is due to its properties, cost-effectiveness, and its process abilities.

Core thermoplastic raw materials suppliers have looked into the formulated powders for rotomolding. Some of the investigated raw materials include nylons, polycarbonate, rigid polyvinyl chloride, polypropylene, and many more.

All these aforementioned powders foam can be strengthened with fiberglass. With more additional raw material suppliers, most people involved in rotomolding use grinding services or their custom-made in-plant grinding capabilities that enlarge the material selection for the rotational molding process.

Why is the Rotomolding Process Important?

The benefits of rotational molding are encapsulated below.

• Cost-effective: Rotomolding requires low tooling costs. And that makes it a suitable choice for those with a budget. There is no pressure involved in the casting process, meaning the molding is inexpensive and the low volume is considered economical.

Do you have a great idea for a new product but you have no idea of the numbers of sales you will make? Or perhaps you like a low production volume? Then you should decide on the rotomolding process.

Also, rotational molding is a great choice for its low initial investment. An example of low-cost tools is Aluminum.

• High durability level: The hollow parts are molded as a single solid piece. Thereby, eradicating the need for a combination of techniques like welding and joint fabrication that creates weak spots.
• Double wall construction: With rotational molding, you can produce complex double-walled construction without the need for secondary processing.
• Appearance: Also, the soft metal utilized in rotational mold tooling accommodates the finishing surface without any hassle.

What Are the Downsides of the Rotational Molding Process?

• Limitation in material options: The raw materials utilized in the rotational molding process are already converted from granules into fine powder. Consequently, the material has high thermal stability and limitation in the selection of material into poly-based material.
• High cost of raw materials: As mentioned earlier, raw materials like nylons, polycarbonate, rigid polyvinyl chloride, and polypropylene are used in the rotomolding process. However, these materials are expensive. Not just that, the cost of additives and grinding these materials into fine powder are factors you also need to consider.
• High cost of labor: The cost of labor is also one of the downsides of rotational molding. The automation and mechanization of rotational molding are yet to be achieved. At the time of this writing, the process requires labor intensity.
• Low level of repeatability: The chances of reusing roto mold tooling are low. The soft metal used in rotational molding tooling is required to be replaced or renovated after 3,000 cycles. Besides, there are often issued will induced quality which is a result of lack of repeatability.