Category: Rotomolding Process

Rotomolding Process

The rotomolding process, also known as rotational molding, is a method that allows the production of small or large seamless hallow plastic components.The technique of biaxial rotation had been around since the early 1900’s. The first printed description of using heat and bi-axial rotation was to manufacture round, hollow weaponry shells written in 1865. But until the innovation of low density polyethylene by the British in 1942, bi-axial rotation was just an interest in the then relatively new plastic industry.

How It Works

The process starts when a mold mounted on the rotational molding machine arm is charged with a known amount of liquid or powdered resin into the mold hollow space. The mold is then clamped shut and begins rotating on its horizontal and vertical axes. The spinning continues as the arm conveys into a vast oven heating the whole surface area of the mold.

Once the resin and the mold surface have reached fusion temperature, the resin starts to melt creating a pond in the lowest part of the mold.As the mold keeps on spinning, each surface of the mold passes through the pond of molten resin repeatedly pulling a thin layer of plastic material on top of the inner surface of the hollow space.Then when the heating cycle has been concluded the arm then shifts into a cooling cavity. The mold is then cooled by water, air or a mixture of both until the component can solidify and retain the hollow shape. The mold is then unlocked and the component is removed and the entire process is repeated over and over.

Benefits of Rotomolding

Look around and see all the plastic products you see in use every day: drink bottles, bags, car components, and even the computer that you are currently working on. Plastic technology has developed significantly in the past few years, creating products that have the following benefits:


Plastic parts are exceptionally impact resistant and they do not dent. In addition, plastic parts can incorporate metal inserts in high stress areas.

Corrosion Resistance

It is a known fact that plastic cannot rust. When it comes to metals, even stainless steel is vulnerable to rust in welded areas.


It takes less energy to operate equipment with plastic components since plastic is lighter weight when compared to metal. Plastic is usually less expensive than metals. And because rotational molding easily allows for one piece construction, assembly times, assembly costs are therefore reduced.

Chemical Resistance

Plastic materials can stand several chemical components, making it the most ideal solution for fuel tanks containers and other containers.


Rotational molded plastic removes sharp burrs and corners and result in an even, seamless product. This helps in reducing injury risk for operators. And since rotomolding allows more control over the process, more ergonomic components can be created.


plastic rotational molded plastic partsWith the rotomolding process a wide variety of colors is available. Because the color is solid throughout the piece, there is no unattractive chipping of color.

The process also gives you the alternative of incorporating a color logo right on the molded piece, which means your logo cannot flake or peel away. And because this technique allows more control over the design, you can match the style of the component along with its function.

One-Part Construction

In crafting the molds for the products, several things can be put into consideration such as metal inserts, flanges, contours, and even detailed logos. In such a mold, the whole plastic item can be designed at the same time that too in one piece without any joints or weld lines. Where as in other different types of plastic molding process, various parts of a single product are molded independently and then joint together, which often leaves the joint marks.

Rotomolding Advantages

Rotational molding process offers many advantages over other types of plastic molding such as thermo-forming, blow molding, and injection molding:

Consistent Wall Thickness

When it comes to rotational molding, the wall thickness of the entire piece remains consistent since the centrifugal force applied on the molten plastic is the same throughout the process. Hence it spreads out uniformly and turns to be relatively stronger with no thin regions that could break or burst. To add more power to the product, designers can even include double walls, kiss-offs, internal ribs or foaming. Even the outersurface corners tend to be strong being almost stress-free. The inbuilt and hidden strength of the rotational molding designs are widely known. To mention just but a few of these design advantages of rotational molding are uniform design and strong outside corners. The corners in question are virtually stress-free. For more strength, a product can be made from reinforced ribs

Greater Design Flexibility

Rotational molded parts can be designed and manufactured to fit just about any space available. Usually, parts that are collected from multiple pieces can be assembled into one rotomolded piece. That enhances design possibilities. And the fewer pieces, the fewer chances for part failure

Superior Strength

There are several factors that contribute to the superior power of rotational molded parts: consistent wall thickness, durable new plastics, corrosion resistance and one-part construction.

Dramatic Cost Savings

Since there is no center core to manufacture, tooling for rotomolding parts is less expensive when compared to tooling for other types of plastic molding. Plastic products are  substantially more cost effective when compared to most durable metals..

Shorter Production Times

Rotational molding manufacturers can often design parts, fabricate the mold and begin prototype production in three to four months. This is basically remarkably faster than the lead times for several other plastic molding processes. What’s more, this molding technique will enable you to get your complete product to market faster when compared to other processes.

Easier To Modify

Fabricated molds are relatively simple; this means that small changes can easily be made to an existing mold to fit your changing production requirements. Whether it’s stiffening ribs, difficult textures, or indentations, every shape can be molded without increasing the tooling cost.

Ability to Do Small Runs

With affordable tooling, rotational molding makes it possible to do small runs on products. As a matter of fact, many consumers find it less expensive to do production batches as small as ten pieces.

The rotomolding process is well known for the manufacture of tanks, but it can also be used to produce complex medical products, leisure craft, toys, kayaks, and highly aesthetic point of sale products.

For more help and detailed information: R & R Technologies LLC, 7560 East County Line Road, Edinburgh, IN 46124, Ph: (812) 526-2655

Benefits of Rotomolding Plastics

Using plastic as a replacement of metal could add to a much more resilient, much longer enduring item. Rotomolding plastics are much more flexible and much more affordable. Rotational molding procedure is great fit to a variety of various applications.The use of plastics products is used in many items such as containers, headgears, car elements, […]

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