Plastic rotomolding. What is it and what advantages does it offer?

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If you have ever wondered how durable hollow plastic parts are made, such as water tanks, plastic drums or car bumpers, but also toys, flower pots, dolls, the answer is with plastic rotomolding.

In this article, Let’s see what plastic rotomolding is, how it is carried out, and What are its benefits.

If you are interested in knowing more about this process or are looking for solutions to manufacture high quality plastic parts continue reading.

What is Plastic Rotomolding?

The rotomolding plastic or rotational molding or roto casting is a technique of polymer processing which is used to create a wide range of partsplastic of different sizes and thicknesses, which can range from very small sizes to very large sizes, even reaching 4.5m in spherical diameter.

Is a technology different from traditional injection or blow moldingparticularly suitable for manufacturing small series of hollow and granular productssize, even geometrically complex ones impossible to manufacture with other technology.

With rotomolding a large number of items can be producedgaps that can betotally or partially closed, with single or multiple walls.

The molding process of thermoplastic parts is carried out from a polymer in
powder that is introduced into a mold that rotates about two axes perpendicular to each other while heating (between 250 and 450 ºC) to achieve fusion of the material.

The rotational force of the spin causes the mass of molten plastic to reach all faces and recesses of the mold cause the molten plastic to spread along the walls of the mold.

During the subsequent cooling phase, the material gradually solidifies on the
interior faces of the mold, creating an increasingly thicker plastic film that guarantees uniformity in the thickness of all faces of the manufactured part, until forming a completely closed hollow part that can be machined later.

It is a process that does not need pressure, so the equipment and molds required are Relatively low cost compared to those used in other techniques.

Although the thickness of the pieces is uniform, different thicknesses can be created in different areas of the pieces by varying the temperature (by increasing the temperature of the mold, the polymer takes longer to cool so more material is deposited) or varying the rotation speed of each axis..

Rotomolding applications

For small parts: such as our motorcycle boxes.

For large pieces: tanks, fuel tanks, barrels, floats,
canoes, etc.

Areas and types of products with rotational molding

Automotive industry:

Rotomolding is applied to the manufacturing of instrument panel components,
armrests and coverings, pipes and fuel tanks. Also the Traffic signs and separation barriers take advantage of its advantages.


A large number of toys and leisure tools are constructed with rotomolding, such as for example water skis, surfboards and the vast majority of garden furniture..


Aircraft containers, refrigerated boxes, barrels, planters and other containers reusable for transport are manufactured with roto casting.

Naval industry:

In the manufacture of everything from leisure boats to kayaks and canoes, rotomolding has proven to be a very useful technique, in addition to buoys, pontoons or protections.

Liquid storage:

Tanks and deposits intended for the storage of fuel, oil or products chemicals, as well as septic and water treatment tanks.

Material transportation:

Medical cases, trash cans, packaging, plastic pallets and other containers special ones for handling and logistics are manufactured with rotomolding

Advantages of rotomolding

Versatility: It allows manufacturing from relatively small pieces, up tolarge pieces impossible to obtain with other methods.

· Low initial investment for production of parts. The cost of the mold is noticeably lower than plastic blow or injection molds.

The molds used in rotomolding are widely customizable for meet the needs of custom manufacturing of plastic parts.

This ensures that the result is adjusted in terms of optimal quality.

Rotomolding recycling possibilities

This is a special point for ABC Rotomolding, since we recirculate the waste generated during the process productive and we also recover those provided by our clients to manufacture to measure with recycled rotomolding.

The low pressure and speed minimizes mold wear, increasing its duration.
You can create pieces with different thicknesses, colors and materials.
Allows complex parts to be molded in a single piece while maintaining the thickness of the wall.

Disadvantages of rotomolding

Air bubbles can cause a problem in parts during installation. fases de diseño y producción. This is not a common problem, but It should not be ruled out in the forecasts during the pre-design phase.

There may be considerable variations in parts due to precision issues. dimensional, although the tolerance is wide, since they are cases that occur in 1% of cases. it is not very good.

The long duration of cooling takes a significant amount of time, which can carry very long cycle times

How is plastic rotation molding done?

The process of rrotomolding of plastic piecesis simple which is carried out inthree stages:loading, cooking and cooling.

First, the powder or micro granules are loaded into a hollow mold.

The mold rotates simultaneously on two axes while it is heated and then cooled. According to
The type of material used, the piece takes on a different shape.

The cooling phase is crucial and depends a lot on the material used, since each
It has different specifications.

The final phase is the opening of the mold to obtain the created part and load new material to start a new cycle.

What materials can be used in rotational molding?

The main material used in rotational molding is polyethylene, a type of plastic polymerKnown for its durability and weather resistance.

In addition to polyethylene, you can Add additives, such as colorants or UV stabilizers, to customize properties of the final piece.

Other materials that can be used to manufacture plastic parts with rotomolding are:

High density polyethylene (HDPE):

It is used to make tanks,, containers, toys, and a wide variety of industrial and consumption. It is one of the most used materials in rotational molding due to its
excellent resistance and durability.

Linear Low Density Polyethylene (LLDPE):

It is commonly used in manufacturing of storage containers, boats and toys. It is similar to HDPE, but more resistant to bending and impacts.

Polipropilene (PP):
It is used for products such as tanks, containers, and household items, as it offers good chemical and thermal resistance.
Poliamydes (Nylon):
They are mainly used to produce resistant and durable parts. high quality, such as fuel tanks, wheels and components machinery

Rotomolding machines

The different rotomolding machines differ from each other mainly in the arrangement of
its different seasons: heating, cooling, loading – unloading and in the form of
transfer molds from one station to another.

The range of rotational molding machines today is very wide and ranges from small laboratory machines, from one arm and one molding chamber, to complex installations with a spherical diameter of up to 5,000 mm and controlled arms regardless.

The different rotomolding machines are the following:

If the heating of the material is carried out in an oven:

Carousel Machines:
It is the most common machine in the rotational molding industry. plastics. It has a wide range of sizes and can reach up to six arms. We can find fixed or independent model machines.

Rock and Roll Machines:
One of the first used for rotational molding.

Oscillating action around an axis (rock) and a total rotation of 360° around a perpendicular axis (roll) allows creating especially pieces of big size.

shuttle machine.
Shuttle rotational molding machines were developed in an attempt to conserve space.
Rotomolding machine Shuttle is frequently used for rotomolding large parts.

It is a single arm rotational molding machine that heats and cools in the same chambers and takes up less space than shuttle machines and swing arm.

If the heating of the mold is carried out in an oven, we have:

open flame machines: In this type of machines, heating is carried outusing several blowtorches, and there is no oven, so the heat losses are larger and the production cycle will be much longer.

The different types of rotomolding machines achieve the same objective, but, without However, they do it in different ways. Therefore, they differ from each other, in the process which is followed to obtain the final piece.

Other plastic molding techniques

In the world of plastic parts manufacturing, plastic rotomolding is just one of several techniques used to create durable plastic products.

Next, we will explore three other common molding techniques: compression molding, injection molding and blow molding, and we will highlight the key differences that make that rotomolding is an outstanding choice in our company, ABC Rotomoldeo:

Compressive Molding

Compressive molding or compression molding is a process in which plastic is placed in a mold and compressed using pressure and heat.
This method is widely used in the manufacturing of products such as melamine tableware and electrical components.

Although effective in producing strong parts, it may be less suitable for
large pieces and complex geometries.

Injection Molding

Injection molding or plastic injection is one of the most common molding processes. popular in the plastics industry. It involves injecting molten plastic into a mold to create a piece.

This method is versatile and suitable for producing high precision parts, such as used in the automotive and medical industries. However, it requires expensive tools and may not be as efficient for large pieces.

Blow Molding

Blow molding is primarily used to create hollow objects, such as bottles of
plastic and containers. In this process, the plastic is heated and inflated in a mold using compressed air.

Blow molding is efficient for mass production of objects with walls thin, but not ideal for solid or large pieces.

Advantages of rotomolding over other plastic molding techniques

Plastic rotomolding, compared to the other methods mentioned, offers a series of unique advantages among which stand out:

Greater Size Versatility:
Rotomolding allows manufacturing from pieces
small items such as toys, parts and components, … to large items size such as tanks, containers, canoes,..

Geometric Design:
This process allows for greater freedom in terms of shape and design of the parts, making it ideal for products personalized or specific.

Tool Cost:

Compared to injection molding,
Tools used in rotomolding are usually more affordable.

The resulting pieces are durable and resistant, making them ideal for applications that require long life.

Chemical resistance:
Rotomolded parts are resistant to products chemicals, making them suitable for a wide variety of applications.

In conclusion, rotomolding is a process of manufacturing plastic parts with different materials that offers a series of advantages over other types of molding for manufacture items for a wide range of sectors: (gardening, automobile, logistics, agriculture, toys, transportation, …)

Its advantages include: the possibility of manufacturing small or large pieces
with a wide range of designs and complexities, with great durability. The cost of molds
and their duration is longer than in other methods.
It’s a clean molding method hardly generates material waste.

If you are looking for quality solutions in the field of plastic rotomolding, do not hesitate
to contact ABC Rotomoldeo.

Our team of experts is ready to provide you with the best solutions in the market
Spanish to obtain high quality plastic parts and satisfy all your needs
of manufacturing.

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