Rotational moulding - What is it?
The rotational moulding process begins with the insertion of polymeric raw materials (usually in powder form) into a mold. This mold is then heated in an oven that rotates simultaneously on two axes in a rotational motion. During heating, the polymer heats up and melts against the internal walls of the mould, forming a uniform layer. After the heating and melting period, the mold is cooled in a controlled manner, allowing the part to solidify and acquire the desired final shape.
At Rotovedras – Plastic Technology, rotational moulding is carried out with a focus on quality and precision, to ensure that the parts meet the specific requirements of each project. We continually invest in innovation and equipment, ensuring solutions that combine durability, efficiency and respect for the environment.
The advantages of
Rotational moulding
Mechanical
Resistance
Versatile
design
Low-cost
Moulds
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Rotational moulding and
Sustainability
The rotational moulding process is an option with reduced environmental impact.
There are a number of advantages that make it less harmful to the environment when compared to other manufacturing methods and that allow us to speak of rotational moulding as a sustainable process.
Products with a long life cycle
Let's start with the durability that the process and materials used give to products. Increasing the life cycle of a product means saving resources for the planet, both in terms of raw materials and energy.
Reuse and production with recycled raw materials
Rotational moulding products can be made from recycled materials and are also 100% recyclable at the end of their useful life. This ability to recycle end-of-life products through rotation moulding reduces their environmental footprint and contributes to their circularity.
Efficient use of material, less waste
With the efficient use of materials, there is less waste and residue than in more resource-intensive processes, such as metal manufacturing. Rotational moulding production therefore becomes a more sustainable process, especially when combined with the use of recycled materials.
Low emission of toxic and harmful gases
The rotational moulding process does not generate significant emissions of harmful chemicals or dangerous toxins. Since it does not involve high pressure or processes such as gas injection, it minimizes the release of volatile compounds into the atmosphere.
Frequently asked questions
about Rotational moulding
ROTATIONAL MOULDING, WHAT IS IT?
Rotational moulding (or rotomoulding) is a plastics transformation process that involves heating a polymer inside a hollow mould that is constantly rotating. This rotation spreads the material evenly, forming hollow, even-walled parts without the need for high pressure. It is especially used for medium to large parts, making it possible to create robust products with complex geometries.
WHAT ARE THE ADVANTAGES OF ROTATIONAL MOULDING?
– Design flexibility: Allows you to create different shapes and hollow parts in one go.
– Uniform walls: Constant rotation distributes the material evenly.
– Relatively low mould costs: Compared to processes such as injection moulding, the initial investment in moulds is usually lower.
– Production of large parts: Rotational moulding is ideal for larger parts.
– Less material waste: The process generally generates little scrap and allows for the recycling of leftovers.
WHAT ARE THE DIFFERENCES BETWEEN ROTATIONAL MOULDING AND INJECTION MOULDING?
Principle of Operation
In Rotational moulding, the mould is heated and rotated in different axes, causing the material to melt and adhere to the inside walls of the mould. In injection moulding, the plastic is melted and injected under high pressure into a closed mould.
Pressure
Rotational moulding does not involve high pressures; injection relies on high pressure to fill the mould.
Mould cost
In rotational moulding, the mold tends to be simpler and less expensive. In injection moulding, the mould is generally more complex and significantly more expensive.
Part format
Rotational moulding is excellent for large hollow parts, while injection moulding is used more for solid, high-precision parts.
WHAT ARE THE PROCESS STEPS LEADING UP TO MASS PRODUCTION?
1. Product development: Definition of requirements, initial prototypes and design validation.
2. Mould design: Creation and analysis of the mould in engineering software (CAD/CAE).
3. Mould making: Construction of the mould in aluminum, steel or other suitable material.
4. Initial tests and adjustments: First rotational moulding cycle to assess product quality and possible mould corrections.
5. Final validation: Adjustment of the production process (temperature, time, rotation speed) to ensure consistent quality.
6. Series production: After final approval, larger-scale manufacturing begins.
About Rotational moulding products
WHAT ARE ROTATIONAL MOULDING PARTS?
These are products made using the rotational moulding process, in which molten plastic is distributed by rotation inside a mould. The result is hollow, resistant parts with a uniform thickness. They are ideal for applications that require durability and freedom of design.
WHAT ARE THE BENEFITS OF ROTATIONAL MOULDING PRODUCTS?
They are highly resistant, durable and can be made into complex shapes without welding. They are lightweight, customizable in color and finish, and adapt to different sectors. The process also allows for low production volumes with more economical moulds.
ARE ROTATIONAL MOULDING PRODUCTS IDEAL FOR OUTDOORS AND INDOORS?
Yes. They are resistant to climatic variations, UV rays, humidity and chemical agents, making them ideal for outdoor use. They are also safe, lightweight and versatile for interior applications such as furniture, equipment and technical components.
CAN I HAVE ROTATIONAL MOULDING PRODUCTS MADE IN ANY COLOR?
Yes. The color can be customized by adding pigments to the plastic material before the rotational moulding process. This allows virtually any combination of colors and shades, according to the needs of the project.
WHAT FINISHING OPTIONS ARE AVAILABLE FOR ROTATIONAL MOULDING PARTS?
– Internal mould texturing: Allows for different patterns on the external surface of the part.
– Post-painting: Can be used to add additional colors or special effects.
– Embossed or bas-relief logos: Made directly on the mould.
– Reinforcements and coatings: Can be applied to improve durability and appearance.
WHAT ARE THE SIZE LIMITATIONS OF ROTATIONAL MOULDING PARTS?
The limitations are directly related to the size of the equipment(oven and rotation station) and the mould’s handling capacity. In general, rotational moulding is known for producing large parts, but it is essential to check the maximum capacity of each production line or machine to ensure the viability of the project.
DOES ROTOVEDRAS WORK EXCLUSIVELY WITH ROTATIONAL MOULDING OR ALSO WITH OTHER PROCESSES?
Rotovedras is part of the Iberpolymers Group, which offers services in rotational moulding, injection moulding and precision metalworking. This is an added value for Rotovedras, which masters three essential manufacturing processes for precision products.
DOES ROTOVEDRAS MAKE PROTOTYPES BEFORE FINAL PRODUCTION?
Yes. Rotovedras develops prototypes in materials such as fiberglass, wood or ABS before the mould is made. These prototypes are used to study the design, validate functionalities and analyze the product’s technical characteristics. However, they are not suitable for resistance tests, as they do not use the same raw material or the same process as rotational moulding. They are an essential tool for reducing errors and optimizing the development of the final mould.
WHAT SERVICES DOES ROTOVEDRAS PROVIDE FOR ROTATIONAL MOULDING PROJECTS?
At Rotovedras, we offer complete services for all stages of rotational moulding product development. We work from reverse engineering, conception and design, development and manufacture of moulds, to the manufacture of rotational moulding parts. We also provide prototyping services, validation testsand technical support, guaranteeing quality and speed at every stage.
DOES ROTOVEDRAS OFFER TRANSPORTATION SERVICES FOR MANUFACTURED PARTS?
Rotovedras does not currently have its own fleet. However, the transportation service can be contracted by Rotovedras, by agreement between the client and Rotovedras. Every day we have more than 10 trucks loading products all over Europe, which can be contracted by Rotovedras or by the client themselves.
WHICH MARKETS OR SECTORS DOES ROTOVEDRAS OPERATE IN?
Rotovedras operates in a wide range of sectors, from agriculture to waste management, the automotive and aeronautical sectors, street furniture, among others. We have clients all over the world, being leaders in Portugal and expanding in Spain, France and Germany.
DOES ROTOVEDRAS SUPPORT THE DESIGN AND ENGINEERING OF THE ROTATIONAL MOULDING PRODUCT?
Yes, we have a strong and cohesive design and product engineering team. This is the only way to achieve quality products, with the extreme attention to detail that makes premium products.
WHAT IS THE MOST COMMON MATERIAL?
The most common material is polyethylene (PE), due to its ease of melting, linear low density (LLDPE) and mechanical strength and processability. However, other polymers can be used, as long as they are formulated to withstand the thermal cycles of the process.
WHAT KIND OF PLASTICS ARE USED IN ROTATIONAL MOULDING?
Although polyethylene (PE) is the most commonly used, polymers such as polypropylene, polyamides and some special resins can also be used in the process, depending on the product’s requirements. The material must be powdered and compatible with thermal cycles.
WHAT IS ROTATIONAL MOULDED POLYETHYLENE?
This is the polyethylene (PE) used in the rotational moulding process, usually in powder form. After being melted in the mould, it produces parts with good resistance to impact, corrosion and UV rays. It is one of the most widely used materials due to its excellent balance between cost and performance.
WHAT ARE POLYMERS?
Polymers are materials made up of long molecular chains formed by repetitive units called monomers. They are the basis of plastics and can have a variety of properties, such as flexibility, rigidity or strength. In rotational moulding, thermoplastic polymers are used which melt and solidify with heat.
WHAT IS THE ROLE OF THE MOULD IN THE ROTATIONAL MOULDING PROCESS?
The mould defines the final shape of the part. During heating, the plastic powder melts and adheres to the inner walls of the rotating mould, forming the desired part. It must be heat-resistant, guarantee good heat transfer and have an adequate finish to reproduce details and textures accurately.
IS THERE A MINIMUM NUMBER OF PARTS FOR SERIES PRODUCTION?
It depends on the project, the dimensions of the parts, the weight of each part and the type of mould.
HOW IS QUALITY CONTROL CARRIED OUT DURING PRODUCTION?
Every time a part is produced, the conditions agreed with the customer in terms of product requirements are checked.
WHAT ARE THE MAIN PARAMETERS FOR A ROTATIONAL MOULDING MACHINE?
Heating temperature, cycle time, shaft rotation speed, cooling system and load capacity are essential. These parameters determine the quality of the polymer melt, the uniform thickness of the part and production efficiency. Precise control guarantees consistency between parts.
WHAT DOES A ROTATIONAL MOULDING ASSISTANT DO?
A rotational moulding assistant helps with the preparation and cleaning of moulds, supplying material, removing moulded parts and minor finishing. They also help organize the space and control the production process. This is an essential role for ensuring efficiency and quality. They work closely with operators and production technicians.
WHAT TYPES OF MOULDS DOES ROTOVEDRAS DEVELOP?
We develop moulds in aluminum and/or sheet steel.
WHAT DOES THE PRODUCTION OF A ROTATIONAL MOULD CONSIST OF?
The production of a rotational mould involves:
1. Concept and design: Definition of the product format and desired characteristics.
2. CAD development: Creation of the digital model of the mould.
3. Making the mould: This can be made from aluminum, steel or similar materials, usually by methods such as casting, CNC machining or even sheet metal welding.
4. Finishing: Application of surface treatments (polishing, textures, reinforcements) to guarantee the final quality of the piece.
5. Tests and adjustments: The mould is tested, and final adjustments can be made to improve the precision or quality of the product.
WHAT IS THE AVERAGE TIME TAKEN TO MAKE A MOULD?
It depends on the type of mould. The deadlines will always be presented in the commercial proposal, assessed on a case-by-case basis. However, we will always have a range between 30 and 90 days, depending on the complexity of the mould.
IS IT POSSIBLE TO INCLUDE LOGOS OR OTHER ELEMENTS IN THE MARKING DIRECTLY ON THE MOULD?
Yes. There is a technique known as “in-mould stickering” (or in-mould labeling/decoration), in which the decal or logo is applied directly to the inside surface of the mould before rotational moulding begins. During the process of heating and melting the polymer, the sticker adheres permanently to the part, becoming an integral part of the product.
WHAT IS THE APPROXIMATE COST OF DEVELOPING A ROTATIONAL MOULDING MOULD?
The cost varies mainly according to the size of the mould, the complexity of the design and the type of material used. To get an exact figure, it is necessary to submit the project and product specifications for technical evaluation.
DOES THE MOLD BELONG TO ROTOVEDRAS OR TO MY COMPANY?
The mould, in the case of bespoke projects, is the property of your company. However, it depends on the contractual conditions of the project and what has been agreed with Rotovedras.
a new product.