All about rotomoulding

The possibilities of plastic rotational molding are virtually limitless. From robust fuel tanks for agricultural machinery and advanced slosh dampers for wind turbines to durable toilet cabins – the bigger the challenge, the better. It requires deep technical knowledge and a bold approach to create solutions that are ready for the future. At Pentas, we have the expertise and resources to tackle any challenge and deliver innovative, future-proof solutions.

The unique rotational moulding process of PentasWhat is rotational moulding?
Machniery at Penta's workshop

The unique rotational moulding process of Pentas

With nearly 50 years of experience and more than 700 different plastic products, our process runs like a well-oiled machine. We can manufacture items up to a diameter of 2,500 mm and a length of 4,000 mm. Do you want to challenge us?

Looking for more information about Pentas and rotomoulding? Use the table of contents to navigate to the topic.

Table of contents

    Why choose Pentas as a rotational moulding expert?

    Efficiency

    At Pentas, our team of 150 people is passionate about technology. There’s always someone who thinks things can be more efficient. We encourage that thinking and are not afraid to make fundamental changes, but only if it leads to more efficient operations, benefiting our customers.

    Quality

    Using FMEA, we prevent design errors, and our ERP systems track the product throughout the entire process. We continuously monitor quality during production. If there’s a deviation from the drawing, we solve it at the source. It’s no wonder we are ISO 9001 certified.

    Sustainability

    We are highly driven to produce as sustainably as possible, continuously monitoring the environmental performance of our processes. Almost all waste streams are reused. We continuously innovate to make our products stronger, lighter, and more sustainable.

    The well-oiled machine

    1. Phase 1: Drawing up the Programme of Requirements

      In order to define the development, it is important to draft a Programme of Requirements (PoR) that your product will have to meet.

    2. Phase 2: Conceptualisation

      The concept focuses on integrating functions and producibility as a plastic rotational moulding product. This phase results in the delivery of one or multiple concepts with a motivation and testing of the concepts against the PoR as well as a substantiation with design sketches.

    3. Phase 3: Analysis

      A risk analysis will be conducted in consultation with yourself. We will test whether the choice of material is suitable for your requirements.

    4. Phase 4: Engineering (Detailing of the design)

      Detailing of the plastic rotational moulding product is an important phase before we can proceed with mould construction and automation.

    5. Phase 5: Mould and automation

      Based on your final 2D and 3D CAD drawings of the plastic rotational moulding product, Pentas will start development and mould construction.

    6. Phase 6: Production

      Before Pentas takes your plastic rotational moulding product into mass production, the product and the process will have to be approved.

    7. Phase 7: Finishing and assembly

      This extension of the production of your plastic rotational moulding product requires associated steps to validate the process

    Working at Pentas

    Successful collaborations

    At Pentas, we take pride in our long-term collaborations with various customers. These sustainable relationships form the foundation of our success. Together with our clients, we strive for innovation and excellence, offering tailored solutions that meet their needs perfectly. These close partnerships allow us to grow and deliver innovative rotational moulding solutions that meet the highest standards.

    A sample of our clients

    Hymer logoClass logoSchmitz cargobull logoSiemens Gamesa logoDaimler logo

    What is rotational moulding?

    Rotational moulding (Rotomoulding) is a thermal forming process used to create hollow plastic components. The process involves filling a mould with fine plastic powder, heating it, and rotating the mould around two perpendicular axes. The powder melts and adheres evenly to the inside of the mould, resulting in a uniform wall thickness and minimal stress in the final product. After heating, the mould is cooled, and the finished component is easily removed from the mould without further processing.

    More information about rotational moulding

    Rotational moulding is a versatile and innovative technique used to manufacture hollow, seamless plastic products. It is renowned for its ability to produce complex and large shapes with consistent wall thickness and minimal stress.

    Moulds and rotational moulding

    We have years of experience in designing and producing high-quality moulds that form the foundation of our innovative rotational moulding processes. Every mould we create is carefully tailored to the specific requirements of our customers, resulting in products of exceptional quality. With our expertise in moulds and rotational moulding, we continuously set new standards in the industry.

    Markets

    At Pentas, we serve a wide range of markets with our expertise in rotational moulding. Our products find their way into various sectors, including construction, agriculture, automotive, and consumer products. Our flexibility and technical know-how enable us to provide customised solutions for every market we serve.

    Rotomoulded packaging material

    Markets

    Rotomoulded packaging material

    Rotational moulding is a versatile manufacturing technique that can also be applied in the production of packaging. This technique is particularly suited for creating hollow products, making it ideal for packaging materials such as plastic pallets, storage tanks, transport and storage containers, IBC containers (Intermediate Bulk Containers), and plastic barrels and drums. In this article, we will discuss the various applications and advantages of rotomoulded packaging materials.

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    More than a thousand products: The versatility of rotational moulding

    Markets

    More than a thousand products: The versatility of rotational moulding

    At Pentas, we take pride in the wide range of products we can manufacture using our rotational moulding process. Rotational moulding is an extremely versatile technique used in numerous markets and countries. Our products range in weight from 500 grams to 100 kilograms, and the applications are just as diverse. Whether it’s urinals for events, fuel tanks for agricultural machinery, buoys at sea, or water tanks in campers – our production currently exceeds a thousand unique products.

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    Rotational moulding in the offshore market

    Markets

    Rotational moulding in the offshore market

    The offshore industry operates in some of the most challenging and unpredictable environments in the world. Whether it’s drilling rigs, wind farms, oil platforms, or maritime installations, the materials and products used in this sector must be exceptionally durable, strong, and reliable. Pentas offers rotational moulding as a versatile and robust manufacturing technique that perfectly meets the demanding needs of the offshore market.

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    Rotationally moulded products at the festival grounds

    Markets

    Rotationally moulded products at the festival grounds

    When you take a break from dancing, you might be sitting on a rotationally moulded picnic bench from our factory in Almelo. Besides picnic tables, we make many more products that make your day at the festival grounds more enjoyable. In this blog, we tell you everything about the rotationally moulded products from our factory that you can spot at your next festival.

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    Rotational molding in the agricultural sector

    Markets

    Rotational molding in the agricultural sector

    Rotational Molding is an essential method across various sectors. In this blog post, we'll discuss rotational molding and its application in producing tanks, fenders, and air ducts for agricultural machinery. To produce these parts and meet the high demands of the agricultural sector, expertise is needed.

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    Quality

    Quality is at the heart of everything we do. We only deliver products that meet the highest standards. Every part we produce undergoes strict inspections to ensure it meets the specific requirements of our customers. We use advanced technologies and tightly controlled production processes to ensure consistency and precision.

    Innovation

    Innovation is the foundation of our success stories. We continuously strive to push the boundaries of what is possible in rotational moulding. By integrating the latest technologies and creative solutions, we remain at the forefront of the industry. Our teams work closely together to develop innovative designs that meet the specific needs of our customers. From concept to production, we are constantly exploring and implementing new materials and techniques to make products more efficient, sustainable, and functional.

    Innovation in knowledge retention: The role of augmented reality

    Innovation

    Innovation in knowledge retention: The role of augmented reality

    Within the manufacturing industry, we face a crucial challenge: retaining our expertise. In collaboration with Saxion University of Applied Sciences, the University of Twente, and other partners, we are making a significant step forward by integrating augmented reality (AR) into our processes. This initiative aims to capture and transfer essential knowledge within our organization.

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    Handyscan 3D Max: Precision in production, mold making, and quality control

    Innovation

    Handyscan 3D Max: Precision in production, mold making, and quality control

    At the beginning of this year, we at Pentas made a technological leap by integrating the Handyscan 3D Max into our operational processes, achieved with the expert support of EMS Benelux. This state-of-the-art 3D scanner, which excels with an accuracy of up to 0.15 mm, is crucial for delivering demanding products to customers.

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    Efficiency thanks to robots

    Innovation

    Efficiency thanks to robots

    The high quality of Pentas’ rotational moulding is realised by our staff and our robots.

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    Sustainability

    We are committed to sustainable production by continuously monitoring the environmental impact of our processes. Almost all of our waste streams are reused. In addition, we continue to innovate to make our products stronger, lighter, and more environmentally friendly.

    About Pentas

    At Pentas, everything revolves around dedication and craftsmanship in rotational moulding. As a leading specialist in the industry, we offer innovative and customized solutions for a wide range of applications. With decades of experience and deep technical expertise, we have built a reputation for delivering high-quality products that meet the strict requirements of our customers.

    Visit of Erwin Hoogland to Pentas for the INDUSTR_I4.0 program

    Pentas

    Visit of Erwin Hoogland to Pentas for the INDUSTR_I4.0 program

    On December 13, 2024, we welcomed deputy Erwin Hoogland from the province of Overijssel. Pentas is the first company in Overijssel to receive a grant under the INDUSTR_I4.0 program, marking a significant milestone. In this blog, you’ll discover more about the program and how Pentas is leveraging AI technology to transform production processes.

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    Knowledge exchange during the Rototour 2024

    Pentas

    Knowledge exchange during the Rototour 2024

    The past two weeks were entirely focused on knowledge exchange and strengthening the rotational moulding industry. During the Rototour 2024 in Brazil, rotational moulders from around the world gathered to share ideas and visit local moulders. In this article, we share our key insights and experiences from this intensive and inspiring journey full of valuable encounters.

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    Which rotational moulding machines do we have?

    Pentas

    Which rotational moulding machines do we have?

    At Pentas, we use various rotational moulding machines to meet the diverse needs of our customers. Our facility is equipped with 10 carousel machines and 1 advanced Rock and Roll machine, together providing a wide range of production capabilities.

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    TÜV certification for plastic fuel tanks

    Pentas

    TÜV certification for plastic fuel tanks

    Obtaining a TÜV certification for plastic fuel tanks is a process that assesses both the quality of the end product and the manufacturing process itself. TÜV is an internationally recognized certification body based in Berlin. They test and evaluate the safety and quality of products, systems, and services.

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    Our history at a glance

    Pentas

    Our history at a glance

    For half a century, Pentas has been at the forefront of innovation, manufacturing the most complex products through rotational molding for a wide range of customers. Our extensive experience has created a treasure trove of history, ranging from producing surfboards to realizing an award-winning plastic tank for CLAAS. We are eager to share more about all our highlights in 50 years of Pentas.

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    Pentas Welcomes status holders

    Pentas

    Pentas Welcomes status holders

    Thursday, February 8th - Today, we welcomed a group of 50 status holders and civic integration teachers at Pentas Moulding. In collaboration with the ROC of Twente, Aqua+, Novon, Kleurrijk & Niverplast, we organized for the third time a company tour along various enterprises in Twente.

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    Rotomoulding glossary

    • Biaxial rotation: The rotation of the mould on two perpendicular axes during heating and cooling, ensuring that the plastic material is evenly distributed along the inside of the mould.

    • Mould: A shape or form used in the rotational moulding process to determine the shape of the final product. Moulds can be made from various materials such as aluminium, steel, or composites and must withstand the high temperatures involved in the process.

    • Draft angle: A slight angle on the sides of a mould that allows the moulded part to be easily removed without damage.

    • Warping: A common issue in rotational moulding where large, flat surfaces deform during cooling. This can be reduced by design modifications such as adding ribs or using appropriate materials.

    • PIAT (Peak Internal Air Temperature): The maximum internal air temperature inside the mould during heating, which is crucial for proper melting and curing of the material.

    • Polyethylene (PE): A commonly used plastic material in rotational moulding due to its good processing properties, impact resistance, and low cost. Polyethylene is available in various densities, such as low, medium, and high-density polyethylene.

    • Polypropylene (PP): Another widely used material in rotational moulding, known for its high heat resistance and chemical resistance.

    • Shrinkage: The contraction of plastic material during cooling, which can lead to deformations if not properly managed.

    • Stress-free: Rotationally moulded parts are typically stress-free because they are formed without external pressure, resulting in a stronger and more durable final product.

    • UV stabilizer: An additive to the plastic material that provides protection against the harmful effects of ultraviolet light, extending the lifespan of outdoor products.

    • Ventilation: The process of creating openings in the mould to regulate pressure and prevent air bubbles or deformations during heating and cooling.

    • Wall thickness: The thickness of the walls of the moulded part, determined by the amount of material in the mould and the rotational moulding process. This affects the strength and durability of the final product.

    • Mould release agent: A release agent applied to the inside of the mould to prevent the plastic material from sticking. This allows for easy removal of the finished product without damage.

    • Kiss-off ribbing: Reinforcing ribs used in double-walled products. These ribs connect the inner and outer walls of the product, providing extra strength without adding significant weight.

    • Sintering: The process where plastic powder melts and adheres to the inside of the mould through the application of heat without pressure.

    • Cooling cycle: The phase in the rotational moulding process in which the mould is cooled after the plastic material has melted and adhered to the inside of the mould. This helps the product retain its shape.

    • Powder flow: The ability of plastic powder to move freely and distribute evenly within the mould during the rotational moulding process.

    • Inserts: Metal or plastic parts placed in the mould before the moulding process begins. These are embedded in the final product to add functionality, such as threads or attachment points.

    • Mould clamping: The mechanism that holds the mould halves tightly together during the moulding process to prevent plastic from escaping and to ensure an accurate shape.

    • Wall thickness distribution: The uniformity of the wall thickness of the finished product. Good distribution is essential for product quality and durability.

    • Parting line: The seam where the two halves of the mould meet. It must be properly sealed to prevent plastic from escaping during the moulding process.

    • Undercuts: Complex shapes in the product design that can be difficult to form and remove without the right techniques and mould designs.

    • Multiple cavity mould: A mould designed to produce multiple parts simultaneously, increasing production efficiency.

    • Crosslinkable polyethylene (XLPE): A type of polyethylene that crosslinks during the rotational moulding process, resulting in improved mechanical properties and chemical resistance.

    Frequently asked questions about rotational moulding

    What is rotational moulding and how does it work?

    Rotational moulding is a manufacturing process used to create hollow plastic parts. In this process, a mould, also known as a die, is filled with plastic powder. The mould is then heated while being rotated on two axes. This ensures that the material melts and evenly coats the inside of the mould, resulting in a strong, seamless part. After that, the mould is moved to a cooling station, where it continues to rotate while being cooled, allowing the plastic inside to harden. The final step occurs at the demoulding station, where the mould is opened and the hollow product is removed. From here, the process begins again.

    What materials can be used in rotational moulding?

    Polyethylene (PE) is the most commonly used material in rotational moulding due to its versatility, cost-effectiveness, and excellent processability. PE has a wide melting range, making it ideal for rotational moulding as it allows for even melting and good flow during the moulding process. Additionally, PE offers excellent properties such as chemical resistance, durability, and flexibility, making it suitable for a wide range of products.

    In addition to PE, other materials can be used, such as polypropylene (PP), nylon (PA), polycarbonate (PC), and PVC. Within these plastic groups, there are different variants, each with unique properties such as color, impact resistance, and aging resistance.

    What are the main advantages of rotational moulding?

    Rotational moulding offers several advantages, including low investment costs for moulds and tools, leading to low production costs for small to medium runs, up to tens of thousands per year. It allows for the creation of complex and large shapes, ensures uniform wall thickness, and results in minimal material waste. Additionally, hollow and fully enclosed parts can be easily produced.

    How does wall thickness affect the strength and cost of the product?

    The wall thickness of a rotationally moulded part is crucial for both its strength and cost. Thicker walls increase the strength and durability of the product but also raise material costs. It is important to determine the optimal wall thickness to meet functional requirements without incurring unnecessary expenses. A smart product design, based on how the product will be used, can help optimize this. By incorporating ribs or kiss-offs, the forces exerted on the product can be better distributed, reducing the need for excess wall thickness or material.

    What problems can occur in rotational moulding and how can they be solved?

    Problems such as warping, poor impact resistance, and uneven wall thickness can occur during the rotational moulding process. These issues can often be resolved by adjusting the process, such as optimizing heating and cooling times, or by selecting more suitable materials and additives.

    What are the design considerations for rotationally moulded parts?

    When designing rotationally moulded products, it is important to avoid sharp corners, ensure uniform wall thickness, and place inserts and ribs strategically for added strength. This helps reduce stress and improves the durability and reliability of the final product.

    How important is material selection in rotational moulding?

    Material selection is critical because it determines the processing parameters, mechanical properties, and chemical resistance of the final product. It is essential to choose a material that is suitable for the specific application and environmental conditions.

    What are common applications of rotational moulding?

    Rotational moulding is used in a wide range of applications, including water tanks, air ducts, containers/packaging, and industrial housings. The process is particularly suitable for producing large, complex, and hollow parts.

    What are the requirements for mould design in rotational moulding?

    Moulds for rotational moulding must withstand high temperatures and have a non-porous surface to ensure a smooth final product. They should also be designed for easy opening to remove the moulded part without damage. Over time, design changes may be necessary, and if the mould is of high quality, these changes can be incorporated into the existing mould, saving costs by avoiding the need for a new mould.