Rotomoulding offers relatively low tooling costs, economical short runs and ability to cope with large moulds. It is ideally suited to new product development and prototype work can be carried out without vast expense.
WHY CHOOSE ROTATIONAL MOULDING?
An ever-increasing awareness of the rotational moulding process has led designers to choose this process for some quite complex parts. Relative to blow moulding, rotational moulding permits much more complex, asymmetrical shapes. Wall thickness distribution is more uniform with rotomoulding and part size can go well beyond anything which is possible with blow moulding. Relative to injection moulding, rotational moulding has major advantages of low mould cost and the ability to produce complex hollow articles.
ADVANTAGES OF ROTATIONAL MOULDING
- Tooling costs are relatively low when compared to other processes.
- Moulds which differ greatly in shape and size can be can be run simultaneously on the same equipment.
- Wall thickness uniformity is good when compared to blow moulding or thermoforming.
- Finished parts can be virtually stress free if designed carefully.
- The process is extremely versatile. Parts can be manufactured with inserts moulded in and surface textures and effects reproduced with relative ease.
- Using automated oil heated Leonardo machines, Rototek can deliver large production runs economically having virtually eliminated the labour content.
Rototek can work with you at concept stage to prove design ideas, input data on new materials and develop new processes. Consultancy is available to ensure efficiency at all stages and prototypes can be fabricated or moulded.
Using the latest software, Rototek’s design department will work with you and the toolmaker to ensure a design that will fulfill all performance criteria whilst remaining economic to manufacture. We can design products for you, or work with your design department or existing designs to ensure a successful end result. Rototek currently run the very latest version of Solidworks – a 3D CAD package.
We offer a full product development service including:
- Initial research and concept generation
- Technical product development
- Development of 3D CAD models and drawings
- Project management of tooling
We are happy to discuss your project in confidence or enter into a non-disclosure agreement beforehand.
Once the designs have been finalised, Rototek can supervise the toolmaking process ensuring the final moulds meet the specification required. Depending on the nature of the final part, Rototek can supply cast aluminium moulds, CNC aluminium moulds or fabricated moulds in sheet steel.
There are three main tooling routes available during the development of a new rotationally moulded product. All three have their own advantages and it’s important that the type of tooling required is considered early on in the project. We’ve developed good relationships with a number of toolmakers and will manage the whole tooling process for you.
Sheet Steel Tooling
Sheet steel tooling is typically suited to products of relatively simple form and limited intricate detail. The cost is lower than other tooling options. Sheet steel tools are usually formed using either traditional metalworking techniques or laser cutting and CNC forming equipment, before being fabricated. The ability to apply surface textures is limited but options are available. High polished finishes can be achieved. Examples of products that are often produced using sheet steel tools are tanks, water butts and planters.
Cast Aluminium Tooling
Cast tools require a pattern to be produced in the shape of the finished product before impressions are created to replicate the required tooling detail. The impressions are then used as patterns in the casting process. The cast tooling process involves a number of stages and this provides the opportunity to view patterns before committing to finished tools. When patterns are developed a shrinkage rate is introduced to ensure that the finished product is moulded to the correct size. The ability to produce multiple tools from a single pattern is an advantage for products where high production volumes are predicted.
There is large range of surface finishes available for cast tooling. Tooling costs are higher than sheet steel but the ability to produce complex forms with attractive surfaces makes cast tooling a good option for products that are seen and interacted with. Examples of products produced from cast tools range from furniture to street recycling units.
CNC Machined Tooling
CNC machined tools are machined from blocks of aluminium. They can be created using CAD data and do not require patterns to be produced. They are ideally suited to products where high accuracy is paramount. This might be because the product is part of an assembly and has to fit components manufactured using other processes. The surface finish and joint lines are superior to those achievable using other tooling methods. CNC machined tools are the most expensive, however, but the complexity of form and detail that can be achieved is high. The ability to produce tools very quickly is also appealing when product development timescales are tight. Examples of products suited to CNC tooling are small intricate parts which are too small for cast aluminium or highly complex and demanding tooling.
Please feel free to call and discuss new work with us and we will be happy to advise the in the design and manufacture of your rotational mouldings.
We have experience of sourcing a wide range of components from fixings and fasteners to fabricated metalwork for product assembly.
With an extensive network of existing suppliers, and the ability to gain the most competitive prices, we can offer a one-stop shop. We can source all of your componentry and assemble your rotationally moulded product in-house ready for despatch to your depot or directly to your customer.
You may require a non-standard component or a specific design which needs to be manufactured to your specification. We can take your rough sketches or engineering drawings and convert them into a tangible product outcome. You might not even be sure what you require to use in conjunction with your moulded product, in any case, we can help. Give us a call and we can develop a solution for you.
A combination of Rototek’s skilled operators and state of the art machinery ensures high quality production. All mouldings are produced using machinery built in house and using control software developed specifically for the purpose. The rotomoulding process allows products to be manufactured in a range of colours and with permanent inserts moulded in. These are just a few of the many advantages.
Trimming and post mould assembly of mouldings is an important part of the manufacturing process and requires skill, attention to detail and knowledge of the requirements of the finished product. Our trimmers and assembly staff have the experience and skill to undertake assembly of complex components.
We offer an assembly service whereby brackets, sensors and other ancillary components can be assembled to your moulding so that when it’s delivered to you, it’s how you want it.
THE ROTOMOULDING PROCESS
The process of rotomoulding is essentially very simple and can be broken down into four key stages.
The metal mould is filled with a predetermined quantity of polymer powder, closed, clamped and then passed into an oven chamber.
The mould is heated externally to a high temperature and rotated around both vertical and horizontal axis. As the powder inside heats up, it begins to melt and adhere to the inner surface of the mould. This continues until an even layer of molten plastic is formed over the surface of the mould.
In the cooling chamber air is directed at the mould and in some cases water jets are used. When the plastic inside the mould has become solid, the mould can be removed from the chamber.
The plastic component is then removed from the mould and allowed to finish the cooling process unrestricted by the mould.
Cycle time can vary from 20 minutes to one hour. The plastic is formed without pressure and as a result has no moulded in stresses.
Below are some documents you may find useful. The downloads are in PDF format. You will need Adobe Acrobat Reader 5 or a higher version to open PDF files. If you don’t already have Acrobat Reader you can download it free from Adobe’s web site.
The main material we use (LLDPE) is completely recyclable. Any scrap and offcuts from the process get recycled and returned back to us as powder to be used on appropriate applications.