Built to Last
Our Process
How We Innovate and Improve Industries
For over 40 years, Saeplast has been a world leader in the manufacturing of rotational molded polyethylene containers for use in the food industry.
When you hear Saeplast, you think of superior quality, innovation, food safety and employee safety.
The rotational molding process lends to some unique features that benefit Saeplast customers, most of whom handle the fluid we eat. So how does Saeplast manufacture containers?
Step 1:
It all starts with a bead.
The process starts with receiving 100% virgin food grade polyethylene in a railcar or in a truck.
Step 2:
The bead
gets pulverized into powder
The resin is ground into powder and food approved colored pigment is added.
Step 3:
The powder is poured into a mould and melted together.
The colored resin is then loaded into steel molds.
The material is fed into the mould in the exact weight of the product. Any parts to be moulded into the product, such as metal inserts, are now placed in the mould.
Step 4:
The mould is heated, and the pellets inside are melted together.
The mould is heated, which melts and compacts the material inside. During this step the mould is rotated around two axes. This step in rotomoulding process creates a solid, uniform layer.
Step 5:
The hot, flexible plastic inside the mould is cooled.
During cooling the heated part is cooled down below melting temperature. The material solidifies inside the mould. This process defines mechanical properties of the product.
Step 6:
The mould is removed from a nearly finished bin.
Demoulding is removing the finished part from the mould. Any undercuts or threaded parts in the mold are removed first. Now the mould is opened and the part can be released.
Step 7:
Excess plastic or imperfections are sanded and smoothed.
After molding, the container goes for additional processing like primary finishing. Then onto quality inspection and remediating minor imperfections.
Other Steps
designing, materials, machines and moulds
Designing Containers
The rotational moulding process offers extensive design flexibility. At Sæplast, we develop proprietary products that are engineered for durability, safety, and sustainability. When designing moulds for new products, we carefully consider the unique strengths of rotational moulding. This includes evaluating material performance, product geometry, hygiene requirements, and manufacturing efficiency. By combining proven expertise with rigorous design standards, we ensure every Sæplast product delivers long-term value and reliability to our customers.
Materials Used
A variety of materials are used in the rotational moulding process, primarily polyethylene. Polyethylene is characterised by its flexibility, resistance to mechanical damage and low weight. Two types are most poular - low-density linear polyethylene (LLDPE) and high-density polyethylene (HDPE), due to its strength, chemical resistance and flexibility, ideal for rotational moulding.
Machines & Tools
Saeplast utilizes Carousel-type rotational molding machines where a carousel-like mechanism rotates multiple moulds at once. Several moulds are mounted on three or four arms that are connected to a central hub, which moves the arms through different stages of the manufacturing process.
The carousel machines design also enables multiple moulds to be processed on the same arm, making it efficient for high volume production.
Types of Moulds
The moulds Saeplast uses are made of high-quality materials such as steel or aluminium, which ensures exceptional durability, long life, and resistance to mechanical damage. Rotomoulding moulds are also highly thermally resistant, as they are heated in ovens to very high temperatures. The choice of material for a rotomoulding mould depends on the type of component to be produced, the life expectancy of the mould, the production budget, and the requirements for quality and repeatability of production.