How Sæplast Containers Are Made

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

Design, Materials and Production Equipment

Designing Containers

Container design starts with the intended application. Relevant considerations include capacity, handling, cleaning access, product protection and the demands of repeated use.
Rotational moulding allows features to be incorporated into the container body. Their configuration varies by model, so handling arrangements and operating limits should always be checked in the relevant product documentation.

Materials and Container Construction

Polyethylene, or PE, forms the moulded body of Sæplast containers.
Sæplast’s triple-wall PE containers combine polyethylene surfaces with a polyethylene foam core. PUR containers combine polyethylene walls with a polyurethane insulation core. These constructions differ and should be assessed against the requirements of the application.
Material specifications, food-contact suitability and end-of-life options should be checked for the selected product. Recyclability claims for PE construction should not automatically be applied to PUR containers or every fitted component.

Machines & Tools

Rotational moulding equipment moves moulds through heating and cooling stages. Process settings are selected for the material, mould and product design.

Types of Moulds

A mould defines the container’s shape and incorporated features. Its design must accommodate heating, cooling and removal of the moulded part. Mould material and construction depend on the product and production requirements.