"Rotational moulding is a highly versatile method for making precise, stress and seam free plastic components at comparatively low cost"

​

Roto Casting usually refers to cold liquid casting - while Roto Moulding refers to hot melt moulding. Although these two terminologies usually are used throughout the industry. 

​

Rotocasting, also known as rotomolding / Moulding or centrifugal casting, is a method for forming thermoplastic resins and even food ingredients where the molten material solidifies in and conforms to the shape of the inner surface of a heated, rapidly rotating container.

​

A rotocast part uses less material to make a larger part, allows for a reduction in weight and amount of material required to make the part

Think easter eggs and plastic hollow footballs as easy examples of hollow casting. 

​

Many different materials can be used in this process, dependent on their curing times, such as the following:

​

• Clay Slip Casting - Casting slip: earthenware, stoneware or porcelain

• RTV Silicone

• Resin and Epoxy Resins

• Thermo setting Plastics

• Sculpting Wax - Candle Wax - Soy Wax

• Foods such as Chocolate and Sugars 

​

It’s a unique plastic molding /moulding process used primarily to create seamless, stress-free, hollow one-piece items. It’s a high-temperature, room pressure manufacturing method that combines heat and bi-axial rotation. Typical molded parts from industrial rotocasting can include containers, tanks, children’s toys, medical and industrial equipment, and automobile parts.

​

In industrial rotocasting, the metal being cast is thrown toward the walls of the mold / mould and forms the casting after hardening. The centrifugal method is widely used in industries for the production of hollow castings with free surfaces, such as cast-iron and steel pipe, rings, sleeves and cowlings.

​

Proponents of the rotational molding /moulding process point to its low production cost and unlimited design possibilities. It’s a competitive alternative to blow molding / moulding, thermoforming, and plastic injection molding , moulding. It produces little waste since the required weight of plastic to produce the part is placed inside the mold / mould.

​

In industrial rotocasting, the process begins with filling a hollow mold / mould with a quantity of powder resin (polymer). More often than not this powdered resin is polyethylene, although other compounds such as polypropylene, PVC, and nylons can also be used. The mold / mould is then heated at high temperatures in an oven and bi-axially rotated as the polymer melts and coats the inside of the mold / mould.

​

In order to maintain even thickness throughout the part, the mold  / mould continues to rotate at all times during the heating phase and also during the cooling phase to avoid sagging or deformation.

Although it may seem like a very machine-intensive process, makers and tinkerers alike are able to perform the same process at home with what we call it the home rotocasting — equivalent to both resin casting and industrial rotocasting. When built at home, rotocasting is when you use a resin cast part, and place it in a home rotocasting tool, spinning it around while gravity makes the mold / mould conform to the walls of the piece, making a hollowed out part..

​

Home rotocasting is particularly useful for cosplayers and fandoms. Check out this video on a home rotocasted iron man leg.

​

https://www.youtube.com/watch?v=bAU3NGI-ZDo&feature=youtu.be

​

​

​

​