Today’s world would not be the same without plastics and the world of plastics would not be the same without rotational molding (rotomolding). We rely on plastic molding manufacturers to produce items from plastic lockers to industrial laundry carts. This is an incredibly versatile process that has a long history.
A Long Time Ago in a Country Far Away
Some historical evidence that indicates the Egyptians used rotational casting type processes for their ceramics. Years later, the Swiss would take up similar methods to create chocolate eggs that were hollow. They may not be industrial laundry carts but the idea is that the process for rotomolding started a long time ago.
The first documented use of bixial rotation molding using heat comes from 1855 in England. This process was used by the British military to make hollow military weapons such as metal artillery shells. Rotational molding saw other advances but it really took the advent of plastics to get the real ball rolling.
The Advent of the Plastic Molding Process
In the early 1950s, toy manufacturers began making some of their products using the rotomolding process. One of the first products that was made was doll heads. In this process, the company took an E Blue box oven machine. They say that the machine used to make the doll heads was inspired by the rear axle of a car. The mould itself was made from an electroformed nickel-copper mould. The plastic that was used was a polyvinyl chloride (PVC) in liquid form. An external electric motor was used to power the apparatus and the heat was supplied by gas burners that were mounted on the floor.
Once the moulding process was complete, the entire thing was cooled by placing it in cold water. The manufacture of industrial laundry carts was still very far off but the dolls’ heads led to the use of this process for other toys.
As companies that manufacture other products learned about the new process, it gained in popularity. The whole thing snowballed and companies began to play around with changing the process. New heating elements were created. Soon the process was used to manufacture marine buoys, car armrests and road cones. Now the heat came indirectly from hot air.
The Engle process was created in Europe in the 1960s. This development included the use of large, hollow containers. Cooling of these containers was achieved by just letting the containers cool naturally.
The Process Gets Official
In 1976, the Association of Rotational Moulders (ARM) was founded in Chicago. This is a global trade association. Today, it represents businesses in at least 58 countries. Their mission is to promote the process of rotational moulding. It is very active in the creation of new rotomolding techniques and technologies. ARM is also active in marketing the process around the planet.
The Popularity Kept Growing
Many plastic molding manufacturers began to streamline the process in the 1980s. To meet the new demand, more and more materials were developed to be used with this plastics process. These new materials included polypropylene, polycarbonates, polyesters, nylons and ABS acrylonitrile butadiene styrene (ABS), low density polyethylene (LDPE) and high density polyethylene (HDPE). Manufacturers of sea kayaks and whitewater kayaks began to be made almost exclusively using rotomolding techniques in 1984.
Queen’s University in Belfast conducted extensive research into this process that led to a greater understanding of the process that allowed for ways to monitor the temperature inside the mould throughout the process.
Today, the process for rotomolding is used to make a plethora of products that range from very tiny to large. Most of the pieces on industrial laundry carts are made this way. You would be hard pressed to find a home that did not have a ton of products made this way.
The process itself has changed a lot. The plastics used today are most often in powder form. They are added to a mould and that is placed in an oven that has been heated to between 500 and 70 degrees Fahrenheit. The mould is rotated on a bi-axle at speeds that do not go over 20 rotations each minute. The cooling process is done via air or water or both.
Rotomolding is an incredibly versatile and crucial process for the manufacture of a wide variety of products we love.