Rotational molding is a fabrication process that is used to make hollow plastic parts. The process is used to manufacture various types of items such as: recreational objects, kayaks, traffic cones, playground slides, special applications, toys, transportation equipment, and pots for planting etc. Rotational molding can also be used for many types of items that are used in the commercial, industry, agriculture, and medical sectors. These include things such as point of sale displays, special storage containers and tanks to store chemicals, water storage, fuel tanks, highway barriers, instrument housings, food service containers, drainage systems, livestock feeders, and vending machines, etc.
The rotational molding process is done in four stages:
- Lightweight aluminum or fabricated molds are charged with the plastic material.
- The mold is then placed in a heating chamber and heated while it is being rotated in two axis. As the plastic melts, it begins to move sideways and sticks against the mold walls. With prolonged rotation at a steady temperature, the material uniformly coats the mold wall.
- The mold is then moved to a cooling area where it is cooled down by using blowers.
- After it is fully cooled, the mold is dismantled and the component is retrieved from it.
The molding process takes about 45-minutes to one hour to complete and many molds are used during it. Additives can easily be placed into the molds during the process as well. These additives are often used in plastic products for a variety of purposes such as making it flame resistant, making it biodegradable, making it microbe resistant, and to prevent the plastic from oxidizing and degrading. If required: metal inserts, wheels, spring mechanisms can be inserted in the molds. The parts have better, more consistent wall thickness than other methods to produce comparable products and because the internal pressure is lower the mold can cost less to make.
Different types of plastic can be used in rotational molding and you are able to create large, seamless items that have a uniform wall thickness. You don’t have to do any welding with this method and that is an advantage as welds often make the product weaker and add to the production costs.