Finding unique solutions for very specific engineered parts can be a challenge. While clients can sometimes dream up an idea or a new concept, finding a fast and affordable way to consistently create the envisioned product is not always easy. Imagine the varied shapes of plastic objects, both large and small, that we see and use in our every day life:
- heavy plastic recycling bins
- car seat bases
- customized seating for boats, stadiums, and other venues
- custom built bulk containers
- plastic lockers
- lightweight but sturdy home decorating pieces
Four basic steps make up the rotational molding process, the more technical term for what those in the industry call making custom rotomolded parts:
- Step 1 Loading the mold and inserting the selected resin. Using a specific machine called the spider, making custom rotomolded parts begins with loading the mold.
- Step 2 Heating the mold. By spinning the mold in a variety of directions, the resin evenly adheres to all sides and surfaces of the mold. During this process, the rotation speed is often quite slow. In fact, sometimes it can be less than 20 rotations a minute. Because this slow process is not centrifugal, irregular shapes are easily formed. The main science behind this plastics production process is the critical timing involved. During this process, ovens are often preheated by convection, conduction, or radiation to achieve temperature ranges from 500degrees to 700 degrees Fahrenheit, depending on the type of resin or polymer used.
- Step 3 Cooling the mold. Throughout the cooling process the resin hardens and retains even walls as it forms into its final plastic shape. Again, timing is everything in this step. The resin must be cooled in a manner that corresponds to the slowing rotation of the spider.
- Step 4 Removing the created part. Once the cooling process is complete, the mold is removed and the uniquely created part is visible. Unique to this kind of production, engineers can easily test and adjust wall width to accommodate the durability needs of the end product.
Although creating custom rotomolded parts is not the only way to engineer with plastic. This specific technique has advantages over both blow molding and injection molding, which both have certain kinds of limitation. Some of the reasons for using custom rotomolded parts include the following:
- can be applied to the engineering of almost any idea
- end products are free of stress points with a variety of wall widths
- molds are quickly produced and easily modified
- additional components can be added to the mold design
- wall thickness can vary according to customer specifications
- both single and double wall constructions are available
- very durable products
- hollow plastic parts are inexpensive to produce
- endless colors are available and it is easy to adhere or imprint graphics
The heavy weight bearing products produced with custom rotomolded parts create custom plastics in a variety of applications. The end products can vary from the most minute sizes to lengths that are up to 160 inches. And while the rotomolding method is not new, this technology first developed in the 1960s and 1970s continues to be used in ever increasing ways. the fact that the Association of Rotational Moulders (ARM) was formed in Chicago in 1976 is an indication of the longevity of this process. Now operating as a worldwide trade association, the ARM currently represents companies in as many as 58 different countries.