Rotomolding is the preferred method of producing many hollow plastic products used in our daily lives, and is actually one of the fastest growing industries in the plastics industry in the past decade.
Unlike other processing methods, the heating, melting, molding, and cooling stages of rotational molding occur after the polymer is placed in the mold, which means that no external pressure is required during the molding process.
The mold itself is usually made of cast aluminum, CNC machined aluminum, or steel. Compared with molds used in other methods (such as injection or blow molding), molds are relatively inexpensive.
Rotational molding process is relatively simple, but it is extremely versatile. First, the cavity is filled with powdered polymer (discussed in the following section).
The oven is then heated to around 300°C (572°F) while the mold rotates on two axes to evenly distribute the polymer. The basic principle is that powder particles (usually about 150-500 microns) will fuse together to form a continuous finished product. The final result of the product depends critically on the size of the powder particles.
Finally, the mold is cooled and the product is taken out for finishing. The cycle time of the basic rotomolding process can vary from 20 minutes to 1 hour, depending on the size and complexity of the product.
Depending on the desired final product, various types of plastic polymers can be used in rotomolding.
One commonly used plastic is polyethylene (PE) because it can withstand high temperatures for a long time and is relatively cheap. In addition, low-density PE is very flexible and resistant to fracturing.
Moldmakers also commonly use ethylene-butyl acrylate because this material has crack resistance and strength at low temperatures. Like most thermoplastics, it has the added advantage of being easy to recycle
Although polypropylene is a widely used plastic, it is not the first choice of many moldmakers. The reason is that this material becomes brittle near room temperature, so manufacturers have little time to shape the product.
Many everyday products are produced using rotational molding methods, as are more customized products. Some examples are given below:
Rotomolding is a very effective molding method, which allows manufacturers not only to produce extremely durable products with minimal design constraints, but also to produce in an environmentally friendly manner at a relatively low cost. In addition, large-scale products can be easily manufactured in an economical manner, with very little material wasted.
Rotomolding can be quickly set up, which can meet unpredictable needs and produce in small batches. It helps to minimize inventory and potential inventory redundancy, making it generally relatively cheap compared to manufacturing, fiberglass, injection, vacuum, or blow molding methods.
The versatility of rotational molding is also one of its main advantages. It enables products to be created without polymer weld lines, with multiple layers and various styles, colors and surface finishes. Rotomolding can not only accommodate inserts, but also logos, grooves, nozzles, bosses and more functions to meet demanding design and engineering requirements. In addition, using this method can form different types of products together on one machine.
Gary graduated from the University of Manchester with a first-class honours degree in geochemistry and a master’s degree in geosciences. After working in the Australian mining industry, Gary decided to hang up his geology boots and start writing instead. When he is not developing topical and informational content, you can usually see Gary playing his beloved guitar, or watching Aston Villa Football Club win and lose.
Rotating Process Machines, Inc. (May 7, 2019). Rotomolding in plastic production-methods, advantages and applications. AZoM. Retrieved from https://www.azom.com/article.aspx?ArticleID=8522 on December 10, 2021.
Rotating Process Machines, Inc. “Rotating Molding in Plastics Production-Methods, Benefits and Applications”. AZoM. December 10, 2021. <https://www.azom.com/article.aspx?ArticleID=8522>.
Rotating Process Machines, Inc. “Rotating Molding in Plastics Production-Methods, Benefits and Applications”. AZoM. https://www.azom.com/article.aspx?ArticleID=8522. (Accessed on December 10, 2021).
Rotating Process Machines, Inc. 2019. Rotational molding in plastic production-methods, advantages and applications. AZoM, viewed on December 10, 2021, https://www.azom.com/article.aspx?ArticleID=8522.
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Post time: Dec-10-2021