Rotational molding, also known as rotomolding, is a production technology that involves manufacturing hollow parts by adding the plastic powder to a mold. The mold is then rotated and heated simultaneously, and the powder blends with a bubble-free liquid layer that takes the shape of the mold surface. Rotomolding is common in industries that manufacture tanks, leisure craft, toys, and medical Products. In this article, we are going to explore the advantages and disadvantages of rotational molding.
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Rotational molding uses
Rotational molding is used in making tanks and containers like septic tanks, oil tanks, fuel tanks, shipping tanks, and chemical storage tanks. Rotomolding is also applicable in a wide range of industries such as the agricultural, automotive, furniture, construction, and sports industries due to its ability to manufacture different shapes and sizes. The technology is mostly used for parts that need prestigious furnishes, aligned wall thickness, and high stability. Some elements, such as spin weld attachments and inserts, are integrated into the rotomold, and foaming is used to generate thermal insulation and rigidity.
Process of rotational molding
The process of rotomolding is quite simple, and it involves four significant operations.
Mold preparation
The first step involved in the process is filling a hollow mold with enough resin or polymer powder. The most commonly used powdered resin is polyethylene, even though sometimes other products like nylons and Polyvinyl chloride is used. The resin powder is blended into the color you wish and then placed on the mold. It is then closed and loaded into the oven, which is preheated to temperatures ranging from between 500° F 0-700 ° F, depending on the type of Polymer used.
Heating and fusion
The mold placed inside the oven is rotated around two axes, with the rotation speed being less than 20 rotations per minute. With time, the Polymer melts and then coats the inside of the mold. Time is a critical factor when it comes to the heating and fusion phase. The longer the mold takes inside the oven, the higher the chance that the Polymer will degrade, minimizing its impact strength. On the other hand, if the mold takes a shorter time in the oven, the Polymer will not fully melt. This means that the Polymer will not fuse on the mold wall, generating large bubbles in the item.
The cooling phase of the mold
After melting is done at the required level, and the timing is perfect, the mold is detached from the oven and then cooled. Typically, cooling is usually done with water, air, and sometimes a combination of both. During the cooling process, the Polymer solidifies the required shape and then gradually contracts before the operator eventually removes it from the mold. It is essential to measure the cooling time because faster cooling causes the Polymer to distort. Note that the cooling process is quite lengthy and may take up to ten minutes.
Demoulding
Once the Polymer cools off and retains its shape, the mold is opened, and the part is carefully removed from the inside. Recurrence of the process involves adding a considerable amount of the polymer powder to the mold again.
Rotational Molding Advantages and Disadvantages
Advantages of rotational molding
Rotomolding technology is prevalent, making it one of the rapidly growing industries in the last decade. There are numerous advantages of rotational molding, from design versatility, reduction of environmental impact, use of lighter materials, and meeting of demand. Why choose rotational molding as the best technology for your next plastic projects? Below are a few advantages that every part designer should be aware of.
The materials used are long-lasting and flexible
At Roto Dynamics, our rotomolded plastic products are made from polyethylene protected from the hazardous UV Rays from the sun. As you all know, Ultraviolet rays from the sun make products to fade quickly and degrade with time. Unlike metals, rotomolded plastic is free from rust, and they do not corrode easily, meaning that your products will be durable. Besides, the products made from our roto molding company are powerful since the walls are thick; hence, they are not easy to break.
Minimum environmental impact
One of the rotational molding advantages is its minimum environmental impact. During the rotomolding process, no chemicals or dangerous toxins are released hence making it environmentally friendly. Unlike metals and concrete, very few materials are wasted when manufacturing is done using plastics. One fantastic feature about plastics is that they are 100% recyclable hence simple to reduce your carbon footprints. This means that for every plastic item that is recycled, fewer materials are mined from the earth, therefore, reducing its impact on the environment.
Wide range of designs
With the rotomolding process, it is simple to generate a variety of shapes, majorly because when hot plastics are placed on a mold, they take the shape of the mold. Many molding processes have few options to choose from, but with rotomolding, any form can be designed from the process. This makes it ideal to be used in many industries. Our roto molding company provides you numerous designs of your choice.
Variety of size options
Compared to other molding processes that accommodate a few sizes, rotational molding allows for diverse sizes to choose from. At Roto Dynamics, we manufacture small-sized tanks, medium sizes, and even the largest sizes. We can design a gallon of between 0 – 1000 pounds with a height of approximately 17ft. The main advantage of creating various sizes is to allow the tanks to be used for different purposes.
Low cost
The initial production cost for rotational molding is way cheaper compared to other molding processes. The low cost incurred is for machining the mold. Before heating, the mold requires finished pieces added to it like color plastics, internal pipes, and metal threads. This saves you both your time and money.
The production process takes a shorter time
Another rotational molding advantages is the process time. Compared to blow molding or perhaps injection molding, rotomolding takes a shorter duration of time. The speed at which we can produce rotational mold, makes it ideal for quick orders or rush orders. For instance, in our roto molding company, production can start in three months or less.
Disadvantages of rotational molding
Like any other plastic molding process, rotational molding has its share of disadvantages, which include :
Few material options
One of the disadvantages of rotational molding is that you have less material options. The raw materials we use in rotational molding must be changed from granules to a fine powder and excellent thermal stability. The only material suitable to be used in the process is resin.
High process durations
The rotational molding process can take as long as three hours to complete one section involving eight turns.
The astounding expense of crude oil material
The cost of crude oil is high because of the costs incurred in converting the materials to powder and the added materials.
High work costs
The use of robots in rotomolding has not been proclaimed hence requires a large workforce to take care of the operations. The cost incurred in paying the workers is high, which would have otherwise been made easier if robots were doing the work.
At our Roto molding company, Roto Dynamics, we offer an amazing portfolio of rotomolded products like water tanks, and plastic products. Our products are very durable and robust mostly since the materials are made from rotomolded plastic which is durable. Rotational molding has both advantages and disadvantages, as mentioned above, although the disadvantages are less compared to the advantages. For more information or clarification, contact us at Roto Dynamics, and we will be at your disposal.