The process starts when a mold mounted on the rotational molding machine arm is charged with a known amount of liquid or powdered resin into the mold hollow space. The mold is then clamped shut and begins rotating on its horizontal and vertical axes. The spinning continues as the arm conveys into a vast oven heating the whole surface area of the mold. Plastic parts are exceptionally impact resistant and they do not dent.
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Rotomolding mainly deals with materials that are solid at room temperature, but turn liquid with a moderate degree of heat — not high enough for liquid metals though mercury and Cyberdyne Systems Model T notably excepted. Safe assumption since this IS a blog about part manufacturing. CDN Inc. To begin, a two or more part mold is assembled together with a specific amount of powdered plastic resin inside. Centrifugal force the same force that plasters you to the edge of whichever Tilt-A-Hurl ride your kids make you go on ensures the plastic evenly coats the whole interior surface before it fuses together.
After enough heat, time and movement, the mold is cooled from the outside to solidify the plastic shell on the inner surface. The mold is then split apart to extract the newly made hollow plastic part before repeating the process to make more of the same. The process works great for complex shapes that hold liquids such as gas cans and water barrels, or for playground equipment where soft curves and double-walled forms both protect and structurally support children at play.
To help determine if it is, Industrial Designers first conceive the part with 2D or 3D sketches. While this serves as the communicative bridge between the design engineers and future consumers for aesthetics, it also highlights what is physically possible.
Design Engineers will develop a CAD model from the concept sketches. In this 3D model, they will identify the parting lines. These are where two or more segments of a mold tool will meet together. Parting lines are important in that they establish tool complexity and how undercuts and draft angles are evaluated. There will also be a small blemish line visible on the outer surface of the final plastic parts where the parting lines trace the surface. Design Engineers also need to determine the specific material to be used in this stage.
Visit our Boomerang Fabrication website to submit your drawings instantly. One benefit of this process is that tooling is inexpensive relative to other types of molding. Aluminum is commonly used for rotomolding tooling, though large simple parts can even incorporate steel sheet metal weldments. One drawback though is that a part well-suited for rotomolding large and hollow with complex geometry lacks a more economical option for prototyping. With the amount of tolerance needed for the beginning of the process, a bit of fine-tuning is unavoidable at the end.
Much of it will be calculation: What is the surface area of the finished part? The desired wall thickness? But calculation will take you only so far. There will always be uneven material that has accumulated because of the process. This is where experience and experimentation are required. Perhaps achieving the thickness required in large flat areas may mean that small convex features are a bit thicker.
Perhaps the weight of the product will increase because of that. The features of the part will accumulate material somewhat unevenly no matter the design and process. For those aficionados of pie charts and diagrams, we have your fix coming up. Stay tuned to our blog for more of this type of information. Skip to content. Rotomolding Process. What is the Rotomolding Process? Learn More. How is it Made? What is the Concept of Rotomolding?
What is the Design Process for Rotomolding? Boomerang Fab. What is the Tooling Process for Rotomolding? What is the Production Process for Rotomolding? Notify of. Inline Feedbacks. Close Menu. Would love your thoughts, please comment.
British Plastics Federation
Rotational molding, rotomolding, rotomold or rotocasting is a production process to form hollow parts of limitless size. This is a cost-effective method to produce large plastic parts. The simultaneous heating and rotation distributes and fuses the resin on the inner surfaces of the mold. The result is a product that contains seamless parts with a uniform wall thickness with more material in corners to absorb shocks and stresses where they occur most.
The rotomolding process allows products to be manufactured in a way that creates extremely strong, long lasting, durable parts. Rotomolded parts are resistant to deterioration from chemicals, the elements or environmental stresses. The applications of this process range from playground equipment to nuclear warhead covers, from agricultural tanks to tornado shelters, from furniture to construction materials. The rotational molding process as well as the materials used during rotomolding pair to create these extraordinary parts.