Rotational molders employ rotational molding techniques to manufacture plastic parts from stock molds, and rotomolding companies often offer custom rotational molding, which requires the fabrication of a unique rotomold. The molds are usually made out of either stainless steel or aluminum, which are welded together or die cast. The plastic rotational molding process is considered slower than other thermoplastic molding techniques, and parts are usually manufactured in smaller runs. Roto moulders are often able to mold different products simultaneously, as long as they are similar in size. Some are designed to fit many different smaller molds on their spindle arms, while other rotational molders are used to fabricate one large molded product at a time. Rotational moulders are used to fabricate plastic products for a wide range of industries and applications, including food and beverage processing, pharmaceutical, waste water management, agricultural, plumbing, sporting goods, packaging, material handling, chemical, fuel/oil, marine, road construction, automotive and toy manufacturing. Tanks, containers, bins and other hollow plastic products are just a few examples of possible rotationally molded plastics.
There are many other advantages to the rotational molding process. While being heated and rotated, the plastic resin adheres to the hot mold, coating it very evenly and seamlessly, producing strong outside corners with virtually no stresses. Rotomolding can produce one-piece constructions, and complex parts are formed without any part assembly required. The plastics used for rotomolds are often lightweight and may be high or low in density. For applications in the food and beverage and pharmaceutical industries, the thermoplastics used can be easily fabricated to be FDA approved, meaning they must not contain any recycled plastic or dies and cannot contaminate substances under any conditions, even high temperatures. The low cost of the materials and tooling makes rotational molding just as cost effective for producing prototypes as it is for large production runs. A variety of finishes, colors and textures are available. Companies are able to mold their logo, graphic or labels right into the parts. These imprints will not come off and are parts of the mold construction. Rotomolding is a versatile molding technique that provides durability to products, eliminates costly fabrication and assembly processes and reduces the need for replacement parts.
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- A common process used to form hollow, thermoplastic shapes, such
as bottles and containers. Two general types of blow molding are extrusion
and injection blow molding.
- The process in which individual polymer particles are joined together by a molecular bond.
- The ability of a material to withstand various chemical agents. Plastic is capable of enduring many of these chemicals, making it very useful for holding tanks and other containers.
- The oxidation and deformation of a material, such as the rusting of iron, due to a chemical reaction.
- The time it takes from the first stage of rotational molding, in which the plastic is loaded, until the plastic completes its final stage and is removed from the mold.
- The removal of unwanted material from a molded product, especially from the areas where parting lines of the mold may have caused excess material to be formed.
- A significant parameter for polyethylene (PE) that affects the properties, such as stiffness and impact strength, of the end product.
- The ability of a material to return to its original form after stress has been applied and quickly removed.
- The temperature at which the plastic resin melts and begins to adhere to the surface of the mold.
- The ability of a plastic to be ground into a fine powder. Most plastics are ground prior to being loaded into the mold.
- The measure of the ability of a plastic to withstand fracture by shock.
- A generic name for semi-synthetic or synthetic materials that can be extruded or molded into films or objects. Plastic materials are also used for coatings and adhesives.
- A chain of molecules that is formed by the bonding of individual repeating units (monomers).
- The measure of the speed of a plastic powder when poured through a funnel. For a plastic powder to be acceptable for rotomolding, it must be capable of flowing at least 185 grams/minute.
- Any of various semisolid or solid natural organic materials that are usually translucent or transparent. Resins are mostly utilized in plastics, adhesives and coatings.
- The "arms" of the rotational molding machine that are responsible for moving the molds between different stages. Spindles also spin on the horizontal and vertical axes to create a uniform filling within the mold.
- The ability of a resin to withstand specified temperatures. Less thermally stable materials can be rotomolded only under controlled conditions with extreme care.
- A material that will soften when repeatedly heated and cooled. Examples of thermoplastics include polyethylenes, polypropylene (PP), vinyl and nylons.