Guide on Injection Molding (versus Rotomolding)

Molding techniques are diverse and varied, each suited to specific production needs. Thanks to new technologies, manufacturing methods have undergone major transformations to meet the modern demands of precision and performance. Among these techniques, injection molding is one of the most commonly used, particularly for its ability to create complex-shaped parts.

Injection molding is particularly suited for manufacturing enclosures and other products requiring high precision. It is used to produce cases, covers, and various components and stands out for its ability to maintain consistent quality, even in large production runs. But how does this technique work exactly? What are its key advantages and limitations?

What is Injection Molding?

Injection molding is a manufacturing process that involves injecting molten material into a mold to create parts. It can be performed with a variety of materials, including elastomers, thermoplastic polymers, and thermosetting polymers, with the latter being most commonly used in this process.

The material used to create the part is placed into a barrel and mixed with a screw before being injected into a cavity where it cools and hardens to the shape of the mold. Once a product has been designed by an industrial designer or engineer, molds are crafted by a skilled expert. These molds can be made from steel, metal, or aluminum and are precisely machined to form the desired parts.

What is the Injection Molding Process?

The injection molding process uses a specialized machine with three main parts: the injection unit, the mold, and the clamp. To facilitate the molding process, the parts to be molded must be carefully designed.

All elements must be perfect, including the materials used for the part, the desired shape and features, the material of the mold, and the properties of the machine. This method is highly versatile, made easier by a wide range of design considerations and possibilities.

The entire process is relatively simple. A material is injected under high pressure into a mold to take the desired shape. It is primarily used for thermoplastics due to their recyclability, versatility, and ability to soften with heat.

Molds for forming products can be single or multi-cavity and are typically made from aluminum or steel. Aluminum molds are generally more cost-effective than steel molds for low-volume production.

The heated material is injected under high pressure into the mold cavity where it cools and takes its shape. The material can be a mix of components that may chemically react to form a solid polymer when using thermosetting polymers.

The process can also involve adding pre-molded parts into the mold, facilitating the creation of composite parts. Manufacturing defects, such as door or ejection marks, can appear on the finished parts, but these may not be significant if the mold is well-designed.

Advantages of Injection Molding

Injection molding is highly recommended if you want to maintain quality during high production. For plastic waste bins, it offers numerous advantages. Often, quality is overlooked in high-speed production methods like blow molding, where the primary focus is rapid production.

Injection molding can also allow for the creation of bins in a wide range of sizes and colors.

The production of parts with complex geometries and precise dimensions can be handled by injection molding. Additionally, the production cycle is generally shorter with injection molding compared to rotomolding or rotational molding.

Disadvantages of Injection Molding

For plastic bins, the injection molding method can present certain shortcomings. First, the tooling cost is significantly higher compared to rotomolding.

Its use is limited to certain shapes and sizes. The flexibility in material choice is also clearly restricted. Finally, plastics produced by injection molding (such as enclosures for electronic devices, children's toys, plastic furniture, kitchen accessories, vehicle components) are sometimes less durable and less resistant. They typically fail under heavy loads and impacts. It is important to understand the type of use these products are suited for.

Which Method is Better Between Injection Molding and Rotomolding?

Rotomolding and injection molding are both highly effective methods for producing high-quality plastic waste bins. Regardless of their advantages and disadvantages, each method is suitable for specific situations or manufacturing conditions. The choice depends on various factors and requirements, including:

• Production volume

• Shape

• Size

• Available equipment and resources

• Desired properties of the plastic material

Injection molding is ideal for complex productions and cost-effective solutions at large scales, while rotomolding offers superior durability, lower tooling costs, and greater design flexibility.

For all your rotomolding needs, contact Rotoplast and ensure professional services with years of experience in the field.