Injection molding is a standard method for the mass manufacturing and production of parts in large volumes. In simple terms, it’s used to produce thousands of identical items like chairs, toys, cases for consumer electronics, disposable cutlery, etc. Some materials used for injection molding include glasses, elastomers, metals, and confections; the most commonly used materials are thermoplastic and thermosetting polymers.
However, not all products can be manufactured at once in large volumes due to the size limitations of injection molding machines and other needed mold tools. When the product/item is bigger than the injection molding machine, it needs to be created in separate parts and then joined together later.
How Does It Work?
Before any product can be manufactured through injection molding, the mold has to be created first. Most molds are usually manufactured from metal materials like aluminum or steel. The molds are designed to fit the features of the product they’re to manufacture.
After the mold has been designed and created (by the mold-maker), the materials for the product or part of the product are inserted into a heated barrel and mixed with the use of a helical-shaped screw. Heating bands melt the materials in the barrel, and the molten plastic, or molten metal, is then injected into the mold cavity, where it cools, hardens, and takes the mold’s shape. It takes time for the molten material to cool, but the cooling time can be reduced by using cooling lines from an external temperature controller. Mold tools are erected on plate molds (also called platens) which open after the material is hardened and solid so that the ejector pins can discharge the part from the mold.
Some products need to be created separately to form a whole; the individually made materials can be joined together in a type of molding machine called the two-shot mold. This method can be used to add finishing touches to plastic products or produce items with different performance features.
Molds can consist of one or several cavities. Multiple cavity molds can have similar parts in each cavity or can be different to create parts with other features, forms, and shapes.
Aluminum molds are not the best option for the high-volume production of products; neither are they suitable for producing parts with narrow dimensional tolerance. This is because aluminum molds have low mechanical properties and tend to wear out, deform, or damage due to the force of injection and clamping. While steel molds are better suited for high-volume production of products, the price of getting a steel mold is higher than getting an aluminum mold.
On a final note:
The injection molding process is an intricate and complex one because it requires careful design, including the shape, structure, and form of the part, the materials for the part and the mold, and the features of the molding machine.
It facilitates the process of producing products in high volume. It saves time and increases the chances of making these products in perfect shape.