Injection molding is a manufacturing process that allows for mass production of parts. It works by injecting molten material into a mold. It is often used as a mass production process to produce thousands of identical products. Most commonly used for thermoplastic and thermosetting polymers.
The first stage of injection molding is to create the mold itself. Most molds are made of metal, usually aluminum or steel, and are precisely machined to match the characteristics of the product they produce.
Once the mold maker has made the mold, the part material is fed into a heated barrel and mixed using a spiral screw. The heating belt melts the material in the barrel and then feeds the molten metal or molten plastic material into the mold cavity, where it cools and hardens to match the shape of the mold. Cooling time can be reduced by using a cooling line that circulates water or oil from an external temperature controller. The mold tool is mounted on a plate mold (or "press plate"), and once the material solidifies, the plate mold opens so that the ejector can eject the part from the mold.
In a type of injection molding called a two-shot mold, separate materials can be combined in a single part. This technology can be used to add a soft touch to plastic products, add color to parts, or produce products with different performance characteristics.
Molds can be made with single or multiple cavities. Multiple cavity molds can have the same part in each cavity, or can be unique to create parts with different geometries. Aluminum molds are not suitable for high-volume production or parts with narrow dimensional tolerances because they have poor mechanical properties and are prone to wear, deformation, and damage due to injection and clamping forces. While steel molds are more durable, they are also more expensive than aluminum molds.
The injection molding process requires careful design, including the shape and features of the part, the materials of the part and mold, and the performance of the molding machine. Therefore, there are various factors to consider when injection molding.
Injection Molding Considerations
Before you proceed with injection molding, you need to be aware of the following:
1. Finance
The cost of entry into injection molding manufacturing can be high, given the cost of the machinery and mold itself.
2. Production Quantity
It is important to determine how many parts you expect to make to decide if injection molding is the most cost-effective production method.
3. Design Factors
Minimizing the number of parts and simplifying the geometry of your product will make injection molding easier. Also, the design of the mold is important to prevent defects during production.
4. Production Considerations
Minimizing cycle time will help with production, as will using a machine with a hot runner mold and well-thought-out tooling. This small change and the use of a hot runner system can save you money on production for your part. Minimizing assembly requirements will also save money, especially if you are producing parts in the thousands or even millions.
