Injection molding is an industrial manufacturing method […]
Injection molding is an industrial manufacturing method for making many parts either by injecting melted plastic material into a mold, or by melting the mold itself and pouring hot plastic material into it. Injection molding can work with a variety of different materials mainly consisting of metals, plastics, fiberglass, epoxy, and many other thermoplastics, alloys, and elastomeric materials. Mold injection molding has become extremely popular because the molds can be made in a variety of sizes and shapes. They are very cost effective when compared to other mold production methods such as blow molding or injection molding machines. This type of molding also provides a high number of repeat jobs and can be produced in a shorter amount of time.
The injection molding process consists of two primary stages. The first stage of injection molding is the cooling process. The plastic is placed into the mold at a temperature of approximately 110 degrees Fahrenheit. During this time the plastic will harden while it is being fed into the mold from the top. Once the plastic hardens it will be moved to the second stage. This stage is known as the injection of molten plastic or 'hardening'.
The second stage of injection molding involves the injection of melted plastic into a cavity. The plastic will pass through a series of mold runners until it reaches the opening of the cavities at the end of the mold. The plastic then moves into the inner chamber of the mold, where it forms the cavity. During this time the plastic continues to harden while it forms the mold cavity, which is known as the injection rest. Plastic that is used in cavity injection molding must be heated in a process called quenching, which prevents it from becoming too soft after it exits the mold
The final step in the injection molding process involves feeding the melted pellets into the injection unit where they will be propelled into the workpiece. In the past, pellets were fed manually into the machines, but today automated systems are used, which make the process much faster and easier. After the pellets are successfully fed into the injection molding unit, the last stage involves the pouring of the melted plastics into the molds.
After the plastic material cools and solidifies, the mold cavity is closed. A device known as a trigger is used to cause the plastic to expand and contract. As the injection molding machine cools, the trigger breaks the solidified plastic into two sections, one section is filled with water and the other with air. As the plastic liquid cools and solidifies, it is forced into the injection unit where it melts and creates the necessary bubbles to form the walls of the cavities. Once the cavities are fully filled, the injection unit can close and the process is complete.
Injection molding machines have changed dramatically over the years. Today they are generally computer controlled and incorporate most of the automatic processes that were once performed by manual labor. Computer automated systems have also vastly improved accuracy and speed, allowing injection molding to be done on a large scale in a relatively short period of time. It is expected that automated mass production processes will continue to improve in the future as more businesses seek to automate their business processes in order to increase profitability.