The manufacturing process where a plastic part is produced in a closed mold into which molten polymer is injected and hardened is called injection molding. This is typically used to mass-produce plastic items. There are a number of steps involved in the process.

A principal reason why injection molding is preferred is because of its ability to mass-produce items. There is an initial cost in designing and producing the mold but once that is paid for, the cost per product is extremely low. The cost further dips as the quantity increases. Another advantage is that there is relatively very little scrap that is left over. Unlike the stamping process where a considerable portion of the sheet or block is cut off as scrap, the injection process has very little wastage. It is only the leftover molten polymer in the feed pipes, and any material that leaks out of the mold that is wasted. Quite often this scrap can also be reused and that further reduces the cost of scrap. A third advantage is that injection molding

is a repeatable process. The parts that are formed are all exactly identical. Injection molding ensures that the number of parts needs to be assembled for a particular product is kept to the minimum. Also, similar parts can be molded by using inter-changeable inserts.

The disadvantages of injection molding are that the initial set-up costs are often quite high. The costs involved in designing, testing, and producing the mold is often quite high. Designing the tool and getting ready for production consumes 1~2 months depending on the part complexity.

Therefore, before going in for injection molding consider the financial aspects including the initial costs and the production quantity. Give consideration to the part design and tool design to ensure that it is advantageous. Take into account the time required for design, tooling, and manufacturing.