Injection (Injection molding) involves injecting the plastic material, melted by heating, into a mold and hardening or heat-curing it to make a molding.

■ Injection Molded Product

■ Process

Mold Closing Process

a) In this stage, the Core and the Cavity (mold) are first closed.

b) After that, the Cavity is fixed, and the Core moves.

c) The moving speed is adjusted by the speed-adjusting device.

Injection Process

a) By the advancing screw, molten resin is injected into the mold through the nozzle.

b) The backflow prevention device attached to the screw prevents molten resin from flowing from the mold back into the injection machine.

Dwelling Process

a) Pressure is maintained until molten material within the Cavity hardens.

Cooling/ Melting/ Measuring Process

a) The molten material within the Cavity is cooled by coolant attached to the mold.

b) Melting and measuring of the material are carried out concurrently within the injection machine.

c) The material in the hopper is introduced into the cylinder by the revolution of the screw.

d) Measuring of the molten material is determined by setback distance.

Mold Opening/Ejection Process

a) The mold is opened with the molding attached to the Core.

b) Separate the molding that remains on the Core in the mold.

■ Resin selection point

Depending on the use for a molded product, the required physical property of an injection molded product varies, and accordingly, the resin selection point differs.

■ The impact of the mold on the molding is as follows:

In practice, when selecting resin for industrial or household use, economic feasibility, specifications of the injection machine owned by the processing company, and design of the mold are important factors in the selection of resin in addition to the required physical properties. In particular, the specifications of the mold require understanding when selecting resin according to the design of the mold below. When developing a new product, the processing company should make a separate mold matching the product.

- Correction of shrinking dimensions and shape

- A method for finishing processing, mold material

- Heat treatment, protruding apparatus

- Runner of the gate 

- Dimension and shape

- Temperature control

- Rigidity transformation