introduction of injection molding

Injection molding machines 

Consist of two basic parts, an injection unit and a clamping unit. Injection molding machines differ in both injection unit and clamping unit. The name of the injection molding machine is generally based on the type of injection unit used. 

 

Types of injection molding machines

  

1.)Hydraulic
Hydraulic presses have historically been the only option available to molders until Nissei Plastic Industrial Co., LTD introduced the first all-electric injection molding machine in 1983. The electric press, also known as Electric Machine Technology (EMT), reduces operation costs by cutting energy consumption and also addresses some of the environmental concerns surrounding the hydraulic press.

2.)Electric 

Electric presses have been shown to be quieter, faster, and have a higher accuracy, however the machines are more expensive. 

3.)Hybrid

Hybrid injection molding machines take advantage of the best features of both hydraulic and electric systems. Hydraulic machines are the predominant type in most of the world, with the exception of Japan. 

How are Injection Molded Plastic Parts Made?

Injection molding generally follows a standard process:

1. The mold is set up for molding operations. A mold generally has two halves that are clamped or pressed together for the molding process.
2. Granular or powdered plastic material is fed into a screw plunger. The plunger is heated, and melts the plastic as it travels through the plunger. The screw plunger also helps to mix different plastics together, or different base components of a thermoset plastic together to create a homogeneous blend.
3. The plunger forces the molten plastic through a nozzle into the mold through gates.
4. The plastic is allowed to cool within the mold. The mold can be air cooled, or be artificially cooled with water or other fluids.
5. The mold is opened, and ejector pins push the part out of the mold. Ejector pin marks are often evident on injection molded parts.
6. Excess material that cooled in the gates or around the parting line of the mold is trimmed away from the part, and further finishing is performed as needed.

Injection molding allows manufacturers to produce quality plastic components repeatably in a cost-efficient manner. Injection molded parts are used in nearly every industry, from toys to automobile components.