Injection molding machine

From Plastics Wiki, free encyclopedia

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.

Contents 1 Types of injection molding machines 1.1 Hydraulic 1.2 Electric 1.3 Hybrid 2 Injection unit 2.1 Feed hopper 2.2 Injection ram 2.3 Injection screw 2.4 Barrel 2.5 Injection cylinder 3 Clamping unit 3.1 Injection mold 3.2 Injection platens 3.3 Clamping cylinder 3.4 Tie Bar 4 Manufacturers of Injection molding machines 5 Links

Types of injection molding machines

Main article: Types of injection molding machines

Machines are classified primarily by the type of driving systems they use: hydraulic, electric, or hybrid.

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.

Electric

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

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.

Injection unit

Main article: Injection unit

The injection unit melts the polymer resin and injects the polymer melt into the mold. The unit may be: ram fed or screw fed.

Feed hopper

The container holding a supply molding material to be fed to the screw. The hopper located over the barrel and the feed throat connects them.

Injection ram

The ram or screw that applies pressure on the molten plastic material to force it into the mold cavities.

Injection screw

The reciprocating-screw machine is the most common. This design uses the same barrel for melting and injection of plastic.

The alternative unit involves the use of separate barrels for plasticizing and injecting the polymer. This type is called a screw-preplasticizer machine or two-stage machine. Plastic pellets are fed from a hopper into the first stage, which uses a screw to drive the polymer forward and melt it. This barrel feeds a second barrel, which uses a plunger to inject the melt into the mold. Older machines used one plunger-driven barrel to melt and inject the plastic. These machines are referred to as plunger-type injection molding machines.

Barrel

Barrel is a major part that melts resins transmitted from hopper through screws and structured in a way that can heat up resins to the proper temperature. A band heater, which can control temper atures in five sections, is attached outside the barrel. Melted resins are supplied to the mold passing through barrel head, shot-off nozzle, and one-touch nozzle.

Injection cylinder

Hydraulic motor located inside bearing box, which is connected to injection cylinder load, rotates screw, and the melted resins are measures at the nose of screw. There are many types of injection cylinders that supply necessary power to inject resins according to the characteristics of resins and product types at appropriate speed and pressure. This model employs the double cylinder type. Injection cylinder is composed of cylinder body, piston, and piston load.

Clamping unit

The clamping unit holds the mold together, opens and closes it automatically, and ejects the finished part. The mechanism may be of several designs, either mechanical, hydraulic or hydromechanical.

Injection mold

There are two main types of injection molds: cold runner (two plate and three plate designs) and hot runner – the more common of the runnerless molds.

Injection platens

Steel plates on a molding machine to which the mold is attached. Generally, two platens are used; one being stationary and the other moveable, actuated hydraulically to open and close the mold. It actually provide place to mount the mould. It contains threaded holes on which mould can be mounted using clamps.

Clamping cylinder

A device that actuates the chuck through the aid of pneumatic or hydraulic energy.

Tie Bar

Tie bars support clamping power, and 4 tie bars are located between the fixing platen and the support platen.

Manufacturers of Injection molding machines

Main article: Injection molding machine manufacturers

• Arburg
• BOY Machines
• Chen Hsong
• Engel Machinery
• Husky Injection Molding Systems
• Nissei Plastic Industrial
• Omf turra (only vertical machine)
• Stork Plastics Machinery
• Toshiba Machine

Links

• [1]