What is Plastic Injection Molding Machine?

The plastic injection molding machine is a highly sophisticated piece of equipment that effectively manufactures an item by injecting molten materials using the reciprocating screw system into a mold.

The plastic injection molding machine consists of multiple mechanical and electrical components like the material hopper temperature controlling devices, a barrel containing a reciprocating screw, the injection mold, and a clamping unit.

How Does a Plastic Injection Molding Machine Work?

The plastic injection molding machine consists of 3 main sections, namely, injection, mold, and clamp. Each of these sections will be elaborated on in subsequent paragraphs:

Injection

Different materials like shavings, flakes, and resin pellets are fed to a barrel or reciprocating screw feed via the hopper. The feeding can be done through a vacuum, automatically, or manually. A heating element then covers the barrel where the raw materials are deposited and exposed to high temperature and pressure until they’re melted and become liquid.

The cutting action of the screw also makes this process possible. The screw directs the molten polymer resin to the sprue nozzle. A check ring set in place prevents the resin from flowing backward. This arrangement ensures that the molten polymer resin is in a constant state at the injection point.

Mold

The molten polymer resin is moved through runners that effectively control the flow away from the nozzle into the split cavity assembly that is made up of a platen-mounted moving core as well as a fixed cavity.

The runners end at the gates within the boundary of the cavity. The type, location, and size of these gates have an overall effect on the quality of the finished molded item or part. Molds are the internal channels through which liquids are stored right after the injection to aid part cooling before ejection. The cooling process is not a complex one; it’s just a phase where the plastic parts take the shape of the mold and solidify. The only halves only open when the molten materials have cooled enough.

The estimated time for the liquid to cool and solidify depends on the properties of the plastic materials involved in the process. Molds specially designed for a part are filled out according to requirements. That’s why it’s easy to recreate the exact copies of a part within a short time.

Clamp

The hydraulically operated clamp ensures the two parts are held closely together to secure the high pressures generated during the injection stage efficiently.

Most plastic injection molding machines are identified by their size and the clamping force it achieves(mainly determined by tonnage). When the part has cooled, the clamp releases it by ejecting it, and the plastic injection molding is ready to start another cycle.

All that the plastic injection molding process entails – which seems simple but sophisticated – has existed for a long time. However, the machine involves the use of the appropriate equipment and expertise.

Though this concept has improved through the years into a more versatile and efficient tool that manufactures products in large volumes.