September 19, 2020

How Plastic Injection Molding Works?

Uses of Plastic injection molding

Plastic injection molding is the most common and widely used method for mass manufacturing of plastic products all over the world for its convenience injection mold and ease of use. Plastic products made using this method include plastic chairs and tables, covers for electronic products and disposable spoons and knives, other cutlery products as well, for commercial consumption.

History of Injection Molding

Injection molding was initially invented to solve a problem faced in abundance by billiard players. 19th century billiard balls were originally made out of ivory, obtained from the tusks extracted from elephants. Celluloid was one of the first plastics used to manufacture billiard balls.

The Procedure Explained

The scientific procedure used for manufacture of plastic products by application of injection molding is quite simple. You plastic is melted and taken inside a giant syringe. Then it is put inside the shaping mold of appropriate shape according to the product being manufactured and cooled down for a sufficient requisite period of time till it attains the desired shape. However, the actual practical process of injection molding is not that simple and can be broadly divided into 3 subdivisions- the injection unit, the molding section and finally the clamp. Plastic pellets are gradually poured into the injection unit through a tunnel which get gradually liquefied and are in a completely molten state by the time they reach the front of the barrel. Once it reaches the shaping mold, it is cooled down to solidify into the desired fixed shape. The mold then goes back to its previous original position in the machinery.

All injection molded objects start with plastic pellets, which are a few millimeters in diameter. They can be mixed with a certain limited amount of pigment, called “colorant” or with up to 15% of recycled material-then the mixture is fed into an injection molding machine. Early molding units used the plunger to push down from the top. However, the outer regions were either too hot or too cold and the melting process did not work properly. The solution to this was a reciprocating screw- often regarded as the most important contribution that was nothing less of a revolution in the plastic products manufacturing industry. The screw induces shearing stress required to melt the plastic- with the rest of the heat originating from the traditional heater bands surrounding the machinery. As the molten plastic is injected into the shaping mold, it releases air from the vents placed sideways. Plastic, which has the viscosity of honey, is thick enough to not be released from these vents, which are only a few microns wide.

Carving witness marks on plastic products are also a significant part of marketing because you need to be able to look and find some witness marks as well as parting lines to authenticate and verify the genuineness of the product. These are created using removable inserts and can prove to be highly useful for tracking down defects,

Why China?

China is well known as a manufacturing hub and foreign export of plastic products. A china plastic injection molding manufacturer assures you quality products which are reliable and long-lasting.


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