Injection moulding process of plastics – a simple guide

The moulding process of plastics is a process that injects molten plastics into the desired shape usually referred to as a cavity and core in a plastic injection mould. Sometimes the item will be hollow
Modern Moulding technologies can reproduce extraordinarily complex designs and shapes used in various industries catering to the automotive, material handling, and engineering industries. They are equally useful for producing everyday shapes too, eg: Buckets, Mugs & Jars, Toothbrush handles etc.

Injection moulding process

A manufacturing process that produces parts after injecting molten material into a mould is known as the Injection Moulding process. This process can be performed by using a host of materials which includes glasses, confections, metals, thermosetting polymers, and thermoplastics. The material for these parts fits inside a heated battle and is mixed by a helical-shaped screw. Later, this is injected in a mould cavity where it can cool down and harden to how the cavity is configured.

Once a product is designed by an engineer or an industrial designer, moulds are created by a toolmaker or mould maker from metals like aluminium and steel. A precision machine is used to form the perfect features of the desired part. The process of Injection moulding is used to manufacture a plethora of parts that range from the entire body panels of a car to its smallest of components. The advancement of 3D printing technology that used photopolymers that don’t melt during this process of some thermoplastics at low temperatures is useful for simple injection moulds.

The injection moulding process requires a machine that has three parts which are the mould, the clamp, and the injection unit.  The parts which are supposed to be injection moulded should be designed carefully to hold the moulding process, the desired features and shape of the part, the mould material, and the properties of the moulding machine. The breadth of design possibilities and considerations are responsible for the versatility of injection moulding.

The injection moulding process can be used to create multiple things like packaging, automotive parts and components, pocket combs, one-piece chairs and small tables, mechanical parts, wire spools, bottle caps, tops, and some musical instruments such as plastic products which are used in today’s day and age. This process is considered ideal for manufacturing products because it allows the production of high volumes of the same object.

A screw-type plunger is used to force the plastic material inside a mould cavity. This material solidifies and conforms to the shape of the mould. Injection moulding is widely used for processing both thermosetting polymers and thermoplastic, where the volume of the latter is higher. The characteristics of thermoplastics make them suitable for injection moulding.

The first injection moulding machine was patented by an American inventor named John Wesly Hyatt. In comparison to the machines used today, this machine was quite simple. It worked like a giant hypodermic needle that used a plunger for injecting plastic, which passed through a heated cylinder and then reached the mould. The industry had started to progress after its first establishment in 1872 and started producing hair combs, collar stays, and buttons.

There are pellets and granules made of plastic materials which are first shipped as raw materials in paper bags. In injection moulding, these pre-dried granules of plastic are rammed by a hopper to be fed into a heated barrel.

The melted plastic is then forced through a nozzle and rested against the mould with the advancement of the plunger. This allows it to run through the mould cavity from a gate. As soon as the mould is filled, it shall remain cold for solidifying the plastic.

This sequence of events is known as the injection moulding cycle. It begins when the mould is closed and is followed by an injection of the polymer inside a mould cavity. After filling the cavity, the material shrinkage is compensated by holding pressure. Then the screw is turned to feed the next shot into the front screw. As the next shot prepares, the screw begins to retract. The part is ejected by opening the mould once it becomes sufficiently cool.