Injection moulding has indeed evolved through the years from the time of its inception in the 1800s to what it is today – an effective process for manufacturing that produces millions of plastic parts and components all over the world.
But what exactly is the injection moulding process, and what does it entail? Below is a guide to the entire process of injection moulding so you can see how it actually works.
In the injection moulding process, plastic in granular form is fed from a specially-designed hopper into a barrel which is heated up. The plastic is then pushed slowly along by a plunger into another chamber (also heated), where it melts. The plastic, already melted, is then forced to enter the cavity of the mould by a special nozzle, where it also runs through a gate and runners. The mould, on the other hand, stays at a cold temperature so that the plastic can turn solid as soon as it fills the mould.
The cycle of injection moulding
The process of injection moulding consists of a cycle, where the plastic is injected into the cavity of the mould. When this cavity is already filled with the plastic, a certain amount of pressure is exerted by the machinery so as to compensate for the shrinkage of the material. The next step involves the turning of the screw and the feeding of the subsequent shot onto the screw at the front. Through this, the screw then retracts and the subsequent shot undergoes cooling and preparation for ejection. When the component has cooled down, the mould then opens in order to eject the part or component.
Variations in the injection moulding process
Even though there is a traditional process for injection moulding (mentioned above), there are also certain variations in the process which produce different parts. These variations include the injection moulding of metal, the casting of die, thin wall moulding, and the injection moulding of liquid silicone, among others.
The importance of troubleshooting in the injection moulding process
But just like other industrial or mechanical processes, there can also be specific flaws in the injection moulding process. In order to prevent flaws in parts or components, troubleshooting is essential. Part of the troubleshooting method for injection moulding is the examination and assessment of parts which may be deemed defective. Once these parts are confirmed to be defective, the defect must be corrected, be it in the actual mould’s design or the cycle itself. This is why injection moulding specialists like www.dataplastics.co.uk also emphasise the importance of performing trials before the actual production of the part, so possible defects can be avoided and the right specifications can be determined.
One test that can be performed for plastic parts before a full run, especially when a mould is new and the proper size of the shot for the mould is unknown, is the gradual filling of the mould until it is 95-99 percent full. When it is filled to this percentage, a certain amount of pressure is applied and the time of holding will be amplified until the solidification of the resin occurs. Determining the time of solidification is essential as it can determine the actual time of the entire cycle as well as the product’s consistency and quality, which, in turn, affects the cost of the product in the end.