A Brief Introduction to Injection Moulding
Injection moulding and extrusion are the main processes used to produce plastics. Injection moulding is an efficient and quick system resulting in large quantities of the same item being made into the disposable consumer products that we see in our High Streets and in stores up and down the country.
Moulding machines are controlled using an inbuilt computer which reacts to sensor fed data.
Most injection moulding machines tend to use materials such as Acrylonitrile-Butadiene-Styrene ABS, Nylon PA, Polycarbonate PC, Polypropylene PP and Polystyrene GPPS. The main benefit of injection moulding is that products of almost any size and shape can be produced, such as medical syringes, wheelie bins, bottles and storage units. These items affect the way we live our lives and are the essentials we use and rely on every single day.
Silicone moulds from companies such as http://www.meadex.co.uk supply custom silicone moulding for a wide variety of businesses, including medical supplies and equipment for the automotive and aerospace industries.
The process involves selecting the most suitable material, which is then applied to the moulding machine via a hopper. The reciprocating screw which is driven by an electric or hydraulic motor then turns the heated barrel – this feeds the molten polymer into a temperature-controlled split mould. The screw then melts the polymer, which is then injected into a tool. This then determines the shape required.
The tools are made of steel to manage the pressure of the injection and aluminium alloys for cutting. This results in the ability to either manufacture the same product over and over again for multiple production or allow it to be altered and adjusted.
Most machines come with either a toggle clamping system or a direct lock system. This is known as the ‘Clamping Force’ and is measured in metric tonnes or kilonewtons. Converted, this is ten 10,000 KN to one metric tonne.
Depending on what the machine is being used for, a smaller injection unit provides better accuracy for producing smaller items. Other options manufacturers need to consider include the size of the injection screw. The larger the screw, the bigger the maximum shot weight of plastic.