Injection moulding is a manufacturing process ideally suited to producing large quantities of identical, one-piece components. Injection moulding in the UK is amongst the most commonly used process to create a wide range of components, large and small, used in all kinds of applications. Products produced by injection moulding include bottle lids, plastic combs, small pieces of furniture and many complex components for the automotive and electrical industries.
The injection moulding process is largely automated and injection moulding machines, also known as injection presses, are machines for manufacturing plastic products by the various injection moulding processes. The machines consist of two main parts, an injection unit and a clamping unit. The injection unit is rather like a heated screw-type plunger in appearance. Granulated plastic polymers are passed into the injection unit and are conveyed towards the nozzle by the action of the screw.. The plastic melts through frictional and conducted heat as it passes along the screw.
It collects at the end of the screw and when a critical amount has collected the molten plastic material is then injected into a mould attached to the clamping unit. The mould is typically made of steel and will have been precisely designed to match the item requirements. They may be attached in either a horizontal (most commonly) or a vertical position. Moulds are fastened to the clamping unit by manual clips via bolts (most commonly), hydraulic clamps or magnetic clamps. The latter two of which have the advantage of allowing fast tool changes. The plastic solidifies into a shape that, after shrinkage, has conformed to the shape of the mould. Once cooled to allow demoulding without distortion, the moulding is removed. A robotic arm is sometimes used to remove the moulded components from the machine although more commonly the items are allowed to drop out of the mould, passing through a chute into a container below.
Most polymers, also referred to as resins, may be used, including all thermoplastics, some thermosets, and some elastomers. Major criteria when selecting a material are the strength and function required for the final part, as well as the cost. Additionally, each material also has different parameters for moulding that must be taken into account.
Injection moulding machines are rated by tonnage, which expresses the amount of clamping force that the machine can exert to keep the mould closed during the process, and injection capacity which is the volume of material that can be injected per cycle. Machines are classified primarily by the type of driving systems they use: hydraulic, mechanical, electric, or hybrid. Mechanical machines were the main option prior to 1983 and are still the most widely-used type of machine in most of the world. However, the other types of machines offer different benefits relating to cost and energy consumption which may be taken into account when deciding which machine will suit a certain application best.
For more information about injection moulding speak to the experts at Plastic Machinery Sales by calling 01299 253338 or visiting http://plasticmachineryuk.com/new-machinery/