Injection molding is a manufacturing procedure for creating intricate parts by injection molding hot liquid material into a fully formed mould, or mould. Injection molding can be carried out with a variety of materials mostly including thermoplastic, thermoplastics, glass, acrylics, and more recently thermoplastic and thermoplastics. Molded parts that are made through injection molding can come in various attractive designs and shapes and are used for a range of applications. Molded parts can also be made using automatic machines, by manually loading the material into the mould, where it is heated to expand the liquid at the same time as the material is injected into the mould.
The two common types of injection moulding are wet and dry. In a wet injection moulding process, an excess amount of heating is allowed to pass through the mould when the material is being inserted, before the material is removed from the mould. The material is left to cool, whilst the cooling takes place, allowing the molten plastic to flow from the mould through a tube, ejecting the cooled plastic into a chamber on the other side of the chamber. A small amount of heat is required to speed up this process.
The process of hot injection moulding means that there is a small excess of molten plastic that is not cooled down before it is discharged into the chamber with the hot plastic. This excess plastic often contains melted plastic additives such as adhesives, clamps and fibre optics. These additives can quickly cause damage to some plastics when they are released into the mould and will therefore require careful cleaning before the injection moulding machine is started again. The use of a hot gun is sometimes preferred to extract liquids from the moulds using a small amount of heat. The speed and pressure of the hot gun can also be increased to increase the speed and pressure of the melted plastics ejection.
The most common materials used in injection mouldings are polyethylene (PE), polyurethane (PU) and thermoform. There are other plastics available but these are the most common and suitable for manufacturing plastic products. Some materials such as polypropylene (PP) are now becoming increasingly popular as these plastics are proving easier to process and allow manufacturers to produce a higher volume of product at a lower price. There are now several manufacturers who specialise in manufacturing PE and PU plastics.
The injection moulding process requires two elements - a heated and cold chamber. These chambers are generally in the form of a chamber separated by a gap, although some are closed. Inside the chamber the melted plastics are passed through a trigger, which activates the flow of plastic to the other side of the chamber where it is ejected or fed into the large cavity. At the other side of the cavity a cooling collar cools the plastic to a liquid state, which is then ejection or fed into another chamber to be cooled further before being ejected again into the injection moulding process.
The injection moulding process allows manufacturers to rapidly build prototypes with limited overheads. They do not need a large number of employees, machinery or support services to manufacture large numbers of identical products, saving money on materials and manufacturing costs. The prototype production runs at a much lower volume than normal manufacturing, due to the reduced time to make a large number of identical products. The process eliminates the need for a large run of goods to be sold to customers, and reduces the costs of handling defective or broken items. The prototype production can be completed within one day of receiving the injection moulded parts.
Injection moulding technology has increased dramatically in recent years, allowing manufacturers to produce high volumes of plastics in a shorter time. Some companies have been able to reduce the production cost by as much as 75 per cent by using the latest injection moulding techniques. The high volume produced plastic parts make it possible for even small changes in design to have an immediate effect on the finished product. For example, if a change such as a different shape of part or color of plastic part helps to make the part more effective and quicker to put together, that change can often be incorporated into the production process.
Although injection moulding does make it possible to make a lot of plastic parts quickly and inexpensively, some injection moulding techniques do not lend themselves well to use in areas of high stress or high production volume. This is because the plastic parts made from thermoplastic polymers are not as strong or resilient as metal or plastic parts made from traditional raw materials. When working with thermoplastics such as plastics, it is important to make sure that you select the right thermoplastic polymer for the project you are working on. Once you have made the right choice for your injection moulding process used, you will be able to make high quality, durable, strong, plastic parts in a short amount of time.
