An injection mould is a common tool, used to mass produce plastic products. The only other manufacturing tools used for plastic production are the deep drawing press and the extruder. These should not be confused with "injection moulds". They work exclusively with metal (mostly aluminium) and use injection moulds for end or intermediary products.
Contrary to simple punch or press forms used for the processing of sheet metal, injection moulds are a lot more complicated in their build up. In addition to the negative contour of the end product, injection moulds need to contain a variety of other components. Injection moulding is a thermal process. Therefore, the tool needs to contain sufficient cooling channels, otherwise the injected workpiece will not harden fast enough thus resulting in an inefficient production process. Air that is displaced from the injection moulding process must be able to escape. The negative shape of the workpiece needs to be fully poured out in seconds. The pouring channels are incorporated in the tool.
Finally, the workpiece needs to be removed from the tool. For this reason, every injection mould contains a built-in ejector. Cooling systems, material supply and an ejector means that the injection mould is a relatively complex system built out of hundreds of different individual parts. The price of an injection moulding tool can easy exceed the price of a second hand machine.
Producing an injection mould is a very complex process. The operation of the machine, as well as the training for the workers, is very challenging. The production of an injection mould is done on special machines. These are EDM machines, tool grinders, CNC-milling machines etc. Since the finished products produced with an injection mould should be of high quality, the moulds themselves need to be of even higher quality. The machines that produce the injection mould then need to be yet another step higher in quality. This is reflected in the price of injection moulding machines.
The dimensions of an injection moulding tool is restricted in terms of the production process of the injection moulding machine. The complete filling of the tool is no longer possible after a certain size. Because of this, most plastic products are less than 5kg. Plastic injectors are used more for the production of small workpieces with a small mass. This way, more products can be repeatedly produced in one step. Complex injection mould products can produce special forms, for example for those with inlays made out of a different material. An injection mould is generally an individual workpiece.
The advantage of injection moulds is that they can generally be installed into any injection mould machines. Therefore, it is usually wise to search the used market for injection moulds. The price can range depending on the complexity of the product and the state of the tool. The hot plastic has a slight abrasive effect, which can cause permanent damage to the dimensions of the tool. Monolithic products are generally not as critical as complex products that are made up of several components. There are no special brands for injection moulding tools.