What are the characteristics of injection molds?

Injection molding is a process in which a raw material is injected under high pressure into a mould to create the desired shape. Injection molds can have a single cavity or multiple cavities to produce identical or unique geometries. Most moulds are made of tool steel, but aluminium and stainless steel are also used for some applications.

There are many aspects of an injection mold that require careful attention, from gating system to temperature control. The temperature control system is an important component of the mold and involves the heating of the mold to its working temperature and maintaining it at that temperature. This feature is closely related to the gating system.

A thermoplastic's flexural modulus of elasticity is an important consideration when choosing a material for injection molding. This property determines the bendability of the material, as well as its heat deflection and water absorption. Common plastics include polyethylene, nylon, and polystyrene. Thermoplastics also include elastomers and thermosets. The number of materials available for injection molding has been growing steadily since 1995. Some of the newer ones are alloys of other materials. Choosing a material for moulding depends on the strength, function, and cost of the final product.

An injection mold's injection time is the amount of time it takes for a plastic melt to fill a cavity, excluding the time it takes to open and close the mold. Although this factor may be of little importance in determining the time needed to produce a plastic part, it can be used to predict the overall length of a plastic part's forming cycle. A well-controlled injection time contributes to improving surface quality and reducing dimensional tolerance.

Another important aspect of an injection mold is its heat output. A high temperature can cause melting to occur. Injection speed can also cause jetting, which occurs when the polymer melt flows in a restrictive area. High injection speed and a poorly designed gate can also lead to jetting. Furthermore, a lack of holding pressure can cause the part to become uneven or too thin.

Injection molding can be done by hand or by machine. With this process, a raw material is fed into a heated barrel that has a reciprocating screw. The temperature inside the barrel is regulated by the gate. The plastic part is kept under pressure for a certain amount of time, ranging from a few milliseconds to several minutes. During this time, a clamp is used to prevent plastic from escaping the tool.

Another characteristic of injection molds is their ability to produce different parts with different materials. They are also designed to produce multiple copies of the same part, and the process of insert moulding allows multiple variations to be produced from one mould. The molds are often used for making plastic parts with fastening screws or protruding metals. In-mould labelling is also a common feature of this process. Injection molds can also have film lids attached to them.