What are moulds?

Have you ever wondered what moulds are and why they are essential to injection moulding? We’re happy to tell you more about injection moulds, the different types of moulds, and how moulds work.

Injection mould

Moulds are used for injection moulding. Injection moulding can’t be done without an injection mould. A mould consists of two steel parts with a cavity between them. The cavity is the reverse, the negative, of the final product. Injection moulds can also be made from aluminium or another metal. At Wicro Plastics, our standard material is high-quality Western European steel. The specific type depends on the raw material used for the product, and the annual volume required.

Each of the two parts of the injection mould has a different shape and function. One part is the injection side (front mould) and the second part is the ejection side. The injection side is fixed to the machine and the ejection side moves during the cycle of each product. Each product or component has its own unique injection mould.

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Different types of moulds

To answer the question of what a mould is, you also need to explain the different types of moulds. In the previous paragraph we mentioned the different types of materials that can be used for an injection mould. In addition, an injection mould can be either single or multiple. A single mould has a single cavity in it and can produce one product every 15-60 seconds (within one cycle). A multiple cavity mould has several cavities in one injection mould. A multiple cavity mould can sometimes produce dozens of products or components simultaneously, in one injection moulding cycle. The number of cavities in a single injection mould is known as the mould’s multiplicity. A mould’s multiplicity is determined on the basis of annual volume and cycle time.

A multiple cavity mould contains several product cavities, which are injected separately. Inserts (both single and multiple) can be added too. These can do things such as embed a name, logo or time stamp in a product, for example.

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How does a mould work?

A mould essentially consists of an injection side and ejection side, but in reality a mould has much more than that. For example it has an ejection system (to eject the product), a safety device (so the mould isn’t pressed closed when there’s something in it that shouldn’t be there), and an air outlet for venting during each cycle. An injection mould is, in combination with an injection moulding machine, an advanced piece of technology with many features that operate in parallel.

Every 15-60 seconds, all these features are called on to inject, cool and eject a product. Each injection, up to and including ejection, is referred to as one injection moulding cycle. The plastic is injected under high pressure. This can be done with cold runner or hot runner systems. The product cavity is extremely precise and is created when the injection and ejection sides of the mould are pressed against each other. Due to the cold mould, the hot mass of liquid plastic solidifies in 15-60 seconds (depending on the thickness of the wall). The two halves of the mould are opened by the clamping unit and the hardened and cooled product or component is ejected.

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Want to know more about molds?

Together we look at the possibilities for mold construction. We are happy to inspire you with our references and show you around our injection molding plant in Kessel. Will I see you soon?
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Theo Wulms

Process Engineer
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