Injection moulding :: Leomuovi Group


Injection moulding is the most common manufacturing method for plastic products. It is best suited for series with stringent dimension requirements exceeding one thousand pieces. Our largest injection moulding product weighs 25 kilograms.


Our injection moulding equipment ranges from our smallest 35-tonne machine to our robust 1600-tonne injection moulding giant. We can manufacture products from one gram to 25 kilograms.

Injection moulding is the most used manufacturing method for plastic and combination plastic-other material items. The products are moulded on injection machines with an automated production line.

Injection moulding is best suited for manufacturing more than one thousand pieces batches. The method is suitable for making products with stringent dimension requirements, and the result is clean-cut and hardly needs post-processing. The benefits of injection molding are the production speed and the high quality of the manufactured product. The raw materials mainly used are thermoplastics (meltable again), but the method is also suitable for working with single-use plastics like thermosets.


Advantages of injection moulding: small changes, significant impact

The injection moulding process is mainly automated nowadays. However, manufacturing high-quality, cost-effective plastic parts requires solid experience and versatile know-how in operating the machines and processing different polymer grades. Moreover, slight differences in injection speed or temperature can significantly impact productivity, part durability, strength and resistance. Leomuovi’s team has the skills and experience to operate our modern production machinery, guarantee high product quality, and thus achieve long-lasting customer satisfaction.


Injection moulding machines – making the moulding possible

Plastic injection moulding is carried out using modern and effective equipment - the most essential device being the injection machine. It is divided into  injection and clamping areas with five system units: the feeding hopper, the screw with the injection valves, the hydraulic clamping part, and the control panel. Each of these units has an important role in the production process. In addition to the machines, a unique, product-specific tool is needed to manufacture the plastic part. Thus, every component has its mould that is fixed on the machine. Once the tool is on, production can begin.

1. Plasticisation

The raw material must be melted or plasticised to be injected into the mould using pressure, friction, and heat. During plasticisation, the screw unit turns the polymer pellets into a melt and maintains a specific temperature evenly. The melted mass should also reach an even distribution of the colourant and the other additives. This phase is important for the raw material to retain its original properties throughout the injection moulding process.

2. Injection

Once the raw material has achieved the desired temperature, it is injected into the mould. Around 95% of the mould cavity’s volume is filled during this phase. The injection can last from approx. 0.1 seconds to a few seconds – depending on the manufactured piece's thickness, size, and shape. In the subsequent pressure-holding phase, the mould cavities are filled to full. The holding should last long enough to prevent unevenness, bubbles, or other moulding defects from forming on the plastic part surface.

3. Cooling

Cooling is the most extended phase in injection moulding. The melt begins to cool down already during injection as the melted plastic fills the cavities. The cooling process continues further during the pressure holding for the piece to retain its shape and size and avoid deformities. The part is only ejected from the tool after it has hardened sufficiently and the risk of deformation has decreased. This process is often aided by cooling the mould with water.

4. Ejection of the ready part

The part moulding process ends with the opening of the tool and the ejection of the parts either straight into the packaging box or their removal from the tool with the help of a robot and placement on a conveyor belt for further handling or packaging.

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