Plastic injection moulding is one of the most widely used manufacturing techniques for moulding plastic parts in series. In this process, you melt thermoplastic plastic and inject it under high pressure into a mould, after which a dimensionally accurate part is ejected in a matter of seconds. In this article, we explain how the injection moulding process works, which materials you can use, and when injection moulding is the right choice for your production.
How does the injection moulding process work
In plastic injection moulding, you melt thermoplastic plastic granules. An injection moulding machine transports this molten material under high pressure into a mould. This mould is a steel or aluminium die with the exact shape of the desired part. After cooling, you open the mould and eject the product. This Plastic parts production process This makes it particularly efficient and repeatable.
The process is cyclical. A cycle often lasts between five and sixty seconds, depending on the material and wall thickness. The next cycle begins immediately after. This makes injection moulding extremely efficient at higher volumes.
A manufacturer of medical devices produces thousands of identical housings per day with consistent dimensions. That speed and consistency are important reasons for choosing this process.
The role of the die
The mould determines the quality and accuracy of every product. A well-designed mould takes into account material shrinkage rates, channels for the molten plastic, and cooling channels for a stable cycle time. The investment costs for a mould are higher than for other manufacturing techniques, but these costs are spread across the entire production run.
At Eurotechniek, we work with dies built to tight tolerances. Tolerances of plus or minus 0.05 millimetres are achievable with complex parts. This is essential for parts that fit into a larger system, such as connectors, housings or mechanical couplings.
Incorrect dimensions lead to assembly problems and scrap. Good mould technology prevents this and guarantees stable production over the entire life of the mould.
Materials and their properties
Plastic injection moulding works with a wide range of thermoplastics. The choice depends on the function, the environment and the requirements for the final product. Commonly used materials include polypropylene, ABS, polyamide and polycarbonate. Each material has different shrinkage and flow properties, which affect mould design.
- Polypropylene is lightweight and chemically resistant.
- ABS has good surface quality and is easy to post-process.
- Polyamide, also known as nylon, is wear-resistant and suitable for mechanically stressed parts.
- Polycarbonate is clear and impact-resistant, ideal for housings with optical or safety requirements.
At Eurotechniek, we advise you on material selection based on function and lifespan. This way, you won't choose materials that are too heavy, but also not too light.
The 2K injection moulding process
Besides standard injection moulding, there is the 2K process, also called two-component injection moulding. This involves injecting two different plastics or colours into the same mould. The result is a product with two material layers or zones, in a single production cycle.
A handle with a hard core and a soft grip is a classic example of the 2k process. The hard core provides structural strength, while the soft layer offers grip and comfort. This eliminates additional assembly steps and improves product quality.
The 2k process requires a specific type of machine and a smarter mould design, but when applied correctly, it delivers time and cost savings in the end assembly.
When do you choose injection moulding
Injection moulding is most interesting for medium to large series. The mould costs are the largest initial investment. These costs are recovered as you produce more parts. From a few thousand pieces per year, injection moulding becomes more competitive than milling or 3D printing for many applications.
Other advantages include surface quality and repeatability. Each sprayed part has the same dimensions and appearance. This is important for quality management and for applications where visual consistency counts. Think of consumer products, medical equipment, or industrial casings.
If your product has a complex geometry with ribs, hinges, or internal channels, injection moulding is often the most logical choice.
Quality control during production
A stable injection moulding process requires constant monitoring of process parameters. Temperature, injection pressure, injection time, and cooling time are the most important variables. Even a small deviation in melt temperature can lead to sink marks, flash, or dimensional inaccuracies.
At Eurotechniek, we measure and record the critical dimensions for each production run. This way, we have traceability throughout the entire lifespan of a mould. This is not an unnecessary luxury, but a basic requirement in sectors such as automotive, medical and food safety.
We use CMM measurements and visual inspection to identify deviations early on. This keeps scrap rates low and delivery times stable.
Frequently asked questions about plastic injection moulding
Spuitgieten is een proces waarbij gesmolten materiaal onder hoge druk in een mal wordt geïnjecteerd, terwijl extrusie een proces is waarbij gesmolten materiaal door een matrijs wordt geperst om een constante doorsnede te creëren.
In injection moulding, you inject molten plastic into a closed mould. The result is a three-dimensional part with a fixed shape. In extrusion, you press plastic through an open mould, which produces a continuous profile such as a pipe, strip, or sealing profile. Injection moulding is used for individual parts, while extrusion is used for profiles by length.
How long does an injection mould last?
A steel mould will easily last for a million cycles or more with normal use. Aluminium moulds are cheaper and quicker to produce, but less durable. These are suitable for prototyping or shorter runs of up to around a hundred thousand pieces. The lifespan also depends on the material being processed, as fillers like fibreglass will wear out a mould more quickly.
Can I also have small batches injection moulded?
That's possible, but you need to factor the mould investment into the cost per piece. For small runs, aluminium tooling or a simplified mould is sometimes a better choice. At Eurotechniek, we'll discuss with you which approach best suits your volume and budget. Sometimes a hybrid approach with 3D printing for the first prototypes is the smartest route.
Injection moulding as a basis for series production
Plastic injection moulding is a mature technology with a broad scope of application. The process delivers dimensionally accurate, repeatable parts in any desired volume. The mould investment pays for itself at sufficient volumes, and the flexibility in materials and processes makes it applicable in virtually any sector.
Do you want to know if injection moulding is the right choice for your product? Contact Eurotechniek. We'll help you with material selection, mould design and batch size. This way, you'll start with a solution that's right from the outset.