Injection moulding processes for engineering plastics: from idea to product
Learn how the injection moulding process works with engineering plastics – from the idea to the finished component. An overview of advantages, materials, process steps and applications.
Injection moulding is one of the most important industrial manufacturing processes in plastics engineering. It enables the series production of highly precise plastic parts with complex geometries – efficiently, reproducibly and economically. The process plays to its strengths particularly in the processing of engineering plastics: high design freedom, short cycle times and excellent material properties make it the preferred choice for many industries. Whether in mechanical engineering, electrical engineering or medical technology – injection moulding provides the basis for high-performance and long-lasting plastic components.
In this article you will receive a detailed overview of the injection moulding process, the selection of engineering plastics, advantages, challenges as well as the typical steps from the first idea to series production.
What is injection moulding?
Injection moulding is a shaping manufacturing process in which a plastic is injected under high pressure into a negatively shaped tool (injection mould). After cooling, the material solidifies and can be removed as a finished component. This cycle repeats automatically and in a highly reproducible manner – ideal for medium to very high unit volumes.
The entire process is highly controllable and can be precisely adapted to the requirements of the respective plastic and the desired component geometry. A wide variety of material types, fillers and additives can be used to achieve specific properties such as stiffness, temperature resistance or chemical resistance. Even multi-component components with integrated functions can now be realised through modern injection moulding processes.
Process steps at a glance:
- Material preparation: Drying and feeding of the plastic granulate
- Plasticising: Melting in the heated screw of the injection unit
- Injection: Pressing the molten plastic into the mould
- Holding pressure phase: Pressure equalisation during solidification
- Cooling: Temperature reduction for dimensional stability
- Demoulding: Opening of the tool and ejection of the finished part
Engineering plastics in injection moulding
Engineering plastics are characterised by high mechanical strength, temperature resistance, chemical resistance and dimensional stability. They are used in demanding applications, e.g. in mechanical engineering, automotive engineering or medical technology.
Commonly used materials:
| Plastic type | Properties | Typical applications |
|---|---|---|
| POM (polyoxymethylene) | High stiffness, good sliding properties | Gears, bearings, slide rails |
| PA 6/PA 66 (polyamide) | Impact toughness, chemical resistance | Housings, connecting parts |
| PC (polycarbonate) | Impact-resistant, transparent | Medical devices, light guides |
| PBT (polybutylene terephthalate) | Good electrical properties | Connectors, sensor housings |
| PEEK (polyetheretherketone) | Extremely temperature-resistant | Aerospace, medical technology |
Advantages of injection moulding engineering plastics
Precision
The injection moulding process allows extremely accurate components with tight tolerances to be manufactured. This precision is particularly in demand for function-relevant components, such as gears, bearing housings or connecting parts in machines and devices.
Cost-effectiveness
Once the tool has been manufactured, the process enables the cost-effective production of large unit volumes. The automated process significantly reduces the production costs per part and makes injection moulding particularly economical for medium to high series sizes.
Design freedom
Complex geometries, undercuts and structured surfaces can be implemented without difficulty with injection moulding. The process allows the integration of several functions in a single component and thus reduces assembly effort and manufacturing steps.
Material efficiency
Compared with machining processes, virtually no material is wasted in injection moulding. Sprue and sprue channels can often be recycled. The low need for post-processing saves additional resources and time.
Challenges and requirements
The processing of engineering plastics places particular demands on:
- Tool technology: Hardness, cooling, demouldability
- Process control: Temperature management, holding pressure strategies
- Quality assurance: Component testing, process monitoring
In particular, shrinkage and warpage during cooling must be calculated and compensated for in advance. Modern simulation tools provide support already in the design phase.
From idea to series component: the process
- Requirements analysis: Definition of the technical, economic and regulatory framework conditions
- Material selection: Selection of a suitable engineering plastic
- Design: CAD model taking manufacturing aspects into account
- Toolmaking: Manufacture of the injection moulding tool
- Sampling: Initial production tests, tool optimisation if necessary
- Series production: Automated manufacture of the final components
FAQ
How long-lasting is an injection moulding tool? Depending on steel quality, maintenance and complexity, 100,000 to several million cycles are realistic.
How high are the entry costs? The initial costs for toolmaking are usually in the four- to five-figure euro range. They are amortised through the low unit costs for larger series.
Can engineering plastics be recycled? Yes, many engineering plastics are reusable or can be recycled by type. However, the material quality often decreases with each cycle.
When does 3D printing make sense instead of injection moulding? For small series, prototypes or geometrically particularly complex components with low mechanical requirements.
