Real comparison: Injection moulding or 3D printing, what suits your project?

Injection moulding vs 3D printing: What I learned from working with companies in different industries

In recent years, 3D printing has revolutionised the way we design and manufacture parts. However, plastic injection moulding is still a key method in a huge number of industry sectors. Having worked with companies in fields as diverse as automotive, healthcare, architecture, industrial design and energy, I have seen first-hand how each technology has its place. So, in this article, I want to help you understand the differences, advantages and limitations of the injection moulding and the 3D printing, and, above all, when to choose one or the other.

What is injection moulding?

Plastic injection moulding is an industrial process that involves melting a plastic material and moulding it under pressure into a metal mould. After cooling, the material solidifies and produces identical serial parts.

It is a well-established technique and widely used in sectors such as automotive, consumer electronics, packaging and medicine. Its great value lies in the mass production of parts with high precision and repeatability.

Advantages of injection moulding

Injection moulding is known for its efficiency and ability to produce identical parts in large quantities. Throughout my experience with different industries, I have seen how this technique is indispensable for projects where consistency and unit cost are critical.

1. High volumes at low unit costfrom a certain volume of production, the cost per part decreases significantly.
2. Repeatability and consistencyThe key is that all parts come out identical, which is key in regulated sectors.
3. Wide range of plastic materials: strength, flexibility, transparency, etc.
4. Speed in mass productionOnce the mould is created, the process is very fast.

Disadvantages of injection moulding

Although grouting is a well-established technique, it is not without its limitations. Understanding these limitations allows for better project planning and the avoidance of unnecessary costs.

1. High initial costMoulds are expensive and require a significant initial investment.
2. Inelastic to changeany modification involves remaking the mould.
3. Not cost-effective in small seriesif only a few units are needed, the costs do not pay off.

What is 3D printing?

3D printing, or additive manufacturing, is a process in which a part is built up layer by layer from a digital design. There are different technologies (FDM, SLS, SLA, among others) and a wide variety of materials: plastics, resins, metals and even composites.

The most interesting thing about 3D printing is its flexibility and customisability, This allows us to manufacture from prototypes to short series, without the need for moulds or tooling.

Advantages of 3D printing

3D printing offers a world of possibilities, especially when you need to experiment with designs, reduce time or customise parts. Throughout my experience working with companies in different sectors, I have seen how these advantages can make a difference in the development phase of a product.

1. Rapid prototypingideal for validating designs prior to mass production.
2. Flexibility and customisation: unique or customised pieces without making them too expensive.
3. Reduction of development timesfrom design to physical object in a matter of hours or days.
4. Production on demandno need for large stocks or moulds.
5. Complex geometriesallows parts to be manufactured that would be impossible to produce using traditional methods.

Disadvantages of 3D printing

Like any technology, 3D printing also has limitations that you should be aware of before deciding how to manufacture a part. Identifying these disadvantages from the outset avoids unnecessary delays and costs.

1. Higher unit cost in large volumesis not competitive with injection moulding when producing thousands or millions of parts.
2. Material limitationsAlthough there are more and more options, the range is still smaller than in fuel injection.
3. Longer production times in large series.
4. Variable finishes and resistanceDepending on the technology and material, the quality may be inferior to injection moulding.

Tip: When to choose injection moulding or 3D printing?

The choice between injection moulding and 3D printing depends on several factors such as production volume, part complexity and time available. Here are a few of them case studies to decide which method to use.

Cases in which injection should be chosen

• Mass production of standardised partsInjection moulding: Mobile phone housings or automotive components benefit from the repeatability and consistency that injection moulding offers.
• Projects where cost per piece is key: When thousands of units are produced, the investment in moulds is quickly amortised.
• Regulated environments: Sectors such as healthcare and electronics require each part to meet strict quality and consistency standards, something that injection moulding guarantees.

Cases in which 3D printing should be chosen

3D printing stands out for its flexibility and speed, especially in development phases or when unique parts are required:

• Functional prototypes: It allows validation of design, ergonomics or assembly before going into mass production, saving time and resources.
• Short or customised series: For example, patient-tailored medical devices or unique components that do not justify the creation of a mould.
• Parts with complex geometries: 3D printing makes it possible to manufacture structures that would be impossible or too costly to produce by injection moulding.
• Projects under development: When the design can still change, 3D printing offers the flexibility to modify parts quickly without additional mould costs.

Injection moulding vs. 3D printing: Quick comparison

In short, when to choose one or the other? 

In my experience working with companies in different sectors, I always recommend looking at three key factors before deciding:

1. Production volumeIf we are talking about thousands of parts, injection moulding is more cost-effective; if there are only a few, 3D printing is more cost-effective.
2. Development time3D printing is the way to go if you need speed and flexibility.
3. Level of personalisationif the product requires frequent adaptations, 3D printing offers more freedom.

In fact, many companies combine the two technologies: they use the 3D printing for prototyping and validate, and once the final product has been defined, they move on to the injection for mass production.

The balance between the two technologies: discover which is best for your project

There is no universally “best” method. It all depends on your project, your budget, the volume you need and the development timeframe. The important thing is to understand that both injection moulding and 3D printing are complementary, The use of these technologies can reduce costs, accelerate time-to-market and improve the quality of the final product.

In Additium 3D we have accompanied companies from different sectors in this decision-making process, advising you according to your specific needs. If you are considering manufacturing a part or product and do not know whether to opt for injection moulding or 3D printing, contact us. We will be happy to analyse your case and recommend the best solution to make your project a success.