Injection moulding – What are the advantages and disadvantages?

1. Efficient high production

Once you have developed the moulds, the process is extremely fast with cycle times as short as 10 seconds. It is excellent for medium and high-volume production runs for anything from 10,000 parts to well over 100,000 depending on what moulds you use. 

Sometimes you can increase production by using a multi cavity or family mould, where several parts are produced from one press to further increase the manufacturing rate.

If you are outsourcing your moulding then it’s also important to consider an efficient front-end design and order process – take a look at our on demand manufacturing.

2. Low cost per part

For high output production runs the cost per part is very low. Even for medium volumes – in the range of 10,000 to 25,000 parts, you can keep the costs down by using aluminium moulds instead of steel.

3. Repeatability

You can manufacturer identical products over and over again. This is ideal when you need to have parts with high tolerances and reliability across high volumes.

4. Large material choice

There is a huge range of plastic materials that you can select from depending on what properties you need from your final part. And you are not limited to plastic, Protolabs also offers liquid silicone rubber moulding. 

You can even use fillers in the moulding material, which adds greater strength to the completed part, and you have a huge range of colours to choose from as well. Talk to us about what you need your part to achieve – there are generally a number of different options.

5. Low waste

The injection moulding process produces very little waste when compared to many other manufacturing processes. Even if there is any unused or waste plastic, you can recycle it for future use.

6. High detail

The process involves injecting molten plastic into the mould under very high pressure. This presses the plastic hard up against the moulds allowing complex and intricate shapes plus a lot of detail.

7. Little or no post processing

Generally, you will need very little post production as the parts usually have good aesthetics post production. We can produce the tooling with a special finish which will show straight away on the moulded part. You can even have your logo or text engraved on it.

1. Initial cost

If you are committing to steel mould tools for high production volumes (100,000+) then it can take a great deal of time and machining to produce and this can be a significant capital cost. If you need lower volumes of parts then this will affect your cost per part price and it may be worth exploring other options such as using aluminium moulds instead.

2. Initial lead times

It can take up to 12 weeks to produce steel tooling. If you need to get production running before this then take a look at our on-demand production; by using aluminium moulds and digitising our front-end process we can ship anything from 25 to 10,000+ parts in 15 working days or less from the point that you first upload your CAD. Sometimes parts shipped in as little as one day.

For very low production runs there are other technologies such as 3D printing or CNC machining which could provide a more cost-effective answer more quickly.

3. Design limitations

You will need to consider certain design elements, such as:

• Using draft and radii to help ejection of the parts
• Avoiding undercuts and sharp edges
• Controlling wall thicknesses

You also need to consider where to place your gates, ejectors and cooling lines if aesthetics are important. And remember it’s also hard to change the design of a mould – you can remove part of the mould, or add plastic to your final part, but not the other way round.

For smaller production runs, 3D printing allows you to design virtually any shape or geometry that you require. As a rapidly developing technology there is an increasing number of plastic and other materials, even metal, that we can produce. 

4. Small part runs are not always cost effective

Most people think that they should only turn to injection moulding for orders of 100,000+ parts; but there are other options when you can use this process for smaller production runs.

Using more affordable aluminium moulds and quick turnaround times (as fast as a day) our on-demand service helps keep your per part cost down. It is ideal for anything between 10,000 and 25,000 parts, but can help control costs for production runs even smaller than this.

For low production runs measured in the hundreds or less then it is also worth exploring other manufacturing technologies such as 3D printing and CNC machining. With these technologies the cost per part will be lower and you will not face the initial set up costs or lead times involved in producing moulds.