9 Tips for Designing an Injection Moulding

A correctly designed and implemented injection moulding is a very efficient and cost-effective piece of plastic manufacturing. They allow the creation of individual parts which are identical in appearance, structure and durability. There are many different aspects to take into consideration when designing injection moulded parts to ensure that you get the best value for money, use the correct materials and protect yourself and your design.

We will now take a look at 9 tips for designing injection mouldings so that you are aware what to look out for when committing yourself to such a project.

Injection moulding machine used for the forming of plastic parts using plastic resin and polymers.

1) What is injection moulding and what can it do for your business?

Before you start the process of designing an injection mould you need to be totally clear in your own mind about the purpose, volumes, strength and durability required as well as the overall costs. In simple terms, injection moulding is the process by which a molten material is introduced at great speed into a mould. Sounds simple? Well a good moulder will be able to expand on your basic requirements and ensure that you receive excellent value for money and a product which is fit for purpose.

2) Know your budget

As with any repetitive process such as injection moulding you need to balance up what can be a significant capital investment against the volumes required and potential returns. It is therefore essential that you discuss budgets and costs as soon as possible to ensure that you are not wasting your time. Even though the cost of injection moulding has fallen with advances in technology it will still require potentially significant investment.

3) Are you using the right material?

The process of identifying the best material for your injection mould is a based on knowing exactly what you require from the end product. There is an array of different plastics available with vast differences in material properties. You need to discuss with your moulder how and where these components will be used to arrive at the right material for you.

4) Cleanliness is next to godliness

While there are many times you can repeat this particular phrase in the world of business it is a vital element of the injection moulding process. The tools need to be sterile and free of any foreign bodies especially for components used in the food or medical industries. As a consequence it is highly recommended that you visit your potential moulding company partner to inspect their premises and ensure that there is minimal chance of the structure of your component being compromised.

5) Ensure that you own the injection mould

Some companies will work with you to create your own unique injection mould to which they will hold the design rights. Unless you own the actual rights to the injection mould design your options will be significantly reduced in the future if you need to move to another provider. This sounds simple but many people have fallen into the trap of leaving everything in the hands of their component provider.

6) Avoiding stresses in your design where possible

It is vital that where possible you avoid the creation of non-rounded corners in your component design. The more pointed a corner the more stress placed on one particular area which can under certain circumstances compromise the design and durability of the product. Again, this is an area where you should work very closely with your injection mould provider and there may be a need to compromise that “perfect design”.

7) Avoid that shrinking feeling

The molten material is injected into the mould at high speeds to ensure that each cavity is filled. Many people fail to realise that inevitably there will be “shrinkage” as the material cools and this must be taken into consideration with the design. Issues such as the material used and the thickness of the outer walls will play a major role in the process which is where an initial prototype could prove priceless.

8) Avoiding drag marks

The clean ejection of the component is crucial because a badly designed injection mould can leave the end component with scuff marks or even damage to the product. Simple adjustments such as tapered sides based upon the products individual characteristics will ensure a high quality finish. It is vital that the designer understands the concept of draft angles and applies them correctly to the design of the part.

9) Getting the right finish

The surface of your plastic moulded component is also an integral part of its functionality and effectiveness. You may require a polished surface or textured surface. Again, this is something which should be discussed with the toolmaker at the earliest opportunity.

There are many different elements to consider when designing  injection mouldings from concept through to manufacture. In many cases you will have the “perfect design” in mind but you may need to compromise with regards to manufacturing constraints and material properties.

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