What are Plastic Injection Moulding Advantages and Disadvantages ?

Plastic injection moulding advantages centre around great precision and high repeatability, combined with speed, a low cost per part and a huge choice of available plastics. Disadvantages include a higher initial cost and lead time than some other processes.

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Plastic Moulding Advantages

1. Precision

Plastic injection moulding is perfect for very intricate parts. Compared to other techniques, moulding allows you to incorporate more features at very small tolerances. Have a look at the image to the right. You can hold this moulding in the palm of your hand and it has bosses, ribs, metal inserts, side cores and holes made with a sliding shut off feature in the tool. That's an awful lot of features on a small part! It would be impractical to make using plastic fabrication and impossible to make using the vacuum forming process.

2. High repeatability

Once your mould tool is made, identical products can be made over and over again. And again. A decently made mould tool has a very long mould tool life, as long as it's treated well by the moulding machine setters !

3. Low cost per part

Whilst there is an initial high investment for the plastic injection moulding tool, after that the cost per part is very low. Other plastic processing techniques may require multiple operations, like polishing, whilst injection moulding can do it all at once. If you chose to CNC machine the part above, it would cost hundreds of pounds per part. If you're looking to go into full production, injection moulding is the way to go.

4. Fast

Cycle times can be as low as 10 seconds. Combine that with a multi-impression injection moulding tool and you get a LOT of products very quickly. That part above takes a bit longer as it's a specialist material and has a lot of features to be moulded correctly, but at about 50 seconds you'd still get 70 parts per cavity per hour. CNC machining a one-off would take half a day - 3D printing it even longer!

5. Material choice

There's a vast amount of materials available for plastic injection moulding. A range of more common materials, but also things like antistatic plastic, thermoplastic rubber, chemical resistant plastics, infrared, biocompostable...and with colour compounding or masterbatch colouring you have an endless choice of colours as well. The moulding above is boring black, but it's made out of PPO - poly(phenylene oxide) - which is an extremely rigid and flame-retardant material.

6. Special Surface Finishes, Engraving & Printing

In addition to a range of colours, the injection moulding tool can be made with a special finish which will show on the moulding. Just about any finish you like, for example leather look, soft touch, sparked, high shine, you name it. You can also have logos or other text engraved in the tool. Finally, you can have your mouldings printed, as a range of inks are available that will print well on plastic.

7. Little plastic waste

Part repeatability is very high for injection moulding. Even the sprues and runners (the leftover bits of plastic created by the 'tunnels' through which the plastic material reaches the actual mould) can be reground and the material reused. You can explore this in more detail on our environmental impact of injection moulding page.

Plastic Moulding Disadvantages

Sounds amazing doesn't it ? Of course there are also some disadvantages:

1. High Initial Cost

Often, several rounds of designing and modelling are needed before the go-ahead or production is given. Then, the injection moulding tool needed to make the mouldings will need designing & manufacturing. The mould tool is an intricate piece of work which costs manpower, material and many machining hours to make and represents the largest cost in getting injection mouldings. Of course, once it's all done, part cost is very low and repeatability very high for hundreds of thousands of mouldings.

2. Initial lead time

From product conception to final part can take months of design, testing and tool manufacturing. That said, if you know what you want, you can have the finished mouldings within 6 weeks. (Toolcraft's Chinese Mould Tools Flowchart shows how that could work). And as mentioned under advantages, once the tool exists, it takes very little time to run the mouldings, especially when you have a multi-impression mould tool. (Here's a list of Mould Tool Types).

3. Large Part Size Limitations

Huge machines are needed to make plastic injection mouldings. Very large parts need an enormous mould tool and become very expensive to make, in which case a process like Plastic Fabrication may be a better choice, depending on the tye of product needed.

4. Careful design needed

Plastic mouldings need very careful design to avoid tooling issues like undercuts (which will send up tooling cost significantly), locked-in features and not enough draft (What Draft Angles for Plastic Mouldings ?). The material and temperature will need to be taken into account in wall design, otherwise the mould may not fill fully. The placement of ejectors and cooling lines will need to be considered to ensure the product is aesthetically pleasing.

Should I choose plastic moulding for my product ?

Well, it depends on so many factors: design considerations, material, size, quantities needed, your budget. An expert will have to assess each product idea to decide the most effective and economically viable way of manufacturing it.

Toolcraft offer plastic injection moulding, vacuum forming and plastic fabrication, including a range of finishing, printing & packing services. Our longstanding experience allows us to help you choose the best manufacturing process for your new project. We also share our knowledge on our plastic moulding advice pages. Or just:

When manufacturing a product, you have a few different options on how to produce your item… one of the most popular choices is injection moulding.

There are plenty of great reasons to use plastic injection moulding and at Dienamics, we know firsthand how beneficial this technique can be. 

However, you should always have the complete picture before diving right into a decision. That’s why we’ve broken down the good and the bad of injection moulding so you know exactly what’s in store. 

Advantages of Injection Moulding

Speed and Efficiency

When it comes to mass production, efficiency is key. Injection moulding is an especially beneficial way of creating products when you have to churn out a high volume. 

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 The rate of production does vary depending on the machine, but they all produce an impressive amount per hour. With injection moulding, you’re talking seconds to make a product, not minutes or hours.  

Complete Flexibility

Regardless of the complexity of your product you will have complete control and flexibility when it comes to the design of your product. 

 Additionally, injection moulding allows for a range of different types of plastics and colours to be used to create your item, meaning you can customise it all to obtain your desired result.

Consistency

In comparison to other production techniques, injection moulding is second to none for its 

consistency. Every part produced is replicated on every turn, which is a huge advantage when it comes to mass production and ensuring quality control. 

 It also doesn’t matter how simple or complex your design is either – if your tooling is built quality and correctly, your parts will be quality and correct.  

 Less Waste

Being environmentally conscious is becoming more and more important for brands, and a great thing about injection moulding is that it’s in line with these values. 

Injection moulding produces very little excess waste. At Dienamics, all of our injection moulding machines are fitted with robotic arms that pick the sprue from the part once it is moulded, and then drop it into a plastic granulator where it is reground, and then it is recycled back into the hopper to be re-injected. This means that even the small amount of waste can be recycled and reused.  

Low Cost

As injection moulding technology is automated, you’ll be saving a significant amount when it comes to labour cost. All mechanics and robotics can be controlled by a single operator…

Essentially, you can just set and forget! 

Disadvantages of Injection Moulding

Up Front Expenses

Initially, injection moulding can be pricey due to the upfront costs of the injection mould tooling required.  

 Injection moulds are incredibly involved steel tools, with heating, cooling, ejection, and injection systems. However, for this upfront cost, you get a mould that can run consistently for a long life span producing parts very quickly and cheaply. The moulds we make for customers are built to last 1 million cycles.  

 While tooling is the most significant cost in the process, Dienamics can assist in this process and offer a great price.  

 

Not Ideal For Low Volume Production

Realistically, injection moulding is not suitable for low volume products. It isn’t really economical to put in the work to create the mould, only to make a few of the parts. 

Ideally, injection moulding should be used for mass production. 

Think Injection Moulding Is The Right Option For You?

If you are considering injection moulding for your product, the expert team at Dienamics can give you all the information you need to make your decision and get started. Contact us today!

Contact us to discuss your requirements of 2k shot injection molding. Our experienced sales team can help you identify the options that best suit your needs.