Frequently Asked Questions

What are the advantages and disadvantages of injection moulding?

Injection moulding is one of the most commonly used methods of producing identical plastic products in high volumes. 

As a result, one might be fooled into thinking it must be simple to get a product to market through this avenue. However, as with every process, it is important to understand the specific design restrictions that must be adhered to in order to facilitate the obvious benefits of successfully producing cost effective, high quality parts. 

To help, we have very simply laid out the advantages and disadvantages to consider. Injection moulding

Please be aware, however, that the following guidelines apply to what we would consider to be conventional injection moulding (quantities of 100,000+) and may appear at first glance to be fairly prohibitive if you are looking to develop a product with numbers out of this norm. 

Low volume production possibilities

The good news is Plunkett Associates have spent many years developing strategies and techniques in order to take away some of the issues identified below, particularly for parts that would traditionally be considered too difficult or unusual to mould.

In addition, we are specialists in making injection moulding far more cost effective for much lower quantities of parts than is more commonly expected.Using a hybrid of techniques, our low volume production tooling allows us to customise to client/geometry/quantities. The result is a mould tool that reflects the requirement and opens up an exciting option to produce high quality, yet low volume components.

As an ISO:9001:2015 Quality System certified supplier, we are confident we can help with your requirements so please feel free to give us a call.  

Advantages of injection moulding

1) Fast production and highly efficient. Injection moulding can produce an incredible amount of parts per hour. Speed depends on the complexity and size of the mould, anywhere between 15-120 seconds per cycle time.Injection moulding

2) Low labour costs. Plastic injection moulding is an automated process whereby a majority of the process is performed by machines and robotics, which a sole operator can control and manage. Automation helps to reduce manufacturing costs, as the overheads are significantly reduced.

3) Design flexibility. The moulds themselves are subjected to extremely high pressure. As a result, the plastic within the moulds is pressed harder and allows for a large amount of detail to be imprinted onto the part and for complex or intricate shapes to be manufactured.

4) High-output production. Thousands of parts can be produced before the tooling needs to be maintained.

5) Large material choice. There is a large selection of polymer resins to choose from. Multiple plastic materials can also be used simultaneously; for example, TPE can be overmoulded onto PP parts.

6) Low scrap rates. Injection moulding produces very little post-production scrap relative to traditional manufacturing processes. Any waste plastic typically comes from the sprue and runners. Any unused or waste plastic, however, can be reground and recycled for future use.

7) Ability to include inserts.  Metal or plastic inserts can be insert moulded. Injcetion moulding

8) Good colour control. Plastic parts can be manufactured in any required colours with the use of masterbatches or compounding.

9) Product consistency. Injection Moulding is a repeatable process, in other wordsthe second part you produce is going to be identical to the first one etc. This is a huge advantage when trying to produce high tolerances and part reliability in high volumes.

10) Reduced finishing requirements. There is often very little post-production work required as parts usually have a good finished look upon ejection.

11) Enhanced Strength. When plastic injection moulding, it is possible to use fillers in the moulding material. These fillers reduce the density of the plastic whilst it is being moulded, and can help add greater strength to the completed part. 

Disadvantages of injection moulding

1) High tooling costs and long set up lead times. Up front costs are high due to the design, testing, and tooling required. There is the initial design and prototyping (probably via CNC or 3D printing), then the design of a prototype mould tool to produce replicas of the part in volume. Lastly, and only after extensive testing during both stages, you can finally injection mould a part. 

2) Part design restrictions. Plastic parts must be designed with injection moulding consideration and must follow the basic rules of injection moulding, for example: 

  • Avoid under cuts and sharp edges as much as possible 
  • Use uniform wall thicknesses to prevent inconsistencies in the cooling process resulting in defects like sink marks. 
  • Draft angles are encouraged for better de-moulding. Injection moulding

Don’t forget, because tools are typically made from steel or aluminum, it can be difficult to make design changes. If you need to add plastic to the part you can make the tool cavity larger by cutting away steel or aluminum. But in order to take away plastic, you need to decrease the size of the tool cavity by adding aluminum or metal to it. This is extremely difficult and in many cases might mean scrapping the tool (or part of it) and starting over.

In addition, the weight and size of the part will determine the tool size and necessary press size. The larger the part, the more difficult and expensive it will be. 

3) Small runs of parts can be costly. Due to the complexity of tooling, and the necessity to rid the machine of all previous material before the next product can be made, setup time can be quite lengthy. Therefore small runs of parts have traditionally always been thought of as too expensive to injection mould.

In summary 

Injection moulding is a great process! The range of materials and colours is huge and there is no “abs like’ that we get in 3D Printing, its the real thing. Parts are repeatable and tight tolerance. The only potential downside is the tooling, but as we said at the beginning of this article, we’ve got that covered, with options to suit most requirements. 

  • “Plunkett Associates have excellent breadth of experience, work with high quality partners and have a flexibility that we have found enables challenges to be met successfully, cost effectively and in a timely manner.”
    Nick Skaer, CEO, Orthox Ltd
  • Plunkett associates always find a solution. Whatever we need to prototype, they have a great grasp on the technologies available, costs and lead-times so we get the right solution tailored to the project needs. Have always delivered and never let us down.
    Naim Audio
  • “I can’t recommend Tim and his team highly enough. We ended up with a design which can be produced and assembled quickly, efficiently and reliably, in volumes that make sense”
    Simon Leggett, Director, Olivewood Technology
  • "Tim's experience, expertise and supplier base have been fundamental to us getting this project off the ground."
    Sam Pearce, Jelly Products Ltd
  • “We were really surprised at how quickly they turned round such a high quality prototype and the parts certainly proved their worth. They were of high enough quality to provide a fantastic visual representation and to undergo rigorous testing."
    Stuart Wilson, Design Director, TRT Lighting
  • “Accuracy, finish and delivery all first class.”
    Andrew Peters, JMDA Ltd
  • “We use Plunkett Associates because we want someone we can trust, that knows what they’re talking about, has all the contacts, will provide reliable advice and feedback and will get the right result for us.”
    Jim Copestick. Design Manager, Thorlux Lighting
  • “We always know exactly what we’re getting and we know we won’t be let down on quality, price or lead times.”
    Mark Williams, Research and Development Director, Johnson Safety Products
  • “Plunkett Associates truly offer a complete turnkey solution with Speed, Effectiveness and Precision.”
    David Harden, Director, Enica Ltd
  • “Kirintec were thrilled with Plunketts. They made a complex process simple and we were just amazed at the lead times achieved. Plus, every single deadline was met without any drama.”
    Penny While, Marketing Director, Kirintec
  • “Thanks to Plunkett Associates flexible, bespoke and cost effective service I was able to produce the objects that I had originally had in mind.”
    Simon Ryder, Artist
  • To create such a consistent quality finish in chrome was an amazing achievement and the prototypes really gave our stand the wow factor.
    James Clark, Group Commercial Director, The Airdri Group
  • Interestingly, people who look at it in its own right with little knowledge of what it does, just like it! It’s tactile and it looks good…
    Tim Collings, Operations Director, Troika Systems Ltd
  • "With their simple to understand language, willingness to go the extra mile and approachability, Plunkett Associates were a great partner for our company. We couldn’t be happier with the results of our project. (A working prototype that they got right first time, by the way). Thank you!"
    Carolina Ballon-Forrester, Director, Kittyrama Ltd
  • Plunkett Associates worked on the design and production of titanium frames for an artificial heart valve where precision and consistency was paramount. Communications were efficient and productive with concepts readily incorporated into the final design, and suggestions for improvements all highly appropriate. The quality of the end product was ideal and I have no doubt that I will use the advice and expertise of Plunkett Associates again.
    David Wheatley, Wheatley Research Ltd
  • “Thanks for the present that arrived this morning, as promised. Parts look first class, as always.”
    Jon Todd, Design Manager, PHS Group
  • “Plunkett Associates have a fantastic supply chain, work with all sorts of production processes and will always do their utmost to solve a problem.”
    Naim Audio
  • “ Plunketts developed a solution that met our precision requirements at a cost significantly lower than alternative manufacturing approaches we had investigated”
    Nick Skaer, CEO, Orthox Ltd
  • “Doing business with you has been an absolute pleasure. You have made my goals a reality. You have been patient, helpful and above all, responsive. Best service that I have experienced in ages. I consider Plunkett Associates to be an integral part of my business plan moving forward.”
    Jet Cooper, Sculptor

Read more expert articles in our FAQ section where we discuss topics on materials, methods and products.

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  • “Plunkett Associates have excellent breadth of experience, work with high quality partners and have a flexibility that we have found enables challenges to be met successfully, cost effectively and in a timely manner.”
    Nick Skaer, CEO, Orthox Ltd
    Nick Skaer, CEO, Orthox Ltd
  • Plunkett associates always find a solution. Whatever we need to prototype, they have a great grasp on the technologies available, costs and lead-times so we get the right solution tailored to the project needs. Have always delivered and never let us down.
    Naim Audio
    Naim Audio
  • “I can’t recommend Tim and his team highly enough. We ended up with a design which can be produced and assembled quickly, efficiently and reliably, in volumes that make sense”
    Simon Leggett, Director, Olivewood Technology
    Simon Leggett, Director,  Olivewood Technology
  • "Tim's experience, expertise and supplier base have been fundamental to us getting this project off the ground."
    Sam Pearce, Jelly Products Ltd
    Sam Pearce, Jelly Products Ltd
  • “We were really surprised at how quickly they turned round such a high quality prototype and the parts certainly proved their worth. They were of high enough quality to provide a fantastic visual representation and to undergo rigorous testing."
    Stuart Wilson, Design Director, TRT Lighting
    Stuart Wilson, Design Director, TRT Lighting
  • “Accuracy, finish and delivery all first class.”
    Andrew Peters, JMDA Ltd
    Andrew Peters, JMDA Ltd
  • “We use Plunkett Associates because we want someone we can trust, that knows what they’re talking about, has all the contacts, will provide reliable advice and feedback and will get the right result for us.”
    Jim Copestick. Design Manager, Thorlux Lighting
    Jim Copestick. Design Manager, Thorlux Lighting
  • “We always know exactly what we’re getting and we know we won’t be let down on quality, price or lead times.”
    Mark Williams, Research and Development Director, Johnson Safety Products
    Mark Williams, Research and Development Director, Johnson Safety Products
  • “Plunkett Associates truly offer a complete turnkey solution with Speed, Effectiveness and Precision.”
    David Harden, Director, Enica Ltd
    David Harden, Director, Enica Ltd
  • “Kirintec were thrilled with Plunketts. They made a complex process simple and we were just amazed at the lead times achieved. Plus, every single deadline was met without any drama.”
    Penny While, Marketing Director, Kirintec
    Penny While, Marketing Director, Kirintec
  • “Thanks to Plunkett Associates flexible, bespoke and cost effective service I was able to produce the objects that I had originally had in mind.”
    Simon Ryder, Artist
    Simon Ryder, Artist
  • To create such a consistent quality finish in chrome was an amazing achievement and the prototypes really gave our stand the wow factor.
    James Clark, Group Commercial Director, The Airdri Group
    James Clark, Group Commercial Director, The Airdri Group
  • Interestingly, people who look at it in its own right with little knowledge of what it does, just like it! It’s tactile and it looks good…
    Tim Collings, Operations Director, Troika Systems Ltd
    Tim Collings, Operations Director, Troika Systems Ltd
  • "With their simple to understand language, willingness to go the extra mile and approachability, Plunkett Associates were a great partner for our company. We couldn’t be happier with the results of our project. (A working prototype that they got right first time, by the way). Thank you!"
    Carolina Ballon-Forrester, Director, Kittyrama Ltd
    Carolina Ballon-Forrester, Director, Kittyrama Ltd
  • Plunkett Associates worked on the design and production of titanium frames for an artificial heart valve where precision and consistency was paramount. Communications were efficient and productive with concepts readily incorporated into the final design, and suggestions for improvements all highly appropriate. The quality of the end product was ideal and I have no doubt that I will use the advice and expertise of Plunkett Associates again.
    David Wheatley, Wheatley Research Ltd
    David Wheatley, Wheatley Research Ltd
  • “Thanks for the present that arrived this morning, as promised. Parts look first class, as always.”
    Jon Todd, Design Manager, PHS Group
    Jon Todd, Design Manager, PHS Group
  • “Plunkett Associates have a fantastic supply chain, work with all sorts of production processes and will always do their utmost to solve a problem.”
    Naim Audio
    Naim Audio
  • “ Plunketts developed a solution that met our precision requirements at a cost significantly lower than alternative manufacturing approaches we had investigated”
    Nick Skaer, CEO, Orthox Ltd
    Nick Skaer, CEO, Orthox Ltd
  • “Doing business with you has been an absolute pleasure. You have made my goals a reality. You have been patient, helpful and above all, responsive. Best service that I have experienced in ages. I consider Plunkett Associates to be an integral part of my business plan moving forward.”
    Jet Cooper, Sculptor
    Jet Cooper, Sculptor