If you ask an injection moulding company how much a plastic component will cost, there is rarely a useful answer without knowing quite a bit more about the project.
Two components that look similar can have very different production costs. Equally, two mould tools producing the same component can result in very different part prices depending on how the tooling and production process have been designed.
The cost of an injection moulded part is influenced by a combination of factors including:
- Plastic material
- Component weight
- Moulding cycle time
- Machine size
- Number of mould cavities
- Production volume
- Labour and automation
- Scrap and material waste
- Inspection requirements
- Assembly and secondary operations
- Packaging
- Mould tool cost and expected tool life
The important point is that none of these should really be considered in isolation.
A more expensive mould tool might produce a significantly cheaper component. A cheaper material might require a longer moulding cycle. Adding another cavity could increase tooling investment but halve the number of moulding cycles needed to produce an order.
The right answer depends on the complete manufacturing requirement.
How much does the plastic material affect injection moulding cost?
Material is one of the most obvious parts of the component price.
Every moulded part contains a certain weight of polymer, along with potentially some additional material in runners or sprues depending on the tooling arrangement.
Different plastics can vary considerably in price. A widely used commercial polymer can cost substantially less per kilogram than a specialist engineering material designed for high temperatures, chemical resistance, flame retardancy or demanding mechanical applications.
However, simply choosing the cheapest polymer is rarely the right way to reduce component cost.
The material has to perform properly in the finished product.
- Processing temperature
- Mould temperature
- Cooling requirements
- Shrinkage
- Tool wear
- Surface finish
- Moulding stability
- Cycle time
This is why material cost and moulding cost need to be considered together.
Why does component weight matter?
The more plastic in the component, the greater the material cost.
That sounds obvious, but product design can have a significant influence here.
A thick-walled component may contain far more polymer than necessary. In some cases, ribs or other structural features can provide the required stiffness without simply increasing wall thickness.
Reducing unnecessary material can therefore create two savings. First, less polymer is purchased for every component. Second, thinner and more consistent wall sections may cool faster, which can reduce the moulding cycle.
That becomes increasingly important as production volumes rise.
Why is cycle time so important?
Cycle time is the amount of time required to complete one moulding cycle.
That typically includes closing the mould, injecting the material, holding pressure where required, cooling the component sufficiently, opening the mould and ejecting the finished part.
If a component takes 20 seconds to mould instead of 40 seconds, the same machine can potentially produce roughly twice as many cycles over the same period.
That difference matters because part of the component price is effectively paying for machine time.
On a run of 1,000 components, a few additional seconds may have a relatively modest effect. Across hundreds of thousands or millions of parts, those seconds can represent a considerable amount of production capacity.
This is one reason Dudley Associates looks at component design, material, tooling and processing together rather than simply trying to run the machine as quickly as possible.
The objective is a stable, repeatable and commercially sensible cycle, not simply the shortest possible cycle.
What affects injection moulding cycle time?
Cooling is often a major part of the overall moulding cycle.
A thick component generally contains more heat and takes longer to cool sufficiently for safe ejection. The material being processed, the design of the component and the cooling system within the mould tool can all affect this.
Ejection matters too. A component that is difficult to release from the tool may require additional time, more complicated tooling or slower machine movements.
So when a supplier suggests a product-design change that reduces wall thickness or makes ejection easier, the benefit may extend far beyond the mould tool itself. It can influence the price of every component produced afterwards.
How does moulding machine size affect the component price?
Not every injection moulded component can be produced on the same size machine.
The mould tool must physically fit within the machine, but the required clamp force and shot capacity also need to suit the component and material.
A larger machine generally represents a greater manufacturing resource than a small machine. If a part can be moulded reliably on an appropriately sized machine, there is little commercial advantage in unnecessarily using a much larger press.
This is one reason an injection moulder needs to understand the proposed mould tool as well as the component itself. Machine selection forms part of the overall production strategy.
How does the number of cavities affect injection moulding cost?
A mould tool can produce one component per cycle or, where appropriate, several.
A single-cavity tool produces one part every time the mould opens. A four-cavity tool could potentially produce four identical parts during the same cycle.
That can dramatically reduce the amount of machine time required per component.
But there is a trade-off. A multi-cavity mould is generally more complicated and expensive to manufacture than a simple single-cavity tool.
That creates an important commercial question: Is it better to spend more on the mould tool to reduce the eventual part price?
The answer depends heavily on production volume.
Why does production volume change the calculation?
Imagine two tooling options.
Tool A costs £10,000 less to manufacture but produces one component per cycle. Tool B costs an additional £10,000 but produces several components per cycle and reduces the repeat-part price.
If you only expect to manufacture 2,000 components, the extra £10,000 tooling investment represents £5 for every component before the moulding process has even started.
Across one million components, the same £10,000 represents only one penny per part. That completely changes the economics.
For shorter production runs, controlling tooling investment may therefore be more valuable than chasing every possible saving in cycle time or unit price. For long production runs, investing more heavily in tooling, cooling, automation or additional cavities can make very good commercial sense.
There is no universal ‘cheapest tool’. There is only the tooling strategy that makes the most sense for the expected production requirement.
How is mould tool cost reflected in the part price?
This depends on how the commercial arrangement is structured.
A customer may purchase the mould tool separately and then pay a repeat component price for production. In other cases, the tooling investment may effectively be considered across the expected production volume when evaluating the true cost of each component.
This is often referred to as tooling amortisation.
For example, if a mould costs £20,000 and is only ever used to produce 5,000 components, the tooling investment represents £4 per component before moulding costs are considered. If the same tooling investment supports 500,000 components, it represents 4p per component.
This is why comparing part prices without considering tooling investment and lifetime volume can be misleading.
Does labour affect injection moulding cost?
Yes.
Modern injection moulding can be highly automated, but the amount of labour required varies between projects.
A component that falls automatically from the mould onto a conveyor requires a different level of handling from one that needs an operator to:
- Load an insert into the tool
- Remove the component manually
- Trim or finish the part
- Carry out visual inspection
- Assemble another component
- Pack each item individually
If that operation takes 30 seconds for every part, the labour requirement becomes increasingly significant as production volume grows.
Sometimes investing in automation can reduce the repeat cost. At other volumes, the investment needed to automate the process may never pay for itself.
Again, expected production quantity matters.
How do scrap and material waste affect the price?
Not every gram of polymer entering a moulding process necessarily becomes part of the finished component.
Depending on the mould design, material may also be used within sprues and runners.
Some materials and applications allow suitable reprocessing of this material, while others require tighter control or cannot use reprocessed polymer in the same way.
There may also be start-up scrap when a process is established, particularly after a tool change or material change.
Good process development aims to keep waste under control, but it still forms part of the overall production economics.
Hot-runner tooling can remove or substantially reduce conventional runner waste in suitable applications, although it adds complexity and investment to the mould tool. Whether that makes commercial sense again depends on the component, material and production volume.
How much does inspection add to injection moulding cost?
Inspection requirements vary enormously.
A relatively simple commercial component may only require appropriate production checks. A technically demanding part may require dimensional inspection, recorded measurements, specialist equipment, batch documentation or a more detailed quality plan.
These activities take time.
But removing inspection simply to reduce the quoted component price can be a false economy where dimensional accuracy or product performance matters.
The right question is not: ‘How little inspection can we get away with?’ It is: ‘What level of inspection does this component genuinely require?’
Dudley Associates operates to ISO 9001:2015 and combines moulding, tooling and inspection as part of the wider production process.
What about assembly and secondary operations?
The moulding machine may only be one stage in producing the finished component.
A part might also require:
- Drilling
- Tapping
- Printing
- Inserts
- Assembly
- Finishing
- Specialist packaging
- Other secondary operations
Dudley provides additional secondary and assembly services alongside its injection moulding capability, allowing these requirements to be considered as part of the complete manufacturing process.
Sometimes a secondary operation is deliberately chosen because it allows the mould tool itself to remain much simpler.
For a short production run, drilling a relatively small number of holes after moulding might make more commercial sense than adding complicated tool movements purely to create those features automatically. For a very high-volume product, the opposite may be true.
This is another example of why the lowest individual process cost does not necessarily produce the lowest overall component cost.
Can product design reduce the cost of an injection moulded part?
Very often, yes.
Product design can influence:
- Material usage
- Cycle time
- Tool complexity
- Machine requirements
- Number of cavities
- Ejection
- Scrap
- Assembly
- Secondary operations
- Inspection requirements
Small changes made while a product is still in CAD can sometimes affect the cost of every component subsequently manufactured.
That does not mean a product should be redesigned purely to make it cheap to mould. Its function comes first.
The opportunity is to identify changes that preserve the required performance while making the component more efficient to manufacture.
Why can two injection moulding quotes be very different?
Because the suppliers may not be quoting the same manufacturing strategy.
One supplier may propose a single-cavity tool. Another may recommend four cavities.
One might use a lower-cost tool designed around modest production volumes. Another might propose a hardened production tool intended for millions of cycles.
One quotation may include inspection, assembly and packaging. Another may only cover the moulded component.
The proposed machine, automation, material assumptions and cycle time may also differ.
So when comparing injection moulding quotations, the most useful question is not simply: ‘Which part price is lowest?’ It is: ‘What assumptions have been used to arrive at this price?’
What information helps an injection moulder calculate an accurate price?
The better the information available, the more meaningful the quotation can be.
Useful information includes:
- 3D CAD data
- Component drawings
- Material requirements
- Expected annual volume
- Expected lifetime volume
- Likely order quantities
- Required tolerances
- Cosmetic requirements
- Inspection requirements
- Assembly requirements
- Packaging requirements
- Whether volumes may increase significantly
- Whether tooling already exists
Volume is particularly important.
A supplier cannot properly optimise tooling investment and repeat-part cost without understanding whether the requirement is 500 parts, 50,000 parts or five million parts.
Frequently asked questions about injection moulding cost
Does a cheaper mould tool always mean cheaper parts?
No. A lower-cost mould may require longer cycles, fewer cavities, more manual intervention or greater maintenance. For low volumes that trade-off may be sensible. For high volumes, investing more in the tool can reduce the overall lifetime manufacturing cost.
Can increasing the number of cavities reduce the component price?
Yes, because several parts can be produced during one machine cycle. However, additional cavities increase mould complexity and tooling cost, so the expected production volume needs to justify the investment.
Why can a heavier plastic part cost more even if the material is inexpensive?
A heavier component uses more polymer and may also take longer to cool. This means additional material cost can be combined with extra machine time.
Is short-run injection moulding expensive?
Not necessarily. The manufacturing strategy needs to suit the volume. Simpler or lower-investment tooling can sometimes make injection moulding commercially viable for relatively modest production quantities.
Can secondary machining make an injection moulded part cheaper?
Sometimes. For lower quantities, drilling or machining a feature after moulding can be less expensive overall than building complex moving features into the mould tool.
When should tooling cost be amortised across the part price?
It is useful whenever you are comparing different manufacturing strategies. Looking at tooling investment alongside expected lifetime production gives a clearer picture of the true cost per component.
What happens if production volumes increase later?
Tooling and production processes can sometimes be modified or replaced as demand develops. This is why it can be useful to discuss both expected initial volumes and realistic future volumes when the project begins.
Can Dudley Associates help reduce an existing injection moulded part cost?
Potentially. The component design, mould tool, material, cycle time, tooling condition, cavitation, inspection and secondary operations can all be reviewed to identify where genuine savings may be possible without compromising the product.
So what actually determines the cost of an injection moulded part?
There is no single factor.
The cost is the combined result of the component design, material, mould tool, machine, cycle time, labour, production quantity, quality requirements and everything that happens after the part leaves the mould.
For buyers, this means the lowest quoted unit price should not automatically be assumed to be the lowest-cost manufacturing solution.
A good injection moulding partner should be able to explain why the part costs what it does, which factors matter most for your particular project and where changes could genuinely reduce the total manufacturing cost.
At Dudley Associates, that is the conversation we would rather have.
Not simply: ‘How cheaply can we mould this part?’
But: ‘What is the most cost-effective way to manufacture this product properly?’
For help with pricing up your next injection moulded part, just give us a call.
Dudley Associates are an injection moulding company in Leicestershire, with our own cad facilities and in-house toolroom.
