There is no technical minimum. Minimum orders exist because of set-up: the time it takes to change the tool and bring the process in. We mould from ten parts, and where there is a set-up charge we show it as a separate line rather than hiding it in the part price.
Why moulders set a minimum
Every run starts with a tool change. The mould goes into the machine, the water and any hot runner get connected, the material is dried and loaded, and the process is brought in until the parts are right. That takes the same time whether the order is for ten parts or ten thousand.
It also takes people. A setter or process technician is on the tool change from start to finish and cannot do anything else while it lasts. A week of small orders can become a week of changeovers, with the setters tied up and the bigger jobs waiting. For a busy shop that is often the real reason for a minimum, more than the money.
Many moulders do not charge for set-up separately. They spread it across the order and build it into the price per part. On a large order that works, because the set-up disappears into thousands of parts. On a small order it does not, so they set a minimum, often around a thousand parts, below which the economics no longer work.
What set-up does to the price of a small run
Round numbers, to show the shape rather than to quote. Say set-up costs £300 and each part costs £3 to mould once the machine is running.
| Quantity | Set-up | Moulding | Price per part | Share that is set-up |
|---|---|---|---|---|
| 10 | £300 | £30 | £33.00 | 91% |
| 100 | £300 | £300 | £6.00 | 50% |
| 1,000 | £300 | £3,000 | £3.30 | 9% |
| 10,000 | £300 | £30,000 | £3.03 | 1% |
At ten parts, around 90% of what you pay is set-up, not the part. That is why a moulder who builds set-up into the part price cannot quote ten parts credibly, and why most will not.
Showing set-up as its own line changes that. You can see exactly what the run costs, and the price per part is the price per part.
Why ten parts can still be the right answer
Injection moulding earns its place on price per part: a repeatable, automatic process with a short cycle time. It is a volume process, and for most small quantities another method is cheaper.
But some parts can only be injection moulded. The material, the properties, or the way the part has to behave rule out a printed or machined version. And sometimes only a few of them are needed:
- A field trial, where the parts have to be the real thing in the real material
- Testing or approval, where a printed stand-in will not be accepted
- A spare or a low-volume product that will never need thousands
- A tool that already exists, and an order that is simply small
In those cases, ten moulded parts are a legitimate use of the process. The tool that makes ten can go on to make thousands later, so the trial parts and the production parts are the same.
How ten parts still come out right
The question worth asking is how a process can be stable on a run of ten. It is not proven on your parts order. It is proven at the mould trial.
When a tool first goes into the machine, we run far more than ten parts, enough to be sure the process is stable and the parts are consistent. That work is budgeted in the mould trial, as part of the mould order itself, not added to your parts order.
Your parts order then runs to the process the trial proved. Whether it is a prototype batch or a production order, you get your ten parts, made to the same process as any larger run.
What to send us
The part drawing or CAD, the material, and how many you need now and later. If you already have a tool, say so and send what you know about it. We will confirm the run cost, set-up included, and whether moulding is the right way to make it.