Quick answer
Injection moulding becomes cheaper when the tooling cost is repaid by the lower unit cost.
Using the default assumptions against 3D printing: GBP6,500 / (GBP18 - GBP0.70) = roughly 376 units.
Worked example
If a part costs GBP18 to 3D print and GBP0.70 to mould, but the tool costs GBP6,500, the cheapest route depends entirely on realistic demand and how confident you are that the geometry is stable enough to tool.
How this calculator works
The lines show total cost, not unit cost. That matters because early manufacturing decisions are usually distorted by low setup options looking cheaper at the start, while tooled routes only win once volume justifies the upfront commitment.
- Use low setup routes for learning and early uncertainty.
- Use bridge routes when demand is growing but tooling still feels risky.
- Use injection moulding when volume and design stability support the investment.