Rapid prototyping vs injection moulding: when 3D printing wins on cost

Ask whether 3D printing is cheaper than injection moulding and you'll get a useless answer, because it depends almost entirely on one number: how many parts you need. Get that number right and the decision tends to make itself.

The cost everyone forgets: tooling

Injection moulding produces consistent parts at a very low cost each — once you've paid for the mould. A production-grade tool runs from roughly £2,000 for something simple to well over £10,000 for anything complex, and it takes weeks to cut. None of that shows up in the per-part price you're quoted. 3D printing has no tooling cost at all: you pay for material and machine time, and nothing else.

That single difference is why our rapid prototyping and low-volume manufacturing almost always undercut moulding below a few hundred parts.

Where the crossover sits

Picture the total cost of an order as a line. For moulding, the line starts high — you've paid for the tool before part one — then rises very slowly. For printing, it starts at zero and rises in a steeper, straight line with each part. The two lines cross somewhere. Below the crossover, printing is cheaper on total cost and faster to deliver. Above it, moulding pulls ahead and keeps winning.

For most small functional parts the crossover lands in the low hundreds to low thousands. If your run is smaller than that — and a great many commercial runs are — printing wins outright.

Speed and iteration are part of the cost

Tooling locks in your design. If part one reveals a flaw, re-cutting a mould is expensive and slow. With printing you change the file and run it again the next day, at no extra setup cost. For any part that isn't fully proven, that flexibility is worth real money — you're not paying to be wrong.

When moulding still wins

We'll tell you when it does. If you genuinely need thousands of identical parts, or a specific moulded finish or material we can't match, injection moulding is the right tool and we'll say so. The common, sensible path is to print first — to validate the design, launch, or bridge early demand — then move to tooling once volume justifies the up-front cost.

Material choice matters too: a functional part in PETG or ABS printed today behaves close enough to its moulded equivalent for most testing and many end-use applications.