Switch from 3D printing to injection moulding when the quantity is large enough that the tool, spread across every part, costs less than the printing premium you would otherwise pay on each one. The break-even quantity is the tool and setup cost divided by the printed price per part minus the moulded price per part. For small parts that is often somewhere in the hundreds to low thousands, but only your own quotes can give the number.
Key points
- Break-even quantity = (tool + setup) ÷ (printed price per part - moulded price per part).
- Printing has almost no fixed cost and a flat price per part. Moulding has a large fixed cost and a falling one.
- The break-even moves a lot with tool cost and with the printed price at volume. Test both.
- A frozen design and a known demand favour moulding. Changing designs and uncertain demand favour printing.
- Geometry can settle it alone: some printable shapes cannot be moulded, and some moulded features print badly.
Why do the two cost curves cross?
Printing and moulding have opposite cost structures.
A printed part, whether SLS, MJF, FDM or resin, costs roughly the same whether you order 10 or 1,000. Each part needs its own material and its own share of machine time. Larger batches help a little, because powder bed machines nest more parts into each build and raise packing density, and handling is shared. But there is no big fixed cost to spread. The 3D printing cost calculation guide shows where each part of a printed price comes from.
An injection moulded part (injection molded, in the US) carries a share of the tooling, which can be thousands or tens of thousands, plus a setup per run. After that, each part is resin and a few seconds of press time, often cents. The injection moulding cost guide breaks that down.
So moulding starts far above printing and falls fast; printing starts low and stays flat. They cross.
How do you calculate the break-even?
Set the two totals equal:
- Printing total = quantity × printed price per part.
- Moulding total = tool + setup + quantity × moulded price per part.
Solve for quantity, and the break-even is:
Q = (tool + setup) ÷ (printed price - moulded price)
The denominator is the saving per part from moulding. The numerator is what you pay to get it. The break-even is simply how many parts it takes for the savings to pay off the tool. This is tool amortisation seen from the buyer’s side.
Worked example: a small nylon clip. Every figure is an example for the arithmetic, not a market price.
Printed in MJF: €8.00 per part at any quantity in this range. Moulded: tool €9,000; setup €300; €0.60 per part.
Break-even: (€9,000 + €300) ÷ (€8.00 - €0.60) = €9,300 ÷ €7.40 = 1,256.8, so about 1,257 parts.
| Quantity | Printing total | Moulding total | Printed per part | Moulded per part |
|---|---|---|---|---|
| 100 | 100 × €8.00 = €800 | €9,300 + €60 = €9,360 | €8.00 | €93.60 |
| 500 | €4,000 | €9,300 + €300 = €9,600 | €8.00 | €19.20 |
| 1,000 | €8,000 | €9,300 + €600 = €9,900 | €8.00 | €9.90 |
| 1,257 | €10,056 | €9,300 + €754.20 = €10,054.20 | €8.00 | €8.00 |
| 1,500 | €12,000 | €9,300 + €900 = €10,200 | €8.00 | €6.80 |
| 5,000 | €40,000 | €9,300 + €3,000 = €12,300 | €8.00 | €2.46 |
At 1,000 parts printing still saves €1,900. At 5,000 parts moulding saves €27,700.
How sensitive is the break-even?
Very. Two inputs move it most: the tool cost and the printed price at volume. Keeping everything else from the example the same:
| Scenario | Calculation | Break-even |
|---|---|---|
| Base case | €9,300 ÷ (€8.00 - €0.60) | about 1,257 |
| Printed price falls to €6.00 at volume | €9,300 ÷ (€6.00 - €0.60) = €9,300 ÷ €5.40 | about 1,723 |
| Hardened steel tool at €20,000 | €20,300 ÷ €7.40 | about 2,744 |
| Simpler tool at €5,000 | €5,300 ÷ €7.40 | about 717 |
The moulded price per part matters less than you might expect. In the base case, halving it from €0.60 to €0.30 only moves the break-even from about 1,257 to €9,300 ÷ €7.70, about 1,208 parts, because the printing price is so much larger. The tool cost and the printed price are the two numbers worth getting right.
A powder bed bureau that nests well can lower its price at volume, which pushes the break-even out. A part that needs side actions in the tool pushes it out too. A simple, flat part with a cheap tool pulls it in. Get real quotes at three or four quantities from both sides before you decide.
What else should decide it?
Price at a single quantity is only part of the decision.
| Question | Points towards printing | Points towards moulding |
|---|---|---|
| Is the design frozen? | Still changing: a new file costs nothing | Frozen, with a long product life ahead |
| How certain is demand? | Uncertain or seasonal | Known and steady |
| How soon do you need parts? | Days | Weeks are acceptable for the tool |
| What material is required? | A printable nylon, resin or filament is fine | A specific production thermoplastic or grade |
| What does the geometry need? | Internal channels, lattices, consolidated assemblies | Thin uniform walls, fine surface, high cosmetic standard |
| What finish is required? | Textured or dyed is acceptable | Gloss or a specified texture from the tool |
| Do variants matter? | Many variants or personalised parts | One design in high volume |
Demand uncertainty is the one people underestimate. A tool bought for a forecast of 10,000 that turns into 2,000 parts has multiplied its share of each unit price by five. Printing the first batches while demand is proven, then moving to a tool, keeps that risk small.
Does the part need to be redesigned to switch?
Usually, yes. A part designed for printing often has features a mould cannot release: enclosed channels, undercuts, varying wall thickness, no draft. Moving to a tool usually means:
- adding draft to faces that slide out of the mould;
- making walls uniform and coring out thick sections, which also shortens cooling;
- removing or simplifying undercuts that would need side actions;
- choosing a parting line and gate position.
The design for 3D printing guide covers the rules on the printed side, and the minimum wall thickness guide compares typical walls across both processes. Budget for this redesign. It is part of the cost of switching, even though it never appears on the moulder’s quote.
What about the middle ground?
Between printing and a hard tool there are options that move the break-even:
- Vacuum casting in silicone moulds from a printed master suits tens to low hundreds of parts in a moulding-like polyurethane. See vacuum casting vs injection moulding.
- Aluminium or printed mould inserts lower tool cost for short runs, at the price of shorter tool life.
- Bridge production: print or cast the first batches while the production tool is made, so sales start before the mould is ready.
Pricing the printed side
The printed side of this comparison is the side that changes with every option: material, layer height, finish, quantity. Getting it right at several quantities is what makes the break-even trustworthy. The SLS and MJF technology pages explain how powder bed prices are built, including how nesting changes the price at volume.
Quotometry prices FDM, resin, SLS and MJF parts from the uploaded file with a breakdown at every quantity, and gives a budgetary injection moulding estimate for the same file: tool and part price, which the shop always reviews before confirming, because draft and flow are not measured. That puts both columns of the table above side by side for a real part, while the tool still needs a toolmaker’s confirmation.
Questions people ask
At what quantity does injection moulding become cheaper than 3D printing?
There is no single number. The break-even is the tool and setup cost divided by the difference between the printed price per part and the moulded price per part. For small parts with a cheap tool it can be a few hundred; for larger parts or a hardened multi-cavity tool it can be several thousand. Run the division with real quotes for your part.
Can 3D printing be used for production, not just prototypes?
Yes, and powder bed processes such as SLS and MJF are often used for end-use nylon parts in low to medium volumes. They need no tooling, so the price per part is roughly flat with quantity, and a design change costs nothing but a new file. They make sense when volumes are modest, designs change often, or the geometry cannot be moulded.
Should I prototype in 3D printing before making an injection mould?
Almost always. A printed part lets you check fit, assembly and ergonomics before the design is cut into metal, where every change is expensive and slow. Keep in mind that a printed part is not a moulded part: it has different strength, surface and shrinkage, so treat printed prototypes as a check on geometry rather than on final material behaviour.
Why does the printed price per part not fall much with quantity?
Because every printed part carries its own machine time and material. Larger batches help a little: powder bed machines pack more parts into each build, setup and handling are shared, and post-processing can be batched. But there is no large fixed cost to spread, so the curve flattens quickly, unlike moulding where the tool share keeps falling.
Quotometry prices every part from your own machines and rates, on your website, in seconds.