Injection moulding has a large fixed cost, the mould, and a low cost per part. SLS printing has no tooling cost, but each part costs more. The quantity at which the mould becomes cheaper is easy to work out.
The break-even formula
Break-even is the quantity at which both options cost the same:
break-even = mould cost ÷ (SLS price per part − moulded price per part)
- Below break-even, SLS costs less in total.
- Above it, the mould pays for itself.
- Use the SLS price for the quantity you need: with SLS, the price per part falls with quantity.
- Count the total volume, not one order: the mould is paid once, for every year of production.
An example
Example values, excluding VAT:
- mould: 60,000 lei
- moulded part: 6 lei
- SLS printed part, at 200 pieces: 110 lei
Break-even is 60,000 ÷ (110 − 6), about 580 parts. If you need 300 parts a year, SLS is cheaper in the first year. If you need 3,000, the mould pays for itself quickly.
The calculator below does the same sum with your own values. You can get the SLS price from the estimate in the quote form or from the price-by-quantity example.
When SLS stays the right choice above break-even
- The design is still changing. A change means a new file, not a modified mould.
- You have variants. One build can hold different parts, each with its own geometry or engraved code.
- The geometry would complicate the mould. Internal channels, undercuts and one-piece assemblies print at no extra cost.
- Yearly volume is uncertain. You pay only for the parts you order, with no money tied up in tooling.
- Time matters. A mould usually takes a few weeks. SLS parts ship in a few working days.
When injection moulding fits better
- Thousands or tens of thousands of identical parts a year, with a stable design.
- A material SLS does not offer, such as ABS, PC or POM.
- Glossy or textured cosmetic surfaces straight from the mould.
- Tighter tolerances than SLS allows across the whole part.
Bridge production
The 2 processes can work together:
- Print the first batches in SLS while the mould is being made.
- Check fit and function on real parts before fixing the geometry in steel.
- Move to moulding once volume and design are stable.
- Keep SLS for spare parts and low-volume variants.
Bear in mind that printed PA12 does not behave exactly like the final moulded material. SLS parts validate shape, fit and function, not the exact properties of another polymer.
Design for both
If you know you will move to moulding:
- Keep walls at a uniform 1.5–3 mm.
- Add 1–2° draft angles from the start. They do no harm in SLS.
- Avoid features only SLS can make, so the mould does not need a redesign.
What to send for a quote
- the STEP or STL file
- quantity per order and estimated yearly volume
- the material, or what the part does
- whether a mould is planned, and when
For repeat batches, see also low-volume production.