Injection molding is the default answer for plastic parts in manufacturing. It's cheap per unit, it's fast once it runs, and it's why 3D printing still gets dismissed as "for prototypes only."
That dismissal is wrong at small volumes. Here's the arithmetic.
The two cost structures
Injection molding has two costs:
- Tooling, paid once: roughly €3,000–€8,000 for a simple aluminium tool, €15,000–€80,000 for a steel production tool.
- Per unit: roughly €0.20–€2 for a small part, depending on size, material and cycle time.
SLS nylon has one cost:
- Per unit: roughly €4–€40 for a PA12 part, depending on volume, packing density and post-processing.
No tooling, no minimum order, no amortisation. That single structural difference is the whole argument.
A worked example
Take a small automotive clip — the kind of part that costs about €1.20 to mould and about €6 to print, with a €5,000 aluminium tool.
| Quantity | Injection molded | SLS nylon | Cheaper |
|---|---|---|---|
| 100 | €5,120 | €600 | Printing |
| 500 | €5,600 | €3,000 | Printing |
| 1,000 | €6,200 | €6,000 | Roughly even |
| 2,500 | €8,000 | €15,000 | Molding |
| 10,000 | €17,000 | €60,000 | Molding |
The break-even for a simple part lands somewhere between 500 and 2,000 units. Below it, printing wins on total cost. Above it, molding pulls away fast and never looks back.
Two things move that crossover:
- Part size. Print cost scales with volume, mould cost mostly doesn't. Bigger parts push the break-even down — sometimes under 200 units.
- Tool complexity. Undercuts and side actions add thousands to a tool while costing a printer nothing. A complex geometry can push the break-even well past 3,000.
When printing wins for reasons other than cost
- Lead time. Tooling takes 4–16 weeks before the first shot. Printing delivers in days. If a line is down or a boat is out of service, that difference is the whole decision.
- The design isn't frozen. Every change means a new tool, or an expensive modification to an existing one. Printing absorbs revisions for free.
- Complex geometry. Undercuts, internal channels, lattices and living hinges are routine in SLS and expensive or impossible to mould.
- Variants. Version A for one chassis, version B for another. Printing doesn't care; tooling means a second tool.
- The part is obsolete. No tool exists and nobody is making one. Scan the survivor, rebuild the CAD, print it.
- You need to hold no inventory. Print on demand means no minimum order and nothing sitting in a warehouse depreciating — which for a discontinued part is often the entire business case.
When molding still wins
- Volume is genuinely high. 10,000+ identical parts, design frozen.
- Surface finish must be glass-smooth straight off the machine. SLS is matte and slightly grainy by nature.
- You need a specific certified polymer with no SLS equivalent — some flame-rated and food-contact grades, for instance.
- Unit cost dominates everything, as it does in consumer goods sold at thin margins.
The hybrid play
The approach most of our B2B customers land on:
- Print the first 500–2,000 units in PA12.
- Ship them, gather field data, fix what the field finds.
- Freeze the design.
- Commission the tool with confidence, once.
Printing de-risks the tooling spend. A €40,000 steel tool cut against an unproven design is a bet; the same tool cut after two years of field data is an investment. In the meantime the product is on the market rather than waiting for a mould.
The same logic applies in reverse at end of life. When a moulded product's volume falls below the point where re-running the tool makes sense, printing takes the tail — spares and service parts on demand, for as long as customers need them.
What we need to run the numbers for you
- The STEP file, or a drawing with the critical dimensions
- Annual quantity, and whether it's one batch or a rolling schedule
- The environment the part lives in — temperature, UV, chemicals, load
- Any certification the material has to meet
We'll come back with a printed unit cost, an honest estimate of where your break-even sits, and a recommendation — including the times the recommendation is "get a tool cut."
Thinking about a production run? Tell us the specs and we'll run the break-even for you.
Related reading: FDM vs SLA vs SLS for the process comparison, 3D printing materials 101 for what PA12 actually does, and custom marine parts for a working fleet for a short run that went exactly this way.
The BMW E30 cup holder vent shown with this article ships in PETG rather than SLS nylon — a straightforward FDM part — but it illustrates the same no-tooling economics: no mould, no minimum order, cost that scales with volume from part one.
SHIPS 3–5 DAYS
