The tooling cost problem
Injection molding requires a machined steel or aluminum mold before a single part is produced. Depending on part complexity, that mold can cost $5,000 to $50,000 or more. That cost has to be recovered across the production run — which means injection molding only makes economic sense once volumes are high enough to absorb it.
For a run of 50, 100, or even 500 parts, the per-unit tooling contribution is too high. The math simply does not work unless volume is there.
Where FDM fills the gap
FDM contract printing has no tooling cost. The cost of a run is based on material, machine time, labor, and post-print handling — not on recovering an expensive mold investment. For low-volume production, that difference is significant.
A practical example: a part that costs $8 per unit at injection molding volumes might quote at $18-$30 per unit in FDM. At 50 units, FDM wins decisively once the mold cost is factored into the injection molding number. The break-even point varies by part, but it is rarely below several hundred units and often much higher.
What FDM does not replace
For parts that need tight dimensional tolerances, specific surface finish requirements, or are heading into true mass production — injection molding is the right answer once volumes justify the tooling investment. FDM surface finish shows layer lines. Dimensional tolerance is part-dependent. And FDM production speeds are slower than high-volume injection.
FDM also differs in material options. Injection molding supports a much wider range of polymers, including many engineering-grade materials not currently available in filament form.
The practical use case for FDM
The sweet spot for FDM contract printing is: parts where volumes are low, where design iteration is still possible, where time to first part matters, or where the annual quantity never justifies tooling. Prototype runs, replacement components, product validation batches, and annual quantities under a few hundred units are all strong candidates.
For companies selling into the U.S. market from abroad, FDM also offers a faster path to domestic U.S. stock than waiting on overseas injection molding lead times.
The decision framework
Ask three questions before choosing a process:
- What is the total volume — first run and expected annual volume combined?
- Is the design finalized, or might it change?
- What is the real deadline for first part availability?
If volume is low, design is not locked, or speed to market matters, FDM is worth evaluating seriously. If volume is high and the design is proven, injection molding will win on per-unit cost once the mold is paid off.