What a 3D printed part will never do

A printed part is anisotropic

This is the fundamental limit, the one everything else follows from. An FDM part is a stack of layers welded to one another: it is strong in the plane of the layers, distinctly less so perpendicular to them.

In practice a part can be twice as strong in one direction as in the other. That is why print orientation is a technical decision rather than a production detail: we orient the part according to the load it will take, which assumes you tell us what that load is.

It is also why we refuse safety parts. A bicycle stem, a lifting component, anything that injures when it breaks: the failure mode of an FDM part is abrupt and hard to predict. No material corrects that.

Watertightness is never guaranteed over time

A printed part can be watertight as it leaves the machine, with enough walls and sufficient infill. The problem is that it rarely stays that way: the micro-interfaces between layers eventually let something through under thermal cycling and pressure.

For a planter cover holding watering runoff, that has no consequence. For a pressurised circuit it is disqualifying, and we do not take those orders.

Lasting food contact is a false friend

A material can be certified food-safe as a pellet without the printed part being so. Two reasons: the nozzle leaves metallic traces, and above all the print striations form grooves that washing never fully cleans. Those are bacteria traps.

A cookie cutter used for a few minutes and then washed poses no real problem. A box holding food for days does. So we never claim food contact, even when the material datasheet would allow it.

Tolerances have a floor

We hold ±0.3 mm as standard, and ±0.15 mm on dimensions identified in advance. Below that the part has to be machined, which we do not offer.

Material shrinkage explains much of that spread: plastic contracts as it cools, and more so over large dimensions. A 300 mm part does not come out with the same precision as a 30 mm one. That is predictable, so it can be compensated, but not eliminated.

If a tight fit is critical, the right method is a test sample before the run: measure, compensate, then start.

The surface finish is the one the process gives

Layer lines are always visible. A 0.1 mm layer makes them discreet, a 0.3 mm layer makes them pronounced, but they do not disappear. Downward-facing surfaces additionally show support marks.

We offer no cosmetic finishing — no sanding, no primer, no paint. What we can do is orient the part so the visible faces come out as clean as possible. Tell us which face will be looked at.

What printing does better than anything else

With those limits stated, one field remains where nothing competes: the one-off or the short run, with complex geometry, no tooling cost and delivery in days.

An injection mould costs several thousand euros and takes weeks. Below a few thousand pieces, printing wins. Above that, injection wins, and we will tell you so rather than take the order.

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