The nominal nozzle diameter is only the first number
A 0.2 mm nozzle has a nominal opening of 200 micrometres, but the liquid does not always pass through a fully open circular bore. The tapered needle creates a variable annular gap, and at low dosing values that working gap can be much smaller than the nominal nozzle diameter.
An isolated, well-dispersed 50 micrometre particle may pass through a widely opened 0.2 mm nozzle. This 1:4 nominal ratio is a useful first estimate, not a reliable operating limit.
Agglomerates and repeated closing usually decide the practical result
Several particles can form an agglomerate larger than the measured primary particle size. Sedimentation can increase their local concentration near the fluid inlet, while drying at the needle tip can create a second source of unstable flow.
The moving needle may disturb a soft accumulation and reopen the passage. It can also trap particles between the needle and nozzle seat, which can prevent clean closure, cause dripping, or change the next spray cycle.
Use the closest available evidence
Stable spraying through a manual airbrush with the same or a smaller nozzle is a strong first indicator. The comparison should include the real liquid preparation, pressure, filtration, cleaning routine, and the time for which the suspension remains stable.
A representative CNC test adds the conditions that a short manual test may miss: small programmed needle openings, repeated stop-start cycles, restart after a pause, and the intended daily duty cycle.
Questions that materially change the assessment
- What is the selected nozzle diameter and expected needle opening?
- Is the stated value a maximum particle size, an average, or a primary particle size before agglomeration?
- How quickly does the material settle, dry, or form deposits?
- Does the liquid already spray reliably through a comparable manual airbrush?
- How many closing and restart cycles must remain stable?