Fuso Seiki ST-6-1.3 Lumina Automatic Spray Gun (0 - 390mL/ min, G1/8, 1.3mm)

1/ How the ST-6 series works (principles and variants)

- The ST series is a needle-and-nozzle type precision spray valve where the needle retracts to open the liquid path and the atomizing air shapes the spray pattern; the ST family offers multiple body styles, nozzle sizes, and liquid adjusters to suit varied applications.

- Two main control axes determine output: mechanical needle stroke (or actuator position) and atomizing/air pressure; liquid flow is a function of nozzle orifice, pressure differential, and liquid viscosity.

2/ Performance factors and how to interpret the 0 - 390 mL/min rating

- The published flow range 0 - 390 mL/min is a maximum theoretical range under manufacturer-referenced conditions; actual flow depends on liquid viscosity, supply pressure, needle opening, and any inline flow restrictions.

- For low-viscosity solvents near water-like viscosity, approaching the upper flow limit requires higher supply pressure and full needle opening; for high-viscosity fluids the achievable flow at the same pressure will be significantly lower.

- Use empirical bench tests (measured dispensed volume over time at set pressure and stroke) to map operating points for each fluid and setup; save those operating points for repeatability.

3/ Installation and piping best practices

- Thread connection: install with correct G1/8 sealing method (PTFE tape or compatible gasket) and torque to prevent leaks without deforming the valve body; avoid over-torquing which can stress the plated brass body.

- Air and liquid supplies: install dedicated filters and pressure regulators upstream. Use a 5 - 20 µm liquid filter and a coalescing/regulating air filter for atomizing air. Place an isolation valve and a purge/flush port on the liquid line for maintenance.

- Mounting: secure valve to a rigid bracket to avoid vibration; when using long nozzles or extensions verify alignment so the valve’s spray axis is perpendicular to the target. The ST series supports long-nozzle attachments for special geometries.

4/ Setup procedure and tuning steps

- Clean system and install a clean nozzle and needle.

- Set liquid supply pressure low and atomizing air to manufacturer-recommended start pressure (if available), then gradually increase.

- Open needle stroke incrementally until a stable spray pattern forms; for fine atomization favor higher atomizing air at smaller needle openings.

- Measure flow at each setting: dispense into a graduated container for a timed period and calculate mL/min. Record pressure, stroke, and measured flow for repeatability.

- Adjust atomizing air vs liquid stroke for the desired droplet size and pattern width; if pattern widens but droplets are coarse, increase atomizing air or reduce stroke.

5/ Maintenance, cleaning, and spare parts

- Clean immediately after color or material changes and at regular intervals: flush with a compatible solvent, then disassemble nozzle and needle for visual inspection and ultrasonic cleaning if required. Avoid hard metal brushes that deform the orifice.

- Inspect nozzle orifice and needle for wear, burrs, or deformation; replace nozzle/needle when orifice diameter changes or pattern degrades. Keep spare nozzles, needles, O-rings, and springs on hand to minimize downtime.

- Replace seals and O-rings when chemical compatibility is in doubt or when leaks occur; store valves with needle retracted and solvent-filled when idle long-term to prevent drying and caking.

6/ Troubleshooting: common problems and fixes

- Clogged nozzle or decreased flow: flush with solvent, remove and inspect nozzle; confirm upstream filter not blocked and supply pressure adequate.

- Irregular spray pattern or tailing: check needle seating for damage; inspect nozzle for partial blockage or eccentric wear; verify stable supply pressures and that atomizing air is clean and dry.

- Excessive overspray or misting: reduce atomizing air or increase needle opening for larger droplets; consider switching nozzle size if coverage needs change.

- Leaks at thread connection: replace sealing tape/gasket and re-torque to spec; replace worn O-rings.

- Flow lower than catalog spec: verify test conditions (pressure and viscosity) were equivalent to manufacturer’s; higher-viscosity fluids and pressure losses in tubing reduce flow.

7/ Measurement and validation recommendations

- Validate flow with timed gravimetric or volumetric collection for each fluid type and temperature. Record: liquid pressure, atomizing air pressure, needle stroke (or actuator displacement), nozzle ID, fluid viscosity and temperature.

- Measure particle size distribution using an appropriate spray analyzer if required for process control; catalog average particle size (e.g., ~43 µm) is a guideline, actual PSD varies with settings and fluid.

8/ Material compatibility, selection, and safety

- Material compatibility: standard nozzle/needle stainless steel (SUS303) and chrome-plated brass body suit many paints, oils, and solvents; for highly corrosive chemistries consult supplier for alternative materials or coatings.

- Safety: handle flammable solvents in ventilated areas, use grounding and bonding for static-sensitive coatings, and follow local regulations for solvent handling and waste disposal.

9/ Choosing accessories and system options

- Filters: 5 - 20 µm liquid filters recommended; consider in-line pressure gauges and flow meters for closed-loop monitoring.

- Actuation: integrate pneumatic or electric actuators for repeatable cycle control; control schemes can enable pulsed sprays, multi-shot dosing, or continuous operation per production need.

- Nozzle variants: the ST family supports multiple nozzle IDs and long-nozzle attachments to tune pattern width and reach.

10/ Practical tips for production reliability

- Keep a written changeover log with the exact operating pressures and stroke settings for each material and color.

- Implement a quick-change spare head module to reduce downtime during maintenance.

- Schedule preventive replacement intervals for nozzles and needles based on throughput rather than visual condition.