Customer challenge

A leading smartwatch manufacturer in India required a robust inline process to deposit adhesive into small threaded screw holes used to secure bezel and module assemblies. The screws rely on a controlled micro-volume of moisture-curing adhesive inside the threads to prevent loosening while avoiding excess that can foul threads or interfere with assembly. Manual application produced inconsistent glue volumes and occasional thread blockage; variability in bead mass (and hence cure performance) led to rework, slower downstream assembly, and occasional field returns.

Technical requirements

• Target deposit mass: 0.2~0.3 mg per threaded hole.
• Deposit geometry: contained micro-dot within the thread root (diameter <1.5 mm, depth 0.8~1.2 mm).
• Adhesive: moisture-curing structural adhesive with medium viscosity and sensitivity to air entrapment.
• Throughput: support a 6~8 station rotary assembly line at native PPH without adding cycle time.
• Integration: robot-mounted dispense head with quick nozzle swaps and inline vision verification; MES logging for traceability.

Mingseal solution 

The customer selected a wear‑resistant concentric auger valve from the KSV1000 series, configured with the KVS1000‑T05 variant optimized for solder‑paste–like viscosities and fine minimum dispense volumes.

Key system adaptations included:

• Low-pulsation positive-displacement metering running at tuned speeds up to 500 rpm to match cycle timing while ensuring linear flow control and repeatable dose.
• Short fluid path and robust wetted materials to reduce air entrapment and prevent premature gelation inside the valve.
• Custom micro-nozzle (T-type) engineered to fit within the threaded-hole opening and to center the fluid jet at the thread root, ensuring containment and avoiding surface overflow.
• Drive profile tuning (start/stop ramp shaping and dwell timing) established by DOE to deliver 0.2~0.3 mg per shot with ±5% shot-to-shot variance.
• Robot end-effector mounting and fiducial-based vision alignment to position the nozzle concentrically over micro-holes with sub-0.1 mm repeatability.
• Inline micro-AOI that inspects bead geometry immediately after dispense and logs mass/vision data to MES for batch traceability.

Process results

• Consistent glue mass: Post-implementation sampling showed average deposit mass within the 0.2~0.3 mg target and shot-to-shot variance reduced to ±3~5%, eliminating the largest source of assembly variability.
• Contained deposits: The tailored nozzle and tuned dispense profile confined adhesive to the thread root without overflow, preserving thread fit and preventing screw seizure.
• Higher yield and throughput: Automated, robot-mounted dispensing removed manual variability and aligned with existing cycle times—assembly throughput was maintained while first-pass yield increased due to fewer reworks.
• Reduced maintenance and downtime: The short fluid path and wear-resistant wetted parts reduced clog events; quick-change nozzles simplified preventive maintenance and recipe changeovers.
• Material preservation: Low-pulse metering and minimized air ingress preserved adhesive performance and cure consistency for reliable thread locking over lifecycle tests.

Conclusion

By deploying the KSV1000 concentric auger solution with a purpose-designed micro-nozzle and tuned drive profiles, the Indian smartwatch OEM achieved precise, repeatable adhesive dosing inside threaded micro-holes—meeting the 0.20–0.30 mg target and eliminating thread contamination issues. The result was higher assembly reliability, reduced rework, and a scalable automated solution that integrates into their existing robotics and MES infrastructure. Mingseal can provide on-site DOE, nozzle variants, and MES integration packages to qualify this solution on customer adhesives and production lines.