This machine tutorial explains how to operate and troubleshoot paper cup leak test failure diagnosis on production lines on paper bag, valve bag, and paper cup forming machines. It is written for shift supervisors, maintenance technicians, and application engineers who need repeatable procedures—not theory alone.
Machine scope and operating context
Yaoshg field teams use this discipline on presses and converting lines built in Wenzhou—from early stack flexo units through CI, gravure, laminating, slitting, bag making, and paper container equipment. The steps below assume normal safety lockout rules, OEM manual limits, and documented substrate specifications for each job.
Leak test failures on paper cup lines are costly because they often appear late after cups are nested and packed. A structured diagnosis path separates bottom seal issues, sidewall seam problems, and rim integrity faults before crews adjust multiple stations randomly.
Bottom channel leaks usually trace to bottom punch temperature, knurl pattern condition, or adhesive/PE activation energy on the cup base disk. If failure maps to one angular position on the turret, suspect indexer alignment or worn bottom tooling before changing global heat.
Step-by-step machine procedure
Sidewall seepage along the main seam implicates ultrasonic or heat-seal parameters, overlap width, and board moisture content. Cups from high-humidity storage can pass forming yet fail hydrostatic test as fibers relax. Log ambient humidity with leak results to spot environmental correlation.
Paper cup and bag machines combine forming, sealing, and rim or bottom operations in tight timing maps. Paper moisture and glue batch affect wall strength—control inbound paper storage.
Double-wall cup lines add sleeve registration and bond control. Valve bag lines need spout placement accuracy to prevent dust leaks at filling partners.
Operator shift checklist
- Confirm paper moisture, glue batch, and former alignment.
- Map servo or cam timing for rim roll, bottom seal, or sleeve bond.
- Inspect wall strength and leak test on first production stack.
- Log tool wear indicators for punch, crease, and fold sections.
Common defects and corrective adjustments
Rim-related leaks show up as wicking along the curled edge during pressurized water or dye tests. These failures connect back to rim heater tuning, curl roller pressure, and top-edge board quality. Do not increase sidewall seal energy to fix a rim-dominated failure mode.
Inline leak testers should be calibrated with known-good and intentional-defect reference cups daily. Sensor drift mimics process instability and sends operators on false hunts through seal recipes that were already acceptable.
Close each leak event with photographic mapping of failure location on the cup circumference. Over several weeks, polar plots reveal whether defects cluster at seams, bottoms, or rims, guiding capital decisions on which tooling module needs refurbishment.
Rim rolling defects on cups often follow glue viscosity or rim temperature drift. Servo cam profile changes should be incremental—large cam edits destabilize related stations.
Maintenance records and when to call service
Log tool changes for punch, crease, and fold sections. QSR customers audit leak and wall-strength data—keep shift samples with machine serial and recipe ID.
If mechanical adjustment, drive parameter changes, or repeated defects exceed on-site scope, log serial number, job recipe, and photos before contacting Yaoshg service. Commissioning engineers can remote-review HMI trends when VPN or data export is available—faster resolution when shift records are complete.