This machine tutorial explains how to operate and troubleshoot paper bag forming: timing map for reliable square bottom geometry 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.
Square bottom paper bags depend on timing harmony between tube transport, bottom opener, and patch applicator. If one station lags, geometric distortion appears as leaning bottoms and unstable standing performance.
Build a timing map from encoder zero to each actuator event, then verify in slow-speed production mode. Jog mode validation is not enough because adhesive transfer and paper stretch behave differently when inertia increases.
Step-by-step machine procedure
Paper moisture variation changes fold memory and affects corner sharpness. Operators should log incoming reel moisture and adjust precondition storage rather than over-correcting machine settings for every lot change.
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
Adhesive viscosity must be verified at actual room temperature near the glue unit. A nominally correct viscosity at lab conditions can become too thick on the floor, causing incomplete spread and random bottom leaks.
Include compressive load testing on filled samples during FAT. Geometry that looks acceptable empty may fail stacking tests when product weight shifts pressure toward one bottom corner.
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.