This machine tutorial explains how to operate and troubleshoot woven bag flexo surface treatment setup before printing on woven-bag flexographic printing 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.
Woven PP bags differ from smooth film because their surface energy and texture can vary significantly by supplier lot. Reliable flexo printing starts with pretreatment verification, not with aggressive impression or heavy ink laydown.
Step 1 is incoming substrate check for contamination, coating residue, and weave uniformity. Step 2 is corona or flame treatment confirmation to target dyne levels recommended by ink suppliers for the specific print system.
Step-by-step machine procedure
Step 3 is trial print using controlled impression and documented drying settings. Evaluate adhesion with tape or rub methods after adequate cure time. Immediate wet checks are useful but should not replace delayed adhesion verification.
Woven substrates demand surface treatment and impression discipline different from film. Confirm dyne level after corona or flame treatment and treat weave texture as part of dot gain calculation.
Use anilox and plate combinations proven on similar fabric weight. Yaoshg woven-bag flexo lines are often quoted with treatment and drying modules matched to ink chemistry—do not bypass treatment to save startup time.
Operator shift checklist
- Confirm surface treatment level on woven PP or PE fabric.
- Match anilox volume to ink solids and plate screen combination.
- Run low-speed proof to check smudge and mottle on fabric weave.
- Document plate cushion and impression for each bag width program.
Common defects and corrective adjustments
When adhesion is poor, do not immediately increase viscosity and pressure. Those changes can mask treatment failure and create smudging. Correct root cause by stabilizing treatment level and ensuring surface cleanliness through handling and storage controls.
Plants that formalize pretreatment release criteria reduce downstream claims significantly. A short preprint protocol costs little and prevents long rerun cycles caused by adhesion loss discovered only after bag conversion or customer filling operations.
Smudge and mottle on woven bags often improve by reducing impression and increasing ink dryness at exit—not by adding ink film weight. Check weave direction versus print direction for differential ink holdout.
Maintenance records and when to call service
Clean treatment electrodes and ground paths on schedule. Fabric dust accelerates anilox plugging—filter ink and increase cleaning frequency versus film jobs.
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.