A film web that clings to rollers, attracts dust, separates badly or gives operators a shock is not automatically a tension problem. Raising tension may make the web look steadier while leaving the electrical charge and its source unchanged. Start by preserving the job condition, locating the first span where the symptom appears and separating static behaviour from tracking, winding or slitting faults. Any shock, spark or suspected ignition risk also requires the plant's safety procedure and competent electrical review before production continues.
Record the symptom without asking an operator to reproduce a shock
Stop and secure the line according to the machine and plant procedure when an operator reports a shock, sees a spark, smells overheating or works with flammable vapour or combustible dust. Do not use a hand, loose metal object or improvised lead to test whether the web is charged. Escalate the safety condition before treating it as a productivity complaint.
Describe what is actually happening. Record web cling, poor separation, dust attraction, double layers, erratic trim, labels lifting, roll blocking, discharge noise or a shock at a specific point. Note the material construction, coating, width, speed, tension zones, slit pattern, roll diameters, line direction, date, time and room condition available from maintained instruments.
Mark the exact event that starts the problem. A symptom that appears only after slitting, at a peel point, during acceleration or as a finished roll grows gives different evidence from a charged web arriving at the unwind. Keep an affected sample and a simple web-path sketch so the location is not lost after the machine is cleaned or rethreaded.
Find the first charged span along the web path
Inspect the route from unwind to finished roll in the normal running direction. Mark every point where the web contacts, separates from or changes direction around a roller, nip, guide, knife, trim device or rewind. The first location where cling, dust attraction or an approved static reading changes is more useful than the place where an operator finally notices the fault.
Compare the same material at controlled low and normal production conditions only after the safety review allows the test. Record changes during acceleration, steady running, deceleration and a planned stop. If the symptom rises sharply with speed or follows one separation point, preserve that result. Do not keep increasing speed simply to create a stronger discharge.
For a multi-lane job, compare lanes and both sides of the machine. One affected lane can point towards local contact, trim routing, core position or a particular roller surface. A full-width change after a material or humidity change needs a broader review. Avoid a master-tension adjustment until this cross-web pattern is known.
Separate static behaviour from mechanical web instability
Check that the parent roll is centred and sound, the web is threaded correctly, rollers turn freely, guides use the intended reference and the trim leaves cleanly. A wrinkled, wandering or rubbing web can create changing contact and separation points. Static can then be a consequence of poor handling rather than the only fault.
Review unwind, process and rewind tension against the approved recipe. Look for a sticking dancer, saturated guide correction, slipping core, unstable nip or a narrow lane entering the rewind at an angle. Correct mechanical faults by the machine procedure. Do not use extra tension to force a charged film against the path, because that may stretch the web or change roll hardness without removing the charge.
Inspect the slit edges and trim route. A narrow trim that whips, wraps a roller or rubs the finished web can make the symptom intermittent. Restore the approved guards, suction or collection route and verify that all lanes separate cleanly. Never reach into a moving web path to pull charged trim away.
Check the installed static-control and electrical condition safely
Identify the static-control devices already fitted and record their make, model, position, distance, angle, cleanliness, status indication and maintenance history. PRATI's published digital-finishing configurator lists carbon anti-static and ionising anti-static bars among available options. That confirms that static control can be part of a finishing configuration, but it does not prove that any device suits this machine, web or hazardous area.
Have competent personnel inspect protective earth, bonding connections, cables, power supplies, interlocks and the machine manufacturer's specified mounting condition. The UK Health and Safety Executive advises earth bonding and other controls to avoid static generation in printing, and it links static control with fire and explosion risk. Do not bypass a protective device or attach an improvised earth to a moving shaft.
Clean and maintain installed eliminators only by the supplier's isolated procedure. The HSE paper-industry guidance says electrostatic eliminators on insulating web-fed material should be suitable for the area, kept clean and properly maintained. A contaminated emitter, damaged cable or unsuitable location needs correction by authorised personnel, not a closer live adjustment during production.
Include material and room conditions in the diagnosis
Compare every layer in the complete construction. Liner, coating, adhesive, print, varnish and lamination can change how the web contacts and separates through the line. Record supplier, grade, batch and conditioning history. If the problem began with a new roll or conversion route, retain both accepted and affected material for comparison.
Use the plant's maintained instruments to record temperature and relative humidity near the line. Treat the values as evidence, not a universal setpoint. The acceptable condition depends on the material, process, building controls and supplier guidance. Do not add uncontrolled moisture, mist or an unapproved chemical to the web to make static symptoms disappear.
Check whether dust, solvent vapour or another hazardous atmosphere can be present. The safe equipment classification and response must come from the site's risk assessment and applicable rules. Production troubleshooting cannot replace that review. If the hazard basis is unclear, hold the job until the responsible safety and electrical personnel approve the test condition.
Prove the correction through the complete production sequence
After authorised corrective work, repeat the same mapped check with the same material, web path, slit pattern and measurement method. Run through startup, acceleration, normal speed, deceleration and the intended finished diameter. Inspect cling, dust attraction, trim behaviour, lane separation, roll faces and any approved static readings at the marked positions.
Confirm that the correction did not create a mechanical defect. Measure finished widths, inspect slit edges and roll build, and check that web guiding and tension remain inside the approved job limits. A lower static reading is not enough if the film now scratches, wrinkles, telescopes or winds with a loose edge.
Save the web-path map, material and batch, room condition, speed, tension, slit pattern, first charged span, device identification, maintenance action, responsible approval and before-and-after readings. Royal Coat represents PRATI finishing technology across India, Bangladesh, Sri Lanka, Nigeria and Kenya. For a finishing review, send the machine and web details, safety constraints, symptom map, photographs taken under safe conditions and the existing static-control configuration.
Questions from production and purchasing teams
What to ask about static control in slitting and rewinding
Should web tension be increased when film clings after slitting?
Not before the cause is mapped. Extra tension may steady the web while leaving charge generation, faulty static control or an unsafe electrical condition unchanged, and it can create stretch or poor roll build.
Can an operator test static by touching the web?
No. Do not reproduce a shock with a hand or improvised object. Follow the plant safety procedure and use competent personnel and approved instruments for electrical and static checks.
Why does only one slit lane show the problem?
Check that lane's contact and separation points, trim route, core position, rewind entry, roller surface and local web handling before changing the master settings.
Does fitting an anti-static bar solve every cling problem?
No. The device type, location, condition, power supply, area classification, web material and actual charge source must be reviewed for the application. Existing web-handling faults also need correction.
What evidence should be sent for a static-control review?
Send the machine and web construction, path sketch, symptom and first affected span, speed, tensions, slit pattern, roll sizes, room readings, static-control device details, maintenance history and safe before-and-after measurements.