Flexo Print Starts Banding Above One Speed? Prove Plate Bounce Before Changing Ink

Capture the speed where the defect begins

Keep full-width samples from setup speed, the first speed where the fault becomes visible, normal production speed and the highest approved trial speed. Mark machine direction, operator side, drive side, station, colour, repeat, speed and time on every sample. If the bands disappear after slowing down, retain that sample too. The entry and exit speeds are useful evidence because resonance-related faults can be limited to a speed range rather than worsen in a straight line.

Record the press, deck, anilox, print cylinder or sleeve, adaptor, plate, mounting tape, substrate and impression settings without relying on the previous-job sheet. Photograph the identification on each physical component. Note whether the fault covers the full web, one lane, one colour or only an image area with a large leading edge or a gap in the printing surface.

Use direction and frequency to narrow the source

The Flexographic Technical Association's troubleshooting guidance treats defect direction and frequency as diagnostic clues. Variation running across the web can be associated with chatter, balance and alignment, gear marks or bounce caused by gaps in print-surface contact. Measure the distance between bands on the retained sample and compare it with the repeat and the circumferences of the plate package, anilox, impression cylinder and relevant idlers.

Do not label every regular band as plate bounce. A defect that matches gear pitch needs a gear and drive check. A mark that repeats once per cylinder revolution can follow damage, contamination or runout on that component. A stationary streak in the machine direction points the investigation elsewhere. The objective is to make the suspected source match the physical frequency before parts are replaced.

Check the image layout and mounted plate package

FTA notes that gaps in the printing surface can create bounce, particularly when the image has large unprinted spaces in the print direction. Review the imposed layout rather than judging only the individual label. A hard leading edge entering impression across several lanes at the same point can load the station differently from staggered graphics with more continuous contact.

Inspect the plate for correct thickness, relief, condition and secure edges. Confirm the mounting tape product and hardness, tape joints, trapped air and complete adhesion to the sleeve or cylinder. The FTA troubleshooting account notes that an unsuitable plate-and-tape combination can contribute to chatter, banding and bouncing, including a tape that is too hard for the plate. That is a reason to compare the approved combination through an optimisation trial, not to substitute tape by guesswork during a live order.

Reset to the approved kiss-impression method after the physical checks. Extra impression may temporarily fill a skip while increasing dot gain, heat and plate loading. Preserve the original and corrected settings with samples so the apparent improvement is not mistaken for proof of the root cause.

Inspect the sleeve, adaptor and air-mandrel interface

Clean and inspect the plate sleeve, adaptor and mandrel under the machine procedure. Check the bore and sealing surfaces, end damage, blocked or weak air outlets, fit, axial location and any sign that a component was forced into position. Confirm total indicated runout by the approved method and compare it with the component and press limits. A perfectly mounted plate cannot correct a damaged or incorrectly seated rotating package.

Polywest describes its POLYCARBON Allround adaptor as having a vibration-dampening multilayer carbon-fibre construction and positions it for improved printing performance at higher speeds. That product information supports a configuration discussion; it is not proof that every speed-dependent band requires a carbon adaptor. The press, hydraulic or pneumatic interface, repeat, wall thickness, face length, load and required speed range still have to be confirmed for the application.

Run a controlled speed and layout trial

Use one representative job and a written speed ladder. Allow the press to stabilise at each step, collect a labelled sample and record vibration observations, register, density or colour readings and the exact point where banding begins. Repeat the ladder after one authorised change, such as the approved tape package, a corrected component fit or a verified alternative adaptor. Do not combine a new plate, new tape, different anilox and altered impression in one comparison.

If image layout is suspected, test the prepress solution through the normal approval route. Staggering lanes may reduce the excitation, but artwork, die position and finishing constraints must remain correct.

Accept the result at startup, the affected speed range, normal production speed, stop and restart and the longest practical run. Check the complete printed web, not only the area where the first band was noticed. Keep the final component IDs, mounting specification, speed limit and approved sample with the repeat-job record.

Send evidence that can separate bounce from another repeat fault

Royal Coat represents Polywest across India, Bangladesh, Sri Lanka, Nigeria and Kenya. For a sleeve or adaptor review, send the press and station, repeat, face length, mandrel and adaptor details, component IDs, plate and tape construction, imposed layout, substrate, anilox, speed ladder, impression method, runout record and marked samples showing the band spacing.

Include the slow-speed sample that passes and the first sample that fails. Those two pieces usually provide more useful direction than a photograph of one rejected label. They allow the print pattern, rotating frequencies and component configuration to be reviewed before a different sleeve, adaptor, tape or plate package is proposed.