Coating streaks are persistent lines or bands in the coated layer. They can originate from contamination, fluid delivery, the coating head, a blade, a roller or the substrate. The shape and location of a streak are clues, not a diagnosis.
Capture useful evidence
Record whether streaks run along the web or across it, whether they stay at a fixed cross-web position, and when they first appear. Photograph both the product and relevant machine components after safe isolation. Mark the machine direction on samples, and note the coating batch, substrate roll, speed, temperature and time since cleaning.
Check fluid and delivery
Review mixing, filtration, contamination, air entrainment and supply consistency against the process procedure. An agglomerate or foreign particle can disturb coating locally; a supply change can affect the pattern over time. Keep retained samples where the plant procedure permits and avoid changing several conditions simultaneously.
Check the blade, roll and web
After lockout, inspect accessible blade edges, holders and working surfaces for buildup, damage or uneven contact, using the equipment maker's instructions. Look for deposits, scratches and wear on the roller, and for wrinkles or substrate defects. A line fixed across the web may suggest a stationary obstruction or local contact issue, but verify it with evidence rather than assuming the blade is responsible.
Test and document
When safe and authorized, make one controlled adjustment at a time and compare marked samples under consistent conditions. Keep a record of cleaning and component replacement. For a manufacturing or repair enquiry, send the roller or blade drawing, machine layout, fluid, photographs and defect history. Qichao can assess the part requirement; the line's root cause requires on-site investigation.