Roller and equipment alignment relies on each roller or machine frame holding highly accurate relative positions. In smaller web lines where all rollers are supported from the same base, the goal is to keep all rollers aligned to each other. In large web lines that span many meters of length, across different sections of the building and possibly moving from one floor to another, holding all the rollers parallel to each other may prove difficult, need ongoing monitoring and occasional re-adjustments as the web or process demands them.

In an ideal web line, the roller and frame alignment would be checked and set upon installation and never need re-adjustment. However, many lines need to expect and plan for problematic misalignment and re-alignment.

Solutions

The most common areas to be alert for web handling equipment misalignment are:

  • Initial installation errors

  • Failure to pin or bolt equipment to the floor.

  • Foundation or earth settling over time.

  • Unpinned roller mounts (relying on bolt friction to hold alignment).

  • Asymmetrical deflection under load.

  • Cantilevered roller or shafts undersized for their load.

  • Off-center web and tension on rollers.

  • Web guides during active correction.

  • Pivoting rollers or rolls (nip roller, dancers, turret winder, or shaft arms) have several misalignment causes, including keyway errors, loosening bolts and pins.

  • Linearly sliding rollers or shafts.

  • Air nozzles and air turns, especially 45-degree turn bars.

  • Asymmetrical thermal expansion.

Solutions and best practices to minimize CD tension variations from equipment misalignment include:

  • Ensure foundation will support equipment weight and is stable over time. For smaller web lines, ensure all rollers and rolls are supported on the same rigid foundation.

  • Ensure equipment framework is rigid and stable. Design web line support to be symmetrical about the centerline to prevent under-load and thermal expansion misalignments.

  • Design equipment and rollers systems with considerations for ease of alignment, re-alignment, and holding alignment.

  • The first step to aligning pivoting rollers or shafts is to align the pivot axis. Make the pivot shaft or axis easy to align. For rollers and shafts that are intended to hold alignment while pivoting (e.g. dancer rollers, turret winders), use keyways or other designs to ensure arms remain parallel through their movement.

  • For dual-end supported rollers, shafts, or pivot shafts, use split cap roller mounts to ease removal and replacement into aligned position.

  • For cantilevered rollers mounted on a reference plate, use large base flanges to allow horizontal and vertical alignment. Avoid three-bolt tripod adjustment.

  • For cantilevered rollers without a thick side frame plate, use either: 1) low-deflection cantilevered beam and a dual-end supported roller. 2) a drive side dual-supported shaft.

  • Measure level and tram with precision alignment equipment capable of measuring less than 2 mils per foot errors (0.2mm/m). This includes optical transits with rulers and mirrors, laser alignment, pi tapes, and tramming sticks. This does NOT include standard tape measures or carpenter’s levels.

  • Drill and pin aligned rollers. Don’t trust bolt friction to hold a roller in place.

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