Slitter Rewinder

Overview

A slitter rewinder takes a wide parent roll of film, paper, foil, or laminate and cuts it lengthwise into several narrower rolls, winding each one up separately. It sits at the end of a printing, coating, or lamination line, where material is made in wide master rolls for efficiency but must ship in the narrow widths a packaging or converting machine actually uses. The machine unwinds the parent roll, runs the web through a bank of knives that slit it into strips, and winds each strip onto its own core at controlled tension so the finished rolls are tight, even, and free of defects. Slitting quality decides how well the narrow rolls run downstream, so edge cleanliness, roll hardness, and tension control are the things the machine is built around.

The web travels from the Unwind Stand through the Slitting Section section, along the Web Path, and onto the Dual-Shaft Rewind. The Drive System holds line speed and winding tension, and the Control System sets the slit recipe and stops the line on a web break.

Unwinding the parent roll

The heavy parent roll is loaded onto the Unwind Stand by a Roll Lift set of arms, then gripped on a Unwind Air Shaft that expands into the core. A Unwind Brake or motor controls how fast the web pays off, holding the tension read by Tension Load Cell sensors. A Edge Guide keeps the web centered as it leaves the roll so the slit positions stay correct across the width. Consistent unwind tension is the foundation for everything downstream, because a slack or surging web slits poorly and winds loose.

Slitting the web

The Slitting Section section cuts the full-width web into strips. The most common method on film and laminate is shear slitting, where the Shear Knife Set set pairs a rotating Top Knife against a Bottom Knife on a Knife Shaft, cutting like a row of rotary scissors for a clean dust-free edge. Thin films can instead be razor slit, where a blade in a Razor Holder slices the web against air or over the Anvil Roll. A Knife Positioner sets each knife to the programmed width. Slitting throws off narrow edge trim, which a Trim Removal system pulls away: a Trim Blower suctions the trim through a Trim Duct to a bin so it does not foul the rolls.

Winding the finished rolls

The slit strips wind onto the Dual-Shaft Rewind. Two Rewind Shaft shafts let the machine wind alternate strips on opposite shafts so adjacent narrow rolls do not interfere, and each strip sits on a Differential Core Chuck differential chuck that lets it find its own torque even when strips run at slightly different effective diameters. A Rider Roll presses on the building rolls to control how much air winds in, which sets roll hardness. Each shaft is driven by a Rewind Drive torque motor that tapers tension as the roll grows, so the core is not crushed and the outside is not loose. When the rolls are full, a Roll Pusher strips them off the shaft for unloading.

Web path and tension

Between the stations the Web Path routes and conditions the web. Idler Roll rolls support it, a Spreader Roll pair separates the freshly slit strips so their edges clear each other, and a Tension Dancer buffers tension swings. A driven Nip Roll sets the master line speed and isolates the rewind tension from the unwind, so the slitting zone sees steady tension regardless of what the winding rolls are doing. Stable tension through this section is what keeps the strips tracking straight into their knives and onto their cores.

Drive, control, and use

The Drive System uses several Servo Motor axes through Servo Drive amplifiers and Gearbox Housing reducers, one for the master line and others for the rewind shafts, so every roll winds to its own tension profile while staying in speed with the line. The Control System system, built on a Machine Controller and an HMI, stores slit recipes giving each knife position and winding tension, counts length with a Length Encoder so rolls finish at a set diameter or meterage, and stops on a web break. Slitter rewinders are used wherever wide web is converted to usable rolls: film and foil for flexible packaging, label stock, flexible printing substrates, and paper. Variants include duplex turret rewinders for non-stop roll change and shaftless designs for very large rolls. Knife choice depends on the material: shear knives suit laminate and foil where a clean square edge matters, razor slitting suits thin plain film, and crush slitting against the Anvil Roll suits soft nonwovens and tapes. Knives are consumable and dull with use, so a worn Top Knife that begins to tear rather than cut leaves a ragged edge that telescopes the wound roll, which is why operators check edge quality at every roll change and reset the Knife Positioner when changing slit pattern.