PAPER INDUSTRY WEB (PIW)

INTRODUCTION TO WINDING

PURPOSE OF THE PAPER MACHINE WINDER

The paper comes off the paper machine in very large rolls called jumbo rolls or reels The jumbo is the width of the paper machine ranging nominally from 100" to 360" {2540 to 9140 mm} wide. The jumbo roll is wound on a shaft called a reel spool. The reel spool diameter and weight is proportionate to the width of the paper machine and the weight of the jumbo. It is not unusual to see reel spools 30"to 36" diameter {762 to 914 mm} and jumbo reels greater than 100"{2540 mm} diameter. On large paper machines jumbo rolls can weigh in excess of 35 tons {31.7 metric tons}.

The purpose of the machine winder is to convert the large jumbo roll into sizes convenient to ship. The size of the "shipping roll" will be determined by the end use, generally referred to as the converting process. Examples of some of the converting end uses are printing presses, corrugating machines, bag machines sheeters etc.

THE TWO BASIC WINDER TYPES.

The most popular type paper machine winder is known as a two drum winder. The two drum winder winds the rolls on a single axis, all the rolls being wound on a common center, adjacent to each other across the width of the winder. Papers wound on a two drum winder are standard newsprint, fine papers such as tablet or copy papers, board grades, tissues, and towel-to name a few. Normally, only a single two drum winder is required to handle the paper machine production.

A second popular type paper machine winder is known as a duplex winder, used to wind papers that are considered difficult to wind, that is: To structure the shipping rolls in a manner that the defects in the roll will be reduced. Papers wound on a duplex winder are generally coated papers such as magazine stock, high gloss specialty papers, enhanced newsprint, etc. These are papers that are filled with coating materials and processed in an additional finishing operation to make the surface extremely smooth and glossy. In looking at a it will be noted that unlike a two drum winder, each individual roll is supported and wound at separate winding stations located on opposite sides of a center drum across the full winder width.

It is important to recognize the dynamics of a paper machine winding process. The equipment used is massive and subject to abuse through hard use. The winder differs significantly in operation from the paper machine. The paper machine is a continuos operation. On the other hand, the winder is considered a batch operation. The process is stopped on a routine basis to load new jumbo rolls in the unwind and to eject finished sets out of the winder. Because the winder is a batch operation, it must operate at a higher speed than the paper machine to stay ahead of the paper machine production. Winder speeds are generally 2 to 2 1/2 times faster than the paper machine.

To satisfy the production requirements of the paper machines, winders, in addition to their inherent high operating speed, must cycle massive components rapidly to reduce down time. Most winding functions are automated both from a mechanical and control standpoint. To appreciate the dynamics of a winder operation, consider the weight of the jumbo roll in the unwind. The jumbo can weight in excess of 40 tons {36.3 metric tons}.

When winding at high speeds it is not uncommon to observe the jumbo roll from the machine reel accelerate from 0 speed to 7500 FPM (85 MPH) {2286 MPM (137 KM/HOUR)}in 1 to 2 minutes, run at a steady state and then decelerate to a stop in 1 to 2 minutes. All this must be done in very strict control to produce uniform roll structure and minimize lost time by sheet breaks in the winder. This cycle can be repeated 160 times per day on a high speed newsprint paper machine processing 40" {1016 mm} diameter rolls at 4000 FPM {1219 MPM}.

WINDER COMPONENTS

There are numerous components in a high speed paper machine winder. Each type winder consists of five basic sections and a large number of lesser size components. The slitter section includes the slitters required to cut the jumbo roll to various widths and trim the front and back edges of the jumbo roll. There can be almost any number of slitters across the width of the winder as well as several versions of mechanical and automatic slitter arrangements. Slitters can number anywhere from 3 or 4 up to 20 or more on a single winder. The slitter section also includes the lead in roll, various rotating rolls to support the sheet during the winding process. as well as the before slitter spreading device.

The windup section (or drum section) includes an additional spreading device, a wound roll ejector, the winder drums that support the winding rolls (called a set) during winding, the necessary heavy framework to support the various other components such as the rider roll, the core chucks, and their associated parts.

The two drum winder and duplex winders have variations of the same components and are arranged differently to accommodate the winding principles. Depending on the winder builder, the slitter section can be an overhead configuration or arranged below the floor in the basement. Various arrangements can have both before and after spreader rolls or a single spreader located before the slitters. In the case of the two drum winder, one winder will generally be sufficient to handle a single paper machine.

The duplex winder, by it's very nature, is less efficient from a production standpoint than a two drum winder. In most cases, on grades where a duplex winder is required there will be two duplex winders following the paper machine.

THE UNWIND SECTION

The unwind section consists of a pair of heavy stands that support the jumbo roll during the unwinding process.  A braking mechanism is located at the drive side (back side) of the unwind stand. The brake can be a mechanical unit, a regenerative electric motor or a combination of the two depending on the duty of the winder.

A simple mechanical brake is used to control the tension in the sheet during winding. The pure mechanical brake does not provide inertia compensation for the heavy mass of the jumbo roll unwinding in the unwind stand. Control of the unwinding process is by the brake holding back on the sheet during unwinding and regulation of the accel/decel rates. This arrangement is cost effective for a simple winding operation. A pure mechanical unwind brake is popular on heavier weight papers such as liner board and pulp.

A popular arrangement on lighter weight sheets when accurate tension control and inertia compensation of the unwind jumbo roll is required is an electric motor configured as a regenerative brake. The regenerative brake has the ability to "motor" the sheet through the winder, permitting higher acceleration rates than a mechanical brake and quicker deceleration rates due to the inertia compensation for the jumbo roll.

A third arrangement, is a combination mechanical/regenerative brake. This arrangement has a couple benefits over either of the above, particularly when higher than normal amounts of HP are required. Very large regenerative brake motors are costly. The high cost of a single large motor can be minimized by using two half size motors coupled in tandem. The cost of spares is somewhat reduced also. Some mills prefer to use a half size motor and couple it to a mechanical brake. It has an advantage of a "back-up mechanical brake at reduced speed if the electric motor requires maintenance.

Depending on productivity or available space the unwind section may also include extended jumbo roll storage rails, jumbo roll injector, empty reel spool ejector and overhead reel spool storage rails.

WOUND ROLL DISCHARGE SECTION

Every winder must have a means to handle the rolls out of the winder. The discharge section generally includes a winder bridge or gate to deliver the wound roll set to a cradle for lowering the rolls to floor level. Most modern winders use a cradle that includes an integral bridge. After the rolls are discharged from the winder, operators plug and label the individual rolls of the set and dispatch them to a roll wrapper for shipment or storage.

ELECTRIC DRIVE SECTION

The electric drive section consists of various electric drive motors for the unwind, slitter, and windup section including drives for paper rolls, rider roll and other rotating elements as needed. The electric drive control hardware and software is included in the drive vendor package and normally installed in a temperature controlled environment. A typical electric drive for a two drum winder will consist of an unwind breaking arrangement using any of the brake arrangements described earlier, to provide sheet tension and inertia compensation of the large jumbo roll. Separate motors are connected to each winder drum. The winder drum drives are configured to provide differential torque (or speed) to the drums to assist in optimizing wound roll structure. There are individual drive motors on paper carrying rolls and spreader rolls as required to reduce friction transients imposed by the inertia of the rolls during acceleration and deceleration There are also fractional motors used for slitters and other winder functions as required.

The basic duplex winder electric drive is similar in many respects to the two drum with the exception of a single drum drive The individual winding positions of a duplex winder require an additional drive and control level to accommodate the center torque of the individual winding stations although some manufacturers may not use centerwind drives.

MISCELLANEOUS COMPONENTS

There are a host of other components associated with the winder including the main operator control station, core loading equipment, empty spool removers hydraulic systems, trim systems and other specialized systems to suit individual installations.

It should be noted, for clarification that two drum winders are used in varying configurations. The slitter sections can be arranged in either a vertical or horizontal arrangement. There are two drum winders that use compliant drums, belted drums, non level drums, inclined ways, three winder drums, etc. Then there are variations of these winders used as reclaim or reprocessing in off machine utility.

Similarly, duplex winders are manufactured in many configurations. Two major groups are the core support and drum support versions. There is also a breakdown in the nip and centerwind configurations. Regardless of the multiple arrangements and configurations, most winders can be sorted in the two classic groups-two drum or duplex. The slitters can be above or below the floor line.

Luigi Bagnato-Paper Industry Web