第二十次课 Reeling and winding

The purpose of the Reeler is to wind the paper web onto a drum spool, also called a shell or a pope. The paper has to be wound on evenly with consistent tension to maintain paper quality for conversion. The Reeler has to be designed so that when a shell is full of paper, then another reel can be started without interrupting production.

Because during reeling the paper quality can not be improved, over several decades the simple pope reel was used with nearly no modifications. This type of reel only applies a line force system in the primary and the secondary arm and has no centre drive. The primary arm handles the spool at the beginning of the winding process and turns the spool around the centre of the reel drum. The secondary arm guides the spool on the horizontal rail. The line force system in the arms has to produce the nip load and compensate for the growth (weight!) of the roll. In the 1990’s demand increased dramatically. E.g. in LWC production coating has been changed from off-line to an on-line process. This means, that paper grades with critical properties (e.g. smoothness, density) have to be wound on the reel at high machine speeds. Furthermore the reel diameter has been increased from e.g. 2,8m to more than 3,2m for better paper machine efficiency.

Winding is the process of unwinding the machine reel off its Shell and rewinding onto a core. It is a stop start process and allows defective product to be removed and joins made as appropriate. It is possible to join two machine rolls together or to produce 2 or more reels for one machine roll at smaller diameters. It is common also to slit the web width into 2 or more narrower widths. With narrower board machines the winding process may be bypassed and the machine reel processed directly on a sheeter normally a Duplex sheeter.

It is common to have web orders and sheet orders run at the same time. The winder will therefore be run to separate the machine roll by next process route or with web orders slitting to the final size. Winders are also used as a subsequent process where the final reel size is too small to slit on a Machine winder. This may be due to narrow width, diameter or high aspect ratio which can not be handled on automated handling systems. For service reels can be processed from an intermediate reel store. Winders used for this process may be referred to as re-reelers or slitters and are characterised by shaftless reel stands.

The Re-winder unit is primarily used for re- winding the parent reel from the paper machine and slit it into smaller width and diameter reels. As can be seen in the diagram, the key controls on a modern re- winder are web tension, to make sure that the reels produced are wound evenly and with the same reel hardness and the slitter units to govern the roll width (to +/- <1 mm).

Reeling and winding 难点

New words

Homework According to the picture below, speak out the process of finishing.

补充内容 表面施胶 surface sizing 表面涂布 surface coating

Size Pressing is a process for modifying the surface of the paper or board. It was the traditional way to impart a degree of water resistance in the material, measured using the Cobb Test. This is important for printing and writing paper.

Surface Sizing is, traditionally, an impregnation process rather than a true surface coating process. Size press treatments can use a number of different ingredients, for example starch solutions, polyvinyl alcohol, polyurethane emulsions, styrene acrylic or butadiene, fluorochemicals etc. they can impart different properties to the sheet, for example water resistance or grease resistance.

The size press consists of a pair of, usually, rubber or polyurethane covered steel rolls which are cambered to provide an even nip pressure across the machine. The sheet passes between the rolls and the size press mix is introduced to the ingoing nip on either one side or both sides of the sheet. The amount of mix picked up is controlled in three ways, absorbency of the paper sheet, viscosity of the size mix and the nip pressure between the rolls. Coatweights can range from 1 or 2 gsm up to 10 gsm or more, on each side. There are three configurations of conventional size press, horizontal, vertical and inclined.

Rod or Bar Coater

The main function of a Rod Coater is to apply an aqueous coating onto the surface of paper, board or film. The Rod Coater has two primary elements, the Coating Applicator and the Metering device, which is the Rod. These coaters can apply a range of coatweights from 2- 3 gsm for a non-filled mix like starch, latex or polyvinyl alcohol through to gsm for a highly filled, high viscosity mix, for example to be applied to a paper board.

Fixed Fountain Blade Coater &Blade Coater

Fountain Blade Coating Line & Blade Profiling Assembly