Glossary

1) Flexible packaging
As the name implies, this type of packaging makes use of flexible substrates including paper, plastic films such as OPP, PET, CPP, PVC, POF and aluminium foil in their plain, printed, coated, co-extruded and laminated combinations. Its main advantages over the traditional packaging methods include economy, aesthetics, adaptability, low weight per unit product and transportability.
2) Center Rewinding
In Center Rewinding, the winding force is derived solely from the rewind shafts and is transmitted to the web through the core and layers of material which have already been rewound. The Rewind shaft is usually driven by a motor.
3) Duplex center rewinding
Two shafts for Rewinding the slit substrate. This ensures a positive separation between adjacent slit reels, which are wound alternately on the two shafts.
4) Surface Rewinding
The winding force is derived from both the Rewind shaft and the contact with the winding drum. Here, both the Rewind shaft and the winding drum are driven by through a clutch mechanism and motor respectively.
5) Center-Surface Rewinding
The winding force is derived solely from the rewind shafts and is transmitted to the web through the core and layers of material which have already been rewound. The Rewind shaft is usually driven by a motor.
6) Differential Center Rewinding
The rewind cores in such type of rewinding are gripped from within by means of mechanically expanding quick locks. The core holding quick locks are are separated by keyed discs which slip against keyless friction discs to create a series of differential slip clutches. Pneumatic pressure is directed axially on the differential slip clutches so that each coil behaves like an individual slip clutch, free to rotate at the correct rpm to compensate for uneven thickness of the substrate. Automatic adjustment of Differential tension in relation to the coil diameter through a diameter sensing device and a Taper Tension preset ensures uniform coil density and good winding quality.
7) Shaftless unwind and rewind
In a machine employing a shaftless unwind section, the reel is not mounted on a shaft but is secured on the machine directly by spool holders which move laterally through the use of pneumatics for loading and unloading. The advantages over a shafted unwind include reduced changeover time and maintenance requirements.
8) Self centering
In a self centering shaftless unwinder, the unwind brackets which house the spool holders move apart or together in equal measure so that the reel remains in the center of the machine irrespective of its width.
9) Razor in groove
This mode is primarily used for films and low thickness foil. Here the material wraps around a special roller with equally spaced grooves cut into it and the razor can pass through the material into these grooves.
10) Razor in air
Also used for film and low thickness foil, in this variation of razor cutting the razor is inserted through the web which passes over two closely spaced idler rolls creating a space where the razor can be inserted.
11) Tangential rotary
The rotary slitting mode is effectively employed for paper, foil and thicker laminates. In this mode a round male knife intersects with a round female knife with a suitable depth of intersection and is loaded against the female knife to form a “scissor” at the point of cutting. In traditional rotary cutting Slitters, the web wraps around a bottom shaft which is loaded with female knives separated with variable size spacers preselected as per the slit width. The male knife can pass through the material into the corresponding gaps between the alternating female knives and spacers. In tangential rotary cutting, the web merely kisses the female knives at the tangent. The absence of a wrap around the female knives permits a bottom shaft without sizing spacers and a much faster set up in which the female knives are moved to the appropriate positions and locked.
12) Quick locks
These are the mechanically expandable core holders designed for use on the rewinder of a duplex machine. The empty cores are gripped and the finished coils released by a twist in either direction. This allows a cantilevered construction of the rewind shafts in which the shafts remain fixed to the machine while the individual cores/coils are loaded/unloaded thus reducing the time and effort for changeover between sets.
13) Taper tension
Unlike the unwinding process where a constant tension is ideal, the tension of a rewinding reel needs to be reduced with increasing reel diameter to obtain good rewind quality free from telescoping, blocking and other undesirable conditions. While this holds true for all rewinding applications, a good taper tension control is crucial on a Slitter rewinder with Differential Center Rewinding for the proper release function of the quick locks and considering that in most cases the output reels are the end product to be supplied to the customer.
14) Splice Table
This unit is positioned after the unwind reel and comprises a table with a transverse slot and a pair of pneumatically loaded full length grippers on either side of the slot. During unwind reel changeover the web is pressed against the table by use of the grippers and thereafter the cut and splice operation between the expiring and new web is made.
15) Differential Rewind shafts
These are a refinement of the quick lock system. Here the pneumatic pressure is directed radially outwards from the center of the shaft towards the inner diameter of the quick locks. The slip action is between the quick locks and friction strips which are fixed to the shaft along its length. In such shafts the quick locks are manufactured in small widths and cover the entire shaft. These shafts allow slitting unequal width coils on the same shaft and also reduce the changeover time between different widths due to their continuous coverage on the shaft.
16) Locked core winding
As against Differential Center Rewinding, the rewind reel/s in locked core winding mode are directly subjected to the torque of the motor and there are no intermediary slip clutch mechanisms which are essential for Differential Center Rewinding. This winding technique is suited to thick materials with no thickness variations.
17) Load cell feedback for Rewind
In case of locked core winding, the feedback for tension control is through a pair of load cells housing an idler roll positioned before for each rewind. These load cells indicate and provide feedback to control the cumulative tension of all the coils being rewound on the corresponding shaft.
18) Segmented Rider rolls
In case of delicate material having large thickness variations, adjacent coils on the same shaft will build up with considerable diameter variations. While the technique of Differential Center Rewinding compensates for these variations between coils by different rewinding rpms, a single rider roll would lose contact with one or more coil, resulting in the affected reels not benefiting from the action of the rider roll. To overcome this limitation, instead of a single rider roll, multiple (segmented) rolls are the best solution.
19) Skew roll
Positioned after the unwind this roll is provided with a mechanism to move it out of line with the unwind reel, to compensate to some extent for lose and baggy edges.
20) Stroboscope
This is a flashing light device which uses the principle of “persistence of vision” to momentary illuminate the area being inspected, giving the illusion of a still image when the flash rate is above a certain threshold and in synchronism with the image.
21) Resizing
One of the functions of a Web inspection or Doctoring machine is to reduce or increase the diameter of the reel to a size more suited for distribution or downstream process/es.
22) Re-spooling
Another possible function of a Web inspection or Doctoring machine is to rewind onto a core having a different diameter more suited for distribution or downstream process/es.
23) Rider rolls
A pre-requisite for any high speed rewinding operation, these rolls are pneumatically pressured against the rewinding reel/s and travel in a predetermined path to always be in contact with the reel as it builds up. The function of this roll is to iron out entrapped air and prevent successive layers of the reel/s from slipping. Well designed rider rolls are particularly indispensable to achieve good winding quality while handling materials (mainly films) having a low coefficient of friction.
24) Telescoping
This is a rewinding condition where due to poor control over taper tension, successive layers of material rewind with more than required tension, squeezing the lower layers and resulting in the formation of a reel which can be best described as a telescoped reel.
25) Cantilevered
A cantilevered shaft is permanently connected to only one side of the machine.It is commonly employed for Slitter Rewinders for the duplex rewind section and offers a quick and effortless way to unload the rewound rolls from the shaft. A temporary device such as a pneumatically retractable slide door is used to support the end of the shaft as it is rewinding. Besides faster changeovers, another advantage of a cantilevered construction in case of Doctoring machines is easy access to the web.
26) Primary slitter
These Slitting machines are used by manufacturers to convert the mill reel from a paper/film/foil producing line into reels smaller in width and/or diameter suitable for distribution or further downstream process/es. The working width of these machines is quite high (upto 15 meters) and generally corresponds to that of the mill.
27) Secondary Slitting and Rewinding
These Slitting machines are used by Flexible packaging and converting companies to convert the jumbo reel (after operations such as printing and lamination) into multiple reels corresponding to the width of the package design. The working width of these machines is generally in the range of 1 meter to 2.4 meters and would depend on that of printing and lamination facilities.