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 aluminum 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 web is driven by the winding drum which is always in contact with the outer layer of the material being rewound. Here, it is the winding drum which is driven, also by a motor in most cases.
5) Center-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.
6) Differential Center Rewinding
This rewinding technique employs differential rewind shafts to enable each coil to act as 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 core 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 core 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
Used primarily for thermoplastic film and laminates, this variation sees the razor inserted into the web at a point where it passes over two closely spaced idler rolls.
11) Tangential rotary cutting
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. Tangential cutting also serves as the foundation over which robotic cutter positioning systems are designed.
12) 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 ball locks and considering that in most cases the output reels are the end product to be supplied to the customer.
13) Splice Table
On a slitter rewinder, 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.
14) Differential Rewind shafts
The torque in these shafts is imparted to the rewinding coils through pneumatic pressure which is directed radially outwards from the center of the shaft towards the inner diameter of the ball locks. The ball locks slip against the friction strips which are fixed to the shaft along its length. In such shafts the ball 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.
15) 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.
16) Lay on rolls
A pre-requisite for any high speed rewinding operation, these rolls are pneumatically pressured against the rewinding reels 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 lay on rolls are particularly indispensable to achieve good winding quality while handling materials (mainly films) having a low coefficient of friction.
17) 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.
18) 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.
19) 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 1.8 meters and would depend on that of printing and lamination facilities.