- 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
- 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
- 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
- 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
- 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.