Banding is the act of applying multiple wraps of stretch film
to a certain area of a load to reinforce and/or unitize a
number of layers or products.
Between Frame Rails: The distance between the (2) outside
frames on a conveyor section. Sometimes referred to as effective
BFR, which would represent the usable width of the conveying
A film extruded by the blown (balloon type inflation) system.
Typically blown film is a tougher but noisier film than cast
The revolutions of film applied by a stretch wrapping system
to the lower layers of a pallet or load. Typically more than
one revolution is applied to this area to increase the load
stability of the unitized load.
A mechanical roller that provides a resistive force that reduces
the film feed rate being supplied to the load. The resulting
"drag" will create an increase in tension between
the load and the stretch film roll.
Molten plastic extruded over full width of a die, then cooled
and crystallized over a drum. Cast film typically is quieter,
more transparent, and glossier than blown film because of
(single side - two sided - differential)
Cling is a bonding agent added to stretch film to increase
the stickiness quality of the film. This is desirable to allow
the layers of stretch film applied to bond to the previous
layers effectively creating a single wall of stretch film.
Depending on the desired effect the bonding agent is applied
to one or both sides. It is most commonly applied using co-extrusion
where the bonding agent is a layer that is co-extruded during
the manufacturing process.
Cold Rolled Steel.
Bar (Dancer Arm)
Is a pivoting roller that measures the film feed requirements
of the pallet. As the pallet rotates, the stretch film needs
to accelerate and decelerate around the corners to maintain
a constant film force (or tension) on the load. The dancer
bar pivots as the load demands more or less film fed. This
is one common method by many manufacturers to measure this
film feed requirement.
Erasable Programmable Read-Only Memory: An electronic device
"chip" that provides a means for storage and communication
for a microprocessor program associated with the PLC.
As a film is applied to a load the speed or velocity at which
it is applied is called film feed. The feeding of the film
is rarely constant as it must be accelerated and decelerated
to compensate for the corners of the load to keep the film
tension constant. Without this corner compensation feedback
the film tension would increase as at the corners causing
potential damage or film breakage issues.
Force (Film Tension)
Film Force is the retaining force applied by the stretch film
on the product being wrapped. This force is typically measured
in pounds. Film force is created two ways. The second method
is by delaying the film feeding out of the carriage. During
wrapping the film is fed out at a constant tension. By delaying
the response (speed) of the carriage film feed, you electronically
increase the film tension. A film force dial is typically
located on the control panel or carriage.
A feature typically used on automatic stretch wrapping equipment
whereby the film force feature is disabled for a time at the
beginning and end of the cycle. This feature prevents unwanted
tension at the two points during the cycle where added tension
would create problems. The stretch film pulling out of the
clamp at the beginning of the cycle and the detaching of the
trailing tail at the end of the cycle are typically remedied
by film force release.
Is the imperial measurement used for measuring film thickness.
See the stretch
film conversion chart for metric to imperial conversion.
Film memory is THE key reason for prestretching stretch film.
Prestretching stretch film creates a memory in the film, which
causes a continuous elastic effect as the film tries to return
to its unstretched self. This ensures that the load integrity
is maintained even as the load shifts or settles during transit.
It is this film memory that differentiates prestretched film
from non-prestretched film or other means of unitizing. For
instance, settling that occurs during shipment can loosen
other methods of unitizing (strapping) where prestretched
film memory takes up the slack and continues to secure the
The film tail is the stretch film end piece that is applied
to a pallet or load to start a wrapping cycle. It is also
the stretch wrap end piece created when cutting the film at
the end of the wrapping cycle.
Stretch film designed to be post stretched or tensioned stretched
by personnel without equipment is called hand wrap. Typically
hand wrap does not have the stretching abilities of machine
wrap and is wound on smaller and lighter rolls for easier
Home position is the position of all the moving sub assemblies
on a stretch wrapping machine when they are at rest and ready
to begin a new cycle.
Idler rollers are used to bias the stretch film direction
as it travels through the prestretch carriage. In some cases
it is to ensure that the stretch film is maintained against
the prestretch rollers to prevent the film from slipping by
the prestretch roller.
Types - A-load, B-Load, C-Load
Stretch film and machine manufacturers have divided the types
of loads wrapped into three load types based on the degree
of difficulty to wrap the load or product.
A-Load: Is the simplest of the load types. Usually a std. pallet
with no sharp edges, clean sides without obstructions that
may interfere with the application of the stretch film
B-Load: This load type may have
C-Load: The most difficult type of load. It may be unstable, with
sharp corners that may have an effect on speed
Is the measurement of a pallet or product load across the
diagonally opposite corners. This dimension is critical in
determining the overall size of a stretch wrapper. The difference
in this dimension in the largest load to be wrapped and the
smallest can also effect how the machine needs to be designed.
The equation for determining a load diagonal of any pallet
is /(L2 + W2). (Click
here for a load diagonal calculator.)
Is the metric measurement used for measuring stretch film
here for a gauge to microns conversion chart).
As film is stretched there is a tendency for the film to narrow
(similar to bubble gum). This narrowing of the film is called
neckdown. Neckdown reduces the coverage a revolution of stretch
film provides thus potentially increasing the number of revolutions
required to wrap a pallet or load. The larger the distance
between the two rollers stretching the film (Primary &
Secondary prestretch rollers) the larger the neckdown.
National Electrical Manufacturers Association: An association
that rates electrical devices for uses in various environments.
Eg. NEMA 12 rated devices are intended for in-door use and
provide a degree of protection from circulating dust and dripping
non-corrosive liquids. NEMA 4 rated device are intended for
indoor/outdoor use and provide a degree of protection from
blowing dust and splashing non-corrosive fluids.
As stretch film is applied to a load the stretch film is typically
applied so that the next layer of stretch film is applied
over the previous layer. This overlapping of film layers increases
load retention. By slowing the vertical movement of the stretch
film carriage the larger the overlap created.
Is the amount of stretch film applied over the top of the
load. As the stretch film reaches the top of the load, the
vertical movement of the carriage can continue so that the
film angles over the top of the load. The stretch film on
top creates a downward force on the pallet load. This is also
used when a plastic top sheet or corrugated top cap is applied
on the top of the load to lock them in place.
Programmable Logic Controller: An electronic microprocessor
device that stores and executes automatically a series of
programmed commands that produce a machines sequence of operation.
(See Tension Stretch)
Prestretch is the process of stretching the film in a prestretch
carriage PRIOR to (Pre-) applying it to the load to be wrapped.
As the stretch film passes through the carriage it threads
past two rubber rollers (Primary roller & Secondary roller).
The secondary roller is usually larger than the primary roller
and its rotational speed is geared to be faster than the primary
roller. This differential of speed where the secondary roller
is pulling the film from the primary roller causes the film
to stretch between the two, thus prestretching the film between
one and the other.
Is the assembly n a stretch wrapper that stretches the film
prior to applying it to the load. Located on a vertical traveling
slide, the prestretch carriage applies a spiraling layer of
stretch film to the load thus encapsulating the load in stretch
Is one of two rubberized rollers located in the prestretch
carriage used to create prestretched film. The primary roller
is the first rubberized roller the film passes by and is usually
the smaller of the two. Its speed is also geared slower than
the secondary roller.
Gathering the full width of the film using a bar or roller
so that it creates a "rope" is called roping. Stretch
film that has been roped is nearly unbreakable and is most
often used to lock a pallet to the product. This is easily
done with a turntable style machine. With rotary arm style
machines an air cylinder can be used to actuate the roping
process. In some cases, roping has eliminated the need for
other packaging materials such as strapping.
- Motor Control Board
Silicon Controlled Rectifier: A means of controlling a DC
motor's rotation speed.
Is one of two rubberized rollers located in the prestretch
carriage used to create prestretched film. The secondary roller
is the second rubberized roller the film passes by and is
usually the larger of the two. Its speed is also geared faster
than the primary roller.
Tension stretch (or post stretch) is the method of stretching
the film by pulling (or tensioning) while the film
is applied to the pallet. Although this increases the film
force, the load being wrapped limits this tension. Empty PET
bottles or light boxes will be crushed or damaged by high-tension
stretch. Layers of product can be swept of a pallet and film
breaks also increase as the tension stretch is increased.
Top sheet dispenser is a piece of equipment that applies a
poly sheet of plastic top sheet to the top of a load to provide
a water resistant layer. Typically, once applied, a top sheet
is subsequently wrapped with stretch film to secure it in
place. The top sheet film is unrolled, cut to size, and applied
to the load automatically by the top sheet dispenser.
Is the poly plastic film that is applied to the top of the
Top wraps are the extra revolutions of stretch film applied
to the top portion of the load to be wrapped. As the top layers
are susceptible to shifting in transit extra layers of stretch
film (top wraps) is applied. These extra revolutions are typically
set using the top wrap counter located on the control panel.
Ultra High Molecular Weight: A type of plastic commonly used
in applications where a linear bearing between sliding assemblies
is required. Low wear and reduced friction properties make
this a commonly used product in stretch wrap equipment.
- Variable Frequency Drive
A device used to provide full control of an AC motors shaft
rotation speeds. VFD's offer a wider range of features as
seen on SCR DC motor control board (see SCR). Features include,
display diagnostics, multiple step speed control features
and fully reset-able from voltage problems such as power surges.
Wrap parameters are the variable settings on a stretch wrapping
system that can be adjusted to meet the load retention requirements
of the product to be wrapped. These parameters typically include
settings like: Top wraps, bottom wraps, film carriage vertical
speed, turntable (or arm rotation) speed, and film force.