Banding
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.
BFR - Conveyor
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 surface.
Blown Stretch Film
A film extruded by the blown balloon type inflation system. Typically blown
film is a tougher but noisier film than cast films.
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Bottom Wraps
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.
Brake Roller
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.
Cast film
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 this process.
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Cling (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.
CRS
Cold Rolled Steel.
Dancer 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.
EPROM
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.
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Film Feed
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.
Film 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.
Film Force Release
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.
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Film gauge
Is the imperial measurement used for measuring film thickness.
Film Memory
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 load.
Film Tail
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.
Hand Wrap
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 manipulation.
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Home Position
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 Roller
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.
Load 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
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Load Diagonal
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).
Microns
Is the metric measurement used for measuring stretch film thickness.
Neckdown
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.
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NEMA
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.
Overlap
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.
Overwrap
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.
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PLC
Programmable Logic Controller: An electronic microprocessor device that
stores and executes automatically a series of programmed commands that produce
a machines sequence of operation.
Poststretch (See Tension Stretch)
Prestretch Film
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.
Prestretch Carriage
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 film.
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Primary Roller
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.
Roping
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.
SCR - Motor Control Board
Silicon Controlled Rectifier A means of controlling a DC motors rotation
speed.
Secondary Roller
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.
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Tension stretch
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
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.
Top Sheet Film
Is the poly plastic film that is applied to the top of the load
Top wraps
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.
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UHMW
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.
VFD - Variable Frequency Drive
A device used to provide full control of an AC motors shaft rotation speeds.
VFDs 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
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.
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Bundling Stretch Film
Engineered Stretch Film
