Slip Sheet
Encyclopedia
Slip sheets are thin pallet
-sized sheets made of plastic, heavy laminated kraft paperboard
, or corrugated fiberboard used in commercial shipping
. Often, these replace the use of traditional wooden pallets. The unit load is usually stretch wrap
ped or shrink wrap
ped for stability.
support device in vehicle delivery and transportation of products. When slip sheets are supported by a pallet board, roller conveyor surface
, flat load carrying surface, or a cart or lift truck, the structural strength of the slip sheet supports the product load's weight. With the slip sheet supported by one of these transportation devices the unit load can easily be transported both internally within a facility and externally between two facility locations.
The variation used would depend on the loading patterns, unit load parameters, and desired maneuverability of the slip sheet/unit load. Normally, the thickness of the slip sheet is less than 0.5 inches.
For most warehouse
s, plant functional material handling equipment
, and the travel-path clearances, this fraction of an inch height increase does not stage a problem. When designing an in-house transportation path for the slip sheet unit load, the slip sheet has a four to six inch lip (tab) that extends beyond one or more of the sides of the slip sheet. The lip extensions permit a push-pull device to lift the slip sheet unit load.
With a single lip, the lip faces the narrow part of the rectangular shaped unit load and the delivery truck door. This slip sheet variation maximizes the delivery truck’s space utilization and loading and unloading process productivity. Also, with a single lip, the travel path clearance is minimized as the lip facing the unit load carrier.
or an ocean delivery vehicle due to the necessary loading/unloading patterns. This allows a loading device to load the slip sheet unit load from one side and an unloading device to unload the load from another side depending on the number and pattern of the remaining lips.
liner board outer surfaces with a corrugated interior that is bonded together with adhesive or glue. This bonded material provides the necessary strength for the push-pull device to clamp the slip sheet once or twice. There are several disadvantages associated with this type of slip sheet material including that it is not very durable, moisture resistant, resistant to high humidity or usable in cold storage areas. The advantages associated with this material are low cost, one-way use, and its ability to be moved by a conveyor or lift truck with a slip sheet device.
d together. The bonding of layers of several flat solid kraftboard sheets increases the slip sheet’s non-tear strength. This, in return, allows the slip sheet to be used several times and in different temperatures. In addition, some fiberboard slip sheets are protected by a plastic coating to improve its use in humid environments. The disadvantages to this type of slip sheet are that it has a medium cost and is not very durable. The advantages with this material are its multiple uses, ability to withstand humid and cold environments, and ability to be handled by conveyors, AGV
, or other power unit load transportation devices.
Overall, discussing advantages of slip sheets vs. pallets highly overrates the disadvantages associated with the two.
Pallet
A pallet , sometimes called a skid, is a flat transport structure that supports goods in a stable fashion while being lifted by a forklift, pallet jack, front loader or other jacking device. A pallet is the structural foundation of a unit load which allows handling and storage efficiencies...
-sized sheets made of plastic, heavy laminated kraft paperboard
Paperboard
Paperboard is a thick paper based material. While there is no rigid differentiation between paper and paperboard, paperboard is generally thicker than paper. According to ISO standards, paperboard is a paper with a basis weight above 224 g/m2, but there are exceptions. Paperboard can be single...
, or corrugated fiberboard used in commercial shipping
Shipping
Shipping has multiple meanings. It can be a physical process of transporting commodities and merchandise goods and cargo, by land, air, and sea. It also can describe the movement of objects by ship.Land or "ground" shipping can be by train or by truck...
. Often, these replace the use of traditional wooden pallets. The unit load is usually stretch wrap
Stretch wrap
Stretch wrap or stretch film is a highly stretchable plastic film that is wrapped around items. The elastic recovery keeps the items tightly bound...
ped or shrink wrap
Shrink wrap
Shrink wrap, also shrinkwrap or shrink film, is a material made up of polymer plastic film. When heat is applied it shrinks tightly over whatever it is covering. Heat can be applied with a hand held heat gun or the product and film can pass through a heat tunnel on a conveyor.-Composition:The...
ped for stability.
Description
The slip sheet is used as a unit loadUnit load
A unit load combines individual items or items in shipping containers into a single "unit" that can be moved easily with pallet jack or forklift truck...
support device in vehicle delivery and transportation of products. When slip sheets are supported by a pallet board, roller conveyor surface
Conveyor belt
A conveyor belt consists of two or more pulleys, with a continuous loop of material - the conveyor belt - that rotates about them. One or both of the pulleys are powered, moving the belt and the material on the belt forward. The powered pulley is called the drive pulley while the unpowered pulley...
, flat load carrying surface, or a cart or lift truck, the structural strength of the slip sheet supports the product load's weight. With the slip sheet supported by one of these transportation devices the unit load can easily be transported both internally within a facility and externally between two facility locations.
Slip sheet types
There are several types of slip sheets that can be used for the transportation of a unit load depending upon the desired use of the sheet. The slip sheet is shaped and dimensioned to the size of the product or unit load. The type of slip sheet varies depending on both the number of lip extensions and the material from which it is manufactured.The variation used would depend on the loading patterns, unit load parameters, and desired maneuverability of the slip sheet/unit load. Normally, the thickness of the slip sheet is less than 0.5 inches.
For most warehouse
Warehouse
A warehouse is a commercial building for storage of goods. Warehouses are used by manufacturers, importers, exporters, wholesalers, transport businesses, customs, etc. They are usually large plain buildings in industrial areas of cities and towns. They usually have loading docks to load and unload...
s, plant functional material handling equipment
Material handling equipment
Material handling equipment is all equipment that relates to the movement, storage, control and protection of materials, goods and products throughout the process of manufacturing, distribution, consumption and disposal...
, and the travel-path clearances, this fraction of an inch height increase does not stage a problem. When designing an in-house transportation path for the slip sheet unit load, the slip sheet has a four to six inch lip (tab) that extends beyond one or more of the sides of the slip sheet. The lip extensions permit a push-pull device to lift the slip sheet unit load.
Single lip
The first type of slip sheet is the single lip (tab) slip sheet.With a single lip, the lip faces the narrow part of the rectangular shaped unit load and the delivery truck door. This slip sheet variation maximizes the delivery truck’s space utilization and loading and unloading process productivity. Also, with a single lip, the travel path clearance is minimized as the lip facing the unit load carrier.
Multi-lip
The second type of slip sheet is the multi-lip slip sheet. This type of slip sheet is generally used on a container placed onto a railroad carRailroad car
A railroad car or railway vehicle , also known as a bogie in Indian English, is a vehicle on a rail transport system that is used for the carrying of cargo or passengers. Cars can be coupled together into a train and hauled by one or more locomotives...
or an ocean delivery vehicle due to the necessary loading/unloading patterns. This allows a loading device to load the slip sheet unit load from one side and an unloading device to unload the load from another side depending on the number and pattern of the remaining lips.
Lip handling options
During the transportation of a slip sheet, there are several options for handling the slip sheet’s lip.- Leave the lip extended allowing for additional clearance for the travel path.
- Tape the lip against the unit load if additional push-pull activities are required.
- Cut the lip from the slip sheet if no additional push-pull activities are required.
Corrugated
The corrugated fiberboard consists of two kraftKraft paper
Kraft paper or kraft is paper or paperboard produced from chemical pulp produced in the kraft process.Pulp produced by the kraft process is stronger than that made by other pulping processes; acidic sulfite processes degrade cellulose more, leading to weaker fibers, and mechanical pulping...
liner board outer surfaces with a corrugated interior that is bonded together with adhesive or glue. This bonded material provides the necessary strength for the push-pull device to clamp the slip sheet once or twice. There are several disadvantages associated with this type of slip sheet material including that it is not very durable, moisture resistant, resistant to high humidity or usable in cold storage areas. The advantages associated with this material are low cost, one-way use, and its ability to be moved by a conveyor or lift truck with a slip sheet device.
Fiberboard or solid kraftboard
The fiberboard (thick paperboard) slip sheet consists of several layers of solid kraft paperboard sheets laminateLaminate
A laminate is a material that can be constructed by uniting two or more layers of material together. The process of creating a laminate is lamination, which in common parlance refers to the placing of something between layers of plastic and gluing them with heat and/or pressure, usually with an...
d together. The bonding of layers of several flat solid kraftboard sheets increases the slip sheet’s non-tear strength. This, in return, allows the slip sheet to be used several times and in different temperatures. In addition, some fiberboard slip sheets are protected by a plastic coating to improve its use in humid environments. The disadvantages to this type of slip sheet are that it has a medium cost and is not very durable. The advantages with this material are its multiple uses, ability to withstand humid and cold environments, and ability to be handled by conveyors, AGV
Automated Guided Vehicle
An automated guided vehicle or automatic guided vehicle is a mobile robot that follows markers or wires in the floor, or uses vision or lasers. They are most often used in industrial applications to move materials around a manufacturing facility or a warehouse...
, or other power unit load transportation devices.
Plastic
The plastic slip sheet is made from recycled high density polyethylene or polypropylene materials. This type of material allows for greater non-tear strength and an increased number of uses in cold and humid environments. The only disadvantage to the plastic slip sheet is the high cost. Yet, its advantages include longer sheet life, durable lips, ability to be stored in cold or humid environments, and that it can be handled by a roller conveyor, slip sheet lift truck, AGV, or powered unit load transportation devices.Slip sheet vs. pallet
When considering the use of a slip sheet vs. a pallet, there are several advantages and disadvantages associated with both.Slip sheet advantages
- Using slip sheets instead of wooden pallets allows for 12-15% more products in material handling containers.
- Slip sheets do not require maintenance, but can easily be replaced.
- Significant reduction in material handling costs.
- Decreases loading/unloading time by up to 60%
- Weighs 1/20 as much as wooden pallets, reducing shipping costs.
- Can be customized to fit any size load.
- Eliminates the need for pallet exchange.
- Reusable and reliable.
- Most are recyclable.
- Is cost-effective.
- Unlike wooden pallets slip sheets are not subject to phytosanitaryAgreement on the Application of Sanitary and Phytosanitary MeasuresThe Agreement on the Application of Sanitary and Phytosanitary Measures - also known as the SPS Agreement is an international treaty of the World Trade Organization...
restrictions.
Slip sheet disadvantages
- Pallets provide a greater clearance between the floor and the unit load, an advantage when loading extra cargo into a container, but they take up more space.
- Slip sheet usage requires special, relatively low-cost attachments on transportation devices such as a lift truck.
- When used alone, pallets provide more structural support than slip sheets.
- Pallets are easily compatible with cranes.
- Lift truck attachment reduces load capacity, except when 'Roller Forks' are used.
- Slower handling, except when 'Roller Forks' are used.
Overall, discussing advantages of slip sheets vs. pallets highly overrates the disadvantages associated with the two.
Further reading
- Brody, A. L., and Marsh, K, S., "Encyclopedia of Packaging Technology", John Wiley & Sons, 1997, ISBN 0-471-06397-5
- Fiedler, R. M, "Distribution Packaging Technology", IoPP, 1995
- McKinlay, A. H., "Transport Packaging",IoPP, 2004