Unit Load Formation Equipment
Unit load formation equipment used to restrict materials so that they maintain their integrity when handling a single load during transport and storage.
Advantages of unit loads:
- More items can be handled at the same time, thereby reducing the number of trips required and, potentially, reducing handling costs, loading and unloading times, and product damage.
- Enables the use of standardized material handling equipment.
Disadvantages of unit loads:
- Time spent forming and breaking down the unit load.
- Cost of containers/pallets and other load restraining materials used in the unit load
- Empty containers/pallets may need to be returned to their point of origin.
The information below demonstrate the major type of unit load formation equipment used.
1. Pallets
Information:
- Platform with enough clearance beneath its top surface (or face) to enable the insertion of forks for subsequent lifting purposes.
- Materials: Wood (most common), paper, plastic, rubber, and metal.
- Size of pallet is specified by its depth (i.e., length of its stringers or stringer boards) and its width (i.e., length its deckboards)—pallet height (typically 5 in.) is usually not specified; orientation of stringers relative to deckboards of pallet is specified by always listing its depth first and width last: Depth (stringer length) x Width (deckboard length).
2. Totes Pans
Information:
- Reusable container used to unitize and protect loose discrete items.
- Used for in-process handling Returnable totes provide alternative.
3. Intermodal Containers
Information:
- Reusable container used to unitize and protect loose discrete items.
- Enables a load to be handled as a single unit when it is transferred between road, rail, and sea modes of transport; e.g., the container can be unloaded from a cargo ship and loaded onto a truck as a single unit.
- Not common to use intermodal containers for airfreight transport because of aircraft shape and weight restrictions.
- Dimensions of intermodal containers are:20 or 40 ft. in length; 8 ft. in width; and 8, 8.5, or 9.5 ft. in height; less 8 in. of length, 5 in. of width, and 9.5 in. of height to determine the inside dimensions.
4. Shrink-Wrap/Stretch-Wrap
Information:
- Used for load stabilization.
- A film or bag is placed over the load and then heat is applied to shrink the film or bag.
- Allows irregular loads to be stabilized; manual or automatic.
- Most shrink-wrap applications are being replaced by stretch-wrapping.
In stretch-wrapping, a film is wound around the load while the film is stretched
- Allows irregular loads to be stabilized
- Manual or automatic
- Lower material, labor, and energy costs.
5. Palletizers
Informations:
Manual Palletizing
- Operators arrange items into the desired pattern used to form the unit load.
- Lift and turn tables are often used.
- Semi-mechanized palletizers use operators to arrange items into the desired pattern for each layer of the unit load.
- Powered device is used to transfer layers onto a pallet and then lower the load for the next layer.
Robotic Pick & Place Palletizers
- Fully automated device to build unit loads.
- Used when flexibility is required.
- Greatest limitation is capacity, typically 6 cycles per minute.
- Capacity is determined by the number of items handled with each pick operation.
- Operators arrange items into the desired pattern for each layer of the unit load
- Powered device is used to transfer layers onto a pallet and then lower the load for the next layer.
Conventional Stripper Plate Palletizers
- Fully automated device to build unit loads.
- Used when high throughput of identical loads is required.
- Capacity is typically greater (30–180 items per minute) than pick and place because an entire layer is placed on the load at one time.
- Not as flexible as pick and place
- Preformed layer of items (cases) are indexed onto the stripper plate (or apron)
- when properly positioned over the pallet, the apron is pulled out from underneath the layer to deposit the layer onto the pallet.
- "In-line" pattern formation (top picture)—flexible patterns are not possible.
- Ideal for high speed operation (up to 180 items per minute).
- Takes up more room (larger machine) than right angle.
- "Right angle" pattern formation (bottom picture)—very flexible patterns are possible
- Can handle a wide variety of case sizes and types
- Limited capacity (up to 80 items per minute)
- Compact design
For more information of Conventional Stripper Plate Palletizers, please visit the following website; http://www.pmtdirect.com/website/article.asp?id=1806.
Source:
http://en.wikipedia.org/wiki/Pallet
http://www.ise.ncsu.edu/kay/mhetax/UnitEq/index.htm
http://www.spectrasystems.co.uk/tote_pans.htm
http://www.kempner.co.uk/shrink-wrap-machines.aspx
http://www.stretchwrapsupply.com/stretch-wrap-machines-c-31.html
http://www.polypack.com/robotics.asp