Warehousing Equipment Tompkins et al., “Facilities Planning”, John Wiley & Sons, 1996: Chapters 6, 9 College-Industry Council on Material Handling Education: Material Handling Equipment Taxonomy: http://www.mhia.org/et/mhe_tax.htm
The role of equipment in warehouse operations • Reduce cost (labor + space) • enhance space utilization by, e.g., • enabling the exploitation of the vertical dimension of the facility • allowing for denser packing • allow for more efficient order-picking by, e.g., • increasing the sku density • supporting the automated transfer of material from storage to sorting and consolidation area • Enhance responsiveness • increase the throughput of the facility, e.g., • increasing the sku density • establishing a more ergonomic environment/arrangement for the warehouse operators • facilitating the parallelization of order picking • by parallelizing the tasks of order-picking and replensihment
The role of equipment in warehouse operations (cont.) • Maintain Quality of Product and Operations • provide an orderly storage environment • provide efficient ways for product tracing and identification • provide safe and secure material handling • facilitate order sortation and consolidation • establish and maintain a controlled environment e.g., • temperature control • access control
Equipment Classification(Tompkins et. al., pgs 170-173) • Containers & Unitizing Equipment • Storage and Retrieval Equipment • Unit Load • Small Load • Conveyors • Warehouse docks and dock-related equipment • Automatic Identification and Communication Equipment
For detailed functional descriptions, discussion on supported efficiencies, and pictures • College-Industry Council on Material Handling Education: Material Handling Equipment Taxonomy: http://www.mhia.org/et/mhe_tax.htm • Tompkins et al., “Facilities Planning”, John Wiley & Sons, 1996: Chapters 6, 9
Pallet Storage Modes • Block Stacking • Rack Storage • Single-Deep • Double-Deep • Drive-In/Through • Pallet Flow • Unit Load AS/RS • etc.
Block Stacking (or Floor Storage) Lane Height Lane Depth (3-deep) Lanes • An efficient storage mode when • there are multiple pallets per SKU; • inventory is turned in large increments, I.e., several loads of the same SKU are received or withdrawn at one time. • Main problems: • Loss of space due to “honeycombing” • not effective utilization of the vertical dimension of the facility
Selective or Single-Deep or Simple Pallet Rack • The “benchmark” storage mode • Due to rack supports, each pallet is independently accessible (i.e. it supports totally random access) • Trade-off: too many aisles => inefficient space utilization
Double-deep rack • Two selective racks placed back-to-back => 2-deep lanes • Each lane dedicated to one SKU => space loss in case of SKU’s with odd number of pallets • Less aisle space required (upto 50% savings in aisle space) • Trade-off: More work and/or specialized equipment for retrieving
Other pallet rack types • Drive-In/Through rack: 5-10 loads deep • Better space utilization • More difficult, even dangerous retrieval • Pallet flow rack: up to 8 pallets deep • The rack shelves are slanted and have rollers, and therefore, every time a pallet is retrieved from a lane, the pallet behind it takes its position. • Allows for simultaneous picking and restocking • Supports FIFO operation • Typically used in high-throughput facilities • Cantilever rack: • Supports long items like timber and pipes
Unit-Load Retrieval Equipment • Key Differentiation factors: • aisle width requirements • lift height/weight capacity • Lane depth they can reach • degree of automation • capital expense • Major types • Walkie Stacker • Counterbalance Lift Truck • Narrow Aisle Vehicles • Automated Storage/Retrieval Machines
Small Load Storage and Retrieval Equipment • Operator-to-Stock (or Man-to-Part or in-the-aisle) system: the operator travels to the storage location to retrieve material • Stock-to-Operator (or Part-to-Man or end-of-aisle) system: the material is mechanically transported to the operator for retrieval • Advantages of STO: • higher productivity • easier supervision • better item security and protection • Disadvantages of STO: • more expensive • more maintenance • more difficult to reconfigure
Operator-to-Stock Storage Equipment • Bin Shelving • Modular Storage Drawers in Cabinets • Carton Flow Racks • Mobile Storage • All the above equipment can also be arranged in mezzanines to get a better exploitation of the building cube.
Operator-to-Stock Retrieval Equipment • Picking Cart • Order Picker Truck (for higher placed loads) • Person-aboard Automated Storage/Retrieval Machine • captive aisle • free roaming • (Robotic Retrieval)
Stock-to-Operator Equipment • Carousels • Horizontal • Vertical • Independently Rotating Racks • Miniload Automated Storage and Retrieval Machine • Automatic Dispenser • Productivity gains • Allow for extensive parallelization of order retrievals • Focus on extracting rather than traveling and searching
Conveyors • (Flat) Belt • Roller • Telescoping Belt • Chute • Sorting • Deflector • Push Diverter • Pop-up Skewed Wheels • Pop-up Roller • Tilt tray • Remarks: • Conveyors change the economics of travel. • They can partition physically the warehouse into zones
Warehouse docks and dock-related equipment • Warehouse docks: The facility interface with the shipping carriers • Dock configurations and dimensioning
Equipment facilitating the interfacing between docks and shipping carriers • Dock levelers: compensate the height difference between the carrier platform and the dock door • mobile yard ramps • permanent adjustable dock boards • truck levelers • scissors-type lifting docks • Bumper pads: absorb the shock from the impact of the shipping trailer with the dock walls (laminated rubber cushions) • 40,000 lb load traveling 4 mph => 150,000 lb force • Dock shelter: a flexible shield that when engaged to the carrier provides a closed-environment interface between it and the inner area of the warehouse • energy savings, increased safety, product protection, etc.
Automatic Identification and Communication Equipment • Permits real-time, nearly flawless data collection and communication, and therefore, it facilitates and increases the real-time awareness of the location, amount, origin, destination and schedule of the material.
Automatic Identification and Recognition • Bar coding technology: • bar codes • bar code readers • bar code printers • Optical character recognition • Radio Frequency (RF) and Surface Accoustical Wave (SAW) tags • Magnetic Stripes • Machine Vision
Automatic Paperless Communication • RF data terminal • Voice headset • Light and Computer Aids • Smart card