Warehousing Systems: Automation Solutions
Storing inventories is inevitable for many companies because of uncertainty of demand for products and inability of instant deliveries on all customer orders. Companies try to store inventories in such a way as to reduce their overall logistics costs and to reach higher levels of customer service through better alignment between supply and demand. Warehousing and product storage mainly take place at nodal points of a supply network. Therefore, warehousing is an important part of logistics systems for a long time.
Warehouses are nodal points at and between the origin and destination points within supply network, which store goods and provide the management with information about the status, disposition, and condition of inventories / stock (Logistics, 2011).
Warehousing envolves all movement of goods (transactions) within warehouses and/or Distribution Centers (DC's) (Berg, 1999).
There are three types of warehousing systems:
Picker-to-product.
Product-to-picker.
Picker-less.
With respect to product retrieval:
unit-load retrieval system.
order-picking system.
Slot (short for storage location) is a generic term for any of a variety of different types of identifiable storage locations, e.g.,
racks,
bins,
marked-off floor areas for block storage.
Each slot-item combination has an associated capacity corresponding to the number of units of the item that can be stored in the slot.
Closest open location (or COL) policy is storing and retrieving a unit at the nearest (i.e., least handling effort or cost) available location in order to minimize the handling costs for the units within a SKU.
Dedicated (or Fixed Slot) Storage policy - each SKU has a predetermined number of slots assigned to it.
Randomized (or Open Slot or Floating Slot) Storage policy - each SKU can be stored in any (usually the closest) available slot.
Class-based Storage - a combination of dedicated and randomized storage, where each SKU is assigned to one of several different storage classes.
Each accessible storage location in a warehouse has a unique address and can be used for each different storage medium:
Pallet racks: Compartment dimension not used since only the front unit of each position is accessible.
Shelves: All dimensions can be used if compartment dimension is accessible.
Drawers: Position dimension not used if drawer has odd shaped compartments.
Block stacking: Only building, aisle, and bay dimensions used to address each lane of storage.
Misc. locations: Receiving, shipping, holding areas, outdoor trailer storage, etc., can all be given unique addresses.
Recently, the automation of warehousing can more accurately be called “physical automation,” which includes all of the methods used to bring inventory right to the order picker, so that movements in the warehouse can be minimized. For that reason, many of these solutions are called goods-to-person, or GTP systems. Popular GTP systems include [IndustryWeek.com]:
carousels,
vertical lifts,
automated storage and retrieval systems (AS/RS),
mini-loads,
and automated material-carrying vehicles,
conveyors that move and direct pick material to the next appropriate operation.
A carousel has storage positions, horizontally or vertically rotating around a closed loop.
An AR/RS is a high-bay warehouse with storage and retrieval machines and stacker cranes that perform operations with storage modules (pallets, containers).
Carousel and AS/RS belong are examples of product-to-picker systems.
An automated storage/retrieval system (AS/RS) consists of an integrated computer-controlled system that implements the storage/warehousing elements (e.g., storage medium, transport mechanism, and controls) with various levels of automation for fast and accurate random storage of products and materials.
Warehouse Management System (WMS) controls all warehouse transaction-management logic, such as
receiving
put-away
counting
storage
order-picking
sorting
packing
shipping.
Order-picking is process of gathering SKU's that have been requested in an order (at one time). It includes
single order picking
batch picking (multiple orders are gathered simultaneously from one or several warehousing systems or separate zones within systems)
Sorting on two ways:
sort-while-picking (during picking)
pick-and-sort (afterwards picking)
Warehouse execution system (WES) is an emerging hybrid technology that blends capabilities from traditional warehouse management systems (WMSs) and warehouse control systems (WCSs) by adding business logic normally found in the WMS on top of the WCS middleware that talks directly to the automation layer (gartner.com).
WES, like WCS, focuses specifically on highly automated warehouses building on WCSs' near-real-time insight into what's happening in the automated warehouse by adding specific business process logic, notably picking, to this layer.
WES is specifically suited to high-velocity warehouse processes, adding capabilities like wave-less picking, seamlessly integrated with the WCS that talks, in real time, to the automation layer.
Warehouse resource planning and scheduling applies the concepts of forward-looking, constraint-based planning and optimization to work activities within a warehouse
References:
Jeroen P. van der Berg (1999), "A literature survey on planning and control of warehousing systems", IIE Transactions, 31, 751-762.
Logistics operations and management. Concepts and models (2011), ed. by Farahani R.Z., Rezapour S., Kardar L., Elsevier Inc., 469 p.
Warehousing / Michael G. Kay ; Fitts Dept. of Industrial and Systems Engineering North Carolina State University. April 23, 2015. - 54 p.