It sounds like pie in the sky, yet one of my clients is considering implementing extensive automation to avoid the ever-escalating costs of labor. His vision would still involve some people, not a totally peopleless warehouse - one in which, day and night, all physical movement of items is handled by automated equipment controlled by software.
Few warehouses are so highly automated, and none are totally void of people. Almost all highly automated warehouses feature totally custom-designed buildings, equipment and software - little off the shelf. The following description of typical systems and machines in an automated warehouse is a look into the future of large warehouses in which many items are stored and many lines are picked per hour.
But no matter how extensively a warehouse is automated, the systems will not function accurately and efficiently unless the warehouse is organized properly, and procedures and controls are in place and followed. In fact, the less automation employed, the more organization and discipline is needed.
Automated equipmentBecause few, if any, even near-automated warehouses exist in this industry, lets start with a general description of equipment for storing and moving items.
Conveyor. Think of a “moving sidewalk” at an airport. That is an example of a powered belt conveyor. Warehouse conveyors move items or cartons or reusable containers (such as totes), not people. A powered belt conveyor may be sloped so that items/cartons/totes move forward and upward or downward. Another type of powered conveyor is a roller conveyor, which is used to move cartons/totes or large items. Instead of a belt there are individual rollers, all of which rotate together under power. A powered roller conveyor can also be sloped downward or upward. Manual roller conveyors are unpowered. If it’s horizontal, people push the items/totes/cartons along. If it slopes downward, items/totes/cartons move under the force of gravity. A conveyor can be loaded manually (as a truck is unloaded into receiving, cartons are placed on a conveyor), or by some other equipment.
Sorter. This equipment either directs an item/tote/carton to one of several conveyors or literally drops an item into the proper carton. Conveyors are designed to handle either small items, large items, totes or cartons. A sorter can be loaded either manually (remember, there are still some people involved) or by a conveyor. Sortation is controlled by software (described later).
ASRS is the acronym for automated storage and retrieval system. One example is a “carousel.” It looks like a cylinder oriented vertically with storage slots at several heights around its circumference. To store an item or carton, the item or carton is placed on a positioning device, a bar code - or increasingly, an RFID chip - on it is scanned and based on data related to the item/carton and carousel, software determines where to store the item/carton.
That software controls the rotation of the carousel so the needed slot aligns with the positioning device and software directs the positioner to the proper level where it pushes the item into the designated slot. For picking, software determines the slot from which to pick and it controls the positioner to retrieve the item (or multiple items for that customer order, branch transfer or multiple orders going on the same truck). A bar code is scanned every time a movement needs to occur (and in some cases, to monitor the condition of an item). Even the bar code of shipping cartons is scanned to determine loading and shipping paths (because the actual carton used is sometimes different from the size and strength of the theoretically calculated carton and there can be changes in assigned trucks).
Automatic guided vehicle is typically a battery-powered, low-height motorized platform that follows along one or more wires recessed into the warehouse floor. A pallet/carton/piece is literally taken for a ride on the AGV. Special software determines the exact path taken when putting away or retrieving something.
Hypothetical systemReceiving. Imagine a powered belt conveyor with one end at a receiving dock and the far end feeding a sorter. The sorter directs inbound cartons to one of two conveyors, each of which feeds an ASRS. Each ASRS stores the cartons in the slots determined by software. At another receiving dock, an AGV takes bulky pieces to an ASRS or to a section of the warehouse where people remove the pieces and place them on storage locations on the floor.
Picking. Based on sales order data and storage location data, an ASRS retrieves one or more cartons and positions the carton(s) on a conveyor. That conveyor feeds the carton(s) to a sorter, which in turn directs the carton(s) to one of two conveyors that contain an on-the-fly labeling workstation and feed cartons to waiting trucks or trailers (on which the carton(s) are stacked manually).
In addition to an ASRS positioning cartons on a conveyor, a person could remove cartons from a forklift that brought them to the conveyor and place them on the conveyor. The forklift driver could use voice-directed picking (described in a previous article) to pick the cartons and take them to the proper conveyor(s). Even in our hypothetical system manual labor is involved because total automation is not realistic.
The cons. In addition to huge construction and equipment investment, a drawback of a highly automated warehouse is that it is designed for a particular mix of product sizes and weights. If the mix changes much, changing the warehouse technology can be an expensive and lengthy process.
SoftwareEnterprise requirements planning. An ERP mainly plans and manages the logical operations and administrative activities of a distributor (entering data for sales orders or generating recommended purchase orders). An ERP performs many functions in real-time (once a PO is created, the on-order quantity of each item on that PO immediately updates), but some are “batch” functions (printing A/P checks). Some ERPs contain a few of the functions that are also in the next kind of software.
Warehouse management system is software that plans and manages the physical arrangement and activities of a warehouse. Examples include: determining where to store items to be received on the next business day based on purchases and customer order data transmitted by the ERP; after items are received, determining where to store an item; and tracking how much of each item is stored in each slot.
A WMS also does higher-level labor planning (how many people to bring in for a particular day and shift). Most WMS functions do not work in real time. However, as soon as data about a picked item is captured, the WMS updates slot-specific and item-level data. The WMS also interfaces to systems of vendors (e.g., receives advanced shipping notices).
Warehouse control system software controls the physical activities of automated equipment, such as starting and stopping conveyors and sorters, directing an AGV, directing an ASRS to store and to pick and directing a sorter to route a carton to a particular conveyor. A WCS works in real time, using both data it acquires (e.g., status of a piece of equipment and from reading a bar code on an item/carton/tote) and data transmitted by the WMS.
A WCS also can control the speed of a particular unit in order to balance loads on specific equipment and through the warehouse. It also makes real-time adjustments. When a jam at a sorter is detected, the WCS would stop those upstream activities that would result in other jams. A WCS also assigns and manages labor. When a packer unexpectedly logs out, the WCS software will determine which other suitable person is available and assign the function to him/her until the packer logs back in.
In the future, look for WMS to take on more of the WCS functions and vice versa. Eventually, the functions of WMS and WCS will be merged into a new category of software that may be termed warehouse planning and control (for large, high-volume warehouses). Look for more warehouses to use more automation, although not to the extent described here.
Don’t wait for automation to reduce warehouse costs and prevent costly mistakes. Many warehouse improvements can be done quickly and at no or little cost, and will also prevent angry phone calls from customers who received the wrong items or quantities. Think organization, procedures and controls.