Order Picking Systems Information
Order picking systems assist in acquiring inventory items to fulfill customer demand. They consist of conveyors, components devoted to data acquisition, and material handling devices for identifying, selecting, and retrieving products to package or ship. The equipment ranges from simple systems to advanced automated versions supporting high capacity warehousing activities.
Order picking comprises a significant part of a distribution center's operational costs. It has a direct bearing on customer satisfaction as it allows prompt dispatch of orders. The traditional method is a labor-intensive practice. It is challenging to identify mistakes in the process and expensive to correct them. This puts a premium on quality when conducting picking operations.
The method is divided into the following five stages:
- Pallet picking - Retrieving of full pallets
- Layer picking - Retrieving of cases by layer
- Case picking - Retrieving of inner packs located in cases
- Split case picking - Retrieving of inner packs from split cases
- Broken case picking - Retrieving of specific, individual items
The practice of collecting orders has evolved to add value to warehousing processes by facilitating quick shipments to customers in specified quantities. This is due to the popularity of "just in time" systems of inventory management. Such an approach permits customers to avoid keeping excessive inventory and instead receive a constant flow of material from suppliers.
Manual, automated, or semi-automated operating systems involve a variety of equipment and procedures. Tools utilized for collection include:
Static shelving is used to store items for piece picking operations. Products are positioned either directly on shelves or in special storage bins. Such shelving is low-cost and works well with small parts or when few picks per SKU are involved.
Carton flow racks feature small partitions of gravity conveyors mounted at angles. Products are kept in cartons or small bins. As containers are emptied, they are taken from a rack and another carton rolls into place. These types of racks are efficient with a high number of picks per SKU.
Carousels are similar to dry cleaning equipment utilized to retrieve clothing. Horizontal carousels engage hanging racks that are configurable for handling various-sized storage bins. Ordinarily, two to four carousels are run simultaneously, eliminating the need to wait while a single unit is turning. Batch picking takes place as instructions are downloaded to the software controlling the carousel.
Automatic storage and retrieval systems (ASRS) comprise rows of racks. Individual rows contain dedicated retrieval units moving in vertical and horizontal directions. These units pick and put away loads as the units move. Although ASRS devices provide superior storage densities, they come with greater costs relative to other piece collecting options.
Pick-to-light systems include lights and LED displays linked to each pick location. Software lights the next pick and displays the quantity to pick. These systems improve accuracy and productivity and work well with carton flow racks as well as with horizontal applications with high picks per SKU.
Bar-code scanners increase accuracy. However, in fast-running applications, they slow down pick rates. The devices are ideal for case picking, pallet loading, put-away, and operations involving order checking.
Voice-controlled picking is an acceptable option for piece, case, or pallet picking tasks.
Automated conveyor sorting systems are found in piece picking systems on a broad scale. Equipment of several types and designs is employed in such systems.
How Order Picking Systems Work
The systems use different processes to fulfill customer orders, including:
Batch picking, where pickers collect multiple orders at the same time. Less travel time to fill demand offers increased productivity. This method is used when orders are selected from a limited number of SKUs and the products chosen are of small size.
Zone picking involves giving distinct zones to pickers. Multiple-zone orders are completed once they pass through all applicable zones. The process uses one scheduled picking period for each shift. Requests received after the cut-off point are placed in a queue for fulfillment during the subsequent shift.
Wave picking is a blend of the batch and zone picking methods. Instead of moving from zone to zone, the order-collecting process is performed in all zones simultaneously, with the items sorted into separate orders at a later time.
Discrete picking involves individual pickers for each request. Every picker handles a single line at a time. One window for scheduling picking occurs per shift. As individual orders are not scheduled, collection occurs at any time during the day. This method is easy to track and offers rapid order fulfillment. A drawback is a lack of efficiency as the process requires a high amount of travel time.
When selecting an order picking system, several operational factors come into play, including:
- Operation types in use
- Amount of orders processed on a regular basis
- Number of picks needed for each order
- Pick quantities
- Product characteristics
- Number of SKUs handled
- Type of loads (piece pick, case pick, pallet pick)
Each system has advantages and disadvantages depending on the requirements. The factors mentioned above should be used to determine which system would be most appropriate for an application. The manufacturer's specifications should be checked to verify if a system satisfies the intended use.