Glenn Barnes, Manager, Parcel Sortation Systems, Dematic , discuss the benefits of automated sortation and the key selection criteria for a range of system options. With increasing labour costs and supply chain pressures for faster, accurate and responsive operations, automated sortation systems are finding their way into supply chains, delivering productivity, throughput capacity, accuracy, and accountability for businesses, and a cost effective and efficient flow of goods to consumers. Within the supply chain, there are a number of points where sortation is relevant and applicable.
Manufacturing: Manufacturers of fast moving consumer goods (FMCG) use sortation systems to handle cartonised products as they come off the production line. Robotic systems are commonly used to automate the process of palletising and high speed sorters are used in conjunction with these to sort the cartons by product type for palletising and/or to distribute the workload to multiple palletising cells.
Retail Distribution: High throughput sortation systems have been used for decades by retailers. Batch picking has long been employed in the grocery and general merchandise industry to improve productivity and accuracy. Instead of travelling around a distribution centre (DC) to pick cartons for a single store, operators perform order picking for a group of stores. Picking the stores in batches increases both the product hit density as well as operators’ picks per hit. This system, combined with cartons being loaded directly onto a conveying system at the pick face, sees picking rates from 500 up to 1,000 cartons per hour being achieved.
While picking the requirements for a group of stores together brings excellent picker productivity, there is a need for a downstream process to “un-mix” the cartons and sort them out to their destination store and hence the need for sortation systems as an integral part of this process.
Cross-docking and Flow Through handling processes are both adopted, with the use of sortation systems to distribute cartons to stores when they arrive at a DC.
The sortation system is not only used for distributing goods to stores, but also in accounting for what has been received and where it has been directed. With an increasing volume of products sourced from offshore, many retailers are engaging consolidators in the source country to gather goods together from multiple local suppliers and pack them into a container as densely as possible for shipping efficiency. In the destination country, the containers are unpacked and an automated system is used to sort them to store resulting in lower distribution costs.
Order Fulfilment: Automated sortation systems have been used in a number of applications for order fulfilment. From pharmaceuticals to electronics to health and beauty, sorters are used in conjunction with a picking system to direct shipping containers to a lane associated with a delivery route, geographical area or delivery provider.
In the mail order industry, there are a number of solutions that utilise the same sorter to sort a shipping container to a sort destination, sorting products such as clothes, cosmetics and CDs into the shipper, and then finally sorting the shipper to a destination assigned to a delivery route.
Parcel and Freight: Many goods are often handled in one or more parcel and freight depots as they move through a transport network between two points in the supply chain. High peak volumes at certain times of the day coupled with the fast turnaround times that are essential to achieve service levels mean that throughput capacity, accuracy and product handling flexibility are the order of the day.
For many freight and delivery providers, automated sortation has become a distinct competitive advantage, allowing them to achieve better service levels and forming a barrier to market entry for new players. For some, it is a necessity due to the nature of the volumes to be processed and the limited time available to connect parcels with their outbound plane, truck or van.
Sortation Technologies: There are a wide variety of technologies available in the market and it is essential to understand the criteria for selection to achieve the best logistics result. In general, the range of sorters is divided into two broad categories – linear and recirculating.
Linear Sorters: Linear or straight line sortation systems are cost-effective where the number of sortation points required is small to moderate, for instance, 10 to 50 destinations. Linear sortation systems include a merge subsystem to collect and combine cartons from multiple sources, an induction subsystem, the sorter itself and often a recirculation subsystem to handle any items that could not be diverted to their assigned lane. For applications below 5,000 cartons per hour and with a low number of destinations, there are a range of different mechatronics available for performing carton diversion including right angle transfers, pop-up wheel diverters and pivot arm diverters, providing reliable and accurate performance and bi-directional sorting capability.
Where there are applications with higher throughput and/or a moderate number of destinations, a sliding shoe sorter is an appropriate linear sorter. With this sorter type, cartons are transported on interleaved aluminium slats and diverted by shoes, which slide across the slats, guided by an angled track integrated beneath the conveying surface. Sliding shoe sorters can perform bidirectional sorting and with new innovations in sorter and carton induction technology, are able to achieve rates of up to 18,000 cartons per hour with a single sorter.
Recirculating Sorters: Recirculating or Continuous Loop sorters are comprised of a continuous loop of linked carriers, which travel around a circuit. These sorters can be designed to handle throughputs exceeding 20,000 items per hour and can accurately sort a wide range of products from large parcels down to small loose items to hundreds of delivery points.
Recirculating sorters are generally considered flexible in terms of layout, throughput and expansion options. Recirculating sorters can negotiate turns, incline and decline, utilise carriers multiple times per circuit and be easily expanded with additional induction points and sort lanes with minimum disruption to an existing operation. Their design also features a higher level of redundancy without the same single critical points of failure as a linear system.
Two general types of recirculating sorters are available – Tilt Tray and Cross-Belt. The Tilt Tray sorter has carriers consisting of a shaped tray with a tilting mechanism that tips the tray to offload the parcel. The carriers of a Cross-Belt sorter have an individually motorised belt conveyor, which is dynamically controlled to offload parcels with a high level of precision according to the dimensions and weight of the items. With the additional offloading control, a Cross-Belt sorter can handle a wider variety of sizes and shapes from small items to bulky general merchandise.
Selection Criteria: One of the first factors to consider in sortation is the nature of the goods to be handled. This covers the dimensions, weights, shapes, fragility, packaging, surfaces and materials. Both the selection of the sorter and the design of the chutes and sort lanes will be influenced by the product characteristics.
Throughput is a second key factor in the selection and design of a sortation system. Throughput requirements should account for daily volumes, hourly peaks, seasonality, operational times and forecasted business growth. It should be recognised that the sustained average operational throughput will be substantially less than the sorter’s machine capacity as it is affected by a range of variables such as availability of product, workload balance, product dimensions, staffing, supervision and barcode quality.
Besides product and throughput, it is essential to understand the number and nature of the sort destinations. The number of destinations is typically directly related to the number of stores, orders or delivery routes to be serviced. With building and land space becoming increasingly scarce and expensive, optimising space efficiency and layout flexibility is becoming a significant solution driver.
Whatever the scale of the application, the best approach is always to begin with an understanding of the business, the business drivers and goals, and all the operational requirements. With this approach, sortation systems are yet another tool in the logistics practitioner’s kit to deliver significant logistics results to their business.
Product Identification: Product identification is typically a key performance indicator (KPI) in sortation and with “no-read” cartons costing operations in terms of potential errors, additional handling and/or reduced system throughput, this makes reliable identification systems an essential part of sortation systems.
Where there is a dependence on upstream suppliers or manufacturers in the supply chain to provide parcel identification (i.e. barcodes), collaboration and vigilance is required to ensure the potential efficiencies of the automated system are optimised. The initial effort of this for new comers to sortation should not be underestimated.
Barcodes are by far the most common method of item identification and a range of technologies exist to read these with accuracy at high speed. Omni-directional laser scanners have long been used in the industry for reading labels. However, advances in camera technologies have seen this type of barcode reader become increasingly popular, especially for applications with variable barcode quality. RFID (radio frequency identification) is now recognised as an identification technology that will find applications in some supply chains. Modern sortation systems are already capable of integrating this technology.