Denisort increases the productivity of international online book seller

The online distribution of books has been booming non-stop for years. This has benefited the Amazon subsidiary Book Depository, which sells books to customers around the world from the English city of Gloucester. According to the company, which bills itself as “the world’s most international online bookstore,” it offers more than 20 million titles. To date, the online retailer is present in more than 130 countries – with the aspiration of making every book available to every person around the world at some point in the future. In order to live up to this aspiration and to ensure sustained growth, modernizing the company’s logistics process was essential. To do so, the processes in the distribution centre in Gloucester, which were over ten years old, had to be optimized with new systems. The main goal was to structure order fulfilment as efficiently as possible, largely through automated packaging and sorting routines, in order to create sufficient flexibility for the further expansion of the online book retailer.

Proprietary layout of the Denisort system

The new Denisort conveyor that was installed in this connection, which has 154 trays measuring 380 x 450 millimetres that can tilt to either side, has a special layout. It consists of two intertwined loops which cross one another at different levels and are linked entirely virtually via an ERP system and control technology. From the start, it was decided that there would be no physical connection between the two loops – for example, via a special transfer zone – in order to achieve the redundancy the customer sought in the form of two separate and fail-safe lines. At the same time, Ferag engineers turned to this concept in order to best utilize the limited amount of space that was available and create a conveyor with very high capacity. They were able to do so thanks to the high level of flexibility and versatility of the Denisort technology. For example, not only can the modular Ferag conveyor be installed in the third dimension, it also allows for a layout with relatively tight radial curves. As a result, the conveyor in Gloucester, which is fully fenced off for safety reasons, only takes up 240 square metres in the narrow facility. 

Both loops can feed all 30 feed-out stations

In total, the Ferag system has a length of 154 metres. The six infeed stations – three on each loop with a unique performance of 2400 units per hour – are connected directly to the upstream section, which is comprised of machines for packaging, strapping, weighing, labelling and scanning the ordered books. This means that the shipments, fully packed and labelled with their destination address are sent through the packaging zone entirely automatically via feeder belts to one of the two Denisort loops. Depending on which of the two lines is the intended destination the rollers send the unit either up or down. What’s special about this system is that although there is no physical connection between the two Denisort lines and they operate entirely independently of one another, both can feed all 30 feed-out stations. To do so, the trays either tilt to the left or to the right to allow the book packages being sorted to slide gently into the target container trolleys defined in advance by the system. Only one chute per line at the very end of the sorter can be filled by the respective line. This provides a high level of flexibility in addressing the shipping destinations.

The Denisort system functions as a buffer

Each feed-out station is monitored electronically. As soon as a container is full, it is blocked by the system. In addition, a light flashes to alert the responsible order picker that the maximum filling level has been reached. This is also the signal to slide the containers with rollers towards the loading portal, in order to load its contents onto the lorry. If one of the containers is blocked, the corresponding Denisort tray will not release the book package it is conveying. Instead, it will simply go around one of the two loops one, two or more times until an empty container trolley is available to accept it. Thus, the Denisort system also serves as a buffer and intermediate storage.

High energy efficiency thanks to “rolling, not sliding”

Despite its enormous sorting capacity of up to 14,400 units per hour, the Denisort system only needs two drives, one per loop. This unique advantage is the result of the “rolling, not sliding” principle, which has proved itself at Ferag for years. The bearing pulleys used for this process, which have been patented by the Swiss material handling specialist, glide so lightly over the conveyor chain that they only need a small amount of operating power. The effect is sustainable in every respect, as customers like Book Depository not only get a technology that is extremely durable and reliable, but also a system that works with a high level of energy efficiency and requires little maintenance. This factor also has a positive effect on the annual operating costs of the British Amazon subsidiary.

Book Depository was founded in Gloucester, England, in 2004 by former Amazon employees Andrew Crawford and Stuart Felton. The new player in online bookselling quickly grew into a thriving company, winning a number of awards in a short span of time, including the “Queen’s Award for Enterprise”. In 2011, Amazon seized the opportunity and acquired the extremely successful and highly profitable newcomer. Since then, Book Depository has been run as a subsidiary of Amazon Holding, which is based in Luxembourg.