High-bay warehouse for Waitrose
In 1974 the Partnership’s Information Services department published a brochure about the high-bay warehouse, which was, at the time, an example of the leading edge warehousing technology and systems.
The text is below and images are published on a separate page.
In 1967 the John Lewis Partnership found that no site large enough for the distribution centre which it proposed to build for its expanding Waitrose supermarket group was available in a suitable location. It was therefore decided to examine the practicalities of high-bay storage and advanced mechanical handling techniques as a means of obtaining the required capacity on a site of limited size at Bracknell, Berkshire.
After an initial period of investigation within the Company, several international organisations prominent in the goods handling field were given a comprehensive brief and invited to submit design proposals. Sixteen did so. There followed a detailed evaluation of the proposals, after which separate studies leading to costed schemes were commissioned from two short-listed companies. Following a comparison of the competing proposals, the German electrical company, AEG-Telefunken, was awarded the contract for the design, co-ordination and construction of an automated computer-controlled high-bay warehouse.
The work of detailed design began in 1969. In November of that year earth moving and piling began, and in January 1970 the main building contractor moved onto the site. The final running-in process began in late 1972 with the gradual transfer from the existing conventional warehouse of all supermarket orders. This process was completed at about the end of the following year.
The new warehouse shares a total site area of three hectares (7.38 acres) with a large headquarters office block and a conventional distribution dock for fruit and vegetables. The floor area of the main warehouse buildings, including all service areas, is about 13,700 square metres (147.400 square feet). Of this, the high-bay storage area takes up 3,000 square metres (32,800 square feet) and has a capacity of just over 10,000 pallet apertures (18,000 cubic metres or 635,660 cubic feet) divided into six aisles 20 metres (65 feet) in height, each served by a remote controlled stacker crane.
The system is designed to hold up to 3,500 items of food, wines and non-food household goods, representing about half of the total range sold in the Group’s supermarkets of which there are, currently, over 50. The ultimate peak throughput capacity is 5,000 order units per hour.
An AEG 60-50 process computer and storage drum with back-up processor and drum, controls the following basic sections in an on-line mode of operation:
Goods receiving area Storage area
Order selection area Goods despatch area
The system controls and monitors the six stacker cranes and the conveyor system; also the warehouse storage locations. It contains an extensive number of functions for fault indications. Several special requirements are met by the design, for example random storage within relative demand areas to optimise the use of equipment and storage capacity; also first-in, first-out and selective distribution within the high-bay of pallet loads to reflect variations in demand and to avoid product damage through temperature extremes and contamination and to ensure continuing availability of as many items as possible during a crane failure.
The data files of the process computer make it possible to obtain up-to-date information regarding stock levels and positions, picking speeds etc, on request. The data exchange with the Partnership’s central computer in London is via magnetic tapes or, alternatively, punched cards.
Due to a natural fall in the land from west to east there are effectively two ‘ground levels’ on the site and in the warehouse. This split level has been put to good use. The high-bay cranes are used for vertical goods movement, thereby reducing the need for lifts and elevators to the single lift used for supplying the detail (sundries) store.
Goods receiving area
Goods delivered to the goods-in dock on the lower ground floor are subjected to the usual checks and, before transfer for storage in the high-bay, are formed into loads on special house pallets captive to the warehouse system.
Conveyors of various kinds are used to handle either full pallet loads or single cartons. Automatic palletising is employed as far as is possible. Goods which are not stackable are placed on special container pallets with collapsible sides and treated as normal pallet loads. Goods destined for the detail store, because of their physical and/or throughput characteristics, are sent there by cage-sided trucks or hand pallet trucks in the conventional goods lift at the eastern end of the receiving dock.
Fruit and vegetables are handled separately and stored in a conventional building alongside the high-bay.
The high-bay is in total 25 metres wide and contains six aisles flanked by steel pallet racking about 20 metres high and 120 metres in length. Each aisle contains a 22-tonne floor-mounted, computer-controlled stacker crane. The roof and sides of the high-bay are supported by the racking.
After the goods have been stacked onto house pallets they are routed to a high-bay entry station in front of the main warehouse. Here the operator feeds the pallet data (such as line number, quantity etc.) into the computer system. The process computer receiving this data allocates the pallet to one of the six high-bay aisles and to a specific location within it.
The storage sequence is then carried out fully automatically, each stacker crane being able to transport and store two pallets in one cycle.
The retrieval of pallet loads for order picking, also in a cycle predetermined by the computer, is in most cases combined with this storing away operation in order to increase the efficiency of the cranes.
Goods retrieved for order-picking and despatch are brought by the cranes to the upper floor level immediately above the receiving area. Pallet loads chosen by the computer are taken from the racking and placed on conveyors leading to the rear of the picking-stations at the aisle ends. There is one station for each aisle.
Warehousemen (order-pickers) working singly or in pairs at these picking-stations take from the pallets presented to them the number of cases indicated on small. computer-controlled digital display screens. They place the cases into a branch truck which has been assigned by the computer to a particular supermarket and which has been moved up to the picking-station by means of the under-floor tow-chain system. Having complied with the instruction the warehouseman presses a button on his control panel and the truck is replaced by another assigned to the next supermarket requiring the same goods. This action is repeated until each of the branch trucks requiring that line of goods has been served.
The computer, having anticipated the total demand for a particular line of goods, will bring forward sufficient pallets to satisfy that demand and will return any unused balance to the high-bay storage area. This procedure is repeated until the full selection of goods required by each supermarket has been picked.
Partly filled trucks leave the picking-station and are taken into a circulating loop until required to be loaded with further goods. Full trucks are removed under computer control by way of the tow-chain conveyor to a preselected van position on the goods despatch dock. The route passes a goods recognition station where there is a print-out of a Branch Transfer Docket (invoice/delivery note) to accompany the truck on its journey to the supermarket.
Trucks and the loop system
Branch trucks are relatively light-weight, detachable sided, four-wheeled trolleys of standard manufacture. For reliability and precision of movement each is mounted on a more robust coded platform cart which engages with the tow-chain of the underfloor conveyor system. The branch trucks are used aboard the vans and throughout the supermarkets, but the platform carts remain in the warehouse.
The underfloor conveyor forms a circulating and sorting loop in front of each picking-station. Each loop will hold 36 trucks with another two at the picking-station. As each truck represents a supermarket, up to 38 supermarkets can be served at anyone time from each picking-station. In order to ensure completion of a supermarket’s total order in the shortest time, each supermarket will normally be represented by branch trucks in all sorting loops.
The use of branch trucks for order collection and the, so far, unique arrangement of bringing pallet loads and branch trucks together at a picking-station reduce manual intervention and enable the branch truck to be used for goods movement within the warehouse and onwards in the supermarket delivery cycle. Speed in the selection and assembly of orders is at the root of the high throughput capacity of the warehouse.
Slow moving or awkwardly shaped goods and part-cases unsuitable for the high-bay store are held and handled in the conventional manner on shelf-racking in the detail store. Orders are selected into cartons from pre-printed Branch Transfer Dockets and loaded into branch trucks. Filled branch trucks are taken by hand to the goods recognition station, introduced into the tow-ch-ain system and sent to the despatch dock along with orders coming from the high-bay.
The despatch dock is 23 metres wide and 122 metres long. Along its length are 84 spurs from the main tow-chain, grouped in twos and threes into 34 loading positions serving 28 van-loading bays, each of which is equipped with a dock-leveller.
The despatch dock area also accommodates an accumulation loop which acts as a buffer between order-selection and despatch-assembly. About 100 branch trucks still mounted on their platform carts can be accumulated in this loop and will circulate continuously until the despatch spurs assigned to them become free.
Also on the despatch dock are areas where branch trucks returned empty are reassembled, serviced as necessary, and placed onto platform carts ready for re-introduction to the order selection loops.
At the despatch dock loading points, platform carts from which branch trucks have been removed for loading into vans are used to take empty return trucks (usually dismantled) via the tow-chain conveyor to the cart and branch truck assembly area.
Instructions for the allocation of dock positions to supermarkets are given by the despatch dock manager through a control desk which enables him to communicate with the computer. Here, also a waybill is produced summarising the Branch Transfer Dockets for each supermarket.