In the days of the Hansa League a hand-written book was still sufficient to monitor the daily coming and going of products to and from the warehouse. The number of items was manageable, one could almost literally “keep an eye on” the stocks. That situation is completely different today. There are far more products and they have different shelf-lives plus a wealth of additional information that is required to guarantee the traceability of every single product. To make sure nothing spoils prematurely all products have to be stored correctly in accordance with their quality and workmanship. At the same time, storage times should be as short as possible since products in storage are “dead capital” – they do not realise their true value until the moment of purchase by the customer. Order times are shorter today, too. Everybody expects their order to be delivered quickly, in the desired quality and correctly picked. These requirements make storage and warehouse management processes a high-tech business that necessitates efficient logistics, a high level of computerisation, and automation. Given today’s high throughput of goods it would be impossible to keep track of the inventory at all times, to re-order missing items in time, or to guarantee complete transparency throughout the entire supply chain without intelligent technologies.
An essential prerequisite for the efficient organisation of all the processes connected to product storage is a fixed order within the warehouse that assigns every pallet and every product to a particular place. This order is so to speak the “hardware” whose structure enables the exact naming and assignment of the coordinates of a product’s storage place so that it can be found as quickly as possible when needed and located via the shortest path. Thanks to modern software it is not even necessary for the products to have fixed positions within the warehouse. In the past, canned herring, for example, might always have been put into the second shelf on the left at the back, but today the products can be put anywhere where there is enough space. If everything is correctly documented the computer will be able to find every single product later on – despite the appearance of chaos. The methods and techniques of modern warehousing range from robust stackable crates that are still sorted by hand to flexible container concepts and complex shelf systems that are computer controlled. In practice there are both standardised industrial storage systems and tailor-made solutions that are specifically designed for the user’s needs.
Eleven boards, nine blocks of wood and 78 nails – that is what is needed to make one of the classic tools of modern logistics: the Euro pallet. First introduced in 1961, it has since then become increasingly significant in the storage and transport sector. More than 500 million of these standardised Euro pallets are in circulation in Europe. And their dimensions of 120x80x14 cm are the “measure of all things” in nearly every warehouse. There are special shelves in different sizes and construction variants for the pallets. Some shelves are fixed installations, whereby every shelf space takes a single pallet. This enables constant stock control and direct access which is of particular advantage when various different products have to be stored on the pallet. Other shelves can be shifted to a different place to achieve better utilisation of the available space: this method saves aisles between the shelves. A single aisle is sufficient because it can always be opened exactly where the desired pallet is. That is particularly valuable in cool and cold storage depots because it means that the space is used optimally and overall storage capacity is increased without having to forgo direct access to individual pallets. The shifting of the shelves and thus the opening or closing of the aisle is automatic, either by hand or upon demand of the computer system.
Logistics becomes a little bit more difficult if the shelves do not only hold one pallet but if they are two, three or four pallets deep. The simplest way of dealing with this is to push the pallets into the shelf one after the other (push back shelves) but the drawback here is that the older products are at the back. In order to take them out all the other pallets that are standing in front of them have to be removed from the shelf first. This takes time and is a strenuous process which is why this system is mostly not used in practice. Because this shelf type means that the front, newest products are usually taken out first (last in, first out) they are less well suited to use for perishable goods such as fish and seafood products.
Products with only a short shelf-life and high product throughput are therefore preferably stored in flow racks – a storage system that is driven by gravity and uses roll conveyors. The pallets are put onto the conveyors at the slightly higher shelf side and then flow forward to the other side where they can be removed as required (first in, first out). The next pallets slide into place behind them. This storage technology fits the logistical requirements of perishable products in the food industry much better. The same principle also applies to silos in which, for example, feed producers store their fishmeal supplies and other loose products. Silos are filled from the top and emptied from the bottom so that older raw materials are always used first. Sensors monitor how full the silo is, and also the prevailing storage conditions; the removal and dosage of the required quantities is automatic.
Automation relieves staff in extreme work environments
High-shelf stores constitute an interesting storage concept for warehouses with only little floor space. Here the capacity of the storage space is determined by the height of the building. Sometimes these stores are constructed in such a way that the high-shelf systems bear the ceiling and the lateral walls. High-shelf stores have a huge storage capacity and are used both for pallets and for smaller product units. In the seafood sector they mainly serve for the storage of frozen raw materials and semi-finished products that occur in very large quantities, for example herring fillets or frozen fillet blocks. Although it is basically possible to manage high-shelf stores by hand, in practice rack retrieval systems are usually used because these are considerably more efficient. These systems’ capacity (maximum load and working height, speed) is adapted to the work environment and the machines often move along rails in the aisles and can access any shelf space with the lifting unit to put away or pick up storage goods. They are rather like fork-lift trucks in their abilities only that they reach heights of 15 or 20 metres. All tasks carried out by such systems run automatically as if by magic. They are centrally computer controlled with the result that the halls are often completely void of any persons. Inventories are monitored and updated in real-time. The technology is not cheap but it is a worthwhile investment because a lot of storage processes can then be carried out much faster and with less errors than would be possible by hand. Automation saves effort, time and money and is also not such a strain on the nerves. And in situations where employees are confronted with extreme working conditions, for example in frozen stores at temperatures of -30°C or when stock turnover has to be particularly quick, automatic rack retrieval systems are always recommendable.
In the past, working in a warehouse was usually a tough job that involved lifting, moving heavy loads by hand within small spaces and then putting them into shelves. Today mechanical support is available for a lot of these jobs. Fork-lifts and pallet transporters carry pallets and other product units to their destinations and lift them easily onto the shelves. In modern warehouses transport vehicles often don’t even need a driver anymore and there are remote-controlled radio shuttles for loading and unloading pallets of incoming and outgoing goods. Such shuttles are capable of carrying out a lot of movements independently, for example when putting the products into shelves. This makes these semi-automatic conveyor systems an optimal solution for cold storage rooms or wet working areas in which the health of the employees is at risk. Automated truck loading systems that place the ordered pallets and mixed product units onto a truck work in a similar way The important devices for in-company transport include roll conveyors and conveyor belts with which goods can be quickly moved from one place to another without much effort. Some companies have fully automatic pallet conveyor systems that connect the production section to the warehouse section so that ready loaded pallets can be efficiently collected, carried, put into intermediate storage, divided up, or put together to form complete deliveries as required.
Inventory management programmes register, coordinate and control
Every company that has to store and manage products needs warehouse logistics that are adapted to the type, quantity and throughput of the products. Warehouse logistics is the sum of all the processes that are in any way connected with the storage of products from their arrival in the warehouse to their delivery. Inventory stocks have to be monitored constantly and any goods that are lacking re-ordered. Control routines are required to be able to guarantee the correct storage of all products. Warehouse logistics also prescribe how transport within the company has to be carried out and what has to be paid attention to and documented when the products leave the warehouse. Without a computer and suitable software these tasks would today hardly be manageable. Using a special warehouse management programme, however, it is possible to monitor, control and coordinate all processes within the warehouse constantly. This programme could be called the brain of the warehouse: it registers all activities within the warehouse, brings together individual data and thereby enables decisions to be taken. Through the introduction of wireless data transmission systems in the storage sector it is today even possible to transmit instructions directly from the warehouse management to product pickers, stackers and other mobile workplaces. This enables fast implementation of the necessary tasks.
Warehouse management programmes are almost indispensable for the constant monitoring of inventory levels. In large warehouses the sheer quantity of goods alone would already make it almost impossible to use traditional methods for keeping control of all products, their shelf space, sell-by dates and cost prices, the number of reserved units, number of units to be ordered, etc. With the help of computer programmes it is no longer a problem, however, as long as all the data of the incoming and outgoing goods are entered correctly. Often the scanners with which the product-specific barcodes on the pallets and cartons are read are even directly connected to the central computer of the warehouse management system. The computer stores all product-related data and thereby enables an absolutely current stock overview all the time, and mostly even in a very user-friendly format since modern warehouse management programmes can portray the structures of the warehouse and its capacity graphically, giving a lot of detailed information on the stored goods. This enables maximum transparency and also makes it much easier to recognize free capacities within the warehouse and, even with large inventories, to track down individual products quickly.
In a lot of warehouse management programmes it is also possible to specify limits above or below which an alarm should be given, for example if stocks fall below a pre-specified minimum inventory level or if sell-by dates reach a critical level. Some programmes even automatically make suggestions with regard to use of storage space so that similar products can be stored as close to one another as possible. This creates a better overview and saves time later on when picking products for orders.
RFID chips revolutionize the monitoring of product-relevant data
Radio frequency identification (RFID) opens up completely new perspectives in warehouse management. This technology enables a contact-free transfer of data. It is considered to be a key technology of the 21st century. It offers fascinating possibilities and might well have similar influence on productivity as the introduction of the barcode 30 years ago. RFID is legible without visual contact, even through plastics, glass, cardboard or other materials. New kinds of RFIDs are even said to be able to penetrate metallic substrates. They can thus be installed in pallets, crates and barrels whose location or path can then be tracked within the warehouse. In contrast to optical barcodes RFID labels are better suited to rough industrial environments and processes. RFID read-and-write tags are almost mini computers which allow the user to change, erase or add to stored information. This does not only save money for the printing and attaching of the barcode labels but also simplifies the collection of important product-related data that are necessary for traceability, for example.
The flat RFID chips have several kilobytes storage capacity and, together with the antenna that is wound in a spiral around the chip, they are only about as big as a stamp. These mobile data storage units have huge rationalisation potential because they connect products with detailed information that is individually collected, stored and further processed by EDP systems. With radio frequency technology it is, for example, possible to monitor the location of a product within the warehouse and follow its path through the supply chain. Such information enables companies to plan internal processes better and to make more efficient use of storage space and working hours. Another particular advantage of RFID technology is that it is not necessary for the RFID reader to have physical or visual contact to the product. RFID chips do not need an electricity supply, an attribute that is based on the construction of the smart chips. They consist of the chip and an electronic oscillation unit that serves both as an antenna and an inductor. As an antenna the oscillation unit conveys the contact to the RFID reader, as an inductor it is stimulated by the electromagnetic field of the reader and supplies the required energy. As long as the RFID chip, which is also called a transponder (from transmit, and respond), is not “activated” by the energy field of the reader it does not transmit any information. Neither water, nor heat nor cold can have any effect on the chips.
Transfer of the stored data takes only fractions of a second. Fork-lift trucks with RFID-chipped pallets do not even need to stop when they pass by the readers. These convey the information to a data base where the number codes are read, decoded and assigned to the products. The electronic product code (EPC) enables the assignment of an individual ID number to every RFID transponder. To prevent duplicates and overlapping the EPC numbers are issued centrally by the company Auto-ID Inc. in Cambridge.
The spectrum of tasks that are fulfilled within the warehouse sector does not end, however, with the qualified storage of goods but also comprises various services for the customer. Some products have to be packed differently, re-iced, re-packed from master cartons, or samples have to be taken for controls or to send to customers. Routine stock reports are given, customers are given support during product data capture for inventory purposes, products are picked for delivery according to customer specifications. A lot of tasks would hardly be possible without automated counting, measuring and weighing processes. And in addition to EDP systems and identification systems, one often finds machines for packing the products, for example for wrapping plastic around pallets or sealing the products in shrink foil, for stapling or strapping the packaging or other techniques in the warehouse. The interaction of all elements within the warehouse is the prerequisite not only for correct product storage but also for their timely delivery in the desired configuration to the customer. mk