Automated crane-served store with magnet lifting equipment

Ordered in the morning, produced in the afternoon, loaded in the evening and shipped the next morning – deliveries of slit strip and material cut to order within 24 hours are just part of the normal daily routine for one of the largest European service centres for flat steel products. To achieve this, Becker Stahl-Service GmbH has invested in innovative production and storage equipment. The automated crane-served store for steel coils is a key element of the new production facility, where two Demag process cranes ensure that material is stored appropriately and staged in time for the production lines. The hardware and the warehouse management computer (WMC) is supplied by Demag Cranes & Components from a single source.

• Two automated process cranes with magnet lifting equipment
• Increase in the effective utilisation of the store by 30 per cent
• Warehouse management system with configurable storage strategies
• Crane controls to meet safety requirements

Becker Stahl-Service

From trader to steel service centre

With more than 6,000 loading and unloading operations per month and shipping in four shifts, six days per week, Becker Stahl-Service in Bönen, Germany, provides just-in-time deliveries to satisfy its customers' wishes.

Established as a steel trader, the company, which is based in Unna-Bönen, has grown to become a steel service centre that has more than 400 employees and which sells, stores, handles and processes steel.

The range of products includes wide band, slit strip, plates, blanks and trapezoid blanks in many finishes and coats. With more than 60 per cent of its products manufactured for customers in the automotive and automotive supply industry, the supplier has to meet the highly demanding quality and production standards of this sector.

An annual sales volume of some 1 million tonnes combined with stocks of approx. 200,000 tonnes and short production lead times has made the supplier a leader in the European steel trade sector. The company has been part of the Klöckner Group since 2010.

Nord facility project

Increased storage capacity thanks to magnet lifting equipment

The cranes operating in the store at Becker Stahl-Service are a major component of the in-house logistics system, which link the production, storage and shipping operations with each other. They have a large impact on the efficiency and the flexibility of the entire processes. The maximum possible availability of the cranes has the highest priority. Two Demag Coilmaster process cranes are responsible for the semi- and fully automated handling of the steel coils at Becker. Reliable operation, is therefore, also ensured by the secondary crane system. Crane 1 serves the coil store in fully automated mode. Crane 2 operates under semi-automated control and is used for loading and unloading the incoming trucks as well as for serving the front zone of the store (quarantine zone). This crane can also operate in automatic mode.

The load handling attachment is innovative: Demag process cranes are being used with coil magnets for the first time in a coil store:

• Optimum utilisation of the available space: since the loads are picked up from above, the steel coils are stored with a gap of only 300 mm between them. This increases the effective utilisation of the store by some 30 per cent.

• Gentle handling of the load: the magnet system ensures that the heavy, but also fragile, steel coils are handled carefully. Strategies can be configured to achieve the best possible placement of the relevant coils in the store – also in three-level stacks.

• High level of safety: in addition to the laser-controlled crane and crab positioning system, light barriers, which operate with two-stage cut-off, also ensure that the cranes maintain a safe distance from each other. The crane anti-collision system is monitored by a safety control system, which is specified to Category 3.

• Optimum efficiency: the store operates 24/7 without interruption with the highest possible efficiency. The required handling rates are achieved with the Demag warehouse management system, which is integrated into the host system infrastructure at Becker Stahl-Service.

• Kind to resources: in addition to optimum utilisation of the available space, the crane systems also perform well in terms of power consumption. The energy recovered when loads are lowered is fed back into the in-house power supply system, which helps to reduce power consumption and the operating costs of the installation.

Process steps

Before the coils enter the store

The material is delivered to and shipped by truck at the Becker Nord facility. The goods are lifted off the trucks and deposited in the quarantine zone by the Coilmaster crane under manual control. In this area, the goods are registered, i.e. labelled and issued with a coil record document . The coil data are transferred to the warehouse management system and the ERP system (Baan), where the data are compared with the specifications saved in the system.

A sample of every coil is cut for quality assurance. The data available at Becker goes all the way back to the steel supplier, which enables all physical and chemical coil data to be accessed.

Safe and reliable pick-up of the coils

After the quality assurance check has been completed, the coil is transported by crane under manual control to the transfer point for automatic handling. When the magnet engages the load, a laser beam checks to ensure that the coil is positioned in the centre of the magnet. If necessary, a correction is made in the cross-travel direction. This ensures that the load is precisely picked up and positioned by the automatic crane in the store. The magnet operates with two levels of safety: in the first stage, the load is magnetised and raised at creep speed. When the magnet is safely engaged, the system automatically switches over to full load mode and the load is raised at maximum lifting speed. 

Transfer to the automatic crane

At the transfer point, the operator switches the crane over to automatic mode. The warehouse management computer (WMC) assigns a location within the fenced-off storage area in front of the automatic zone. After the coil has been handed over, the crane returns to the quarantine zone, where it waits for the next unloading operation.

The WMS assigns a storage mission to Automatic crane 1 with details of the source and destination co-ordinates. Using laser sensors, the crane positions its hoist precisely above the coil and picks it up, while the crane weighing device measures the exact weight of the coil. The hoist unit raises the magnet and load to the highest hook position, where they engage a mechanical guide to prevent any load sway. The automatic crane then travels to the pre-defined storage position at maximum speed and transfers the coil to the store.

Store structure

The store was designed according to geometric conditions. The widest coils are stored in the outer lines to utilise the crane approach dimension at the edge of the store. The warehouse management computer is aware of the dimensions, surface finish and grade of the materials. This enables the system to store the items appropriately.

The coils rest on so-called coil blocks, which reflect the different widths and diameters. Storage strategies that allow for the various types of material, including multi-stage restrictions for stacking items, for example, ensure maximum utilisation of the available space as well as safe and reliable treatment of the material.

Retrieval processes

Items are retrieved as required in production or to customer order according to a coil staging list. Items are transferred to production via cross-shaped turntables, which represent the interface between the store and the machines. The process crane deposits the coils and reports completion of transfer to the machine tools via a „handshake“ procedure. Partly used coils are also returned to the automated zone together with a data module via the turntable. To do this, the crane determines the current weight of the coil by means of an integrated weighing device.

Production and finished goods store

Becker Stahl-Service has installed cut-to-length and slitting lines in bays 12 and 13, which are located immediately next to the store. Four manually operated Demag ZKKE double-girder overhead travelling cranes, which are equipped with radio controls, are used for handling the products in these production bays.

Bay 13 is equipped with a 35-tonne crane and a 28-tonne crane. Both of these cranes work with C-hooks for handling slit strip. Two 20-tonne cranes equipped with DR-Pro rope hoists and grabs for handling palletised goods operate in neighbouring bay 12, where sheet metal measuring up to 4 millimetres thick is processed.

Technical data

^*) ZKKW: Process crane with winch unit
   ZKKE: Double-girder standard overhead travelling crane