Space craft

Two automated stacker cranes have helped an automotive supplier utilise a constricted storage area for buffer stock

An automotive supplier has used advanced automated-handling systems to make the most of the limited space available in its production facilities and create a storage area that it said helps it to meet a ‘just in time’ contract with BMW.

The integrated conveyor and order-picking system is claimed to be a key element of Magna Intier Automotive‘s facility in Redditch, where it manufactures 255,000 unique cockpits (fully assembled dashboards) each year for the Mini.

Due to space constraints, the automated storage area for buffer stock was created next to the assembly line.

The solution devised for the storage facility is fully integrated with the assembly line and consists of two automated stacker cranes from Excel Automation, able to pick up and place to either side of two beamless drive-in racking aisles. Despite the limited space available it is able to store 140 cockpits.

Bob Clifford, Intier production manager, said: ‘Our contract with BMW is for “just in time” deliveries of Mini cockpits, so we need to ensure that every one of the 255,000 unique cockpits leaving Redditch every year is united line-side with its unique Mini, 40 miles away on the assembly line in Oxford.

‘We also wanted to maintain a buffer stock in Redditch, so the decision was taken to create an automated storage area adjacent to the main cockpit assembly line. There were severe constraints on the space available in the plant, which was further restricted by the location of a roof-support column.

‘The number of cockpits we were able to hold in the storage area would therefore depend on the resourcefulness of the design put forward by the materials-handling manufacturer.’

The build process at Intier starts each Monday when an electronic file is sent from BMW in Oxford detailing the build schedule for cockpits required the following week. From this point the whole operation, including assembly line, conveyors, cranes and despatch, is run by an Intier-designed system called Magic that instructs the assembly line via a Siemens PLC (programmable logic controller) to begin production.

Once a cockpit is completed and transferred from the assembly trolley to the shipping palette, the PLC writes a tag detailing which cockpit is on the palette, its order number and sequence number.

This is sent directly to an off-board Siemens PLC in the storage facility, telling the crane to expect a delivery, which cockpit is in transit and where to store it in the racking.

When the lorry is due to collect the next shipment, the crane already knows the picking order needed to ensure that it is loaded in sequence to arrive line-side in Oxford to meet its designated Mini.

The assembly and storage systems are capable of delivering 60 cockpits an hour, with the Excel cranes automatically sequencing them to ensure that the right cockpits are put into the two-tier accumulating conveyor system, or ‘transport cassette’, and delivered to despatch for loading in the correct order. Each cassette acts as a lorry with 15 cockpits loaded on the upper level and 15 on the lower.

Any faulty cockpits coming into the store are placed in a special area to await rectification, which has to be completed within the cycle of 140 units in order to maintain the build sequence dictated by the Oxford plant.

The cockpits are given numbers and the crane is programmed to retrieve them in a pre-determined sequence.

The change-round time allowed for emptying and filling the 11 lorries that deliver continuous batches of cockpits to Oxford is just five minutes, so the lorries themselves are also fitted with an Excel conveyor system, which increases the efficiency of the feed by enabling the 30 cockpits to be loaded straight onto the lorry in a single operation.

The fully automated high-speed cranes operate on a dual-redundancy arrangement allowing one to continue working while the other is ‘parked’ for maintenance. They were built by Excel in its Worcester factory and can accelerate at one metre per second and deposit a cockpit, empty and pick up again, in just one minute.

The cranes are based on a standard industry format, but for the Intier application are customised with two sets of forks and special-purpose drives and controls to provide the speed and accuracy to order-pick for this demanding operation.

The cranes also use a laser guidance system that positions them to within 2mm, a high level of accuracy being necessary due to the space limitations in the area.

An onboard PLC allows manual, semi-automatic and fully automatic control of the cranes and in the event of a complete failure of the off-board control system, an operator can continue the process by extracting order numbers from Magic and entering them manually into the onboard PLC.