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UK manufacturer automates lift truck movements between factory and warehouse

It is acknowledged that in a competitive global marketplace, automation is one of the best ways for manufacturers in relatively high-wage countries to reduce costs. Robots and other computer-controlled handling systems are ideal for automating production plant locally, but for wider scale unmanned operations, automated guided vehicles (AGVs) and laser guided vehicles (LGVs) have a long and successful track record.

One such AGV system has recently been installed at a UK FMCG (fast moving consumer goods) factory that produces beauty and grooming products. It is a multi-vehicle installation designed, manufactured and installed by E&K AUTOMATION. Its purpose is to reduce the labour costs associated with transporting materials and components from a nearby warehouse to the production area and delivering finished product back to the warehouse.

Previously, pallet transport was carried out using ride-on pallet trucks. A dozen drivers were needed on each shift for two or three shifts per day, five days a week, or up to six and a half days in the run-up to Christmas and during other busy periods. The on-going cost of employing such a large number of operators was considerable and is allowing the investment in the original AGV system to be amortised quickly.

The blue chip, multinational FMCG group manufactures its brands worldwide. It therefore has to look carefully at production costs in countries where wages are a high proportion of overall operating costs. The group is highly accomplished at these evaluation exercises and undertook a forensic financial analysis of AGV purchase and operation before placing the order with E&K.

Key benefits of the AGV system
A description of the automated system and its operation follows, but it is worth highlighting at the outset the main advantages to the user of employing AGV technology, in addition to the significant operational cost savings.

First, the company is being asked to supply smaller quantities of personal care products to its outlets, but on a much more frequent basis. This is in line with most of manufacturing industry these days, which has to produce ever smaller batches for just-in-time delivery. So greater flexibility and responsiveness are required in handling materials to and from the manufacturing and filling lines, which is exactly what the E&K AGV system delivers.

Secondly, efficient control of material and component stock levels was difficult to manage from the shop floor, with line operators previously tending to play safe and call up more than they really needed. Stock deliveries are now automatically optimised, with full management reporting.

A third benefit centres on modern AGV systems being highly flexible. They can be expanded inexpensively as a company grows and may be readily altered to take account of operational changes, reflecting how far vehicle control and laser navigation techniques have progressed in the past couple of decades. Since first installing this AGV system, the FMCG company added three vehicles within the first 12 months, two more vehicles recently and has made several AGV track layout changes to support developing production needs.

Lastly, automated handling tends to result in less damage to both the goods being transported and the factory infrastructure, as much of the potential for human error is taken out of the equation. Many of the products are of high value, so safe transportation was an important consideration. In this application, for additional security, two rotary encoders are fitted on the AGV lift mast for fork height measurement, rather than the usual single encoder, to ensure that the vehicle can cross-check the precise position of its forks when a pallet is being handled. Each fork tip includes a photoelectric sensor for extra safety.

System operation
Manned reach trucks and counterbalance trucks still service the warehouse. Previously, full and partially loaded pallets of materials and components destined for production were taken to a drop zone near the factory, from where they were picked up by the rider pallet truck operators. This interface has been pulled back to near the warehouse exit, where a new buffer zone of roll-forward gravity racking has been installed for the AGVs to access. The racking demarcates the current line of separation between the manned truck area and the automated handling network.

Three levels of gravity roller conveyors hold pallets five-deep, there being 37 lanes for goods-out to production and three lanes for returns to the warehouse. Heavy pallets over 750 kg are loaded only onto the bottom level, with braking rollers being included to ensure that pallet momentum is not too great when reaching the stops. Light pallets are handled on the top level and have a different requirement, namely to ensure they always reach the bottom of the slope, so the top conveyors have been more steeply inclined.

Pallet weight is up to 1,150 kg and both Chep and Euro pallet types are in daily use. Plastic IBCs (intermediate bulk containers) of liquid on pallets are also handled by the AGVs. The Chep pallets presented a particular challenge when devising a robust method for driverless handling at the inclined gravity roller conveyors. The AGV forks need to go in between the top and bottom boards of the Chep pallets, so E&K used a fork tilt mechanism on the lift masts of its COMPACT CB vehicles to give them the ability to simultaneously drive, lift or lower and tilt the forks during automated pallet collection and delivery. A lift height of around four metres is needed to access the top level of the gravity racking.

When material and component pallets arrive in the factory, they are placed on the floor to an accuracy of ± 10 mm at one of over 220 designated transfer positions, of which there are eight by each of the production lines. During product changeover, any partially depleted pallets are returned from production to the warehouse. Finished product is transported to an export conveyor which feeds a stretch wrapping machine. Stacks of empty pallets are also moved by the AGVs between the production area and a store adjacent to the factory. Bins of waste material are also taken away automatically to waste compactor stations, while palletised waste is delivered to waste conveyors adjacent to the compactors.

The AGVs originally matched the 110 moves per hour made by the rider pallet trucks, although the number of moves has since increased due to higher production levels. The target delivery time, from order placement to delivery in the production area, has also been met by the driverless vehicles which travel around the network at up to 1.6 metres per second. Each vehicle has no less than 16 safety devices and features on board, ranging from emergency stop buttons and contact strips to laser scanners and warning indicators.

The vehicles take instructions from the E&K OS830 central AGV system controller over a wireless LAN and guide themselves using E&K’s NAV800 laser triangulation, with the help of reflectors positioned on the walls and columns. This navigation technology simplifies the design and optimisation of the transport network and allows AGV routes to be modified easily to suit new requirements, all via a CAD workstation.

There are currently six opportunity charging stations around the site for automatically topping up the 48-volt, lead-acid batteries that power the AGVs. A high current is periodically delivered over short intervals to bulk-charge the batteries rapidly.

Real-time control
The whole operation is driven by the factory’s own warehouse management system. The WMS interfaces with E&K’s MES-CON OS platform, a middleware Manufacturing Execution System that optimises the transport process between production and the warehouse. MES-CON OS effectively sits between the customer’s WMS in the office and E&K’s OS830 real-time AGV controller on the shop floor and is capable of coordinating and monitoring all materials handling facilities including manual fork lift trucks and conveyors, in addition to the AGVs.

The E&K OS830 shop floor AGV controller consists of a System PC (server) that manages the AGV fleet in real time and is linked to a number of Human Machine Interface (HMI) terminals at the operator level. Its primary tasks are communicating with the WMS via MES-CON OS, handling transport orders, optimising AGV task allocation, traffic control including vehicle-to-vehicle blocking and interfacing with fire doors, communication with the AGVs, and data logging. HMI screen graphics show the positions of AGVs dynamically, with colour coded icons to reflect their status. Analysis and reporting of operating data can be carried out with the EK-REPORT management tool. A high level of system resilience is built in.

A facet of the E&K MES-CON OS control software peculiar to installations like this is the way in which it sequences delivery of the correct pallets from storage to the factory via the interface gravity racking. When a production line puts in a request for components, the WMS sends an instruction to a warehouse lift truck which picks the pallet and places it on the gravity racking, scanning the bar code to confirm to the system which lane it is in. The WMS records the sequence in which the pallets are delivered to the gravity racking.

Multiple items are required to make a finished product. It is a function of E&K’s MES-CON OS control system to identify the position of all required pallets and ensure their on-time delivery to the right production line. It maps the order in which pallets are sitting in the gravity racking and is able to remove the front pallets to one or more of the 90 positions in the so-called unlock racking so that the required items behind can be accessed. Similarly, procedures for dropping and picking up pallets in the production area are built in to the system. Achieving this level of functionality and flexibility is a complex process and one for which E&K’s MES-CON OS software modules and highly experienced engineers were ideally suited.

It is hoped that this project is the first phase in a wider scheme to exploit the benefits of automated materials handling right across the FMCG firm’s production facility. The modular nature of E&K systems will make it easy and cost effective to integrate the different applications as well as to alter and expand their operations to suit the customer’s growing business. Other automated or manual handling duties and a diverse range of peripheral automated systems can be brought under the E&K umbrella.

E&K is a European market leader in driverless industrial trucks (AGVs and LGVs), with a history going back 45 years and a portfolio of more than 10,000 vehicles in over 1,000 systems, many designed for 24/7 operation.

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