(2000), "Materials handling automated at car component factory", Assembly Automation, Vol. 20 No. 3. https://doi.org/10.1108/aa.2000.03320caf.003
Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
Materials handling automated at car component factory
Materials handling automated at car component factory
Keywords: Denso, AGV
Much has been said of the negative effects of automation on employment but the reverse is true at the Telford factory of DENSO Manufacturing UK Ltd, a leading supplier of automotive air-conditioning and heating equipment to world markets. In April 1999, the company installed an automated guided vehicle (AGV) system from Indumat to transport components from the warehouse to production lines (see Plate 3). The results are that working practices have been improved, productivity has increased and the delivery service to the production lines is more frequent, according to logistics engineer, Graham Milner.
Key to these improvements is the elimination of a large proportion of tedious manual delivery of parts over relatively long distances by lift truck, tow tractor and ride-on pallet truck. Operators are therefore able to concentrate on one task - picking, sorting empty boxes for return to component suppliers, or delivering parts to those lines not served by the AGVs. Previously, two of these jobs would have been combined. As a consequence, staff are now more focused and picking errors have been reduced.
Plate 3Boxes which have been emptied at the assembly lines are offloaded and sorted before the AGV continues to the warehouse to start the cycle again
There are benefits too in terms of more flexibility of supply to the assembly lines, says Mr Milner. Kanban-based delivery of components used to be every two hours by manually driven trucks but intervals are now generally 75 minutes. Response to parts requests is consequently faster and there is less work-in-progress at the lines.
DENSO's financial management is also impressed. During a time of rapid factory expansion it has been able to increase materials handling proportionately without any additional staff. An alternative to the £170,000 investment in the AGV system would have been to employ a further five lift truck drivers. Based on savings derived from not having to pay additional driver wages and acquire extra lift trucks, payback has been calculated to be within five years.
The AGV system works hard. Five of the 11 lines served by the vehicles operate on double shift from 7.00am to 11.00pm, the remainder being on single shift at present. One of the lines has all of its component parts delivered by AGV - the one which assembles climate control units for just-in-time, line-side delivery to Toyota's manufacturing plant 16 times a day.
The rest of the assembly lines receive a majority of components by AGV. Generally it is only heavier items which continue to be transported from store to the lines by lift truck, as the machine would be needed at the other end, in any event, to handle the parts.
The three AGVs are "Handimats" from the Indumat range. Each tows up to three DENSO trailers, of which there are 37 on site, in a clockwise direction around a 700-metre inductive guide path. The vehicles are also equipped with ride-on facility to enable them to be driven away from the guide path if required.
A vehicle takes 15 to 20 minutes to travel around the rectangular loop at up to 1m/s from the parts store to one of three stopping points serving the 11 production lines, on through the finished goods area where empty boxes are offloaded and sorted, and back to the store to pick up trailers which have been loaded for the next parts deliveries. When an AGV tractor and trailer train is ready for its onward journey, the new destination(s) is/are entered by the operator into the vehicle's on-board keypad using a two-digit code and the start button is pressed. Maximum trailer movements are 27 per hour.
Trailers are uncoupled manually from the train only in the production area to enable components to be transferred conveniently into racking. A trailer may be reattached at any time, to another vehicle if expedient; and while an AGV normally continues its journey towing three trailers, it could just as easily be pulling one or two. Each trailer carries boxes of various sizes laden with parts weighing up to 200kg, although loads are normally less than half of that figure. The 1.5 tonne towing capacity of the Handimat tractor is more than adequate for the task.
A particular feature of the AGV system is its flexibility. Mr Milner says that there are plans at DENSO to increase the material flow rate, extend the travel route to serve additional lines and use the vehicles to transport "in-house" boxes carrying sub-assemblies such as evaporators and heater cores between the production lines. The Handimat network may be easily altered to accommodate all these new requirements. Extra vehicles could be added and the control software upgraded to oversee more complex traffic movements. Links are possible in the future with DENSO's facility network so that AGV operation becomes part of a wider integrated system.
The Indumat system computer, and a separate computer displaying a graphic mimic of the guide path with vehicle positions, are located in DENSO's production control office. Coupled to the system computer is a radio data modem and antenna for two-way communication with the Handimat tractors. A telephone modem has also been provided to allow the software to be upgraded remotely when necessary.
Two 24-volt batteries were supplied with each vehicle so that one battery is always on charge ready for immediate exchange after about 16 hours' normal use. A vehicle signals to the controller when its battery charge has fallen below a predetermined level, whereupon it travels automatically to the battery exchange area. Although Handimats have the ability to be driven manually off and on the guide path, DENSO chooses to wheel the battery exchange trolley to the vehicle, so reducing the time it is out of action to just a few minutes.
As personnel and lift trucks move in the same areas as the AGVs, comprehensive safety features have been built in. For example, a front fender is fitted which stops the AGV the instant it touches an obstacle. However, so that productivity is not unduly compromised, the vehicle will try to restart itself three times before operator intervention is necessary.
Some of the common areas in the Telford factory are particularly busy, such as by the production lines and at aisle intersections, and in these locations as well as when negotiating curves the Handimats are programmed to travel more slowly. Visual and audible warning systems are built into the vehicles, the latter having been made louder than normal for the DENSO application owing to the presence of competing sounds within the factory.
For further information please contact: Tony Caulkett, Managing Director, Indumat Systems Ltd, Kingsclere Road, Basingstoke, Hampshire RG21 6XQ. Tel: +44 (0)1256 470079; Fax: +44 (0)1256 470072.