Automated aerospace component manufacture

Citation

(2000), "Automated aerospace component manufacture", Aircraft Engineering and Aerospace Technology, Vol. 72 No. 6. https://doi.org/10.1108/aeat.2000.12772fab.001

Automated aerospace component manufacture

Automated aerospace component manufacture

Keywords: Hamble Structures, Components

It is reported that Hamble Structures has invested £12 million over the past three years in new production plant, including 15 CNC machine tools. Part of the budget was spent on a Fastems automated pallet storage and retrieval system which links three of the machines – a five-axis Makino machining centre and two four-axis models – to form a flexible manufacturing system (FMS) (Plate 1).

Currently devoted to producing leading-edge wing sets for the Boeing 737-700 and trailing-edge sets for the Airbus A340, the high-speed machining facility joins two older FMSs having two and three machines respectively which were installed in stages between 1994 and 1998. As their main purpose was to produce a mixed package of some 40 different components for Boeing in considerable quantities, there was insufficient capacity to fulfil the new contracts.

These two manufacturing facilities and the new system operate in adjacent machine shops, providing an unusual opportunity to compare older FMS technology with one of the latest generation of computer controlled, multi level pallet handling systems from Fastems in Finland, whose UK subsidiary is in Dartford, Kent.

Plate 1 The new flexible manufacturing system at aerospace subcontractor, Hamble Structures

One obvious advantage which boosts productivity is thought to be the considerably higher speed with which machine pallets move along the store – 150 m/min compared with just 20m/min for the earlier FMS. (The latest Fastems cranes can travel at up to 240m/min). Cost is also said to be significantly lower, which is not surprising considering that the Finnish company specialises in manufacturing pallet handling plant whereas automation for the other lines was supplied by the machine tool builder.

However, there are further benefits which were even more important to Hamble Structures, according to principal engineer Gary Pitman. One is the floor area taken up by the Fastems store, which with 40 pallet positions provides 20 per cent more storage capacity than the earlier system yet occupies half the space. This was an important consideration, as the available space on the shop floor in the new facility was limited.

The other advantage is said to be that the Fastems rail-guided stacker crane is able to move vertically to access the two storage levels and can therefore accommodate the different table heights of the machines in the fine. In this instance, the table height for the two Makino A77s is 1,300mm whereas the MC 1010 has its table set at 2,050mm. To overcome this difficulty in the case of the former FMSs, it was necessary to lower the foundations for some of the machines and sink them into the floor. In principle, this has implications in terms of cost, access for servicing and in some areas, flooding.

Flexibility to extend the system at minimum cost was another important consideration for Hamble Structures. The 737-700 work is regular, involving machining 14 sets of around 140 components per month for Boeing. The Airbus contract, however, will increase significantly. The first set of 210 components was delivered in December 1999 and the requirement for 2000 is approximately one set per month, but by the end of 2001 this production rate will have trebled. With a conventional hardwired storage system, it would be difficult and expensive to extend the cabling to serve one or more extra machine tools. Fastems solves this problem using an infrared link between the stacker crane and the other elements of the FMS, so it is necessary only to extend the communications bus and guide rails.

In Hamble Structures' opinion, the versatility to enlarge the system so easily has allowed it to start bringing back in-house a considerable amount of machining work which has hitherto been subcontracted to other firms, thereby saving money and extending control over its manufacture. The latter is particularly desirable as much of the company's production is for just-in-time, line-side supply to aircraft factories worldwide and continuity of supply is critical.

Included in the turnkey package supplied by Fastems were two workset stations where components are loaded onto pallets and unloaded after machining (Plate 2). Supplied also was PLC-based process control software with a tool management package running in tandem under Windows NT.

The software is described as powerful and providing comprehensive safeguards. Scheduling is on a first-in/first-out basis but it is easy to progress a rush job through the system quickly. This highlights one of the main advantages of a Fastems solution over a conventional pallet pool, as with the latter it is difficult to change priorities once the machining sequence has been set.

Plate 2 A component being fixtured at a workset station before entering the Fastems pallet store. The rail-guided stacker crane moves vertically to access two storage levels and different machine table heights

The control screen's default graphic is a full colour mimic diagram of the FMS, giving an 'at-a-glance' view of the system's status. Pallets in use have an emboldened outline which turns to red if there is a problem, such as no program or insufficient tooling at the destination machine. Clicking on the pallet concerned provides the reason. A crane status panel informs the operator of the crane's current location and task, reveals the work-to list and can be used to override its operation.

Each machining centre is represented by an icon whose colour indicates its status – white: machine available for work; green: work in progress; yellow: ready but waiting for an operator to change tools, insert a program or prove-out a first-off component; red: machine fault. The work-set station mimics also communicate data including current job, next scheduled job and any fault such as "door open".

Robert Humphreys, sales manager heading up the newly-formed Fastems UK, points out that the control technology is progressing quickly. The company's latest integrated MMS (manufacturing management system) control, he says, is entirely PC-embedded and uses inverter drives for even greater flexibility, doing away with the older PLC units.

At present only 16 of the 40 pallet positions are used in the Fastems system at Hamble. This is partly because the facility is being developed during the A340 ramp-up phase; and partly a function of the expense of every extra 630mm² machine pallet and cube fixture, a combination which costs several thousand pounds. However, Gary Pitman says that as the system matures, he would like to see all pallet positions filled. This would allow unattended machining for longer periods and economise on the labour cost content of projects which are put into the cell. As it runs 24 hours a day, seven days a week, 51 weeks a year, the scope for savings is considerable.

Details available from Fastems Division, Heivar Ltd. Tel: +44 (0)1322 282276; Fax: +44 (0)1322 282250; E-mail: robert.humphreys@fastems.com