Shopfloor gauging of aerospace components

Citation

(1999), "Shopfloor gauging of aerospace components", Aircraft Engineering and Aerospace Technology, Vol. 71 No. 1. https://doi.org/10.1108/aeat.1999.12771aab.005

Shopfloor gauging of aerospace components

Shopfloor gauging of aerospace components

Keywords Measurement, Software, United Kingdom

With 95 per cent of its sales dependent on the aerospace industry, Lancashire subcontractor Cleveland Guest Engineering places a high priority on quality. So when the company established a second manufacturing site two miles from the main factory at Colne, acquisition of additional high precision co-ordinate measuring machine (CMM) capacity was written into the business plan (Plate 2). The role has been filled by an LK G90C 6.5.4 computer controlled CMM configured as a pre-programmed automatic gauge for the majority of parts produced at the satellite plant.

Stuart Grant, deputy managing director of Cleveland Guest, commented, "The second factory was set up initially for a particular contract involving supply of parts direct to line. There is therefore quite a heavy inspection and documentation responsibility attached to the job. Having a machine on site that is capable of fulfilling around 90 per cent of the relevant inspection requirements makes a great deal of sense.

Plate 2 Cleveland Guest's new LK CMM has been configured as a pre-programmed automatic gauge for the majority of aerospace parts produced at the subcontractor's new Colne factory

"The LK machine is ideal for the job. Simplicity of operation means all of our machinists are able to use it, while the mechanical design and ceramic construction of the machine makes it well suited to shopfloor conditions without the need for special installation provisions."

Cleveland Guest manufactures a wide range of airframe and engine components for UK aerospace suppliers; the split is roughly 80 per cent structural to 15 per cent engine. Its customer base includes OEMs and first tier subcontractors, all demanding the highest standards. Component size ranges from a few centimetres up to four metres, mainly in steel or aircraft grade aluminium. Tolerances are dependent on the component but individual features may be under 10 microns.

The company's level of involvement with a project has risen in recent years, following a management buy-in by Stuart Grant and Steve Hollis in 1994. Like a number of front ranking subcontractors in many industry sectors, Cleveland Guest now operates as a project partner with its clients. In practice, that means it can receive scheme drawings and is then responsible for all detailed design work. Ultimately it results in development of the CNC programs used to drive the manufacturing process.

Mr Grant continued, "On this particular project we are manufacturing a range of fairly complicated parts, each up to 450mm in length. Monthly call-off from the client is typically between 16 and 24 components, but though we supply on a just-in-time basis we like to maintain a buffer stock to cope with fluctuating demand, so our batch quantities can be larger. The nature of the components means that there is some complicated surface geometry which has to be tied back to the original CAD data and the only way of doing this is by use of a CMM."

Cleveland Guest has operated a large (3 metre capacity) LK CMM for some years at the main factory. However, this already carries out a moderately heavy workload and the frequency of checking associated with activities at the new factory would probably have overloaded the old machine. Moreover, the time delay associated with transporting first-off jobs to the main works for inspection would have been unacceptable.

"Investment in another large capacity CMM was not on the cards", Mr Grant explained. "However, about 90 per cent of throughput at the new factory falls within the capacity of a half-metre machine like the G90C 6.5.4. Larger jobs can still be handled on our existing machine."

Having decided to buy a new CMM, the company began to look at the wider implications. Software, for instance, has developed considerably over the last few years but Cleveland Guest has many programs developed for its older machine. Ideally it wanted compatibility between the new machine and the old. This automatically elevated LK to the short list.

Inspection foreman Jack Sudall commented, "Though modern LK machines use the Visual CMES PC-based software package there is backward compatibility with older LK programs via the Launchpad feature. From the standpoint of new program development we were impressed by the user friendliness of CMES and its all round capability. In the longer term the company will want to upgrade the software on our older machine and this system is well up to the job."

Mr Suddall's comments were echoed by Ian Imeson, one of the inspectors assigned to the machine. "The system is very easy to pick up. I had virtually no computing experience prior to this assignment but I have been able to make good progress, building on what we learned during the three-day training course at LK's Donnington factory. The machine is also easy to use in manual mode so one-off checks are easily carried out."

As well as basic measuring, visual CMES allows operator set-up prompts to be illustrated with diagrams on the computer screen. For Cleveland Guest's application, in which the machine will ultimately be operated by skilled machinists, features like this may provide a vital online reference. Moreover, the software provides capability to format inspection reports exactly in accordance with customer specification.

The mechanical design of the G-90C also inspired confidence. The machine is of moving-bridge type using ceramic structural parts to combine low mass for high traverse speed with mechanical stiffness and very good thermal stability. This allows the machine to be sited in a shopfloor environment without compromising its measuring performance.

Mr Grant added, "The LK design scored on all fronts and also came in at a very competitive price. In terms of our application it is very able to provide the inspection facilities we need now and in the future. It has been noticeable that aerospace components have become more complex over the last few years while the inspection requirement has increased in parallel. With the G-90C we are confident of being able to meet that requirement."

Further details can be obtained from LK Limited. Tel: +44 (0) 1332 811349; Fax: +44 (0) 1332 850149.