Hermle 5-axis machines a solid investment for Aerostructures

Citation

(1999), "Hermle 5-axis machines a solid investment for Aerostructures", Aircraft Engineering and Aerospace Technology, Vol. 71 No. 2. https://doi.org/10.1108/aeat.1999.12771bab.013

Hermle 5-axis machines a solid investment for Aerostructures

Hermle 5-axis machines a solid investment for Aerostructures

Keywords Aerostructures Hamble, Machine tools

There have been many changes at Aerostructures Hamble Limited since it became independent of British Aerospace in 1992. From being mainly concerned with military aircraft, today it is predominantly a manufacturer of parts and sub-assemblies for civil aircraft undertaking work from Airbus, McDonnell Douglas and Boeing as well as from British Aerospace.

But perhaps the biggest change has been in the production technology. No longer are airframe components produced as sheet metal assemblies but rather are made from solid metal, which reduces costs and increases quality. This has meant major investments in 5-axis machining, culminating in the installation of two Hermle C800U universal machining centres from Traub-Heckert UK Limited.

Aerostructures Hamble is one of the eight companies making up the Hamble Group that operate from a single site on the east side of Southampton Water. Since 1992 the Group has undergone a number of corporate reorganisations and today is part of Dowty, a member of the Tube Investments Group. Throughout this period Aerostructures has continued to develop as one of the leading subcontractors to the world's aircraft manufacturers and has been particularly successful in North America which now accounts for some 60 per cent of its business.

This world class ability was recently confirmed when the Hamble company won a major contract from Boeing to produce the wing leading edge sub-assembly for the new 737/700 aircraft. It was the largest order the company has won since it separated from BAe and was the incentive to purchase the latest technology 5-axis machining centres.

Ribs for the 737 wing leading edge are machined from solid aluminium billets in an FMS that incorporates three large CNC machining centres, two of which are 5-axis machines.

The billets are shaped on all six sides and rough bored in the cell before being despatched off-site for shot peening. They are returned for final precision boring and drilling, which requires the part to be probed on the machine before machining in order to meet the required tight tolerance limits.

Bill Taylor, production engineering manager, says, "Originally we finish machined the ribs on our large machining centres, but realised that manipulating a touch probe and light boring on a large powerful machine tool was somewhat inefficient. What we needed was a fast, more compact 5-axis machine that we could effectively use as a CNC jig borer and we found it in the gantry-style Hermle C800U."

He continues, "When I first saw the Hermle machine I was immediately impressed with the 5th axis trunnion, which is similar to that on our larger machines. It gives a large working volume for the size of machine with all the drives being positioned outside the working area and well protected. It is also a very accurate machine and the Granitan bed is unaffected by our harsh working environment. And the clever spindle crash protection arrangement gives us a great deal of confidence."

There are several features of the gantry C800U that Mr Taylor identifies as giving productivity benefits. "Its high speed mobile spindle is advantageous considering that half the cycle is taken up in probing datum on the rib components and all five faces have to be accessed. Then, the fast toolchanger (5s chip-to-chip) helps to minimize the time to exchange the 20 or so different tools required to finish machine each rib. Third, the excellent access to the trunnion is key to reducing loading times for both fixtures and components."

The first Hermle machine is fully occupied in its jig boring role working two shifts, seven days per week. It is equipped with a quick change pallet system so that, even though it is a single pallet machine, a changeover takes just a few seconds compared to around 15 minutes for a normal clamping system. The effect of the introduction of the Hermle machine has been to significantly simplify operations on the larger machining centres as well as achieve the high levels of accuracy demanded. Parts are not only probed prior to machining but are also probed afterwards.

"We have set up the system so that parts are now bought-off on the machine, eliminating the need to post-inspect every part on a CMM. Only samples are measured for audit purposes", says Mr Taylor. Data obtained on each component are continually analysed for SPC and stored for traceability. On-machine inspection is another way that the Hermle machine has increased the efficiency of leading edge component manufacture at Aerostructures.

The achievements of Aerostructures in machining complex 3D components from solid has further encouraged the designers to seek this solution for more and more components and of increasing complexity. The result has been an increased demand for 5-axis machining, which is why Aerostructures, encouraged by the success of the first Hermle, purchased the second one. It will be used to machine smaller components completely including milling from the solid billet as well as the type of finishing work done on the first machine. It will further relieve the load on the larger machining centres.

To accommodate this wider machining function, Aerostructures ordered the second machine with an extended 87-position tool magazine, rather than the standard 30 capacity unit on the first; otherwise the two machines are identical, and each is fitted with a laser tool breakage sensor.

Mr Taylor concludes, "Obviously, buying the second machine indicates our satisfaction with the Hermle machine. I think that it is the best 5-axis vertical machining centre for its size currently on the market."

The Hermle C800U is available in three versions, each with a working traverse range of 800 × 600 × 500mm. In addition to the 5-axis machine as supplied to Aerostructures, there is a 4-axis machine with a four-sided clamping yoke which can hold multiple fixtures on each face and is aimed at automotive sub-contractors, and a 4-axis with a chuck and tailstock for machining rota-symmetric components. Two other types complete the 800 series: the 3-axis C800V with a rigid table and the twin pallet indexing C800P. The Hermle range of gantry-style centres has recently been extended with the introduction of the smaller C600 series and the larger C1200, with respective XYZ working traverse ranges of 600 × 450 × 450mm and 1,200 × 900 × 500mm.

All the Hermle machining centres and the Hermle range of CNC universal milling machines are solely distributed in the UK and Ireland by Traub-Heckert and fully supported from the Brackley Technical Centre with applications engineering, installation, spares and full service back-up.

Further details available from Traub-Heckert UK Limited. Tel: +44 (0) 1280 705 482; Fax: +44 (0) 1280 705 606.