TPT January 2008

T echnology U pdate

Laser cutting in sports car chassis production Caterham Cars, UK, celebrated the 50 th anniversary of its iconic sports car with a two-day event at the Donington Park racing circuit. Created by the late Colin Chapman and launched as the Lotus Seven, the car was re-named the Caterham Seven in 1973 when the former Lotus dealership headed by Graham Nearn purchased the manufacturing rights and re-started production. The Seven’s design is based around Chapman’s ethos of ‘adding lightness’, and while Caterham has refined and enhanced the original design, the car remains much the same in terms of appearance and construction. However, while the traditional tubular chassis is instantly recognisable, the method of manufacture has undergone substantial changes. One of the most significant productivity improvements in recent years has resulted from a switch to tube laser machining of the numerous individual components needed for

› The Caterham’s low mass makes it inherently agile

Chassis components are stored in racks ready for making up a ‘kit of parts’, a key element in a production process that has to deliver each chassis complete with body panels to the assembly facility on schedule, within budget and to the agreed specification. The latest parametric software is used to design the chassis and to model its component parts, and this CAD data provides the basis for programming the Siemens Sinumerik 840D CNC of the LT120 tube laser cutting system. Joints between tubes that would have been impossible or too expensive to produce by traditional machining methods take just a few minutes programming for the tube laser, with prototypes and re-designs also requiring just a few minutes to program. The accuracy and repeatability of laser cut parts ensure they always fit the welding jigs without further dressing. Chassis components are designed for ease of fabrication, with tabs and profiles combining to minimise the time needed to assemble them in a welding jig prior to robot welding. Once the chassis is complete it is washed in a series of phosphate baths to remove all traces of dirt and grease, before being powder coated and the body panels attached.

the variations of the ten or more Caterham Seven chassis produced every week by subsidiary company Steel Fabrications Ltd, UK. This investment in new production techniques has also contributed to a 12 per cent greater torsional stiffness, that has further improved the car’s road-holding capability. Steel Fabrications uses a BLM Adige LT120 LaserTube with a capacity from 12mm to 120mm OD tube or box section, to cut and profile steel chassis components prior to welding. Supplied by BLM Group UK Ltd, the LT120 takes up to four tons of 6.5m tube in its bundle loader, and nests finished parts cut to an accuracy of 0.1mm at the other end. As well as cutting and notching tubes for chassis, wishbones and A-frames, the LaserTube’s diffusion cooled CO 2 laser source pre-cuts rivet holes in the chassis components, reducing the time taken to attach body panels.

fi The BLM Adige LT120 tube laser is capable of cutting tube components to an accuracy of 0.1mm

fi The Caterham Seven’s welded chassis is phosphate washed and powder coated prior to fitting of the body panels

BLM Group UK Ltd – UK Fax : +44 1525 402 312

Email : sales@blmgroup.uk.com Website : www.blmgroup.uk.com

BLM SpA – Italy Fax : +39 031 715911 Email : export@blm.it Website : www.blmgroup.com

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J anuary 2008

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