The seventh generation of Jaguar’s XJ saloon, which pioneers a new lightweight aluminium monocoque construction, was announced at the Paris Motor Show last year and is now in full production. The car is 200 kg lighter than the outgoing steel-bodied model yet 60 per cent stiffer. Stamping of aluminium panels is an emerging technology and no other car manufacturer has achieved such complex bends and curves in this material.

Designed and engineered by Jaguar, the body for the new car is built at the company's Castle Bromwich plant in Birmingham, where the press shop is managed by Polynorm Stadco. Throughout the development of the body-in-white, quality control requirements have been underpinned by metrology partner, LK.

The company manufactured and supplied to Castle Bromwich during mid 2001 an HC-90 co-ordinate measuring machine (CMM) and at the same time, an LK programmer was seconded on site full-time to create measuring programs for all 125 major body panels that go to make up the XJ. This was carried out directly from car design data downloaded from Jaguar’s I-DEAS CAD system into CAMIO, LK’s CAD-to-CMM interface software.

The ‘simultaneous engineering’ approach helped to minimise lead time from drawing board to volume manufacture, as measuring routines required only minor modification when the prototype panels became available later on. The CMM also supported the job of proving out the tools and dies.

Once this was complete, the HC-90 was moved within the factory and retrofitted with a pallet transfer system and second PC to form a cell capable of handling the large volume of production parts to be inspected. It supports the XJ press shop 24 hours a day, 7 days a week. First- and last-off components from each batch undergo a level 3 measuring cycle and in addition, the middle-off has a level 4 check; the same applies to all 125 panel types.

Take for example the door opening panel, which is the largest component to be inspected. A level 3 routine requires 160 features to be measured and takes 11.5 minutes, while level 4 involves checking just 13 features in a 3.5 minute cycle. Level 2 inspection, however, which took place during PSW checks on a batch of 30 parts, consisted of a 2,300 feature cycle taking nearly three hours. Required tolerances on all panels are surprisingly tight, ranging from ± 0.08 mm and ± 0.5 mm on hole diameter and position respectively to ± 1.5 mm for non-mating trim edges.

The LK measuring cell has three pallet positions and two pallets, each of which can accommodate up to five fixtures depending on panel size. Thus between one and five panels can be checked in successive measuring routines, during which time a new set of components is fixtured on the second pallet. The first is then shuttled along to the spare position and the second pallet takes its place underneath the CMM. In this way, virtually continuous measuring

productivity is maintained as the second PC is ready with the new sequence of programs already loaded and ready to run.

Various packages within the software provided by LK simplify running of the machine. For example, Launchpad software makes it easy to load the correct program for any panel, which is easily identified from the stored record of its name, part number, tool number and issue level. Statistical process control software allows SPC analyses to be created automatically, giving early warning of parameters within the press lines that are moving out of tolerance.

Additionally, graphical reporting software greatly speeds and facilitates the compilation of pictorial, results file, and control chart reports which are circulated within the company in PDF format.

"Pictorial reports can be quite extensive," said Polynorm Stadco’s senior controller, John Turland. "For instance, the door opening panel report runs to 293 pages for a level 2 check. After the reporting structure has been initially set-up in the LK control, creation of these documents is fully automatic, saving an enormous amount of time." They are used predominantly by quality engineering staff, Polynorm Stadco’s toolroom engineers as well as Jaguar stamping engineers.

Results file reports contain lists of X/Y/Z values for the measuring routines and were used mostly during PSW, although they are still used routinely in the press shop QC room. Most detailed are the control chart reports which have embedded in them multiple SPC analyses. "Despite their complexity, these reports need only a small amount of construction and maintenance," continued Mr Turland, "and are used mainly by management to assess production quality performance."

LK has a long history of supplying CMMs and metrology expertise to Jaguar, as well as Ford’s other Premier Automotive Group companies, to support their quality control needs. In the past it has supplied equipment for checking individual components, sub-assemblies and/or complete body-in-white for X-type, S-Type, XJ and XK models. Indeed, an HC-90 installed in another building at Castle Bromwich, which is used for inspecting the S-type body-in-white, now doubles for similar checks on the new aluminium XJ body.

Download: Jaguar uses LK HC90 for inspection of aluminium panels (PDF file)

Print this page