You have to hand it to Jaguar Cars - they have style - and when it comes to employing radical production technology, they have style there too, reports Mike Page.
You have to hand it to Jaguar Cars - they have style - and when it comes to employing radical production technology, they have style there too. No, I am not a Jaguar salesman, but I had been invited to tour the new production facilities for the aluminium-bodied XJ. The XJ is probably the first riveted and adhesively bonded all-aluminium monocoque bodied series fabricated car.

The only welds used are in the joints between the A and E pillars and roof and a number of drawn-arc stud welds.

Otherwise, the body assembly uses Henrob zinc and tin-coated self-piercing rivets and SCA Schnecker Betamate 4601 structural adhesive.

Planned production capacity for the XJ - or the X350 as the project is known at Castle Bromwich - is 30,000 - 35,000 units/year.

To achieve this, Jaguar Cars, a member of the Ford group of companies, has completed a new press shop and has completely stripped out and refurbished an existing assembly building.

Essentially, Jaguar Cars in the UK and Ford1s technical centre in Dearborn, Michigan, USA, had had to start from ’square one’.

Engineers had no historical forming and joining CAD database for the series production of aluminium Obody-in-white1 (BIW).

The company had used aluminium before in limited production cars, such as the XK180, built by Jaguar1s Special Vehicles Operation, in the 1990s.

The shape of that car demonstrated the possibilities of aluminium.

The company had also used bonded aluminium construction in its XJ220 supercar at the end of the 1980s.

The company1s first working of aluminium occurred in the beginning, with the aluminium paneled motorcycle sidecars in the Swallow Sidecar Company back in 1922.

Why riveting?

- Jaguar has chosen riveting because the XJ?

Ford1s technical centre in the USA had determined that electrical resistance spot welding would not provide the strength and fatigue resistance demanded by the XJ1s designers.

So the technical centre had performed extensive research and development in riveted and bonded aluminium assemblies.

The riveting systems have been developed jointly with self-piercing riveting systems manufacturer, Henrob (UK-01352 762555), a company invited in 1998 by Jaguar to become its technical partner.

Henrob has been involved in prototype build support of aluminium bodied vehicles in North America, materials development in Germany and production equipment trials in Spain.

The company has supplied systems for several automotive body-in-white (BIW) applications as well as light metal enclosures and class 8 truck cab assembly.

Henrob had successfully developed hydraulic and electric servo-motor self-piercing riveting systems, including automatic riveting head changer systems for robotic manipulation.

The design of the XJ involves a number of multi-layer sheet metal joints as well as riveting pressed sheet metal components and sub-assemblies to aluminium castings.

In all, on the XJ, there are 15 castings, 235 pressings, 29 extrusions (including an internal hydroformed extrusion) and 60 nut plates.

There are 3180 Henrob zinc and tin-plated steel self-piercing rivets and some 102m of SCA Schnecker Betamate 4601 structural adhesive used in the X350.

88 Kawasaki robots (UK 01925 713000) are used in the assembly lines.

New press shop - to produce the aluminium panel pressings for the XJ gave Jaguar a reason for re-establishing a press shop facility at Castle Bromwich, after an absence of some 20 years.

From a short list of two German and one Japanese supplier, Jaguar selected Schuler, of Goeppingen, Germany (+49 (0)7161 660).

Jaguar placed a purchase order for 13 hydraulic presses was placed in November 1999.

The first press arrived in November 2000 and the two press lines were handed over to Jaguar in October 2001.

Polynorm manages the press shop for Jaguar.

It is laid out in two tandem press lines.

The five-press Line A presses the larger skin panels and structural elements.

A 20MN single action deep draw press equipped with a high tonnage four-point draw cushion leads a line of four 8000kN follow-on presses.

A 20MN tool tryout press is positioned at the end of, and at 90ø to Liner A.

It can be linked in as an 8000kN production press.

Line B consists of two four-press and three-press cells, each led by a 6000kN lead press and 4000kN follow-on presses.

The cells can operate individually or be linked as a seven-press operation.

Some 18 ABB robots (UK- 01908 350300) serve the presses and three Schuler de-stackers.

The latter employ an air knife and bending cylinder system, backed up by double blank sensors to ensure efficient parting of the pre-lubricated aluminium blank stacks.

The press shop is a very slick operation.

The conveyors are flexible in operation feeding and taking off from individual press groups.

With the help of double moving bolsters, dieset change over time is down to 40min on Line A and 15min on Line B.

The goal is to be under 20min and 12min respectively.

Reached through a ‘hole in the wall’ of the press shop is a tool maintenance, repair and modification centre served by a Konecranes 32/16t travelling gantry crane (UK - 01355 220591) and a F Zimmermann CNC travelling gantry miller (Denkendorf, Germany, +49 (0) 711 93 49 350).

Pressing aluminium - to supply aluminium blanks to Jaguar, Alcan1s Nachterstadt plant in Germany (Alcan Automotive, Switzerland, +41 52 674 91 11) has a new Schuler decoiling, levelling and linear motor driven flying shear cut-to-length line.

It produces blanks in bake hardenable 6111 grade, as well as 5754 and 5182 grades, for Jaguar.

The linear motors accelerate the 9 tonnes mass of the flying shear to 120m/min.

The biggest challenge in the press shop was in die design.

Dies have been under development for some three years.

For example, the first trial deep drawing of the relatively complex rear fender resulted in 7mm and 12mm outboard discrepancies.

‘As soon as the dies released the fender, it springs and twists,’ said Jaguar1s principal stamping engineer, Ken Close.

‘It was a significant challenge to us - the panel was a difficult one in steel, let alone aluminium - but L„pple did a good job for us.’ L„pple, Germany, was one of five diemakers involved in the XJ diesets development.

The others are Ford of Cologne (Koeln)1s die shop, Nothelfer, Fagro and Allgaier - all in Germany.

When deep-drawn or formed, aluminium behaves very differently to double deep draw quality steels.

For example, al;uminium has a different spring-back characteristic, which led to much basic ‘trial and error’ work to produce the subtly complex bonnet skin panel.

Edging up in aluminium is different too.

One can not coin narrow, sharp corner radii like one can with steel.

Close pointed out the dashboard panel pressing.

He commented that in steel you can get sharp radii, but you can not in aluminium so the designers had to re-think the packaging layout for the instrumentation boxes.

The limitations imposed by the forming characteristics of aluminium prevented Jaguar from producing a one-piece side panel.

So the body side had to be separated from the rear fender.

Consequently, the only welds made in the whole of the BIW structure - apart from stud welds - are the four dual-phase MIG welds made using Austrian Fronius equipment (+43 (0) 7242 241 311) at the junctions between the roof and A and D and E posts.

The operation uses type 4043 welding wire of 1mm diameter.

Quite assembly - walking into the BIW assembly shop, one was met with a quietness and airiness that one did not normally associate with car assembly lines! Those of you who are well-used to the sights and sounds of electrical resistance spot welding assembly lines would be in for a surprise at Castle Bromwich! The manually operated hydraulic self-piercing rivet guns and the heavier duty servo-driven riveters wielded by the Kawasaki robots are inherently quiet in operation.

The heavier duty servo-electric rivet guns are necessary for the multi-thickness material combinations joined in the floor pan area for example.

The ‘kid glove’ handling of the aluminium panels, sub-assemblies and assemblies generates little sound.

The manual riveting guns appeared to be somewhat more cumbersome to move around than spot welding guns.

Having to locate the reels of rivets near the guns themselves imposed mobility restrictions.

For these reasons, Jaguar is using more robots than it normally would have done (when compared with spot welding steel BIW) for an output of 30,000 - 35,000 units/year).

There are 3180 Henrob zinc and tin-plated steel self-piercing rivets and some 102m of SCA Schnecker Betamate 4601 structural adhesive used in the XJ.

The layout of the BIW line is very similar to a spot welding line.

The rather different size and shape of the riveting guns and adhesive placement equipment - when compared with a spot welding system - determined the detailed line layout, which had been derived from the extensive use of simulation techniques.

Joe Macknamara, Jaguar’s principal engineer, Body Construction, said that the RobCAD simulation tools had proven invaluable in the layout design for the body shop and determining the positioning of the rivet guns and accessibility to the BIW assembly.

For example, the size and shape of the rivet guns determined that the main BIW structure be assembled from five, and not the four sub-assemblies as would have been the Onorm1 with a spot-welded steel BIW.

The rear floor assembly is built up with wheel arches and seat panel and is manually riveted.

It was commented that the placing of rivets is much like placing spot welds.

Guides are used to ensure the correct placing of critical rivets.

A Comau engineered cell (Turin, Italy, +39 011 68 45448 or 48640), using Kawasaki robots, rivets the dash assembly (LH or RH drive).

The dash is then assembled into the front structure.

Front and rear structures are married, side panels riveted in place and the assembly presented to the roof followed by the final roof and framing.

Three Faro portable CMMS (UK, 024 7623 6151) are in use for the on-site regular checking of all fixtures.

The complete underbody assembly is checked in a Perceptron rig carrying out 68 checks using 37 cameras.

A second Perceptron installation carries out 72 checks, using 41 cameras, on the body shell.

Surprisingly, perhaps, the XJ BIWs, after a body wash in a Durr system (UK-01926 418800), follow the path of the steel S-type and XK bodies through the same paint shop.

The same phosphating, primer and paint systems are used - after some ‘tweaking’ - on the XJ bodies.

Overall, the finished BIW is very pleasing.

In spite of the larger corner radii imposed by the use of aluminium, the closure gaps are comparable with a steel BIW.

Hood and deck gaps are within 3.5mm and doors, a nominal 4mm.

The XJ represents a significant achievement by Ford, Jaguar and all concerned.

It is also regarded by Jaguar as setting a precedent for the Ford empire’s future expeditions into all-aluminium cars.