Like many automakers, Jaguar has long used structural in-hem adhesives, which are precured by induction heating equipment immediately after hemming. This provides handling strength and dimensional stability prior to the adhesive reaching full strength during the paint process.
Where Jaguar differs from some European manufacturers is its preference for Spot-Bonding® as opposed to full-ring systems. The spot-bonding principle is to provide sufficient strength to maintain geometry, but with a lower energy input to the component to reduce the potential for distortion. The lower energy input also allows faster cooling of the heated areas. Spot-bonding has, however, proven problematical in the past. This was due to the potential for temperature variations caused by panel condition changes and panel deformation during heating (particularly with aluminum). These temperature variations resulted in reduced strength and increased distortion—the degree of which depended on the temperature change.
The introduction in 1999 of the U–Coil addressed the limitations of spot-bonding by ensuring that inner and outer panels are heated simultaneously. Also, the self-aligning coil ‘head’ allows the coil/panel relationship to be maintained, even in the event of panel differences or movement while heating. The extra cost of moving the coils into position was somewhat offset by the cost of the clamps that were no longer needed to maintain panel/shape position. Tooling costs, too, were much reduced. Actual savings in the form of less downtime and re-working far outweigh the initial increase.
The Jaguar X400 (X Type) body shop in Halewood, England, has Ucoil spot-bonding systems for curing closure panels. The systems have delivered a reliable, high-strength, zero distortion process since commissioning and setup of pre-production panels in the summer of 2000. But it was the move of Jaguar’s Castle Bromwich facility towards aluminum body and closure construction that reallyhighlighted the benefits of U-Coil. Aluminum hoods and truck lids are now heated on table type tools, and the aluminum doors of the X350 (XJ) are heated while on the cell output conveyors—with considerable savings in tooling costs and floor space requirements.
EFD Induction UK Product Manager for Bonding Systems, comments: “The growing use of adhesives in the automotive industry, plus ever-decreasing cycle times, underscores the need for robust, flexible curing processes. Our product improvements are the direct result of working with customers such as Jaguar. Their innovative hem-bonding processes are the successful result of a team built by Jaguar engineers who had the open-mindedness to encourage freethinking input from their selected partners. They also had confidence in the team’s ability to provide solutions that have taken a once troublesome pre-curing process to new levels of performance.