Baked to perfection
Jaguar is using a new method to fit rear spoilers on its S-Type with a custom-built infrared oven at its Castle Bromwich, Birmingham manufacturing plant.
The pyrometer-controlled oven, which is small enough to fit at the spoiler fitting point on the production line, has proved faster, more accurate and more energy efficient than alternative options such as hot-air systems.
The rear spoilers are supplied to the production line with an integral adhesive strip that must be pre-heated before fitting so the adhesive can flow.
Jaguar looked for a design for a pre-heating system from infrared technology specialist Heraeus Noblelight, based in Cheshire, which had previously designed an infrared pre-heating system for the body mouldings on another type of Jaguar car.
Ian Bartley, Heraeus business manager, said the challenge for this application was that Jaguar needed a system to fit a much smaller footprint on the production line. 'We needed to design a bit of kit that would allow two boxes of mouldings to be loaded in at a time and maintain a uniform, accurate temperature control,' he said. 'The last thing you want is for a mould to be fitted on to the Jaguar, then fall off because it hasn't been heated at the right temperature.'
The 37.8kW fast-response medium-wave oven heats components more accurately and efficiently than a hot-air system. 'With a hot-air system you switch it on and leave it switched on all day long,' Bartley said. 'The mouldings sit in there for a long period, one on top of the other, so you can get problems with the mouldings deforming.'
Bartley said this is not the case with the infrared oven. At the Jaguar plant, the mouldings are transported to the oven by a gravity-fed roller conveyor. The top of the oven contains a heater cassette with 12 emitters, arranged so only one emitter leg is used. Effectively, Bartley said, this doubles the emitter lifetime.
The contents of about two boxes are heated by the infrared cassette, which is inclined to match the angle of the conveyor to ensure uniform heating.
An optical pyrometer monitors the temperature of the sixth moulding in the first box, to ensure that pre-heated spoilers are always available, even if only one box is loaded.
The required pre-heating temperature for the mouldings is 30ºC, and green and red lights on the machine indicate whether the temperature is within the required range of ±5ºC. When the spoilers are outside the specified temperature limits, a light is activated and if an operator tries to remove a spoiler, an alarm will sound until reset with a control panel key.
Bartley explained that the system uses little power. 'When the mouldings are in, we heat them up to the temperature required then the emitters just switch down and run at a few hundred watts,' he said.
'Then if a new box comes in with cold mouldings, the infrared emitters switch up to a higher power and bring the mouldings quickly up to temperature and just hold them there.'
The system can pre-heat about eight spoilers in 30 minutes.
The unique thing about this oven is Jaguar wanted it to not only heat spoilers but also its emblem badges. So Heraeus designed a smaller, 1kW badge-heating oven to sit on top of the main oven and heat the badges.
The oven can accept two badges at a time and PTFE blocks are included to locate these. It is operated by a simple push button on the associated control panel and a red light indicates when the heating is on. Typically, heat is applied for four to six seconds, after which a green light indicates that the badges can be removed and fitted to the vehicle on the line.
Bartley said since installation, Jaguar has told his company the oven allowed 'perfect adhesion of the spoilers and badges' and the two operations can be easily carried out to meet the speed of the production line.