Product category:
Jigs, fixtures, special tooling and gauging
News Release from: Brookhouse Holdings | Subject: Composite carbon fibre composite jig
Edited by the Manufacturingtalk Editorial
Team on 25 December 2003
Composite jig helps produce Bentley's
new car
A lightweight, carbon fibre composite, setting and measuring jig, is precisely locating the driver and passenger door windows of the new Bentley Continental GT during final assembly.
A lightweight, setting and measuring jig, manufactured in carbon fibre composite by Brookhouse Composites, of Darwen, is being used on the production line of the new Bentley Continental GT to help in the precise location of the driver and passenger door windows during final assembly The new Bentley, which was launched this Autumn, is of two door Coup? design
This article was originally published on Manufacturingtalk on 14 Nov 2003 at 8.00am (UK)
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It has no door pillars between the two front windows and the rear quarterlights, making the sealing of the windows vital to passenger comfort by eliminating wind noise.
As a result, the final fitting of the glazing is a very precise operation.
This is made even more critical by the fact that an automatic mechanism within the door acts to lower the window by a small amount when opening the door and then raises the window back into its sealed position when the door is closed.
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This action ensures minimum wear on the window sealing arrangement to prolong seal life.
A specially designed and precisely manufactured jig is used both to set the final position of the door glazing and also to check and verify its geometrical location.
Originally, this jig had been made in aluminium and had been manhandled into position by two production line operatives, with the aid of an overhead hoist.
This involved clipping the jig over the window and door assembly and setting the window correctly in all of its operating positions, according to the measurements taken by the various measuring instruments fixed to the jig.
However, because of the weight of the complex jig, which made it difficult to lift and control when attached to the hoist, Bentley engineers decided to investigate alternative materials of construction.
In order to reduce the weight while maintaining the rigidity and strength of the structure, it was decided to investigate the use of engineering composite materials and Bentley contacted Brookhouse.
Working from original Bentley drawings, Brookhouse produced a precisely engineered jig, from carbon fibre tube, which weighed just 10.5kg compared with the 26kg of the aluminium equivalent.
The cut lengths of tube were bonded together using a structural adhesive and the metal and nylon attachment points for the measuring instruments were bonded and bolted in position.
When tests were carried out with the new jig, it was soon realised that the change to a composite structure had also introduced more benefits than a simple weight saving.
Apart from improving the portability of the jig, the reduced weight also decreased its momentum when suspended from the manipulation tool above the production line.
This, in turn, improved the controllability of the jig, which was very important, as the window setting and checking is one the later production operations and is carried out when the car is already sprayed, so that there must be very little possibility of damage to the painted bodywork.
An important characteristic of composite materials is temperature stability.
This is essential in a precise measuring jig, as any change in jig dimension caused by ambient temperature variation is obviously detrimental to the accuracy of any measurements taken.
The composite jig also offers a further benefit over the aluminium equivalent in that any damage to the jig is immediately obvious so that repairs can be carried out before new measurements are taken.
With aluminium, slight damage can go unnoticed so that the integrity of inspections could be compromised.
Although the original design requirement of improved portability no longer applies, as the jigs are now stored on the manipulation tools above the production line to release ground space, the conversion from aluminium to carbon fibre has still proved more than justified in terms of guaranteed repeatability of measurements, controllability and reduced possibility of car bodywork damage during window setting and checking.
Brookhouse Composites is one of a group of companies within Brookhouse Holdings plc, which together provide the expertise, facilities and resources in design and manufacture to meet the extremely high demands of today's aerospace sector and the automotive and general engineering industries.
This total capability includes the production of moulding tools in composite materials and metals, the manufacture and repair of composite components to international approval standards, the manufacture of detailed components, such as metal skins and panels and the precision engineering of tooling, jigs and fixtures.
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