TECHNICAL ANALYSIS // 20.09.2011
85% of a Formula One car is produced from carbon fibre. That carbon fibre goes through its first manufacturing process in the Kit Cutting room, where every carbon fibre car component is prepared for laminating.
There are several grades of carbon fibre used for the car components and these fall into two categories - woven fabric and uni-directional. They are used in combination to maximise the strength and stiffness of a component while keeping weight down to a minimum. All materials have a “twill” stripe running through them and by manipulating the orientation of this twill, you can strengthen a component in a chosen direction.
The carbon fibre arrives at the factory impregnated with a resin system and this material is known as ’pre-preg’. It is the resin system which, when cured between 135°C and 180°C, becomes solid and gives the material the hardened form which you see on the car.
Different resin systems have different life spans which can vary from 30 days to just 8 hours in ambient conditions. When uncured material is left out at room temperature, it gradually cures and, in doing so, becomes dry, crispy and unusable. However, pre-preg is costly stuff, so material preservation is of the upmost importance – which is why it’s stored at -18°C in two large walk-in freezers. Under these conditions, the material has a 12-month life span. A roll requires six to eight hours to defrost before it is ready for cutting.
The “cutting table”: 14,000 different ways to maximise efficiency!
Once a new component has been designed, the technical drawings and specifications are transferred to a lay-up manual. This has nothing at all to do with basketball: the manual is essentially the instruction book from which the part will be built. Why ‘lay up’? A single part contains many different individual shapes of carbon fibre, each of which needs to be ‘laid up’ in the mould in a precise sequence.
Using the manual and component moulds, templates for the part are made which are then brought to the kit cutting room. The templates are transferred to a large digitising board and then onto the computer by tracing around them with an electronic puck. Using the lay-up manual as a guide, all of the shapes are then named by their sequence number and have material types and quantities added to make up the full kit – ‘kit’ being the word that’s used for the set of shapes required to produce an individual part.
The system holds data from eight seasons of car components and it is always interesting to look back through and see how dramatically they have changed over time. The software can work through 14,000 different ways to maximise efficiency with all the shapes crammed into a ‘nest’, (Tetris style!) and the shapes are then ready for cutting.
The hard work is then done by the cutting table. The relevant material is rolled out onto an airbed which sucks the material down tight onto the bed. A computerised arm equipped with a tungsten carbide blade then cuts out all of the shapes in the nest. The airbed conveys the shapes through a printer which stamps the sequence number and material type onto the shape.
The kit is then bagged, labelled, dated and placed back into the freezer until it is required for manufacture. When required, the kit then goes into the Composite Clean Room for laminating, the process of laying all the materials piece by piece into a mould to give the component its form.
We kit the entire car - every component from steering wheels to chassis, from nose boxes to gear boxes, suspension to wings. Try to imagine cutting it all out by hand with just a pair of scissors!
Quick Facts:
- The cutting room operates 17 hours a day, five days a week over two shifts
- Carbon fibre is four times stronger than steel.
- The computer can work out 14,000 nesting equations.
- Although 85% of a Formula One car is made from carbon fibre, this only accounts for 30% of the car’s mass.
(With thanks to Adam Broomfield and Steven Tynan)
Credit: Mercedes GP (www3.mercedes-gp.com)
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