This article was taken from the October 2014 issue of WIRED magazine. Be the first to read WIRED's articles in print before they're posted online, and get your hands on loads of additional content by subscribing online.
From Henry Ford's industrial production model to the introduction of robots in the late 20th century, there has been significant change in the way mass-market cars are made. However, the rapid ascent of automation, alongside new environmental standards, in the auto industry has demanded an even greater level of innovation in the way cars are manufactured.
Take BMW. The German company was aware that the assembly of its i Series of electric and hybrid vehicles (the i3 was launched in November 2013, the i8 in June this year) required a new approach to manufacturing. So, between 2009 and 2012, it spent €400 million (£310 million) building a new factory near Leipzig in east central Germany.
The company claims that the facility, which covers an area of 2.1 million m<sup>2</sup>, is one of the most sustainable automobile plants in the world. The differences with the older plants are striking. On the new line, there is no need for a paint shop as the thermoplastic outer body panels can be sprayed in small, shed-like rooms. A traditional press shop is absent because the construction of the passenger section of the vehicles doesn't require steel or aluminium. In the body shop, there is no more welding, just robots silently applying glue.
The result is that making the i models requires 50 per cent less power and 70 per cent less water per car compared to the BMW production average which, in 2011, was 2.43mWh per vehicle. All of the electricity needed for the i models is generated on-site using wind power from four 2.5mW turbines.
Generating around 26GWh per year, these turbines produce 2GWh more electricity than is required for the i Series. The surplus is channelled into other areas of the plant.
A ventilation-control system ensures all of the air in production areas is replaced several times a day via the overhead and side lighting in the assembly hall. Natural ventilation provides the cooling
to counteract the heat in the pressing plant.
This means that no additional fans or air-conditioning systems are needed anywhere in the plant's ventilation system. To further reduce power consumption, white foils on all the strip lights in the hall ceiling reflect natural sunlight to reduce the use of artificial lighting.
Perhaps the most obvious change in i-model production is the extensive use of carbon fibre, which allows the manufacturer to offset the weight of the heavy electric components with lightweight, yet extremely stiff, body construction.
Unlike most vehicles with an integral body and frame construction, the horizontally split LifeDrive architecture of the i Series consists of two independent modules: the "Life" carbon-fibre passenger compartment and the "Drive" powertrain and aluminium chassis section beneath.
The carbon-fibre fabric is first moulded into its eventual shape in the preforming process. The laminate is heated to create a stable, three-dimensional form. Several of these preformed pieces can then be assembled into a larger component. This makes it possible to manufacture much larger body components for the i8, which are difficult to produce in aluminium or sheet steel.
After preforming, the next step in the process is resination.
The resin-injection procedure -- which is used in aerospace, boat and wind-turbine construction -- involves injecting liquid resin into preformed fabric sections under high pressure. The bonding of the fibres with the resin and the subsequent hardening gives the material its rigidity -- and its name: carbon-fibre-reinforced polymer (CFRP).
In a pressing plant with a closing force of up to 4,500 tonnes the resin is bonded with the hardening agent and the section is cured. This eliminates the need for an additional curing process or a classic paint-shop and cathodic immersion-bath coating. These time savings mean that BMW can produce preformed parts in a matter of single-digit minutes.
During assembly of the i8 Drive module, the aluminium chassis is fitted with a high-voltage battery. It's then assembled with the drivetrain and transmission units. Once the pre-assembled front- axle carrier and other parts have been mounted, the Drive module is ready to move for final assembly.
Meanwhile, the CFRP passenger cell -- half the weight of steel and 30 per cent lighter than aluminium -- makes its way from the body shop to the assembly where, on the i8 assembly line, its customer-specific equipment is fitted. This is the final step before the "marriage" of the two modules, where the CFRP passenger cell and the aluminium chassis are bolted and bonded together. For this, BMW has developed an adhesive that takes half an hour to bond, ten times faster than normal. Finally, the i8 is given its thermoplastic exterior skin.
The 110-metre i assembly line -- normal production lines can be more than 1km -- comprises just 14 workstations. "This, of course, is due to the parallel assembly processes and the fact that the new CFRP structure comprises many fewer parts," says Carsten Breitfeld, the i project director. "At 20 hours, the total processing time in the body shop and on the assembly line is half of what would be required in a conventional production process."
Jeremy White is product editor at WIRED. He wrote about Koenigsegg in 06.14
This article was originally published by WIRED UK
