Mercedes McLaren SLR Production 2

At the McLaren Technology Centre, advanced materials from the aerospace and F1 are used for the first time in the series production of the body and chassis. The SLR's doors, bonnet and complete BIW are made from carbon-fibre composites (CFCs). Previously, CFC components were built by hand in a time-consuming process. In order to achieve a high degree of automation, McLaren worked with the Mercedes-Benz Technology Center in Sindelfingen to divide the production process into a 'preform' stage and a resin saturation stage followed by the hardening phase. Traditional textile processes such as stitching, knitting, weaving and braiding were adapted for the production of high-performance CFC fibers.

The longitudinal members of the front body structure consist of a central cross member and the encircling moulded part or internal web. The cross member comprises several layers of carbon fiber stitched together by a machine. After the form has been cut to shape, the web blank is inserted into a braided polystyrene core. This core element is then clamped into a specially developed braiding machine that produces the longitudinal member from 25,000 ultra-fine carbon filaments unwound simultaneously from 48 reels. This process allows the fibers to be braided around the core at a precisely defined angle to create the desired contour. Several layers are overlapped in certain areas, depending on the thickness required.

In an additional process, a computer-controlled tufting machine (as used in the textiles industry) joins the cross member to the braid of the longitudinal member. The braid core is removed and the preform of the longitudinal member is cut to the correct size. The preform is then injected with resin. A cycle time of just 12 minutes is required to manufacture the complex fiber structure of the longitudinal members using a braiding machine. This illustrates the potential production capacity that this innovative manufacturing technology offers for the future.

The rear shelf structure of the SLR further illustrates the new production techniques used for carbon-fibre processing. Despite being a very complex shape with several apertures, it is automatically manufactured as a single component. To achieve this, Mercedes-Benz and its partners adapted the Sheet Molding Compound (SMC) method to create 'Advanced SMC'. The key advantage is that the carbon fibre mats are no longer manufactured by hand but by machine. Here, a handling system positions individual CFC layers at precalculated angles and in preset positions which correspond to the principal shape of the component, thereby creating the blank. Under heat this blank is then pressed, and in the process it takes on the precisely calculated form of the rear shelf. No subsequent reworking is therefore required
McLaren Composites also manufactures over 50 carbon fibre components for the car. The entire floor assembly, including all support members and securing elements, is made from one piece. The core of the carbon fibre composite roof frame structure (also manufactured as a single piece) is automatically filled with foam before the resin injection, creating a crash-resistant sandwich structure. High-strength bonding and riveting techniques ensure a reliable connection between the individual components of the chassis and the bodyshell. The aluminum engine mounts are bolted to the carbon fibre composite bulkhead and also bonded in place. The carbon structure includes integral mountings for the aluminum and steel rear axle.