Built to order – fast and eco-friendly vehicle manufacture

Materials World magazine
,
1 Jul 2008

Within a decade, a car buyer could walk into a dealership, choose the vehicle he would like to purchase, including the model, colour and add-on’s, and have it built and delivered to him within five days, all in an eco-friendly and cost-effective manner. That was the aim of the four-year European Intelligent Logistics for Innovative Product Technologies (ILIPT) project, which concluded on 30 June.

Working with industry, including team leader ThyssenKrupp Automotive, Daimler AG, Hella and Siemens, researchers from Fraunhofer Gesellschaft and the Technical University of Dresden (TU Dresden) in Germany, and the Universities of Bath, UK, and Patras, Greece, have created a modular car (ModCar) design that is lightweight and can be manufactured quickly using plastics and steel.

‘Traditional mass manufacture starts by stamping out the body in a large steel pressing,’ explains Dr Glenn Parry of the University of Bath, who led the interoperability and validation focus of the project. ‘So right from the start, you define what automobile you are making, whether it is a saloon or a coupe.

‘With the ModCar, you do not define the whole car but only its elements, such as the bumper or engine bay. That gives you greater flexibility later in production, and reduces your cost base significantly because you have greater commonality of the car parts and can rapidly reconfigure [the vehicle] to match an order. We’ve reduced the [potential] number of body parts from 105 to 22,’ he says.

Material measures

The car uses flexible polymer body frame panels split into seven main modules (front end, rear end, exhausts, covering, etc), which are built separately. The application of paintless film moulding, using coated or dyed foils on the outer surfaces of the panels, eliminates the need for paint shops, which provides energy savings and reduces the use of volatile organic compounds.

Using computer-aided engineering simulations, researchers defined which materials would work best in terms of stiffness and manufacture. The lightweight panels which fit over the body frame display were designed by TU Dresden. These are not meant to bear substantial mechanical loads, and therefore lightweight and easy-to-produce polymers such as non-reinforced thermoplastics (polyamide, polypropylene and polybutylene terephthalate), glass mat-reinforced thermoplastics, long fibre-reinforced thermoplastics (LFT), as well as bulk and sheet moulding compounds, can be used.

The proposed layered panels for the ModCar consist of a long fibre injection polyurethane base, then film carrier acrylonitrile styrene acrylate, followed by a dyed poly(methyl methacrylate) (PMMA) paint layer, and a PMMA top coat. A LFT buffer layer can be added to reduce non-uniform shrinkage from the base. These panels have a good torsional stiffness of 11,800 Nm/º, but their bending stiffness of 7,406 Nm/º needs further optimisation.

Framework

For the frame, a hot press hardened manganese boron steel MBW-K has been chosen for the front bumper because it offers high strength and can be produced in large volumes. The engine crossbeam carrier uses retained austenite steel RA-K, which displays higher energy absorption capacity under heavy loads than cold rolled dual-phase steels, meaning less of it can be used in the same capacity. The researchers also identified X-IP steel, a new grade still under development at ThyssenKrupp, as having the strength and formability required for the car’s pillars.

As the body frame is not assembled until after it has been equipped with components, hot joining techniques cannot be used, so screw bonding is applied instead.

‘There will be significant operational changes required to make build-to-order cars,’ says Parry. ‘But having the customer come to you and tell you what they want, and then you create it, is the holy grail of car manufacture, because you don’t have your capital sunk in thousands of finished cars waiting to be sold.’

Parry says the ILIPT partners will continue to work to adopt the research and are
considering creating a generic guidance framework for all European car
manufacturers.

Some of the results of the ILIPT project will be published this August by Springer. Build to Order – The Road to the 5-day Car is edited by Parry and Andrew Graves.

Further information:

European Intelligent Logistics for Innovative Product Technologies

Springer