Researchers in Europe believe the 5-day car will revolutionize automotive production. They have developed a lightweight modular car that features plastic body panels and new assembly methods.

Typically, it takes less than 30 hours to build a car, from stamping steel to driving it off the assembly line. But, if you order a car built to your individual specifications, it takes an average of 55 days to receive it. To reduce that time gap and improve customer service, automakers must develop a cost-effective build-to-order system.

“The traditional mass-production system has a great deal of inventory within it,” says Dr. Glenn Parry, senior research fellow in the school of management at the University of Bath (Bath, England). “There is an average of 53 days worth of cars being held as inventory within the U.S. by each car manufacturer,” adds Parry, author of a recently published book entitled Build to Order: The Road to the 5-Day Car (Springer, New York). “This is the worst place to have capital employed, as you have [already invested in raw materials, equipment and other costs].

For the 5-day initiative to be successful, Parry believes automakers must convert to a more modular assembly process. “This allows you to manufacture a number of modules up front and then configure them into the vehicles the customer actually wants,” he points out. “Modularity includes the body structure and surface styling.”

Parry and his colleagues have developed a ModCar concept that features a modular body. This would be achieved by decoupling a car’s “styling skin” from its spaceframe body, interior seating and cockpit. Parry says the body skeleton would be steel, while the surface would be plastic. “Plastics give you the high quality surface finish that customers demand,” he explains.

Engineers at the Institute of Lightweight Structures and Polymer Technology at the Dresden University of Technology (Dresden, Germany) designed the body shell and panels. They used transparent light thermoplastics, such as polycarbonate, polymethyl methacrylate and polystyrene, coupled with two-step injection molding technologies, to create modules.

Instead of using a traditional paint shop, the 5-day car concept uses precolored surface panels. By using technologies such as paintless film molding, the engineers addressed traditional challenges associated with cost, environmental issues and late configuration changes. Parts would be made from fiber- or textile-reinforced polymers such as Twintex, which is made by Saint Gobain Vetrotex (Chambery, France).

“The ModCar body frame is made up of colorless steel profiles with a constant cross-section, avoiding complex geometries and section sweeps,” says Parry. “The paint-free body frames will be covered by connector elements. To fulfill the requirements of modularity, stiffness and strength, the connector elements will be fixed by screws in highly stressed areas and snapped on in secondary structural areas.

“The connector elements, produced by injection molding, provide a perfect surface onto which to bond the outer panels,” claims Parry. “The adhesive can be preapplied during the production of the connector elements and activated before the marriages of the frame and the outer panels. The outer panels will primarily be joined to the connector elements by adhesives and hook-loop fasteners. Self-tapping screws will be used in well-hidden areas where bonding or Velcro fastening is not possible. Bonding will be used in areas where impact and misuse are most likely.”