BERTRANDT Functional Prototyping: Frontloading - The Crossblade Outside Mirror Dr. Ing. H.-C. Ludwig, Dipl.-Ing. (FH) A. Stuhlmüller, Bertrandt Technikum GmbH, Ehningen Many will have heard of it, some may have seen it, but very few will have driven it: the Smart Crossblade. General contractors Bertrandt developed this car for Smart GmbH in just six months, and built an exclusive series of 2000 with Binz, their production partners. The redesign of this vehicle, based on the Smart convertible platform, resulted from the extraordinary concept of the Crossblade - a car that has no roof, no convertible top, no screens, and no doors. Crossblade outside rear-view mirrors The new concept raised a number of issues, among those the question of a new mirror system. How should they be mounted? Can we do without an "interior rear-view mirror"? What should the new mirrors look like? Starting with the first design models of the vehicle, the initial option that was reviewed was whether the standard mirror could be taken over as a carry-over part, or whether the mirror system available on the market should be attached to the Crossblade. It quickly became clear that the best solution was to develop a new mirror system. The team of developers decided to take the mirror and its casing from the standard series. But a new mirror base had to be designed for mounting to the door pillar. The first step involved making a clay model of the mirror base and, once that had been approved by the designer in charge, to scan the surface. These scanning data were then used to generate the data model in the CAD system. The next step was to draw up a concept for mounting the upper and lower shell and their attachment to the body. To safeguard the design, the solution to this task was represented via selective laser sintered (SLS) parts. In this case, the invaluable advantage of using sintered prototypes was the fact that they were quickly available. Through early iterations at the design stage, this method helps to avoid costly changes and modifications in the injection moulding tools. The components were built at the Bertrandt Technikum using an SLS system by 3D Systems and DuraForm PA material. Type approval under ECE R 46 Vehicle mirrors are systems requiring type approval. The new development of the mirror base called for a new type approval under ECE R 46. This regulation specifies a number of requirements which a mirror system must meet. These include, among others, the number and the positioning of the mirrors, adjustability, minimum size of the mirror area, field of vision studies, and pendulum impact tests. The requirements regarding minimum size and adjustability had been met because the mirror had been taken from the standard series. Field of vision tests and hence the positioning of the mirror on the door pillar were carried out and determined on the CAD system. But a completely new mirror system was needed for the pendulum impact test. Pendulum impact test One of the items the pendulum impact test ECE R 46 investigates is whether the mirrors fold to the rear or to the front when a collision occurs with a pedestrian in order to prevent injuries. Because the development deadline for the entire car was tight, it was necessary to perform functional tesing, even before the injection moulding tool was made. The ECE R 46 pendulum impact tests were eventually made with the prototype mirror base sintered at the same time as the tool design. To do so, the Bertrandt Technikum built a model of the door pillar which allowed the mirror and the laser sintered part to be positioned on the test rig. This configuration was to correspond to the later position on the Crossblade. After a few minor modifications, the prototype passed the tests for the driver's side. This outcome secured the design, and in-house toolmaking began. The final ECE R 46 tests were then made with the injection moulded parts. This example clearly demonstrates the efficiency and effectiveness of prototypes made with SLS™ technology. Even the most complicated components can be made and tested quickly and reliably within just a few hours. They show at the earliest possible stage if and where changes, modification, and improvements must be made, and so help to optimise the development process (target-specific frontloading). During the work on the Crossblade by the project partners and Smart, these methods have helped to develop a car from a design study into a car with a very high fun factor and all this within a very short period of time. Anyone who will have the opportunity to drive a Crossblade will be able to confirm this. 3D Systems Established in 1986 and present on the international stage as pioneers and market leaders in solid imaging systems, 3D Systems' processes allow users to produce physical patterns from digital, 3-D designs within the shortest possible time. The process also allows small series to be made directly on the system. Larger quantities are made with rapid tooling processes. The process accelerates the time-to-market for new products and drastically cuts development costs. 3D Systems product range includes the patented stereolithography process (SLA® systems), selective laser sintering (SLS systems), the InVision™ and ThermoJet® 3-D printers, and Accura® materials (including photopolymers, metals, nylons, engineering plastics, and thermoplastics).