Metal+Forma: What is behind Tesla´s new BIW manufacturing concept

Tesla plans to simplify the design of its future transport platforms and achieve greater automation in the manufacturing process, starting with the Model Y.

The Model Y

"We're moving to an aluminum casting instead of a series of stamped pieces. We'll go from 70 parts to 4, then 1 with a reduction in weight, improvement in MBH, reduction in cost, and a significant drop in capital expenditure for all the robots that used to put 70 parts together."

The Patent

The patent title is “Multi-Directional Unibody Casting Machine for a Vehicle Frame and Associated Methods.”

Tesla describes the problems that come with the die casting process in vehicle manufacturing today:

“Typically, in the context of vehicle frame manufacturing and the die casting process, multiple die casting machines are each used to cast different components of a vehicle frame. For example, a single die casting machine cell in a factory may be dedicated to casting a single frame component. These components from each casting machine are then assembled or secured together (e.g., via welding) by factory workers or robotic systems to form a vehicle frame (e.g., a unibody vehicle frame). Because die casting generally involves higher capital costs relative to other casting and manufacturing processes including assembly of many individual components (e.g., due to high costs of casting equipment and metal dies), there remains a need for an improved die casting machine and associated methods thereof, particularly as related to casting a vehicle frame to reduce work required to achieve a final assembled product.”

The system that Tesla describes in its patent application fixes this problem with several ejector die portions meeting at a central hub. According to the patent application, it was designed by Matt Kallas, a long time “Mold Making Supervisor” at Tesla who has since left to become a casting toll designer at GF Linamar.

Tesla believes that this design will “reduce build time, operation costs, costs of manufacturing, factory footprint, factory operating costs, tooling costs, and/or quantity of equipment.” The automaker even notes that it will reduce the number of casting machines required to build a vehicle frame and that it could even build “a complete or substantially complete” frame itself.

Below: some drawings from Tesla’s patent application for the giant casting machine

Source: Tesla

Is this the future of body-in-white fabrication? If yes, how long it will take to reach the manufacturing plants? It may apparently take a long time, when we think how different it is from the manufacturing today. But remember, they didn’t take so much to reach space, with a new concept (reusable rockets). They know rocket science...

And actually, there are more reasons to (partially) believe in Tesla's vision of a new era in BIW manufacturing technology. Below I´ve listed a few:

1) Crash management key parts are being cast for luxury models for over a decade.

The idea is not new. Audi already uses aluminum casting nodes combined with extruded aluminum profiles on its ASF concept (Audi Space Frame, see images below). In the Audi A8 vehicles, for example, the front suspension structure in produced with die-cast aluminum for generations, with ten sheet metal parts being combined into one die-cast part. This concept has now been adopted by all premium brands and can even be found in the middle class, e.g. Mercedes-Benz C-Class. The weight saving at Audi was 10.9 kilograms per vehicle.

Audi Space Frame - R8, cast alu in red.

Audi Space Frame - A8

In the bodies of the second and third generation of the Audi A8, one third of the body weight was already made of die-cast aluminum.

This trend can also be found in the Cadillac CT6, as shown in the next picture.

Cadillac CT6

2) Cost savings by means of individual parts reduction.

Regarding cost saving, reducing the number of parts is indeed very worthwhile. The reduction in the number of parts is a very large lever for reducing costs, regardless of the material in consideration. The investment costs for deep drawing tools are much higher than those for die-casting. A medium deep-drawing tool costs a few million euros, a medium die-casting tool a few hundred thousand euros. In addition, fewer clamping fixtures and other assembly devices are required than in sheet metal assembly. Less connections and unions between parts mean less production time. And, last but not least, fewer parts mean fewer assembly stations and fewer logistics, consequently less production space.

3) There is a potential of weight-saving through the use of bionic structures

In principle, geometries with optimal bionic structures could be realized with the new cast parts, whereby force flows could be supported free of bending moments. Tesla have now the challenge of developing aluminum-compatible geometries, which are possible to be manufactured using die-casting and that take advantage of bionic based engineering designs.

4) Manufacturing plants are normally renewed for every new model.

With every model change, production facilities are largely renewed anyway. Modern car bodies are currently material hybrids, the production systems are already set up for flexible material pairings. The alternative drive trains require new interfaces and flexible modularity. The changes to be expected from the popular Tesla body concept should not cause any headaches in the factories.

But, how realistic is Teslas´s ambition?

Designing a complex structure such as a body with extremely different load cases from just one type of material does not correspond to the state of the art in order to achieve the best compromise in functionality and economy. Material hybrid concepts are clearly in demand for this. Therefore, the Tesla body concept will not consist exclusively of cast parts. Every material requires its specific concept. Although it is theoretically possible to reduce the number of stamping parts and with it the manufacturing costs, new structure designs and lots of testing and improvement is needed to reach the performance we have in today's BIW structures.

Instead of being a totally new concept it is, in reality, an improvement of already available technologies. The term “body made from one piece” is certainly a bit exaggerated, since a variety of material concepts is needed to produce a vehicle structure which is both safe and lightweight. It leaves enough space for the use of other materials or semi-finished products and is first and foremost a marketing campaign.