More art than technology: today, aerospace, automotive production or medical technology rely on 3-D metal printing. Laser technology and hair-thin powder layers are the ingredients for miniature workpieces that stand up to any comparison with elegant sculptures. Michelin uses precision technology to create three-dimensional filigree tyre profiles.
The precisely aligned, hair-thin metal webs are reminiscent of a futuristic radiator grille. But the tiny elements are not meant to cool at all - quite the opposite: the pegs and edges made of heat-resistant alloy, precisely aligned to the micrometre, reach up to 200 degrees Celsius when they press into the soft rubber blank under high pressure in the tyre cooking mould. After a few minutes, the steaming metal shell opens with a loud hiss and reveals a new car tyre. The reflection of the ingenious metal mould shines on the surface of the black round blank: up to 3,000 elastic sipes, positioned at different angles and distances from each other, spread over the winter tyre.
But it is only after many kilometres that the tread reveals what is really inside: While the tread height decreases over time, new sipes and grip edges open up in depth, ensuring maximum traction with the road over the entire running time. To create such complex tyre profiles, conventional techniques for designing the tyre's cooking shape finally reach their limits. That's why, 15 years ago, Michelin started looking into 3D metal printing, which at the time was still in its infancy and offered completely new design possibilities.
Sculptural art: pioneering mould design for premium tyres
It was a long way to production maturity for 3-D metal printing: in the early years, the technology was only used for prototyping and model making, but today Michelin has firmly established the so-called additive manufacturing of three-dimensional tyre cooking moulds in the production process. Once the new tread design for a tyre has been decided, mould construction begins in specially designed equipment. Metal is applied in powder form to a base plate in layers of less than 500 micrometres - the equivalent of two to three sheets of paper. A laser beam liquefies the metal powder along precisely calculated paths. As soon as the material has cooled down, the base plate is lowered, another layer of powder is applied and heated again in a very short time. Once the process is finished, the mould only needs to be freed from powder residues and can then be used directly for tyre production. In the process, filigree shapes are created that approach the elegance of sculptural art objects and have long been impossible to represent with classic metal forming processes.
The metal bars produced in 3D metal printing enable a design of the tyre tread that is not possible with conventional methods.
Shapeless production: resource and environmentally friendly
The production process has several important advantages: only as much material as necessary is used, and there is no material waste that is unfriendly from an environmental and cost point of view. Furthermore, thanks to digitalisation, a mould that has been programmed once can be reproduced at any time, even at a different production site. Similarly, once developed, moulds can be modified and further developed quickly, flexibly and cost-efficiently by reprogramming. This significantly reduces conception times and costs. The development time for the negative profile moulds was reduced from three to one week by the new production process.
Today, Michelin uses around 30 3D printing machines in North America and France to create cooking moulds for a wide variety of tyre models: These include the MICHELIN X Line Energy truck tyre as well as the widely used MICHELIN CrossClimate for passenger car use or the MICHELIN Road 5 motorbike tyre.
High-tech partnership: the AddUp joint venture
In cooperation with the French technology developer and equipment manufacturer Fives, Michelin founded AddUp in 2015.
The start-up specialises in the additive manufacturing of metal parts and can produce workpieces based on steel, nickel, titanium or aluminum alloys. On request, AddUp also supplies complete 3D printing systems. The customer spectrum ranges from the aerospace industry to the automotive, energy and luxury industries to medical technology.
2018 saw the acquisition of BeAM in Strasbourg, a specialist in DED (Directed Energy Deposition) technology, which complements the laser beam melting technology perfected by AddUp. With the majority shareholding in Polyshape, AddUp also has a competent partner for small series and prototypes - especially in car racing - at its side.