n mystery and shrouded in secrecy. So heavily protected, according to Michelin North America (MNA) insiders, that very few company employees have even seen the tiremaking equipment in person, let alone in action. Outsiders, especially tire trade journalists, haven’t even gotten that close.
The problem with such overwhelmingly tight security and secrecy is that after awhile people begin to wonder if the thing you are hiding actually exists. Such became the case with C3M.
Like the magician who produces a half dozen fully grown rabbits after claiming to have nothing up his sleeve, Michelin touted C3M only through finished products, the most visual example of which has been multi-colored BFGoodrich Scorcher T/As.
Two factors, however, forced Michelin to lift some of the secrecy, albeit in bits and pieces – Pirelli’s July 2000 introduction of its MIRS (Modular Integrated Robotized System) process, and mounting pressure from investment analysts who began to openly question C3M’s very existence and the real-world potential for the system.
In an April 2001 report, Schroder Salomon Smith Barney’s European tire analysts acknowledged these concerns. "We believe the well-publicized introduction of Pirelli’s MIRS progress®ƒ and, generally speaking, a more open attitude toward investors, have led Michelin to reveal its C3M technology to analysts in Almeira (Spain)," the report read.
Michelin didn’t actually reveal much at the early 2001 analyst conference at its Almeira facilities. However, in Houdini-like fashion, it proved that C3M was no ghost. The night before its presentation to analysts, Michelin took them to an empty warehouse. Twelve hours later, the analysts returned to find a fully functional C3M module producing tires. And while Michelin provided details as to how it intended to leverage the process, the tight-lipped tiremaker didn’t explain how C3M worked.
Chasing the Grail
For the last three years, Tire Review has made dozens of requests to see C3M in action. Finally, the magazine was invited on a trip to Europe that was to result in a close look at the process. Unfortunately, that trip was scheduled to start just seven days after the Sept. 11 terrorist attacks.
Earlier this year, however, MNA sent Tire Review an early Christmas present – pages from its Spring 2002 Bib Beat employee newsletter containing the first publicly released drawings and descriptions of the elusive C3M process and equipment. MNA spokespeople would not confirm or deny the exactness of the illustrations and information, but they did insist they were "very representative" of the process.
Based on our interpretation of those drawings and descriptions, as well as past reports and speculation based on other known Michelin manufacturing systems, here is an "inside" look at the highly touted, and still top secret, C3M process.
On the surface, there doesn’t appear to be anything revolutionary about the C3M equipment or process. Various elements, from the computer workstation control area to the multi-head extruder to the solid-steel building drum to the in-line curing presses, appear in tire manufacturing systems already used by Bridgestone/Firestone, Goodyear, Pirelli and even in Michelin’s own plants.
What is unique is that these elements have been pulled together in one complete tire building/curing module small enough to fit comfortably in a standard commercial trailer. At just over 330 square feet, one C3M module takes up just over half the space of a conventional 54-foot trailer.
Michelin says that C3M is not designed to be a cost-saving process; energy costs – C3M requires only electricity and compressed air, saving some 60% over conventional manufacturing – and resource utilization savings are claimed, but additional savings could be realized by lower rejection rates.
Manufacturing flexibility is more important, says Michelin, in the form of efficient short production runs of specialized to-order tires (Scorcher T/As) and OE-quality ultra-high performance and SUV tires, and the ability to physically place a C3M module virtually anywhere.
C3M does away with the multi-step component manufacturing and assembly processes of conventional tiremaking in favor of a two-step building/curing process. Central to this are computer controls, multi-head extrusion, single-strand body cords and belts, and heated, solid donut-shaped building/curing drums – similar, in many respects, to Pirelli’s multi-station MIRS process.
Each tire – by brand, make and size – has a certain "recipe," including rubber compounds, amounts and configurations. The operator need only call up the desired recipe on the computer and start the program. The computer does the rest.
Though each module is a "complete" manufacturing plant, rubber compounds used by C3M are still created and mixed off-site. Special pigments – such as those for the multi-colored BFGoodrich Scorcher T/A – are also mixed separately and batched by color. The module includes its own electrically-heated curing press which cures one tire as another is being created on a heated solid drum.
Multiple extrusion heads (three to as many as seven) with changeable dies, extrude and place all rubber elements. First, the innerliner is laid down. Next, the first of two bead segments is placed. An arm on the back of the module lays the body plies laterally from bead to bead, feeding the rubber-coated single strand cord from a spool. Once the body plies are laid, the second bead segment is placed, effectively sandwiching the body plies in place.
Once the body plies and beads are down, the extrusion heads travel from bead to bead placing chafer and shoulder strips as well as sidewall and bead rubber. Steel belts are laid in strips, starting from one shoulder then diagonally across to the opposite shoulder. Any required nylon cap plies are also wound circumferentially.
Multi Heads for Multi Compounds
The extruder heads then place a layer of undertread before delivering tread stock in circumferential strips. Depending on the tire being built, the tread stock may be of various compounds, based on desired tread color or performance (traction or wear) factors.
Multi-compound tread stock is generally laid groove-to-groove. That is, one tread section ends at a circumferential groove and another begins at that point. The multi-head extrusion approach allows Michelin to use multiple tread compounds based on performance or color requirements. One tread segment can enhance wet traction, for instance, while another delivers long wear and still another promotes cornering grip.
Other more specialized tread stock – such as the speckled tread seen at trade shows – is also laid in-line, though it is not clear whether this is accomplished with one extruder head or many of them working in unison.
Once the green tire is completed – usually in about 15 to 20 minutes, according to various reports – the tire and its building drum are moved across the module to the built-in curing press. Molds are selected from a nearby "library" and moved into placed automatically as each green tire is being constructed.
The heated building drum aids in the curing process, and because the tire is built in its finished form and profile the tire and its components do not undergo any physical changes in shape, as with conventionally built tires.
There are still a lot of unanswered questions about how C3M works, and Tire Review will continue pressing for a complete tour. But, for now, we have a somewhat clearer picture of what all the secrecy is about.