MAKING A CASE
Agreat movement is nothing without a case to protect it – and everything else – from the ravages of the outside environment. Of course, details such as water resistance and a scratchproof sapphire crystal are non-negotiable. However, the choice of material and production technique for the case are less clear cut given the permutations of the available options.
Metals and coatings
By eliminating precious metals like gold and platinum, as well as exotic ones such as tantalum, only stainless steel and titanium are left when it comes to metallic cases. Both are available in several variants. Grade 2 titanium, for instance, is close to steel in terms of its hardness, but it is far less dense, and therefore much lighter. Grade 5 titanium, on the other hand, is significantly harder than its Grade 2 sibling and just as light, but lacks the latter’s unique drab grey appearance.
Both steel and titanium cases can be toughened with a diamond-like carbon (DLC) coating applied via physical vapour deposition (PVD), which significantly increases their surfaces’ hardness. This is commonly done nowadays for both practical and aesthetic reasons, and its only drawback is perhaps the hassle and costs of repairing a chipped/damaged coating – the original layer of DLC must be completely stripped before the case is polished and a new coating is reapplied.
Instead of steel or titanium, ceramics and carbon can also be used to make a watch’s case. These materials vary in hardness and density, but generally exhibit a high level of toughness with a touch of the exotic. Ceramics are fairly straightforward – compact the powdered formulation in a mould, bake it under high pressure to sinter it into a solid, then machine this mass to create a finished case. Carbon, on the other hand, can be forged, baked, or vacuum-moulded together, often with other “ingredients” such as quartz fibres to enhance its properties. The last step is still machining though, to achieve the desired shape and contours.
New production techniques
The available materials described above are fairly well understood, and new ones being introduced tend to be variations on existing themes, with marginal improvements over current offerings. New production techniques, however, sometimes create paradigm shifts. Direct Metal Laser Sintering (DMLS), for example, was introduced by Panerai earlier this year in its Lo Scienziato Luminor 1950 Tourbillon GMT Titanio PAM578. The technique is already in use elsewhere, including the aerospace and medical industries, and works just like 3D printing – a solid component is “built” from a metal powder using a laser, which sinters the powder layer by layer. Unlike subtractive production, which involves removing material by cutting/milling out unwanted parts, DMLS is additive, and capable of producing solid components with hollow interiors. As the PAM578 shows, a hollow titanium case can be made with DMLS, with no loss of structural strength or water resistance thanks to the manipulation of the internal space’s shape.
|| THE VERDICT ||
The clear winner here is the latest and greatest technology available – DMLS. Titanium, especially its Grade 5 variant, is already light and hardy enough to stand up to general abuse. With DMLS, further weight savings can be had for an extremely comfortable chronograph with no loss of strength.
Audemars Piguet Royal Oak Offshore Diver chronograph in steel, with ceramic pushers
Bulgari Octo Velocissimo Ultranero Panerai PAM578 Oris Williams Chronograph Carbon Fibre Extreme