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THE MANUFACTURING OF COMPONENTS BY SELECTIVE LASER MELTING (SLM)

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1. The SLM process

2. Introduction

This Additive manufacturing process was developed and patented in 1997. As its patent expired in 2017, it has been gaining in quality and precision, thus finding new fields of application. Medtechs and the aeronautics and aerospace industry were the first to adopt this technology. Its rapid evolution is now opening the doors to the world of jewelry and horology.

3. Eligible Materials

This method exclusively concerns Alloys metallic, however diverse they may be. Titanium, stainless steels or the Main plate are, to date, eligible for this technology.

4. Manufacturing Principle

The principle of selective laser melting manufacturing consists of depositing the chosen alloy in powder form, with grains reduced to the finest particle size (between 20 and 200 µm depending on the alloy), onto the surface of a build plate. While perfectly respecting the volumetric plan of the component, the laser melts the powder with a determined intensity and duration, with a precision equal to the size of one particle (i.e., between 20 and 200 µm). The build plate is then lowered by an amount equal to that of the first layer produced. A new layer of alloy powder is added and then melted. The process is repeated in this way, layer by layer, in strict accordance with the volumetric plan of the component to be produced.

Unused powder (that has not been melted) can easily be reused later, without requiring any reprocessing.

5. Multiple advantages

The advantages of this technology are numerous. It allows the creation of components with structures and designs previously unseen (rigidity, lightness). This method generates no material waste and, consequently, no recycling-related costs. This is a particularly valuable benefit when it comes to precious metals. Finally, the material density is exceptionally high. No mechanical stress is exerted on the component during its manufacturing, which does not require Heat treatments afterward. Even better, depending on the laser intensity, the exposure time, and the cooling time, possible heat treatments can be applied during the manufacturing process.

With this technology, style and design no longer have limits, and the boundaries of technique are pushed further every day.

6. Limitations

However, given its current level of precision, this technology can, to this day, only find applications in the external parts (case, dial, hands) of the watch (Cases, bracelets, dials). In the case of a Case, subsequent machining will make it possible to achieve the required precision and obtain the desired finishes (surface conditions).

The level of precision of selective laser melting is, to date, insufficient to produce Movement components using this technology, which nevertheless proves very promising for watch External parts (case, dial, hands) and prototyping.

7. Ongoing research

To date, most research focuses on developing Alloys specifically designed for this technology. By adjusting their parameters according to the intensity and duration of the melting process, it is possible to harness new mechanical or physical properties of the material.