Damasko Watch Technology
The Oil-Free Escapement
For over 100 years the Swiss Anchor Escapement has been the most precise and reliable escapement for wrist- and pocket watches. In order to work properly it needs to be oiled regularly on the palettes and on the teeth of the escape wheel and in addition to that, watch manufacturers recommend to service a mechanical movement every 2-3 years by disassembling, cleaning, and lubricating it. An insufficiently oiled or even dry escapement ultimately results in bad accuracy or even worse, in worn out parts. Since 1998 Damasko has experimented with different kinds of coatings which should lower the friction coefficient between anchor and escape wheel. Latest technological achievements showed that coatings made of various layers of amorphous carbon (Diamond Like Carbon/ DLC) are probably the most advanced solutions to create a dry escapement. The process to generate such a layer is called Plasma Activated Chemical Vapour Deposition (PACVD). Apart from its black colour the coating features the following characteristics:
- Extreme hardness of approximately 1800 – 3000 Vickers
- Excellent wear resistance
- High chemical resistance
- Superior surface quality
- Extremely low friction coefficient. DLC – Steel: 0.07 (without lubricant)
- Movements parts can be coated at a temperature that does not affect the structure of the metal (< 200 degrees)
This coating process was originally designed to increase the wear resistance of moving engine parts, cutting tools, and even medical implants. In addition to the hardness and wear resistance of the layer, the extremely low boundary friction coefficient makes this method of coating so interesting. Damasko started by coating the escape wheel of the ubiquitous but reliable ETA 7750 with amorphous carbon. As mentioned above, the combination of the ultra-hard carbon layer and the polished synthetic rubies (AL203) of the anchor already lead to a very good boundary friction coefficient, which allowed us to construct an escapement which works fine without any lubricant at a daily accuracy of approximately +- 2 seconds. Furthermore the escapement delivered an amplitude of 290-325 degrees, which is already very good, but the combination of DLC on DLC should deliver even better results. Going one step further, Damasko engineers designed a new one-piece anchor with a modified geometry and slightly different parameters. After polishing, tempering, and again polishing this anchor was also DLC coated and fitted to the movement. The result was absolutely amazing! Due to the extremely low friction coefficient of DLC on DLC the escapement delivered an amplitude of 300 – 347 degrees without any lubrication. Of course this was only a test run. In order to make sure that this result will also be achieved during serial production it is necessary to establish an effective quality control. After two years of extensive testing on different movements, no signs of wear can be regarded and the escapements still deliver excellent amplitudes. During the latest test run the synthetic rubies of the anchor were replaced with palettes made of silicon carbide and it was found that this innovative material is another outstanding friction partner for the DLC coated escape wheel.
Boundary friction coefficients of the most important material combinations:
- DLC – Steel: 0.07
- DLC – Synthetic ruby: 0.05-0.06
- DLC – DLC: 0.04-0.05
- DLC – SiC:0.03-0.04
- For comparison the traditional, lubricated escapement: Steel – Synthetic ruby (oiled): 0.05
All in all it is clearly visible that the efforts of Damasko in this field have led to a major progress, with emphasis in the future on the design of a completely oil-free movement.
Damasko testing continues with specially prepared movement plates. On these parts the drill holes that support the gears are DLC coated on their inner surface to eliminate friction. In addition, the inner surface of the main spring barrel has been coated. Although still conducting extensive tests, the movements already work excellent and the treated parts show absolutely no signs of wear. Damasko looks to the furure with the goal of presenting a completely oil-free movement.
The results of Damasko research and the use of new materials for the escapement are patented.