Electrochemical machining features

In electrochemical machining, the removal of the metal to form a hole or other feature is by anodic dissolution (Fig. 8.3). Clearly for the process to have the... 

Figure 8.5 Components manufactured by electrochemical machining (a) turbine discs (the cathode tools to form the complex features are also shown), (b) turbine blade with longitudinal cooling holes formed by machining (the holes are seen on the X-ray of the blade and (c) angled square holes for air cooling. Photographs supplied by Rolls Royce Ltd, Aero Division.

Fig, 2. An example of a product of electrochemical machining. An engine casing and the cathode tool used to form one of the features. 

Because of the presence of several redox-active units, the cyclic voltammogram of this rotaxane shows a complex redox pattern. However, the comparison to the electrochemical behavior of its molecular components and suitable model compounds (Fig. 13.29) enables to obtain useful information not only on its coconforma-tional features, but also, and most importantly, on its machine-like operation. 

Liu etal. reported a series of unsymmetrical donor-acceptor [2]catenanes (Figme 44), which could be switched by electrochemical stimuli. Such a feature makes these catenanes appealing candidates for the construction of molecular machines and rotary motors. It should also be noted that these interlocked molecules can be reversibly switched among several states, opening interesting routes for the development of molecular electronic devices that go beyond binary logic. 

On the oxidation side, the behavior of the folly desymmetrized catenanes 6 and 9 is particularly interesting from the viewpoint of molecular machines and it is the only one here discussed. Their electrochemical patterns are very similar and consist of three oxidative processes (for 6 " see Fig. 9.5a) the first two (Fig. 9.5c) are assigned to the two consecutive monoelectronic TTF oxidations [12], while the third one is ascribed to the oxidation of the DON unit. The first and second TTF oxidations exhibit the same features observed for a previously studied catenane [13, 14] and can be interpreted as follows after the TTF " oxidation, the electron donor ring circumrotates with respect to the electron accepting ring, delivering the DON unit into its cavity. 

A new technology called electrochemical micro milling (ECF, where F is the German acronym for milling) has been recently introduced to machine hard materials like stainless steel and other electrochemical active materials. Feature dimension below SOpm have been obtained [4]. The very small removal rate (6x10" mm /min) allows for high resolution in machining and therefore is suitable to manufacture the finest details in a pre-machined structure. 

---