Microtools shape

Utilizing the principle of the drop-off technique, electrochemical dissolution can also be controlled selectively from the microtool by applying insulation at the desired portion of the anodic electrode as shown in Fig. 6.13(a). During machining, electrochemical dissolution will not take place from the insulated area hence, the desired microtool shape can be achieved as shown in Fig. 6.13(b). 

Cle05] Clemens FJ, Wallquist V, Buchser W, Wegmann M, Graule T (2005) Silicon Carbide Fiber-Shaped Microtools by Extrusion and Sinterning SIC with and without Carbon Powder Sinteming Additive. Ceram Int - submitted... 

Since hydrogen gas evolution is the only reaction at the cathode microtool, the shape of that microtool remains unaltered during the electrolysis therefore it can be reused multiple times. 

Different types of EMMs require microtools with different features such as shape and size. For through-mask EMM, the shape of the tool electrode is simple because a mask will mainly restrict the machining area and in turn control the final shape evolution, with a very low aspect ratio. However, for maskless EMM, the shape of the tool electrode will localize the machining area to generate the desired microfeature with a higher aspect ratio. Hence, the shape and size of the microtool are vital factors in the case of maskless EMM. Depending on the types of EMM as discussed in Chapter 4 and shown in Fig. 4.1, EMM tools can also be of various types. 

Figure 6.3 shows the schematics for the fabrication of microtools by reverse EDM. Hole or desired geometrical shapes are machined by EDM or some other machining process on the metal plate. The plate with a hole is made negative and immersed in the dielectric fluid. By applying a positive voltage... 

Single electrical discharge can be utilized for generating spherical end shapes of the microtool electrode that are sometimes needed in EMM for machining taper-free microstructures [11],... 

By taking advantage of the flexibility of electrochemical anodic dissolution, different EMM techniques have been developed over the years by scientists. EMM can also be successfully utilized for fabrication of cylindrical microtools [16-18]. By controlling different machining parameters, conditions and influencing factors, geometrical shape, size, and finish of the cylindrical microtools may also be varied. 

EMM, it can be categorized into two groups (1) microtools with different complex end features and (2) microtools with a simple cylindrical shape. 

The shape of the cylindrical microtool and form of the tip of the microtool also play an important role in machining microfeatures in EMM [32]. There can be various types of the cylindrical microtools according to the shape of the shank and shape at the tip. Schematics of some microtools such as cylindrical, conical, reverse conical, cut edge electrode, spherical and disk-end shaped microelectrode are as shown in Fig. 6.16. 

Microtools of different shapes (a) cylindrical, (b) conical, (c) reverse conical, (d) cut edge electrode, (e) spherical end, and (f) disk end. 

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