**5.1. The modification of experimental grinder**

132 Tungsten Carbide – Processing and Applications

where nwi =(*βi+1*−*βi*)/(*ti+1−ti*), i =1,2, ..., N.

**Figure 14.** Video images of the rotating workpiece

Workpiece rotational speed

n

w [rpm]

1 *N i wi*

*N*

Fig.15 shows the relationship obtained between *nw* and *Vp–p*. Clearly, *nw* increases linearly with *Vp–p*. This is in close agreement with the prediction described above, and indicates that the workpiece rotation speed can be precisely controlled by the elliptic motion of the shoe.

*n*

(2)

*w*

*n*

**Figure 15.** Relationship between the workpiece rotational speed and the applied voltage

Voltage Vp-p [V]

In order to confirm the validity of the proposed new method, fabrication of micro-part of tungsten carbide will be carried out. The grinder is modified by the conventional grinder of μ micron grinder MIC-150, the product of μ micron Corp. The regulating wheel unit will be uninstalled and a fine feed unit, which is composed of a fine feed table and stepping motor, will be installed. In the experimental grinder, for the finish grinding of micro parts with sizes of less than 1mm in diameter, the depth of cut must be less than 1μm in order to make the grinding force small. The fine feed and fine adjustment unit is shown in Fig.16 (a and b). The shoe can be fine adjusted in Z direction by handing the fine adjustment screw. The adjustment component can be locked when the height of shoe is adjusted to an appreciable position by operating the lock handle on the back of the unit, as shown in Fig.16 (b). The fine feed and fine adjustment unit can be rotated in XY by surrounding the rotating pin, and then fixed the unit by locking other three fixed screw bolts. A fine feed unit composed of a shoe holder, a linear guide, a ball screw and a stepping motor has been designed and produced that carries the shoe toward the grinding wheel at a feed rate of less than 1μm. A pre-load is then applied to the shoe at its left end face in its longitudinal direction using a coil spring in order to prevent the shoe from breaking due to resonance and is fixed by the screw at its right face of shoe foot.

**Figure 16.** Fine feed and fine adjustment unit
