A grinding unit assembly, a plurality of which is placed around a cylinder of a grinding machine. The method includes forming a trench in a semiconductor substrate and forming an isolation collar on a sidewall of the trench. Because said method and device according to the present invention adopts the automatic real-time detection for the current usable bandwidth of the network playback device connected to, and it changes the quality of content requiring downloading, seamless playback can be realized, while avoiding the trouble due to the quality selection by the user himself. Optionally, the wedge member may have two orientations, namely a first orientation and a second orientation, wherein the first and second sides are flipped with respect to one another in the first and second orientations. The invention includes a method of sequentially folding and thereafter tucking the overhang of the overlaying layers into the peripheral slot. Based at least on the load distribution, a controller commands the motorized drive arrangement.