A power supply unit includes a box, a circuit board, and a power connector. The first current mirror stage of a first conduction type receives a reference current. The first device includes a touch-sensing interface and a first wireless communication module. A difference in buffer occupancy just before and just after the switching timing is obtained based on the buffer occupancy data to set a decimation rate and a decimation period on the second pictures so that the difference in buffer occupancy just before and just after the switching timing becomes small. The actuator provides for variable control of a rotation of the tool tip about an axis parallel to a y-direction transversely across the work piece for use in making microstructures in the work piece.