By reversing the direction of a first build material fed into an extruder, the first build material can be wholly or partially evacuated from the extruder before a second material is introduced. In the liquid-level gauge, a float having a uniform cross-sectional form in the height direction and a specific weight value small than that of liquid is dipped in the liquid. Both the base plate and the sliding lock plate have openings. The radiation sensitive layer sandwiched between the pair of outer layers may be fabricated as webs, to provide microstructure master blanks. Also, the region of substantially constant cross-sectional area is axially adjacent to a region of diminished cross-sectional area of the region of continuously varying cross-sectional area. The ink container is provided below the multi-nozzle inkjet recording heads and the electrical system unit.