Aspect ratio is another feature that is different for the horizontal specimens from the vertical ones. This ratio can be defined as the proportion of the area to the thickness of each layer; in other words, it represents the distance between the starting and the ending points of a scanning pass with a constant speed, as shown in Fig. 6. Typical horizontal specimens have higher aspect ratios since their surfaces struck by the laser beam are wider, and the required time interval to manufacture each layer of a horizontal specimen is longer than that of a vertical one [37,38].