## 3 Test and Analyses Results
  
Condensation of the spectrum in the 30-370 Hz band, marked with a red continuous line in spectrograms, informs about the movement of the platform and/or head positioning. For steps I and V the characteristic line is at a level of 340 Hz, and the spectrum condensation ranges from 30 Hz to 100 Hz (the fields marked on the X spectrogram with a continuous and a dashed blue line, respectively). Then, the head moves along the X axis and prints the b leg. Figure 10: The spectrograms of printer vibrations when the trihedron object was printed. Figure 11: The spectrograms of printer vibrations when the tube object was printed. Figure 12: The spectrograms of printer vibrations when the tetrahedron object was printed. For steps II and IV one can notice double lines in both spectrograms (X and Y) at frequencies of approx. 320 Hz and 360 Hz and a spectrum condensation within the range from 30 Hz to 100 Hz on both X and Y spectrograms (the fields marked with a yellow continuous and a dashed line, respectively). Then, the head moves along the diagonal related to X and Y axes, printing the c hypotenuse. For steps III and VI a clear line is visible at a level of 340 Hz, and the spectrum condensation ranges from 30 Hz to 100 Hz (the fields marked on the Y spectrogram with a continuous and a dashed green line, respectively). Then, the head moves along the Y axis and prints the leg. For the object with a horizontal cross-section in the form of a circle (tube, Figure 7b) one can distinguish the characteristic printing steps marked as I, II, III, IV, V, VI, VII and VIII, and P1 and P2 in Figure 7. These steps may be defined as follows:  
* the printhead performs the positioning movements (without printing), the platform is lowered by one level;
* the printhead prints the wall of tube (outer path, perimeter quarter I), along the arc from point A to B;
* the printhead prints the wall of tube (outer path, perimeter quarter II), along the arc from point B to C;
* the printhead prints the wall of tube (outer path, perimeter quarter III), along the arc from point C to D;
* the printhead prints the wall of tube (outer path, perimeter quarter IV), along the arc from point D to A;
* the printhead performs the positioning movements (without printing);
* the printhead prints the wall of tube (inner path, perimeter quarter IV), along the arc from point A to D;
* the printhead prints the wall of tube (inner path, perimeter quarter III), along the arc from point D to C;
* the printhead prints the wall of tube (inner path, perimeter quarter II), along the arc from point C to B;
* the printhead prints the wall of tube (inner path, perimeter quarter I), along the arc from point B to A. Characteristic arches and spectrum condensations can be observed for particular printing steps. Depending on the share of the X or Y component while printing particular quarters of the tube's walls, the arches appear on X and Y spectrograms, respectively. The areas marked respectively with a continuous and a dashed line of the same color represent printing steps where the same quarters of the tube wall are printed, but when the head moves in opposite sense. Please note that the head trajectory in steps I-IV occurs on the outer wall line being printed, while in steps V-VIII, on the inner path. A significant item in the process of reproducing the printed objects includes the information of the printhead movement direction. It is also the head movement sense that is important. To check if it is possible to identify the feature that would reveal this phenomenon, an object (Figure 7c) in the form of a square cross-section tetrahedron was printed. In this case, the printhead performs two movements along the X or Y axis in the opposed directions to print a specific wall.