PSI - Issue 42

Taško Maneski et al. / Procedia Structural Integrity 42 (2022) 1503–1511 T. Maneski at al/ Structural Integrity Procedia 00 (2019) 000 – 000

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increased to approximately ±6 m/s 2 . This suggested the dynamic behavior of the structure had deteriorated slightly between the first and second investigations. When considering the dynamic behavior of structures, most often Standard ISO 10816 (2372) prescribe desirable parameters. IOS 10816 divides machines into four classes based on machine power and support structure. In the case of the Magneti Marelli paint shop robots, the acceptable values of displacement and acceleration are: - Displacement: peak - desirable ≤30  m, acceptable 60  m; RMS - desirable ≤21  m, acceptable 42  m; - Acceleration: peak - desirable ≤1.0 m/s 2 , acceptable 2.0 m/s 2 ; RMS - desirable ≤0.707 m/s 2 , acceptable 1.4 m/s 2 . 5. Partial repair to the robot support structure The study indicated the basic causes of robot gearbox failure, i.e., large displacement amplitudes and vibration speeds, as well as the resonant behavior of the structure. Numerous natural resonances that developed in the support structure had very low frequencies that coincided with the natural resonances of the robots fixed to the support structure. The forms of oscillation in the support structure show that the first few modes corresponded to the movement in the horizontal plane in the transverse direction, which coincided with the highest oscillation speeds of the robots themselves.

Before repairs

After repairs

Figure 14. Repairs to the robot carriage structure

Remedial repair works were carried out at the end of December, and all observed deficiencies were remedied. One troubleshooting procedure, i.e., changes to the carriage, is shown in Figure 14. Therefore, the main problems leading to gearbox failure that needed to be remedied were: lack of global rigidity of the support structure in the horizontal plane; lack of local rigidity of the robot carriers in both the horizontal and vertical planes, and; elimination of the deficiencies observed during visual inspection. 6. Conclusion Displacement and acceleration were measured twice more after remedial repairs. The rehabilitation included only interventions on the construction of the paint shop. Displacement and acceleration measurements before and after the structural repairs are shown in Table 3 for robot R2.

Table 3. Displacement [mm] and acceleration [m/s 2 ] on robot R2

Longitudinal

Transverse Measur. 1

Vertical

Measur. 1

Measur. 2

Measur. 2

Measur. 1

Measur. 2

After the structural repairs Before the structural repair

Displ. Accel. Displ. Accel.

 0,1  1,5

+0,17 / -0,10

 0,07

 0,08

 0,07

 0,03

 0,4

 1,2

 0,4

 0,3

 0,3

+ 0,35 / - 0,10

+ 0,40 / - 0,20

+ 0,40 / - 0,20

 5,00

 5,0

 3,5

 4,5

 0,3

 0,3