Analysis of variations in vibration behavior of vibratory feeder due to change in stiffness of helical springs using FEM and EMA methods

Helical springs are mostly subjected to compression and expansion in their life cycles under working conditions in vibratory feeder. The continuous reversal stress leads to permanent deformations in pitch of coils of the helical springs due to creep phenomenon in which reversal stresses under various ambient conditions act as catalyst. The reduced pitch in coils of helical springs over period of time change the dynamic behavior of the vibratory feeder unit. The reduction in pitch in springs also leads to performance loss of the vibratory feeder. Therefore, it is essential to understand the dynamic characteristics of the feeder unit in order avoid catastrophic failures and performance losses. The objective of this research is to study the variations in dynamic behavior of vibratory feeder with old (reduced pitch) springs through modal analyses using FEM and EMA methods. The modal analysis using FEM technique is conducted in ANSYS workbench 14 using a three-dimensional model, which was developed in SolidWorks software. A working model of vibratory feeder was fabricated similar to the FE model for the experimental modal analysis (EMA). The instruments used in the EMA method are: one 4-channel FFT analyzer, one dynamic shaker, three accelerometers and a force transducer.