A numerical and experimental investigation of vibratory bowl feeders
Vibratory bowl feeders are widely used in automation processes for the storage, feeding and orientation of identical components for presentation to workstations or other mechanical handling devices. The investigation described here has been directed at modelling the dynamiC behaviour of vibratory bowl feeders, both to improve understanding of their behaviour, and to facilitate improvements in their design. The work undertaken has involved the following stages: i) A numerical model for the prediction of the eigenvalues and eigenvectors of the bowl feeder was developed, modelling the structure as a lumped parameter eight degree-of-freedom system; ii) The natural frequencies and mode shapes predicted by the model were compared with those obtained from experimental modal analysis. There was good agreement for the first three natural frequencies. Differences in the higher frequency modes indicated an overconstrained model which could be accounted for by the flexural vibration of the bowl; iii) A numerical model of the forced response of a bowl feeder when driven by a harmonic excitation was developed using a spreadsheet package, and verified experimentally; iv) The spreadsheet package was developed further, varying the geometric parameters of the bowl and springs over specified ranges. Changes in spring angles were investigated experimentally to verify the predicted values; v) A customised design tool was developed using the spreadsheet package to enable engineers to investigate the behaviour of different configuration feeders; vi) An investigation of the causes of dead-spots was undertaken. These were shown to be due to the asymmetrical arrangement of the springs and electromagnetic coil relative to each other; and vii) Solutions proposed to the problem of dead-spots were the use of four spring banks instead of three, and the specification of an annular shaped pole piece for the electromagnetic coil.
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