Application: Vibrational velocity analysis
As a result of the production process, manufactured parts for roller bearings are often affected by deviations from their ideal geometry in terms of roundness and waviness. In components for high-speed bearings (such as those found in computer hard disks, for example), form deviations of raceways from the ideal, smooth circle can lead to uneven running, development of noise, and reduced service life due to increased wear.
It is therefore important for the manufacturers of such bearings to have the ability to test for conformance to specified tolerances relating to the roundness deviations and waviness amplitude sizes of the individual components, preferably before the bearing is assembled. Vibration speed analysis is a very powerful tool in this respect, as the method permits speed-dependent, quantitative prediction and assessment of the influence and effects that any form deviations of the individual components will have on the subsequent behavior of the fully-assembled, rotating bearing.
Because it is supplied as dedicated, independent analysis software, it can be used with raw profiles that have been captured at an earlier time using MarForm measuring machines (fully-closed radial circles at raceways on generated surfaces, or closed end-face circles on end-faces of corresponding bearing components).
Before a vibration speed analysis can be carried out on a roller bearing component, it is necessary to first measure a complete, closed polar profile (full circle over 360° with no gaps) in the area of the raceway (normal to circumferential surface/perpendicular to end-face) using a MarForm measuring machine. The axis of the bearing component must first be aligned mechanically with the rotational axis of the measuring machine. The vibration speed analysis software initially calculates the Fourier amplitude spectrum (FFT analysis) corresponding to either the unfiltered raw profile or a band-limited profile using user-defined wavenumber cut-off threshold for the filter.
Each term in this spectrum is weighted (multiplied) by the ordinal number of the term (corresponding to the number of vibration periods associated with a complete rotation of the component), by the notional rotational frequency for the term specified by the user, and by an additional fixed factor. This allows the software to calculate the vibration speed spectrum corresponding to the specification provided.
In each record sheet the band threshold parameter values are calculated for three bands of the spectrum which are then output in the form of an attributes table in the measuring record. The limits of each band are freely selectable and set by specifying the ordinals of the threshold spectrum terms.
These parameter values are the value and ordinal number with the maximum vibration speed in each band and the RMS (root mean square) 'sum' of all vibration speeds in each band. The RMS parameters serve as a measure of the vibrational energy contained in the respective spectral bands during the subsequent rotational motion of the bearing components due to the reciprocating movements induced by any radial and/or axial form deviations of the raceway. Evaluations with up to 15 bands can easily be performed in this way.
For use in conjunction with MarForm MMQ 100, MMQ 200, MMQ 400, MFU 100, MFU 110 WP, MFU 800, MFU 8 Retro, MFK 500 and MFK 600, with MarWin 3 or higher evaluation software and EasyForm, AdvancedForm and ProfessionalForm.