The shock pulse measurements were carried out on test bearings to ensure that the bearing fault due to contaminated lubrication condition existed. Surface roughness measurements of a turned workpiece was carried out as an offline monitoring method. Talysurf-6 (Taylor Hobson) was used for this purpose.To minimise the effect of cutting tool wear and breakage on acoustic emission and surface roughness, care was taken to ensure cutting tool sharpness. For each set of experiments a fresh cutting tool insert was used; i.e., the tool was not allowed to wear more than a standard specification.
4 Conclusion
In this study, critical subsystems and components have bee identified for lathes using failure data.The application of condition monitoring techniques like vibration, acoustic emission (AE) and surface roughness monitoring have been successfully implemented for diagnosing faulty bearings in a lathe. We have reached the following conclusions:
·Headstock subsystem is critical because it faces a longer downtime and frequent failures of components like spindle bearings and gears.
·For defective bearing conditions, overall vibration levels at headstock spindle beatings are higher than those in defect free lathes. This increase in vibration level is much greater at higher feed and depth of cut values.
·For defective beating conditions, significant peaks at the beating fault frequencies are observed.
·Larger sized contamination particles increases surface waviness considerably. As a result, the vibration level increased considerably at larger particle sizes.
·AE levels show an increasing trend with an increase in feed rate and depth of cut.
·For defective bearing conditions, AE levels are higher than those measured under healthy conditions. The increase in AE levels is much greater for higher values of feed and depth of cut.
·For defective bearing condition, surface roughness value increases sharply.
·It is observed from the FAAS study that smaller contaminant particles ease the wear out of the bearing elements.
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