Machining thin-walled components involves continuous decrease in mass and stiffness of the parts being machined, causing increase in vibrations and instability. This leads to undesirable machining errors in dimensional and form tolerances as well as surface finish which adversely affects the quality of machined parts.

To track and quantify the changing dynamic behaviour of Aluminum 6061-T6 workpiece, first, numerical simulations are carried out in ANSYS Workbench 18.2 to extract its modal properties. To validate this, off-line modal hammer tests are carried out on a number of semi-machined fixtured components, representing intermediate stages of machining. The results of the numerical simulations match well with the experimental measurements. With thinning of the walls from 6mm to 4.5mm the natural frequencies and damping ratios are found to drop by a factor of 1.5 and the magnification factor is found to rise by 25% signifying rise in the vibration levels. This obviously would reflect in enhanced vibrations of the workpiece when subjected to dynamic forces during machining. In this paper, this problem is addressed by deploying strain gauge bridge in the feedback and thereby regulating clamping pressure by proportional hydraulic clamping mechanism in an on-line mode. The method is found to compensate the vibration level by 40% and can be integrated in the design of a smart fixtures.

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