Stability of variable helix milling: model validation using scaled experiments

摘要

Regenerative chatter is widely known to be one of the main obstacles to improving the productivity of machining. In milling, one approach to suppress regenerative chatter is the use of milling tools with non-uniform helix angles. There have been a number of studies that have developed alternative analytical formulations of variable helix chatter stability. Whilst some of these have included detailed experimental validation, in general, there is a limited validation of the different analysis methods. In particular, the potential for variable helix tools to stabilise at higher axial depths of cut is of significant practical value but needs detailed experimental validation. The present study aims to provide variations to commonly used configurations, by implementing copolymer acetal as a workpiece material mounted on an intentionally flexible platform. Using this configuration, the force magnitudes can be reduced to lower levels, whilst also ensuring that low-order linear structural dynamics can be assumed even at high axial depths of cut. This provides a pathway to validate the stability predictions for variable helix tools, even if further work is then needed in order to understand non-linearity and other un-modelled effects. Based on the experimental data, the accuracy of the model predictions, and the validity of the model assumptions are discussed. Finally, conclusions are drawn regarding the potential for well-designed variable helix tools to offer significant performance improvements in practical applications.