Chatter avoidance via structural modification of tool-holder geometry

Chatter is a self-excited vibration that can occur during milling operations causing undesirable consequences such as poor surface finish and increased levels of tool wear. One possible solution to this problem is to optimise the dynamics of the machine by tuning parameters such as tool stickout length, e.g. by using receptance coupling substructure analysis. Unfortunately, experimental limitations of the method, such as the requirement to model interface dynamics and the inefficient optimisation process, have hindered its advancement to the industrial sector. This paper looks to resolve these issues by proposing a new structural modification method for chatter avoidance. Firstly, tool-holder diameter is investigated as a potential tuning parameter: a new experimental dataset demonstrates that this design parameter can have a significant and valuable impact on the chatter stability. Secondly, the direct structural modification method is introduced, allowing the tool-holder diameter to be modelled without any knowledge of the interface behaviour between tool and tool-holder. Thirdly, the inverse structural modification method is proposed, allowing tuning and stability optimisation by solving a single equation. Lastly, a new tunable-mass tool-holder is presented, allowing the dynamics of a milling machine to be tuned for each tool diameter and length range with a single tool-holder. This eliminates the need for manufacturers to purchase a wide range of tool-holders, a significant financial investment.