Theoretical and experimental study of tooling systems : passive control of machining vibration

Sammanfattning: Vibration control has been and still remains a subject of primary importance in modern manufacturing industry. To be able to remove high volumes of material in shorter time as well as to be able to get the right quality of the parts at the first time are goals that many shops would like to achieve. Tooling systems, and especially cantilever tools, and cantilever structural units of machine tools are the least rigid components of machining systems and therefore the most prone to vibration. Boring tools are often encountered as rotating tools in machining centres or as stationary tools in internal turning. In this thesis the focus is on internal turning. Internal turning is widely known as a very delicate operation and it is often carried out with cutting parameters far from optimal, from a productivity point of view, due to limitations imposed by vibration. Another type of tooling system whose functionality is impaired by vibration is the parting-off tool. The design of damped parting-off tool is one of the focus of this thesis as well. Vibration control has the purpose to achieve an efficient energy dissipation of a vibrational system. Basically this is achieved by controlling the damping of the system. Since damping involves the conversion of energy associated with a vibration to other forms, there are several mechanisms to remove energy from a vibrating system. Typically these mechanisms are divided in two classes: 1. Mechanisms that convert mechanical energy to heat, i.e. passive damping. 2. Mechanisms that transport energy away from vibrating systems, i.e. active damping. Both these techniques have been used during the years and both have been giving excellent results. The active vibration control mechanisms are more expensive and not suitable for machining due to the cables they necessitate that could interfere with the machining operation. This work proposes an original approach to vibration damping in machining systems, the objects of vibration dissipation being the structural components on the link between turret and cutting insert. The idea is to use composite materials to create damping interfaces between and within the different structural components. Different clamping system designs are being compared in order to see how these influence the performance of the machining system and different cutting inserts have been compared for machining hardened steel. The newly designed components have been going through both extensive off-line (modal analysis) and on-line dynamic testing (machining test) and the results show that the new tool holders used in combination with hydrostatic clamping system are the most optimal solution among the tested ones. The new design for the turret has been giving promising results and more can be achieved by bringing minor changes to it, these changes are being implemented at the time of writing this thesis.