Damping support fixture for vibration suppression in milling of thin-walled casing
Machining vibration is one of the main phenomenon occurs in milling of thin-walled workpiece, it will lead to poor surface finish and low machining efficiency. Especially for challenging situations such as large dimension closed casing, vibration is one of the main factors affecting the improvement of machining efficiency. In this work, a method by applying damping support fixtures for machining vibration suppression is developed. It can be mounted at different positions on the inner surface of casing to suppress vibration. This method has been validated by finite element simulation and cutting experiments. The results show that vibration can be suppressed with the presence of damping support fixtures. The new method can be used to get higher machining efficiency and better surface finish in milling of thin-walled casing.
Optimization of multiple tuned mass dampers to suppress machine tool chatter
Abstract Chatter is more detrimental to machining due to its instability than forced vibrations. This paper presents design and optimal tuning of multiple tuned mass dampers (TMDs) to increase chatter resistance of machine tool structures. Chatter free critical depth of cut of a machine is inversely proportional to the negative real part of frequency response function (FRF) at the tool–workpiece interface. Instead of targeting reduction of magnitude, the negative real part of FRF of the machine is reduced by designing single and multiple TMD systems. The TMDs are designed to have equal masses, and their damping and stiffness values are optimized to improve chatter resistance using minimax numerical optimization algorithm. It is shown that multiple TMDs need more accurate tuning of stiffness and natural frequency of each TMD, but are more robust to uncertainties in damping and input dynamic parameters in comparison with single TMD applications. The proposed tuned damper design and optimization strategy is experimentally illustrated to increase chatter free depth of cuts.
The application of tool path compensation for the reduction of clampinginduced geometric errors
Spherical-tipped locators and clamps are often used for the restraint of workpieces within machining centres. For structurally rigid fixtures and workpieces, contact region deformation, slip, and lift-off are the predominant modes of workpiece displacement. Experimental evidence obtained thus far indicates that this displacement can be severe during clamping. In addition it can be a significant source of geometric error. However this error can be reduced significantly through tool path compensation. This paper describes two different techniques that can be used to determine workpiece displacement during clamping. The first applies eddy current displacement sensors to measure workpiece displacement online. The second applies an analytical model to predict workpiece displacement during clamp actuation. This paper also shows how workpiece displacement data can be used to compensate tool paths prior to machining. Lastly this paper describes an experimental study used to validate both techniques.