Abstract
This article discusses the problem of vibrations during machining. The manufacturing process of generator turbine blades is highly complex. Machining using Computerized Numerical Control (CNC) requires low cutting parameters in order to avoid vibration problems. However, even under these conditions, the surface quality and accuracy of the manufactured objects suffer from high levels of vibrations. Hence, the aim of this research is to counteract this phenomenon. Basic issues related to vibration problems will also be also discussed and a short review of currently available solutions for both active and passive vibration monitoring during machining will be presented. The authors developed a method which does not require any additional equipment other than modified CNC code. The proposed method can be applied to any CNC machine, and is especially suitable for lathes. The method seeks to eradicate the phenomenon of vibrations by providing enhanced control through Input Shaping Control (ISC). For this purpose, the authors present a method for modeling the machining process and design an ISC filter; the model is then implemented in the Matlab and Simulink environment. The last part of the article presents the results, together with a discussion, and includes a brief summary.
Highlights
One of isthe assumptions of thisduring research is the use of turning operations in difficult operating conditions, for example, milling turbine blades, noninvasive methods to address vibration issues
Passive methods are basically characterized by the lack of the ability to generate additional force or the displacement introduced into a machine-tool-work piece system; they are not equipped with a control system and cannot change the operating parameters depending on the machining conditions, which means that the effectiveness of such solutions may be limited
The modified input shaping (MIS) technique simplifies the selection of the appropriate filter coefficients, eliminating the need to use numerical optimization, which is necessary in the case of some of the above-mentioned Input Shaping Control (ISC)
Summary
Machining is a basic production technique which has been widely used for many years. contrary to what one might expect, it is a complex process which is accompanied by many unresolved problems. The authors of [42] presented a method for continuous spindle speed control with a vibration prediction algorithm intended to improve the quality of machined long thin blades. After can be achieved through the use specially designed, dedicated fixtures and clamping changing the forcing signal, vibrations of a specific frequency, depending on the paramdevices which fix the turbine blade in place during machining [43–45]. One of isthe assumptions of thisduring research is the use of turning operations in difficult operating conditions, for example, milling turbine blades, noninvasive methods (i.e., which do not interfere in the control system or the construcwhich thin and susceptible to vibrations, as well as turning operations holes, detion ofare the machine) to address vibration issues. Of our innovative approach, which is presented in the form of a simulation of a turning process (including the modeling machining process as well as the control system design)
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