In this study, the response surface (RS) method and forced rotordynamic analyses together with Finite-Element-Analysis (FEA) have been established to optimize the factors affecting the vibration characteristics. The spindle specification, bearings locations, cutting force, and motor-rotor unbalance mass are proposed to represent the design factors and then they are utilized to develop Machine Motorized Spindle (MMS). The FEA-based Design of Experiment (DOE) is adopted to simulate the output responses with the input factors, wherein these DOE design points are used to carry out the RS models to visualize more obvious factors affecting the dynamic characteristics of MMS. The sensitivities of these factors and their contributions to the vibration of imbalance response have been evaluated by using the RS models. The simulation results show that the motor-rotor shaft inner diameter, the distance of the back bearing location, and the rotating unbalance-mass are highly sensitive to the vibration characteristics compared to the other factors. It is found that more than two-fifths of total vibration response amplitude has been conducted by induced rotating imbalance mass. The results also showed that the proposed factors optimization method is practicable and effective in improving the vibration response characteristics.
The quality loss caused by tolerance of factors can be reduced when the nominal values of design-factors are carefully chosen. Therefore, the parametric optimization method is significant to an optimally define the Quality Loss cost (QLc). In this work, the Design Exploration (DE) and Taguchi Methods along with unforced Rotordynamic analysis have been used to find the optimal levels of factors affecting the QLc. Under definite constraints, the mathematical models are developed for an optimization problem and then utilized to develop Machine Motorized Spindle (MMS). In order to find the optimal levels of the factors, the sensitivities of factors on structural weight and First-Order-Nature-Frequency (FONF) has been analyzed using Response-Surface (RS) method, while the Taguchi method is used to find the QLc. The results found shown that there are significant enhancements in signal-to-noise ratio for structural weight and FONF. The QLc has been saved to about more than half-time by comparing to its initial values. The results also indicated that the proposed optimization approach is feasible and successful in improving dynamic characteristics and QLc saving for the MMS. Keywords: Machine Motorized Spindle, Finite Element Method, Unforced Vibration, Rotordynamic Analyses, Response Surface Method, Taguchi Quality Loss cost.
In this work, the dynamic of MMS exposing several excitation forces has been studied using forced Rotordynamic analysis. The Finite-Element-Model (FEM) based Design of Experiment (DOE); the sensitivities of factors on vibration response and their levels optimization have been carried out based on Response-Surface (RS) method. The results showed that the vibration response is considerably influenced by the rotating unbalance force. The vibration amplitude conducted by rotating unbalance force is more than two-by-five-time when compared to the other factors. In addition, the results obtained also showed that there are significant improvements in Structural Weight (SW) and vibration response. Thus, the factors level optimization technique, not only reduce in total material consumed but also the vibration response can be improved. The proposed vibration design approach is significant and successful in improving vibration of unbalance response.
A machine-tool structure optimization is an important technique that improves the machining efficiency and saves materials and the energy resource. In this work, dynamic design optimization method for Machine-Motorized-Spindle (MMS) subjected to a number of rotating unbalanced forces effects is presented. Linear forced-Rotordynamic analysis with design explorer method has been used to simulate the output response. The Design Variables (DVs) and their limits were carefully chosen and applied to develop the Design-of-Experiment (DOE). The Box-Behnken Design (BBD) method, because of its good organization in providing much information in a minor number of required statistical experiments was used to generate the DOE. The influences of DVs on the dynamic of MMS and their levels optimization were evaluated by utilizing the Response-Surface (RS) method. The results showed that the spindle shaft inner diameter of the motor-rotor seat and its rotating unbalanced mass, and modulus of elasticity have the highest contribution in effect on the dynamic of MMHS. As well, it is found that the proposed optimization method not only improves the structural weight of MMS, but also the potential saving can be achieved in term material and energy resource.
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