In high-speed precision machining, thermal deformation caused by temperature rise affects the accuracy stability of the machine tool to a significant extent. In order to reduce the thermal deformation of ball screws and improve the accuracy, a new adaptive method based on carbon fiber reinforced plastics (CFRP) was proposed in this study and the thermal deformation of ball screws was determined. By using the sequential coupling method, the thermal–structural coupling analysis of a ball screw was conducted based on the finite element method (FEM). The analysis results were verified through a comparison with the experimental results. Based on the verification, an FE model of the improved ball screw was established to study its thermal characteristics. The key design parameters of the improved ball screw were optimized based on the Kriging model and genetic algorithm (GA). The thermal reduction effect of the improved ball screw was validated through the experimental results. The results indicate that the adaptive method proposed in this research is effective in reducing the thermal deformation of ball screws.
Thermal error of ball screws seriously affects the machining precision of CNC machine tools especially in high speed and precision machining. Compensation technology is one of the most effective methods to address the thermal issue, and the effect of compensation depends on the accuracy and robustness of the thermal error model. Traditional modeling approaches have major challenges in time-series thermal error prediction. In this paper, a novel thermal error model based on Long Short-Term Memory (LSTM) neural network and Particle Swarm Optimization (PSO) algorithm is proposed. A data-driven model based on LSTM neural network is established according to the time-series collected data. The hyperparameters of LSTM neural network are optimized by PSO and then a PSO-LSTM model is established to precisely predict the thermal error of ball screws. In order to verify the effectiveness and robustness of the proposed model, two thermal characteristic experiments based on step and random speed are conducted on a self-designed test bench. The results show that the PSO-LSTM model has higher accuracy compared with the RBF model and BP model with high robustness. The proposed method can be implemented to predict the thermal error of ball screws, and provide a foundation for thermal error compensation.
Increased epididymal T1 signal intensity (likely due to proteinaceous material lodged within the epididymal tubules) at preoperative MRI in patients undergoing vasectomy reversal suggests vasal/epididymal tubular occlusion and requirement for vasoepididymostomy rather than vasovasostomy.
To reduce the thermal deformation of ball screws, a novel approach inspired by silver ants is proposed. The Saharan silver ant maintains low body temperatures in one of the hottest terrestrial environments by radiating heat to the surrounding environment. Inspired by this, bio-inspired graphene-coated ball screws, which can enhance heat dissipation due to radiative heat dissipation of graphene coating, are designed to reduce the temperature and thermal deformation further. Finite element analysis is conducted to validate the excellent performance of the proposed bionic design in reducing thermal deformation. In order to verify the advantage of this method, comparative experiments between graphene-coated ball screws and the ordinary one are carried out on a self-designed test bed as well. The result shows that the bio-inspired design obviously reduced the temperature rise, thermal deformation, and temperature balance time. This bio-inspired approach will provide a new idea to solve the thermal issue of machine tools.
National Development and Reform Commission, National Energy Administration printed Energy Production and Consumption Revolution Strategy (2016~2030), planned clean and efficient production and utilization of coal industry from three aspects: centralized use of coal, promotion of clean coal utilization, and promotion of green coal production. For the coal-fired power industry, promoting clean coal utilization has become the most important target task for the current and future period. This paper analyzes China’s energy development status in terms of China’s energy, power development and power energy structure. Based on the existing application of China’s clean and efficient coal-fired power technology, we investigated the resource efficiency and environmental benefits of clean and high-efficiency coal-fired power generation, and offered suggestions for the upgrading of China’s energy system at a lower cost.
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