Research On Thermal Characteristics Optimization And Thermal Error Compensation Technology Of TK6916 Heavy Type Milling Boring Machine Tool

With the proposal of the strategy of reinvigorating China through manufacturing – "Made in China 2025", as an important machine tool in heavy equipment manufacturing, heavy Type NC machine tool’s accuracy is getting more and more attentions. Owing to the characteristics of wide ranges of movement, large workpiece and heavy load, the heavy Type NC machine tool is easily causing errors leading for the influence of the internal and external heat source. Therefore, it is an urgent problem to effectively reduce its thermal error.This thesis takes the TK6916 heavy type milling boring machine tool as the research object, which is developed by the “Qiqihar No.2 Machine Tool(Group) Co., Ltd”. It focused on “the research of thermal characteristics optimization and thermal error compensation technology of TK6916 heavy type milling boring machine tool”. On the one hand, based on FEA, the thermal characteristics of critical systems was analyzed and optimized to prevent thermal deformation. On the other hand, a real-time thermal error compensation control system suitable for this machine tools was designed; By doing the experiment of thermal error compensation under different work conditions, this thesis proved that the thermal error compensation model is high in robust and predictive accuracy. The main research issues and results are as follows:1. Based on the analysis of heavy milling boring machine heat source and corresponded boundary conditions, the heat fluxes and heat convections boundary coefficient were calculated though theoretical models and empirical formulas. The temperature field and the deformation distortion finite element model of this machine tool critical system was established. By analyzing the field of temperature and thermal deformation, the critical assembly affecting machining accuracy was achieved. Multi-objective optimization method was used to optimize parameters of cooling jacket structure and thermal characteristics of the machine spindle were improved.2. According to the experience of engineering experience and temperature point optimal selection and theories involved, the fuzzy clustering grouping and the global optimization method were used to select the input variables of thermal error modeling. The temperature variables was reduced from 18 points to 4. Based on thermal error measurement with a laser tracker and analysis of data, a FA-LSSVM modeling method based on fireworks algorithm optimize the minimum squares support vector machine model was proposed, Comparing with other modeling ways, the results of this model is better in prediction accuracy.3. Based on the analysis of key technologies in error compensation, a real-time thermal error compensation system was designed based on 840 D CNC system origin offset compensation strategy. The error compensator’s hardware based on STM32F4 and software systems were developed, realizing the connection of the system with the numerical control system of the machine tool.4. By analyzing the thermal characteristics experiments in different work conditions, the law of the key temperature points and spindle thermal deformation were received. According to above theoretical analysis of thermal error modeling, the error model validation and compensation experiments were designed based on the theoretical analysis of thermal error modeling, which laid a foundation for applying and popularizing thermal error compensation technology in the heavy-duty CNC machine.