| As the manufacturing technology on machine tools trends to a higher level, many kinds of advanced technology emerge at this time, so the process efficiency and quality have been significantly improved. CNC machine tool is the basic equipment in manufacturing, and the process accuracy is one of the most important indicators to measure the overall performance of the machine. The machine tool error refers to the difference between the ideal tool position and the actual position in the movement of machine parts. It determines the quality of the finished product, and it can be calculated through the kinematics modeling.In this context, aimed at three-axis machine tool, an accuracy prediction method is presented based on comprehensive error model on machine tool. It combines error model, process parameters and tool path to predict accuracy. By simulating the process of two typical working surface, it can show the simulate surface with error and process parameters, which provides theoretical reference for machining path planning, machine design and so on. The detailed contents are as follows:(1) According to the development of machine error modeling, current research at home and abroad is summarized, and the deficiency existed in the present study is pointed out. Aimed at the shortcomings, the research direction is clear, and the contents in this paper will follow this route.(2) Before error modeling, we must make clear the error factors and error sources. Since there are so many factors affecting the process, it’s impossible to take all the factors into consideration, so only the main ones are considered. Geometric error is one of the main factors, and it is analyzed in detail from the perspective of kinematics. There are 26 items about geometric error in three-axis machine tool. Besides, it also discusses the error detection technology, and puts forward to build the digital sensor network. By using sensor technology, we can acquire the key data from the machine tool, thus it will make sure the accuracy of data source for error modeling.(3) Based on homogeneous coordinate transformation theory, four kinds of comprehensive error model are established according to the different structure of three-axis machine tool. This model shows how the error elements on machine parts are quantitatively converted into relative position between tool and workpiece. By establishing a series of coordinates, this conversion can be realized. The error model can be used to analyze and predict the effects of geometric errors on process accuracy, provides theoretical basis on accuracy simulation.(4) For practically using error model, we need to effectively detect and identify the error elements in the model. There’s some relationship between error elements and component errors. The component errors can be easily detected, so we use this relationship to get the values of error elements. The discrete measurements can be expressed as relevant functions related to displacement. Thus, we can predict the trends and the scope of the error element, which is very important to error prediction.(5) According to the geometry of the tool, the tool model is established. Based on the principle of kinematic transformation and the tool model, tool-path model is established. By introducing time variable, the model can reflect the actual machining path as time changes, so we can get the tool position at any time. By simulating the process of two typical machining surface, we can not only see the theoretical and practical surface on the computer, but also can get some accuracy parameters. This simulation results have great theoretical significance in accuracy prediction. |
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