Study On Static Stiffness Estimation Method Of Precision CNC Machine Tools For User Demand

In the machining process of CNC machine tools,the tool is subjected to the cutting force,and the machine tool is deformed due to insufficient static stiffness,which causes the deviation between the actual position and the ideal position of the tool and the workpiece(direction and position deviation),which seriously affects the machining accuracy.Static stiffness is one of the important indicators for CNC machine tool design.The static stiffness of a CNC machine tool refers to the ability of the machine tool to withstand constant loads and resist deformation under the action of cutting forces.Insufficient static stiffness will cause deformation of the CNC machine tool,and will affect its machining accuracy and machining efficiency.How to determine the static stiffness of the machine tool is an important part of the current machine tool design.Based on the research of static stiffness of existing CNC machine tools,based on the demand meta-model,a medium-sized vertical machining center is taken as the research object,using milling force coefficient identification modeling,machine tool cutting force error modeling and machine static stiffness modeling.The research on the static stiffness of the whole machine provides theoretical basis and practical guidance for the machine tool design.The main work of this paper is as follows:1)This paper summarizes the domestic and international status of research on machine tool requirements and static characteristics,and puts forward the shortcomings of current research on static stiffness of machine tools.Based on the existing literature,further analysis and research are carried out.2)Establish a demand meta-model for users of precision CNC machine tools.Summarize the classification and characteristics of user requirements,perform requirements meta-description,demand decomposition and demand modeling,and decompose the customer’s original abstract fuzzy demand information into the designer’s specific and explicit demand meta-information.Taking numerical control machine tools as an example,a multi-level hierarchical demand meta-model based on user requirements is constructed.3)Establish a milling force coefficient identification model.Taking milling as an example,the milling force coefficient identification model is constructed by milling force micro-element modeling,instantaneous milling force modeling and integral upper and lower limits.The experiment was carried out by orthogonal test design method,and the data regression analysis was carried out by MATLAB The milling force coefficient identification model under the condition of the milling cutter-test piece was obtained and verified.4)Establish the cutting force error model of the machine tool and the static stiffness model of the whole machine.Based on the multi-body system theory,a medium-sized vertical machining center is taken as the research object,and the topological structure and low-order body sequence are used to derive the characteristic matrix between adjacent bodies.The cutting force error model is constructed by homogeneous equation transformation;the static stiffness coefficient is utilized.Determine the method,through the analysis of the force and deformation of the machine tool,the mathematical model of the static stiffness of the machine tool is constructed.5)Set up a milling test platform and carry out the static stiffness test of the whole machine.The test piece was designed for milling test,and the force measurement was performed by the force gauge KISTLER9129;the vertical measurement was performed by the Croma686 coordinate measuring machine.Based on the experimental data,the theoretical results are compared with the experimental results,and the static stiffness of the machine is estimated.