Energy Consumption Modelling In Milling Process And Parameters Optimization

With the increasingly prominent energy problem,energy saving and emission reduction have attracted more and more attention of scholars all over the world.Manufacturing industry consumes enormous energy every year,and is also the focus of energy saving and emission reduction.Machining is an important way to complete the manufacturing of product parts.Therefore,it is an effective way to achieve high efficiency and low consumption to develop a reasonable CNC machining scheme for the parts to be processed.Establishing energy consumption model of machine tools is the basis and premise of realizing energy-saving process planning for parts.The existing energy consumption models are mainly used to reveal the energy consumption law in processing,and less from the perspective of the workpiece to be processed to complete the model.Therefore,the main contents of this thesis are as follows:Firstly,the un-load energy consumption model of three-axis milling machine is established.The energy consumption characteristics of NC machine tools in cutting process are analyzed.The theoretical power models of energy consumption components in standby and auxiliary states of machine tool are established respectively.On this basis,the influence factors of the un-load energy consumption of three-axis CNC machine tool are revealed.In order to obtain the energy consumption data of CNC machine tools,a real-time monitoring platform for energy consumption of CNC machine tools is established.The mathematical relationship between cutting parameters and energy consumption of CNC machine tools was established by mechanism and empirical analysis.The power models of CNC machine tool spindle and feed axes in un-load state are established.After simplifying the theoretical models,the piecewise linear relationship between spindle power and spindle speed and the non-linear relationship between feed axes power and feed rate are proposed.It is found that the spindle power increases with the spindle speed in each segment interval,and basically subject to the linear equations.The power of the feed axes has a non-linear function relationship with the feed rate.Secondly,the cutting energy consumption model of CNC machine tool considering the shape of cutting edge is established.The mathematical models of cutting power and processing time are established respectively.Based on the analysis of the energy consumption mechanism of metal cutting,the theoretical cutting power calculation formulas including shear deformation power consumption of metal and friction power consumption of tool and workpiece contact area are derived.Finally,the relationship between cutting parameters and cutting energy consumption is obtained.Using the real-time monitoring platform of CNC machine tool processing energy consumption built in this paper,the validity of the energy consumption model is verified by milling experiments,and the accurate prediction of energy consumption in processing is realized.By theoretical and experimental analyzing of step milling process,the influences of spindle speed,feed rate,cutting depth and cutting width on cutting energy consumption are elaborated.It lays a foundation for energy consumption prediction in subsequent milling process and optimization of CNC machine tool processing process towards high efficiency and low consumption.Then,a modeling method of cutting energy consumption model based on typical machining features is proposed.Based on the Standard for the Exchange of Product Model Data-Numerical Control(STEP-NC)and the characteristics of machining features,the machining features are decomposed into machining elements.Based on the above modeling method of cutting energy consumption,the contact state between tool and workpiece during cutting is analyzed.Four processing units which are linear machining element,curve machining element,cut-in/cut-out machining element and hole machining element are established.Considering the cutting energy consumption of the same machining features under different machining strategies,the calculation methods of energy consumption model of six typical machining features which are side,step,slot,face,pocket and hole are given respectively.Thus,the energy requirement of machining is obtained.The feasibility and validity of the proposed energy consumption modeling method for machining features are verified by milling a part containing the established machining features.Finally,taking the energy consumption of machine tool processing as one of the objectives of cutting parameter optimization,a multi-objective optimization method considering the trade-offs of machining efficiency,energy consumption and surface quality is proposed.The objective functions of energy consumption,processing time and surface roughness in CNC machining process are established respectively.Minimum energy consumption and maximum production efficiency are taken as optimization objectives in rough.Minimum energy consumption and best processing quality are taken as optimization objectives in finish.The optimization variables are determined as spindle speed,feed rate,cutting depth and cutting width in rough and finishing respectively.Then,the model is optimized by using the NSGA-II algorithm.Based on the above research,energy consumption prediction and optimization software is designed and developed.Through cutting experiments,the feasibility of simulation software and optimization results is verified.Effective tool is provided for the selection of cutting parameters towards high efficiency and low consumption.