Research On Characteristics And Performance Evaluation Of Energy Consumption Of Heavy-duty CNC Milling And Boring Machine Tools

Industrial production has brought heavy pressure on the ecological environment,on which human beings depend,while enriching people’s lives.The development of human society is increasingly constrained by energy,resource and environment.Therefore,we must switch the current development way to a sustainable mode from all aspects,for which,energy conservation and emission reduction would have the first priority.Machine tools,as one of the most widely used equipment in industrial production,are consuming vast energy with very low efficiency.Thus,significant energy-saving can be achieved by improving their energy efficiency.Unfortunately,due to the complexity of machine tools,understandings of their energy consumption characteristics are still insufficient.So far,it is difficult to accurately predict the energy consumption of machining processes in actual production scenery because of the unavailability of effective and integrated tools.In addition,it is not possible to classify and manage machine tools according to their energy performance due to the absence of evaluation indicators.The aforementioned knowledge gaps have caused great difficulties for the manufacturing industry to reduce their energy intensity.Taking the heavy-duty milling and boring machine tools as an example,this dissertation aims at bridging these gaps by investigating from the four aspects: i)power consumption modelling of machine tools,ii)energy consumption prediction of complex machining processes,iii)energy consumption characteristics of machine tools and iv)evaluation indicators and methods of energy performance of machine tools.First,the power consumption model of the machine tool was established.Starting from the definition of the boundary of the direct power consumption,the total power consumption of the machine tool was divided into two parts,i.e.the power consumed by fixed subsystem and by movable ones.Then the detailed power consumption model of the spindle and feed axis system were established based on power flow analysis.By comparing the difference between cutting power and air-cutting power,the additional power requirement(APR)due to cutting was modelled.The APR bridges the gap between the air-cutting power and cutting power,which can significantly simplify the complexity of study on power consumption characteristics of machine tools by eliminating the variation due to versatile cutting conditions,e.g.cutting parameters,cutting tools,work-piece materials.Secondly,the energy consumption characteristics of heavy-duty CNC milling and boring machines were studied by experiments.A power measurement system for the machine tool was built,and based on it,the theoretical power consumption model was validated by experiments,including the air load power of spindle system and feed system,the additional power requirement(APR)due to cutting.And based on APR,the relationship between air load power and cutting power was established.At the same time,taking the energy-saving oriented optimization of cutting parameters as the starting point,the energy consumption characteristics of heavy-duty milling and boring machine when performing various cutting parameters were studied.It was found that under the most working conditions,the basic power of the machine tool accounts for the largest proportion in its total power,followed by the spindle power while the power of feed axes is usually negligible.Thirdly,a virtual manufacturing(VM)technology based energy consumption prediction method for complex machining task was proposed,and a comprehensive study of the energy consumption characteristics of machine tools when performing typical machining tasks was conducted.For the first time,a spatially and temporally joint controlled boundary of the comprehensive energy consumption of a machining process was defined,based on which,the comprehensive energy consumption was divided into the direct part and the indirect part and the calculation methods of each of them were also established.By integrating an energy consumption analysis module into the traditional VM system,the VM based machining energy prediction method was put forward.A demo VM system integrating energy consumption analysis was developed and validated by case studies.In addition,the multi-perspective analysis of energy consumption of a typical sophisticated machining process was demonstrated.Finally,to guide the energy-saving in manufacturing companies,the evaluation method for the energy performance of machine tools was established based on the aforementioned energy consumption characteristics.The general principles and requirements of machine tool energy performance evaluation were explored regarding different groups relating to machine tools,i.e.,machine tool designers,users and managers.Key indicator sets for the energy performance evaluation were proposed from both the subsystem level and the whole machine tool level based on the energy consumption characteristics of machine tools under different cutting conditions.A comprehensive index for energy performance evaluation was established by synthesizing all key indicators proposed aboveby DEMATEL method,which can fully reflect the energy consumption characteristics of the machine tool with clear physical meaning.The proposed indicator is easy to measure and can meet all evaluation needs of different machine tool related groups.An energy performance label was designed and the energy performance of two TK6920 type CNC heavy-duty milling and boring machines tools were compared to demonstrate the application of the proposed method.