Research On Formation Mechanism And Optimization Scheme Of Roundness Error In Deep Hole Machining Of Gun Drilling

With the rapid development of society,continually increasing demand of public have driven the high requirement of industrial manufacturing technology.At the same time,the development of industries such as aerospace,transportation,national defense industry and intelligent manufacturing has also raised the higher demand to manufacturing technology.As an important part of equipment manufacturing industry,there are also trending towards more precise,efficient and intelligent of deep hole processing.Roundness is a key criterion for measuring the quality of deep hole processing.Assembly accessories and high-precision parts have high requirements for roundness.In the general process,additional process are often required to reduce the roundness error,which decrease the efficiency obviously.Gun drilling is the main processing method for the deep-hole with smaller aspect ratio.Due to its special structural and working characteristics,roundness errors generally occur in machining holes,so it is necessary to deepen the research of roundness of gun-drilling deep hole.Firstly,this paper describes the formation mechanism of the roundness error.It is considered that the roundness of the machined hole is mainly caused by the whirl of the drill pipe,and the cutting force of the gun drill during the machining process is analyzed and calculated.The relationship between the processing parameters(rotation speed and feed rate)and the whirl of drill is put forward through the cutting force,meanwhile the trajectory of the drill is obtained.The whirl trajectory of drill under different situation is obtained through calculation and simulation.The effect of parameters on the roundness error is further verified by the experiment.First of all,the influence law of the rotational speed,feed rate and the depth of hole on the roundness error is studied by the single factor method,and the model established previously is verified.The Taguchi method and the variance method are used to study the influence of various factors on the roundness.The response surface method is used to study the comprehensive effect of all of the parameters on the roundness.The optimal combination range of the parameters is obtained and the prediction equation which include rotation speed,feed rate and depth is deduced.In this paper,the influence mechanism of the guide-pads on the surface of machined hole is analyzed,and a kind of optimization structure of three guide pads is proposed while combing with the gun drill structure.Through simplifying the gun drilling system into Euler-Bernoulli beam and decomposing them into several discrete units,comparing the force condition between optimized structure and the common one,the calculation formula of the roundness is obtained,and the optimization effect is appeared.The statics analysis and dynamic analysis of the optimized structure and common structure are carried out by finite element analysis to analyze the stress and strain,model and optimized effect.In summary,the formation mechanism,influencing factors and optimization methods of roundness is studied in this paper.A roundness shape model is established and the relationship between machining parameters and roundness is researched from which,the optimal parameters combination range is obtained.A kind of optimized structure with three guide pads is proposed.The research has a great theoretical significance for the study of the roundness of deep hole machining in the future.