基于神经网络的微孔钻削力的实时监控

建立了基于神经网络的微孔钻削力实时监控系统,以轴向力和扭矩信号为监测对象,应用BP神经网络进行多路传感器信息融合,判断微钻头工作状态,为微孔钻削加工力的智能化在线监控提供一种有效的技术方法.     

微孔钻削加工的钻削力监控

对以钻削力为监测对象的微孔钻削实时监测系统进行了研究。建立了一个BP神经网络模型,利用该模型对钻削过程进行监测。有效地避免了微钻头的折断,提高了微钻头的利用率。     

基于虚拟仪器的微孔钻削在线监测自动控制系统

为防止微孔钻削过程中钻头折断,开发了基于虚拟仪器的微孔钻削在线监测系统.该系统能够完成主轴电动机电流信号的采集、数据处理、存储显示以及报警退刀等操作.具有硬件结构简单、监测精度高、抗干扰能力强等优点.实验结果表明,应用该系统进行微孔钻削在线监测,可以有效避免微钻头的折断,提高钻头的利用率.     

基于多信号模糊融合的微孔钻削在线监测

利用轴向力、扭矩和主轴电机电流信号来监测微小钻头在钻削过程中的状态,提出了运用模糊控制作为多信号融合来监测微钻头状态的监测模型。结果表明,利用该模型得到的监测阈值进行在线监测可有效避免钻头折断。     

微钻头螺旋槽对称性对钻头折断的影响

在微孔钻削过程中,影响钻头寿命的因素很多：如微钻头自身的直径,微钻头钻芯厚度,微钻头材料及制造工艺,以及微钻头螺旋面等。集中研究微钻头螺旋槽对称性对钻头折断的影响,并在前人提出的钻头制造方法及钻削过程中钻头受力情况研究的基础上,分析了微孔钻削过程中,由于微钻头螺旋槽的制造误差,造成两主切削刃上的钻削力不平衡,导致微孔钻削过程中微钻头的折断。同时,提出了改善微孔钻削过程中微钻头折段的措施以及最适合制造微钻头的方法。     

基于粗糙模糊神经网络的微孔钻削在线监测方法

提出了基于粗糙集理论的模糊神经网络对微孔钻削进行在线实时监测的方法,能有效利用粗糙集理论对控制规则进行约简,再利用钻削力、钻削扭矩和主轴电机电流信号作为神经网络的输入,构建相应的模糊神经网络模型,对系统进行训练,进而对提取的精简规则参数进行优化,从而解决了常规粗糙集控制规则缺乏学习能力,自适应性差的问题.采用该方法可获取微细钻头磨损状态的信息,对微孔钻削过程进行在线实时监测,可有效避免微钻头折断,并降低制造成本,提高生产效率.     

0Cr18Ni9不锈钢的微小孔钻削

在不锈钢材料的微细钻削加工过程中,切屑易缠绕甚至粘结在微钻上,不易折断且排屑困难,导致加工难度大、制造成本高。分析了微细钻头对材料性能的要求,以及不同几何参数对微钻性能的影响。由于具有很高的硬度和断裂韧性,超细晶粒硬质合金材料被选用于制作微细钻头,并在微细刀具数控刃磨机上制造了钻头。在不同切削参数条件下对0Cr18Ni9不锈钢进行了微孔钻削,测量了钻削过程中的轴向力,观察了微钻的磨损与破损情况,分析了微钻的不同失效机理,并观察了不同钻削条件下的微孔表面。通过试验研究了切削速度、进给速度等钻削工艺参数对轴向力的影响规律,从而达到提高微钻切削性能以及使用寿命的目的。     

基于粗糙集模糊控制的微孔钻削在线监测

提出了一种基于粗糙集模糊控制的微孔钻削在线监测的方法。克服了当模糊系统输入维数高时,系统模糊规则过多,计算过于复杂的缺点。在MATLAB环境下,应用构造好的模糊系统对主轴电机三相电流信号进行实时数据处理,获取隐含微细钻头磨损状态的信息值,对微孔钻削过程进行在线监测实验,结果表明,适当选择监测阈值,可以有效避免微细钻头的折断。     

斜孔钻削中钻头折断的判据实验研究

斜孔钻削大量存在于现代制造业中,由于其出钻的特殊加工状态,钻模等辅助方法无法使用。钻头在相当长的时间内处于断续切削状态。轴向力和扭矩均以冲击力出现,极易导致钻头的折断。钻头折断时,轴向力和扭矩均发生了徒增。扭矩的剧烈变化,是折断的主要因素。这为进一步控制和预防钻头折断提供了实验依据。     

高速微孔钻床主轴系统的动态特性分析

依据转子动力学理论,利用Timoshenko粱轴理论,建立了包含旋转惯性力、陀螺力矩、离心力、弯曲变形、扭转变形、钻削轴向力和钻头的三种边界条件在内的高速微孔钻床主轴系统动力学模型。在利用实验和现有文献对所建立的模型进行了检验的基础上,对高速微孔钻床主轴系统的临界转速、临界轴向压力进行了分析。结果表明高速微孔钻床主轴系统的临界转速随钻削轴向压力的增大而减小,并且钻削过程中比刚入钻时能承受更高的转速,更大的轴向力;临界轴向压力随高速微孔钻床主轴系统转速的升高而降低,即随着钻削转速的提高,应适当减小钻削轴向力。     

Tool life evaluation of CFRP drilling with three kinds of drill

Serious tool wear in CFRP drilling is one of the key problems to be solved urgently. Firstly, a suitable indirect evaluation index of tool life is selected according to the literature. The critical delamination force was obtained by blind hole pushing experiment. Then, tool wear experiments were carried out with double point angle drill, stepped drill and reverse edge compound drill to analyze the variation rules of the thrust force, exit burr, exit delamination and tear with tool wear. Threshold values of exit delamination, tearing and critical thrust force were compared with each evaluation index one by one to study the causes of drills failure. The results indicated that the maximum tool wear position was the outer corner. Among the three types drills, the thrust force, delamination factor and burr angle of the reverse edge compound drill are smaller. The double point angle drill fails due to the excessive thrust force, while the stepped drill and the reverse edge compound drill fail due to the hole exit delamination exceeding the threshold. The number of drilled holes of the reverse edge compound drill is 100 % and 25 % higher than that of the double point angle drill and the stepped drill, respectively. Therefore, the reverse edge compound drill is suitable for drilling CFRP.

     

Analysis of temperature changes on the twist drill under different drilling conditions based on Taguchi method during dry drilling of Al 7075-T651

In this work, effects of drilling parameters (drilling depth, feed rate, and spindle speed) on the twist drill bit temperature and thrust force in the dry drilling of Al 7075-T651 material were experimentally investigated. During dry drilling experiments, drill bit temperature and thrust forces were measured. Drill temperatures were measured by inserting standard thermocouples through the coolant (oil) hole of TiN/TiAlN- coated carbide drills. The settings of drilling parameters were determined by using the Taguchi experimental design method. An orthogonal array, the signal-to-noise (S/N) ratio, and the analysis of variance (ANOVA) are employed to analyze the effect of drilling parameters. The objective was to establish a model using multiple regression analysis between spindle speed, drilling depth, feed rate, and drilling method with the drill bit temperature and thrust force in a Al 7075-T651 alloy material. The study shows that the Taguchi method is suitable to solve the problems with a minimum number of trials as compared with a full factorial design .     

钎焊套料钻钻削碳纤维增强复合材料层合板出口撕裂缺陷的成因分析

针对碳纤维增强复合材料钻孔时钻头寿命短、易产生加工缺陷等问题,将钎焊金刚石套料钻应用于碳纤维增强复合材料的钻削加工中。为更好地说明钎焊金刚石套料钻的加工性能,选取了复合材料钻削中常用的金刚石涂层麻花钻进行比较,并选择了实际加工中严重影响加工质量的出口撕裂缺陷进行成因分析。通过检测与分析出口处加工质量,得到以下结论：对于不同结构形式的钻头,仅依靠轴向力及扭矩并不能判断是否产生撕裂缺陷;在相同工艺参数下,钎焊金刚石套料钻的轴向力及扭矩均小于金刚石涂层麻花钻的轴向力及扭矩,使用钎焊金刚石套料钻更有利于减少撕裂缺陷,提高加工效率。     

Investigation on thrust force in rotary ultrasonic drilling of CFRP using Brad drill

Abstract

The carbon fiber reinforced plastic (CFRP) has been widely used in manufacturing industry due to its excellent mechanical and physical properties. Brad drill, as a representative of new-type structural drills, is applied in processing of CFRP. Meantime, rotary ultrasonic drilling (RUD) is regarded as a superior method for machining composite materials, due to its outstanding performance in lowering thrust force and improving processing quality. However, there are few reports about RUD with Brad drill in CFRP drilling. In this study, the theoretical model of thrust force for RUD of CFRP using Brad drill is developed. The dynamic uncut chip thickness and average uncut chip thickness in RUD are obtained based on kinematic characteristics analysis. After that, the structure of Brad drill is analyzed and thrust force of the cutting lip is molded. Then a theoretical model is proposed to predict the thrust force. Finally, pilot experiments are conducted for the model verification. Experimental results show that the trends of thrust force agree well with the thrust force model and the prediction error is less than 10%.     

Experimental evaluation of polycrystalline diamond tool geometries while drilling carbon fiber-reinforced plastics

Polycrystalline diamond (PCD) drills are commonly employed in carbon fiber-reinforced plastic (CFRP) drilling to satisfy hole quality conditions with an acceptable tool life and productivity. Despite their common use in industry, only a small number of studies have been reported on drilling CFRPs with PCD drills. In this study, drilling performances of three different PCD drill designs are investigated experimentally using thrust force, torque, and hole exit quality measurements. Results show that work material properties, drilling conditions, and drill design should all be considered together during the selection of process parameters, and the relationships among these factors are quite complex.     

Effect of tool wear on delamination in drilling composite materials

Among all machining operations, drilling using twist drill is the most frequently applied for secondary machining of composite materials owing to the need for structure joining. Delamination is mostly considered as the principal failure model in drilling of composite materials. Drill wear is a serious concern in hole-making industry, as it is necessary to prevent damage of cutting tools, machine tools and workpieces. The industrial experience shows the worn drill causes more delamination. This paper presents a comprehensive analysis of delamination caused by the drill wear for twist drill in drilling carbon fiber-reinforced composite materials. The critical thrust force at the onset of delamination for worn drill is predicted and compared with that of ideal drill. The experimental results demonstrate that though the critical thrust force is higher with increasing wear ratio, the delamination becomes more liable to occur because the actual thrust force increases to larger extent, as the thrust factor (Z) illustrates. Compared to sharp drill, the worn twist drill allows for lower feed rate below which the delamination damage can be avoided.     

Investigating the feasibility of DLC-coated twist drills in deep-hole drilling

The ideal coating for twist drills used to drill deep holes should have both a high hardness and a smooth surface. The latter property is considered to ease chip evacuation through the drill’s chip flutes and, therefore, reduces the risk of chip clogging and possible premature drill fractures. For this reason, diamond-like carbon (DLC) appears to be a well-suited type of coating. This paper presents the results of cutting tests using DLC-coated HSS and cobalt-HSS twist drills when drilling deep holes of diameter 1.5 mm into plain carbon steel. Their capability to extract swarf from the borehole as well as their tool lives were investigated and compared to uncoated and TiN- and MoS₂-coated drills. Although the DLC-coated drills showed a very good swarf disposal capability, they did not exhibit a longer tool life when compared to off-the-shelf drills.     

Tool wear monitoring in drilling using force signals

Utilization of force signals to achieve on-line drill wear monitoring is presented in this paper. A series of experiments were conducted to study the effects of tool wear as well as other cutting parameters on the cutting force signals and to establish the relationship between force signals and tool wear as well as other cutting parameters when drilling copper alloy. These experiments involve four independent variables; spindle rotational speed ranging from 600 to 2400 rev min⁻¹, feed rate ranging from 60 to 200 mm min⁻¹, drill diameter ranging from 5 to 10 mm, and average flank wear ranging from 0.1 to 0.9 mm. A statistical analysis provided good correlation between average thrust and drill flank wear. The relationship between cutting force signals and cutting parameters as well as tool wear is then established. The relationship can then be used for on-line drill flank wear monitoring. Feasibility studies show that the use of force signal for on-line drill flank wear monitoring is feasible.     

Experimental studies of the cutting force and surface morphology of explosively clad Ti–steel plates

The present work pertains to the study of clad material such as titanium plated steel in drilling process. The study was conducted for two types of indexable insert drills with different configuration of the tool coatings (TiAlN/AlTiN + TiN and TiAlN/TiN), the same geometry of insert and fixed machining conditions. Drilling process was assessed by the analysis of thrust force, torque and signal fluctuations of PSD function. In this context, surface morphology of the drilled holes and contact area was analysed. It has been observed that the use of the PSD function allows assessment of the drilling process in different layers of clad materials. Also was found that the parameters of the surface morphology are dependent upon the type of layers of the clad and the type of drill. Furthermore the reduction in torque results in obtaining smaller values of surface roughness parameter especially in the area of volume parameters of the bearing area curve.     

钛合金微小孔钻削试验研究

应用自行研制的TiC涂层和类金刚石（DLC）涂层硬质合金钻头以及市售硬质合金钻头（WC-Co）对钛合金材料进行微小孔钻削性能对比试验,研究了进给速度与切削力和扭矩的关系,分析了刀具的磨损特征以及孔的表面质量和孔入口处的毛刺情况。结果表明：DLC涂层硬质合金钻头比普通硬质合金钻头和TiC涂层硬质合金钻头更适合加工钛合金材料微小孔。