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 .     

Investigation of the feasibility and effectiveness in using heat pipe-embedded drills by finite element analysis

Drilling is a sufficiently severe machining process coupled with thermomechanical effect, in which mechanical work is converted to heat through the plastic deformation involved in chip formation and friction between tool and workpiece. The elevated temperature at the tool–chip interface has deleterious effects on the dimensional accuracy of the workpiece and shortens the service life of the tool. In this paper, the feasibility and effectiveness of heat pipe cooling in drilling operations are investigated numerically. A new embedded heat pipe technology was utilized to remove the heat generated at the tool interface in the foregoing cutting process. Numerical studies involved four different cooling conditions, i.e., dry drilling, fluid cooling, heat pipe cooling, and heat pipe cooling with cutting fluid supplied. The thermal, structural static, and dynamic characteristics of the drill were investigated using a numerical calculation with fast finite element plus solvers based on explicit finite element analysis software COSMOS\works. The results demonstrate that the heat pipe drill is most feasible and effective in the actual drilling processes.     

Effects of different cooling conditions on twist drill temperature

In the past, many researchers have studied wear developed on drilling tools mainly due to the high temperatures generated which accelerate thermally related wear mechanisms and thereby reducing tool life. This paper deals with an experimental investigation on the effect of an internal coolant approach (for different air pressure) on drill bit temperature, comparing it with an external coolant approach and dry cutting. Drill temperatures were measured by inserting standard thermocouples through the coolant (oil) hole of TiN/TiAlN-coated carbide drills. Experimental studies have been conducted using Al 2014 alloy materials. In the drilling tests, cutting conditions had different spindle speeds, coolant approaches and feed rate values. 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) were employed to analyse the effect of coolant approaches and drilling parameters. The objective was to establish a model using multiple regression analysis between spindle speed, coolant (air) pressure and feed rate with the drill bit temperature. Mathematical models for drill bit temperature are proposed that agree well with the experiments.     

硬地层单牙轮-PDC钻扩联合钻头破岩特性

提出了新型单牙轮-PDC钻扩联合钻头,先依靠单牙轮破岩钻孔,释放地应力,产生岩石损伤,再助推PDC钻头刮切破岩。运用有限元法,建立钻扩联合钻头、双级PDC和常规PDC钻头破岩的非线性动力学模型。通过对岩石本构关系进行D-P准则描述以及确定岩石破碎的判据,分析钻扩联合钻头钻进硬地层的破岩机理,开展了3种钻头动态破岩过程的对比研究。结果表明：钻扩联合钻头在钻进过程中井底井壁的岩石应力得到明显释放,大大提高了岩层可钻性;在硬地层中钻扩联合钻头钻进速度提高的主要原因是拉应力破岩;钻扩联合钻头在硬地层钻进过程中的扭转振动大大降低,破岩效率更高,钻头寿命更长;由于单牙轮领眼破碎岩石的作用,钻扩联合钻头对井底岩石的冲击破碎能力更强,在硬地层中钻进更快。研究结果为新型单牙轮-PDC钻扩联合钻头的研发提供了参考。     

麻花钻的数学建模及钻削过程有限元分析

为预测麻花钻的几何参数及钻削用量对钻削力和钻削温度的影响,通过对标准麻花钻的几何造型及锥面磨法的研究,用UG做了3D实体模型,基于Deform3D建立了有限元模型,并对钻削过程的钻削力和钻削温度的分布做了仿真研究。结果表明,扭矩、轴向力和切削温度均随麻花钻的直径增加而增大,随进给量的减小而降低。     

可转位浅孔钻的实体建模及网格划分

可转位浅孔钻内外刀片的径向非对称分布,导致钻削时将会产生径向合力,从而影响被加工孔的质量。为最大限度的减小加工时的径向合力,有效研究浅孔钻钻削过程,需借助有限元软件对其进行三维斜角切削分析。由于浅孔钻结构复杂,为创建有限元分析所需要的几何模型,采用Solid-Works软件建立可转位浅孔钻三维模型,并详细介绍了其建模过程;同时在有限元分析软件ANSYS里对其进行网格划分,为后续浅孔钻的应力、应变等分析做好充分准备工作。     

Modeling transverse motions of a drill bit for process understanding

A model for drill bit transverse motions is proposed that identifies process conditions affecting hole quality and helps in the interpretation of drilling signal patterns produced during the hole-making process. A two-dimensional model of a drill rotating in a hole with clearance is presented. The simulation results, drilling force signal patterns, and hole geometry were found to be in close agreement. Drill rotation speed, drill stiffness, structural damping, drill hole clearance, and amplitude modulation of the forces acting on the drill appear to have a significant effect on drill bit transverse motions and on hole quality.     

不同沟形金刚石钻头刚度和强度的有限元分析

利用Pro/E建立金刚石钻头的三维模型,模拟钻削过程中钻头受力情况.应用ABAQUS有限元分析软件研究不同排屑沟槽、不同径向截形金刚石钻头的刚度和强度.并通过改变钻芯厚度、螺旋槽长度及螺旋角度等结构参数,研究钻头结构参数变化对钻头扭转刚度、弯曲刚度、轴向抗压刚度的影响规律.     

Drilling of woven glass fiber-reinforced plastic—an experimental and finite element study

Drilling in woven fiber-reinforced plastics is a well-known practice in modern-day manufacturing. The high fracture toughness of woven fiber-based composites over unidirectional counterparts is increasing demand in aviation and electronics industries. Hence, failure of these materials at harsh environments is a matter of concern. Very few numerical studies on drilling of these composites have been carried out; hence, the present scope may be considered as a trial de novo. Delamination was studied in the present work at different feed–speed combinations. Drilling responses were estimated using finite element as a numerical simulation tool. An equivalent elastic macromechanical model was assumed for the woven composite workpiece. A 3D drill bit was modeled using commercial CAD package Pro-Engineer and Ansys Autodyn was used as the solver environment. The simulation and validation experiments were carried out at planned feed–speed combinations. The effect of process parameters on exit and entry delamination is also documented. The thrust determined by finite element techniques showed good prediction with the experimental results.     

Thermal modeling of drilling process in titanium alloy (Ti-6Al-4V)

Abstract

In drilling in titanium alloys, heat trapped in a hole adversely affects tool life, hole surface quality and integrity. Therefore, modeling temperature distribution in drilling is vital for effective heat dissipation and improving quality of drilled surfaces. The existing numerical and finite element models consider only frictional heat, whereas the effect of shear heat generation and tertiary heat generation is neglected. In the present work, a comprehensive thermal model of the drilling process is developed by considering all heat generated in shear, friction and tertiary zones. The drill cutting edges are divided into a series of independent elementary cutting tools (ECT). The calculated heat flux loads are applied on an individual ECT in the finite element model to determine the temperature distribution and the maximum temperature around the cutting edge. The temperature in the drill was also measured experimentally with the help of an Infrared (IR) camera. The results of numerical simulations lie within the error of ～8.75% when compared to the prior studies, and ～5.41% when compared to our experimental work. The thermal model gives the temperature distribution, and the maximum temperature observed at the corner of cutting edge was 604.2°C at a cutting speed of 35?m/min.     

麻花钻加工20Cr的断屑仿真分析

利用有限元软件DEFORM-3D,对麻花钻钻削20Cr的断屑过程进行了仿真分析。根据塑性材料断裂强度理论,以切屑卷曲变形为断屑判据。通过模拟分析,得出了工件的等效应力、应变及其分布,以及工件上P点最大等效应变的变化规律,阐释了该点最大等效应变与切屑卷曲变形的正相关性。提出并验证了P点最大等效应变的峰值可作为麻花钻加工20Cr的断屑判据。     

Design and experimental study of an end effector for robotic drilling

This paper presents the development of a drill end effector for use on industrial robots. The end effector has low weight and high rigidity. The drill end effector is fully programmable and will realize different drilling mode. The real-time force feedback can detect dull or broken bits, drill to breakthrough, and plot thrust force while drilling. Additionally, the end effector can also be equipped with a coolant/lubricant device. Based on the drill end effector, an experimental study on dry drilling of Ti-6Al-4V alloy and 7075-T6 alloy bimetal stacks was performed by using an uncoated cemented carbide drill. The hole quality (hole size, surface roughness) and thrust force were evaluated at various spindle speeds, feed rates, stacking sequence, and clamp force. This study indicates that the spindle speed and feed rate have an effect on the hole quality and thrust force by means of changing the temperature and plastic deformation of cutting zone. The results show that drilling 7075-T6 alloy firstly would be most efficient because of the high hole quality and the low thrust force. It was also found that high clamp force is helpful to improve the hole quality.     

An experimental investigation of the effect of coatings and cutting parameters on the dry drilling performance of aluminium alloys

As a result of the need to automate assembly in the aircraft industry, along with economic and ecological reasons, industry and research institutions have been pushed to develop dry drilling for aluminium alloys to eliminate the need for cooling fluids. The main difficulties in dry drilling are accelerated tool wear due to workpiece material adhesion on the tool and the formation of bigger-sized burrs. This paper describes an experimental research study on machinability in the dry drilling of aluminium alloys and on the potential of the new design of tools and coatings. Dry drilling tests were performed using uncoated drills and two different coatings produced by means of an arc evaporation PVD process. Experiments consisted of machining with a 10-mm diameter three-edged drill to produce 25-mm deep holes. Tool wear evolution and burr size were analysed, as well as the impact of the process parameters on torque, power, feed force and tool temperature.     

麻花钻钻削钼圆材料过程有限元分析

通过对标准麻花钻数学模型的研究,用Deform 3D建立了麻花钻钻削钼材料的有限元模型,并对钻削过程的应力应变、钻削温度和钻削轴向力的情况做了仿真研究。结果表明切削温度和轴向力都随麻花钻的转速及进给量的增加而增大,而选择合适的转速和进给量能使得材料的应变变小,切削形状良好。为钼材料的钻孔加工,工艺参数的选择提供了相关的理论依据。     

Artificial neural network based tool condition monitoring in micro mechanical peck drilling using thrust force signals

Micro scale machining process monitoring is one of the key issues in highly precision manufacturing. Monitoring of machining operation not only reduces the need of expert operators but also reduces the chances of unexpected tool breakage which may damage the work piece. In the present study, the tool wear of the micro drill and thrust force have been studied during the peck drilling operation of AISI P20 tool steel workpiece. Variations of tool wear with drilled hole number at different cutting conditions were investigated. Similarly, the variations of thrust force during different steps of peck drilling were investigated with the increasing number of holes at different feed and cutting speed values. Artificial neural network (ANN) model was developed to fuse thrust force, cutting speed, spindle speed and feed parameters to predict the drilled hole number. It has been shown that the error of hole number prediction using a neural network model is less than that using a regression model. The prediction of drilled hole number for new test data using ANN model is also in good agreement to experimentally obtained drilled hole number.     

钻铤螺纹粘扣失效有限元分析

钻铤在井眼中受力复杂,在正常的旋转钻井过程中要承受预紧、拉压、扭转、弯曲、内外压力等多种静载荷或动载荷,此外,还要受到钻井液和地层介质的腐蚀作用。因此钻铤失效事故频繁发生,严重地影响了钻井工程的正常进行。钻铤螺纹粘扣是主要失效形式之一,本文建立了普通API钻铤螺纹连接部位的有限元模型,并用有限元方法分析了在不同钻压条件下的应力分布情况,确定了引起这种失效形式的主要因素是由于井深加大产生的压载不断增大。在钻铤材料确定的情况下,只能通过提高钻铤本身抗粘扣性能来避免发生这种失效。     

A fundamental investigation on rotating tool cold expansion: numerical and experimental perspectives

In this study, we present the development of a novel technique for cold expansion using a rotating tapered mandrel that friction processes the cylindrical wall of the fastener hole and simultaneously cold expands it. The developed technique, named as rotating tool cold expansion (RTCE), is experimentally and numerically investigated. A 3D thermomechanical finite element model for predicting the compressive residual stress, responsible for delaying crack propagation from the edges of the holes, is introduced. The efficacy is that RTCE is assessed for varying degrees of cold expansion under different lubricating conditions at the tool–workpiece interface, such as dry, metal working fluid, and nanopowder. The plastic deformation combined with friction stirring at the tool–workpiece interface helps the RTCE in controlling the surface damage at entry and exit of the hole that is most often observed with the conventional cold expansion technique. Enhanced friction due to the nanopowder at the tool–workpiece interface helps in sustaining efficacy of the RTCE even at a higher degree of cold expansion which otherwise leads to surface damage with other mediums.     

BTA深孔钻射流孔参数的优化与仿真

针对射流孔几何参数对BTA深孔钻喉部流场的影响,对射流孔直径、角度与射流孔距离喉部的位置进行有限元数值模拟,提出一种最优的新型喉部结构。在设置有限元模型的湍流强度和耗散率基础上,进行不同几何参数的深孔钻头喉部结构的排屑能力对比试验,测量冷却液系统的冷却液出口断面流出平均速度。试验结果表明:最优喉部结构为∅38mm BTA深孔钻头所组成的冷却系统,冷却液出口断面流出的平均速度提高9.6%,同时提高了冷却液系统整体的排屑能力。由相似定理得出,冷却液系统的排屑能力提高9.6%。     

HIGH THROUGHPUT DRILLING OF TITANIUM ALLOYS

The experiments of high throughput drilling of Ti-6Al-4V at 183 m/min cutting speed and 156 mm3/s material removal rate using a 4 mm diameter WC-Co spiral point drill are conducted. At this material removal rate, it took only 0.57 s to drill a hole in a 6.35 mm thick Ti plate. Supplying the cutting fluid via through-the-drill holes and the balance of cutting speed and feed have proven to be critical for drill life. An inverse heat transfer model is developed to predict the heat flux and the drill temperature distribution in drilling. A three-dimensional finite element modeling of drilling is con-ducted to predict the thrust force and torque. Experimental result demonstrates that, using proper machining process parameters, tool geometry, and fine-grained WC-Co tool material, the high throughput machining of Ti alloy is technically feasible.     

A sustainability comparison between drilling and milling for hole-enlargement in machining of hardened steels

Abstract

Hole-making is one of the most important processes of metal shaping domain. Although, drilling is a commonly used approach to cut holes in metallic parts, the process cannot be completed with the cutting action of one drill bit if the work material is hard and diameter of the hole is large. Usually, a drill having diameter equal to the required diameter of the hole is utilized to enlarge a predrilled hole of a smaller diameter. In this work, we have investigated sustainability of using another method of enlarging a pre-drilled hole, namely side and end milling and compared it with the drilling-based approach. The work material used in the study is a high carbon steel, which is heat-treated to two distinct levels of surface hardness. Besides process type and work material hardness, the other two parameters tested in the investigation are cutting speed and depth of hole. A total of 16 experiments were performed to generate data regarding the sustainability measures, namely hole surface roughness, specific cutting energy and tool wear. Process choice (drilling or milling) for hole-enlargement was found to possess a significant effect on all the measured responses. Analyses carried out on the experimental data revealed that although the drilling-based option led to an immensely better surface finish, the milling-based option performed better with respect to the other measures of economic and environmental sustainability.