Comparative analysis of chipping mechanics of float glass during rotary ultrasonic drilling and conventional drilling: For multi-shaped tools

Float glass has immense applications such as sensor glass, micro-processor glass and decorative glass; because of its exceptional wear resistance, chemical and thermal characteristics. Nevertheless, researchers are still bearing decisive issues, which affect its application. These issues are profile inaccuracy and chipping because of its poor machining characteristics and hence high precision machining. The objective of the present study is to condemn the chipping related hindrances while using multi-shaped diamond abrasive tools to create blind holes. The tools, which applied, are named as hollow abrasive tool, pinpointed conical tool, flat cylindrical tools and concave circular tool. The experimental trials were performed by rotary ultrasonic drilling (RUD) and CNC conventional drilling (CD). The actual industrial conditions and parameters were considered throughout the experimentation. Physics behind the formation of chipping on hole periphery by RUD and CD are revealed. In addition, individual mechanisms of multi-shape tools with respect to chipping are analyzed. The results show that RUD process has attained the smallest measurement of chip radial distance as compared to CD for all types of tool. Finally, the concave circular tool is found as the best tool particularly to get least chip radial distance during drilling i.e. 0.1145?mm.     

SiC陶瓷旋转超声振动套磨制孔有限元仿真及实验研究

为解决SiC陶瓷加工时容易出现崩边、裂纹等问题,结合仿真与实验对其进行旋转超声振动套磨制孔技术研究。根据SiC陶瓷宏观力学本构模型,建立SiC陶瓷制孔仿真有限元模型并进行加工过程仿真分析,相比常规制孔,超声振动制孔的仿真轴向力最大可减小26.1%。常规加工和超声振动加工的对比实验研究表明,旋转超声振动加工可减小轴向力达32.9%,可大幅减少陶瓷材料脆性断裂,显著改善孔壁表面质量。有限元仿真与实验研究所得的轴向力在超声振动下最大相差7.5%,常规条件下两者最大相差14%,验证了有限元模型的正确性。仿真和实验研究结果表明：超声振动加工可显著减小轴向力和刀具磨损、提高刀具耐用度、改善制孔质量、降低加工成本。     

ROTARY ULTRASONIC MACHINING OF CARBON FIBER-REINFORCED POLYMER: FEASIBILITY STUDY

Carbon fiber-reinforced polymer (CFRP) has been widely used in aircraft components, automotive parts, and sporting goods. Hole machining is the most frequently employed operation of secondary machining for fiber-reinforced composites. However, challenges (delamination, splintering, burr, short tool life, low machining precision, and low surface quality) still remain for their widespread applications. Rotary ultrasonic machining (RUM) is a non-conventional machining process that has been used to drill holes in composite materials. However, it has not been used to drill this type of CFRP. In this article, RUM is introduced into drilling holes in this type of CFRP for the first time. The feasibility to machine carbon fiber-reinforced epoxy using RUM is investigated experimentally. Chips, edge chipping, surface roughness, tool wear, and thrust force were measured. Effects of RUM process variables (rotation speed, vibration amplitude, and feedrate) on thrust force and surface roughness were studied. Results showed that RUM could be used to drill holes in CFRP with high productivity and low tool wear. A better surface was produced by higher rotation speed and lower feed rate.     

超声波振动钻削微小孔的研究

对采用超声波振动钻削微小孔时钻头的寿命、出口毛刺和加工表面粗糙度等问题进行了研究。结果表明,超声波振动钻削明显优于普通钻削。     

飞机紧固孔超声振动精密加工技术研究

针对飞机蒙皮复合材料与钛合金叠层(简称复钛叠层)紧固件大孔传统手工多步制孔加工中存在的工艺路线长、加工质量不高、刀具寿命低等问题,开展了超声精密制孔技术的研究,提出了超声振动套-铰-锪的新工艺方法,并研制了超声振动制孔工具系统。实验结果表明,超声振动套-铰-锪新工艺方法及振动制孔工具系统可以高质、高效、低成本加工复钛叠层紧固件大孔,能满足飞机复钛叠层紧固孔精密装配的工业要求。     

Chipping minimization in drilling ceramic materials with rotary ultrasonic machining

Ultrasonic machining (USM) has been considered as a new cutting technology that does not rely on the conductance of the workpiece. USM presents no heating or electrochemical effects, with low surface damage and small residual stresses on workpiece material, such as glass, ceramics, and others; therefore, it is used to drill microholes in brittle materials. However, this process is very slow and tool wear dependent, so the entire process has low efficiency. Therefore, to increase microhole drilling productivity or hole quality, rotary ultrasonic machining (RUM) is considered as a strong alternative to USM. RUM, which presents ultrasonic axial vibration with tool rotation, is an effective solution for improving cutting speed, precision, tool wear, and other machining responses beyond those of the USM. This study aims to reduce the microchipping or cracking at the exit of the hole, which inevitably occurs when brittle materials are drilled, with consideration of tool wear. To this end, response surface analysis and desirability functions are used for experimental optimization. The experimental results showed that the proposed RUM scheme is suitable for microhole drilling.     

Experimental study of rotary magnetic field-assisted dry EDM with ultrasonic vibration of workpiece

Dry electrical discharge machining (EDM) is a green machining method which replaces the gas instead of liquid as dielectric medium. Due to the environmentally friendly nature of this method, recently, researchers focused on characterization of this process. In this work, effects of rotary magnetic field and also ultrasonic vibration of workpiece were studied on dry EDM process performance. Conducted experiments were divided in two main stages. At first stage, preliminary experiments were carried out to determine the best tool design in material and geometry points of view by considering the material removal rate (MRR). Also, effect of magnetic field was studied in the first stage. Results of the first stage of experiments indicated that the brass tool with two eccentric holes has the highest MRR rather than the other existing tool. In the second stage of experiments, parametric study on dry EDM process were implemented by using a brass tool with two eccentric holes and by applying rotary magnetic field for all experiments of the second stage. Influences of parameters such as pulse current, pulse on-time, pulse off-time, tool rotational speed, air injection inlet pressure, and especially power of ultrasonic table were studied on MRR, surface roughness (SR), electrode wear rate (EWR), and overcut (OC). Results showed that magnetic field has positive effects on MRR and SR. Also, by application of ultrasonic vibration achieving to superior MRR is feasible. At the end of the work, mathematical models were developed to correlate a relationship between process inputs and main outputs.     

Mathematical model for cutting force in rotary ultrasonic face milling of brittle materials

Rotary ultrasonic machining of brittle materials, such as glass, ceramics, silicon, and sapphire, has been explored in a large number of experimental and theoretical investigations. Mechanistic models have been developed to predict the material removal rate or cutting force in the rotary ultrasonic machining of brittle materials. However, most merely describe the rotary ultrasonic machining process of drilling holes in brittle materials. There are no reports on the development of a cutting force model for flat surface rotary ultrasonic machining, i.e., rotary ultrasonic face milling. This paper presents a mathematical model for the cutting force in the rotary ultrasonic face milling of brittle materials under the assumption that brittle fracture removal is the primary mode of material removal. Verification experiments are conducted for the developed cutting force model and show that the trends of input variables for the cutting force agree well with the trends of the developed cutting force model. The developed cutting force model can be applied to evaluate the cutting force in the rotary ultrasonic face milling of brittle materials.     

硬脆材料超声振动钻磨表面特征试验研究

将超声振动引入普通钻磨中,对不同加工参数时普通钻磨和超声钻磨两种模式下的表面粗糙度进行了试验分析,并对超声与普通钻磨过程中的被加工表面微观形貌进行了试验研究.结果表明,超声振动钻磨加工是适合硬脆材料等的一种高效加工方法.     

Effect of backstitch tool path on micro-drilling of printed circuit board

As electronic components have become smaller, micro-drilling tools have been developed and used to drill holes in the hundred-micrometer range on printed circuit boards. To improve the productivity of the drilling process, printed circuit boards are generally stacked in several layers and drilled simultaneously. In this process, however, misalignment of the drilled holes on the top and bottom layers occurs, and this consequently degrades the overall product quality. To solve this problem, a new tool path strategy is proposed, which we refer to as the backstitch tool path. The basic scheme of the suggested strategy is to make a balance on the substrate. We compared this approach with a conventional tool path by examining the hole positioning error, drilling thrust force, drilling torque, and drilling duration under various drilling conditions. The effects of each process parameters were analyzed, and the suggested backstitch tool path has a positive effect on low bending stiffness tool, too much adjacent holes, and higher in-feed rate, respectively. Applying the backstitch tool path strategy to a micro-drilling operation improved the productivity and product quality.     

Experimental Investigation on Electrical Discharge Drilling of Ti-6Al-4V Alloy

This article describes the experimental investigation related to creation of holes in aerospace titanium alloy workpiece using static electrode machining and electrical discharge drilling (EDD) process. Special attachment for holding and rotating the tool electrode was developed and installed on electrical discharge machining (EDM) machine by replacing the original conventional tool holder provided on die sinking EDM. The effect of input parameters such as gap current, pulse on-time, duty factor and RPM of tool electrode on output parameters for average hole circularity (C_a) and average surface roughness (R_a) have been studied. It is observed that the effect of rotating electrode machining has considerable influence on the output parameters over stationary electrode machining. The micro-graphs and photographs of few selected samples were taken by SEM and metallurgical microscope, which also commensurate with the findings of the study.     

旋转超声钻削加工的研究现状及发展趋势

针对硬脆材料加工孔过程中出现的各种问题,选择一种有效的加工方法显得尤为重要。而旋转超声钻削加工已经成为一种有效的特种加工方法,其应用前景可观。综述了旋转超声加工技术的加工机理及发展历程,概述了国内外学者在硬脆材料工艺特性及装备研发等方面的研究成果,重点阐述了近年来国内外研究者在旋转超声钻削加工孔工艺特性方面的主要研究成果,对旋转超声加工技术的发展趋势进行了展望。     

Structural alterations in the workpiece by ultrasonic drilling

The surface integrity of glass workpieces in ultrasonic drilling was investigated. X-ray diffraction studies on glass workpieces drilled by ultrasonic machining revealed the apparent formation of a layer of crystalline material on the surface of the holes drilled, a hitherto unreported phenomenon.     

Evaluation of micro-drilling technologies for metal-injection-molded 420 stainless steel

Metal-injection-molded (MIM) 420 stainless steel is a commonly used material for high-value products such as fuel injector nozzles. However, the trade-offs involved in using different micro-drilling processes on this material are not well-documented in literature. This article presents a micro-drilling study of MIM 420 stainless steel using four candidate processes: micro-electrical discharge drilling (micro-EDD), ultrasonically assisted micro-EDD, micro-mechanical drilling (micro-MD), and ultrasonically assisted micro-MD. The micro-EDD results shows that the use of ultrasonic vibrations significantly improves the overall process time, spark erosion efficiency, and material removal rate of the process. However, this improvement comes at the expense of increased tool wear and surface roughness, especially while machining under high-discharge-energy conditions. The micro-MD results show that the use of ultrasonic vibrations is beneficial in lowering the thrust force, drilling torque, and tool wear at chipload values greater than the minimum chip thickness of the material. However, the ultrasonic vibrations do not have a notable effect on the surface roughness or on the size of the exit burrs. The results obtained from this study have been used to develop a Likert-type comparison scale to enable application-specific selection of micro-drilling processes for MIM 420 stainless steel.     

Abrasive wear in ultrasonic drilling

Material removal in ultrasonic drilling is caused by the abrasives in the slurry. As a given charge of abrasive circulates, the mean particle size decreases and the initially sharp cutting edges become dull, reducing the machining rate. This paper discusses the mechanism of wear of the abrasive in ultrasonic drilling; the size of abrasives in the working zone governs machining rate, tool wear and production accuracy of the holes drilled     

超声振动改善深孔镗削加工质量

深孔加工在航空发动机制造过程中广泛存在,由于其刚性弱,静态让刀量大,导致加工颤振和刀具磨损严重,使得其加工质量难以得到保证。超声振动切削作为一种特种切削加工手段,具有降低切削力,提高系统刚性和抑制加工颤振等优势。将超声振动应用于深孔镗削,进行了断屑条件验证,孔径误差测量,已加工表面粗糙度测量以及表面形貌观测等试验。试验结果表明,超声振动镗削能够有效缓解深孔镗削过程中的堵屑问题,减小孔径误差和表面粗糙度,抑制切削颤振,从而改善深孔镗削加工质量。     

旋转超声钻削的切削力数学模型及试验研究

通过分析硬脆材料脆性断裂去除机理和旋转超声加工特点,确定旋转超声加工时单颗磨粒的切削时间、切削深度、切削速度及切削轨迹长度,建立旋转超声恒进给率钻削硬脆材料的切削力数学预测模型。光学玻璃加工试验研究表明,切削力随进给速度的增大而增大,随主轴转速的提高而减小;在高进给速度条件下,切削力对主轴转速的变化更为敏感,在低主轴转速条件下,切削力对进给速度的变化更为敏感;从而很好地验证了已建立的切削力数学预测模型。旋转超声加工和普通加工的对比试验表明,旋转超声钻削加工可以有效降低切削力,一定程度上减小出孔崩边尺寸,从而提高加工效率、降低加工成本。根据旋转超声加工的表面粗糙度值略高于普通加工,提出硬脆材料脆性断裂去除时磨粒实际切削深度决定加工表面粗糙度的判断。     

Al2O3工程陶瓷超声振动钻磨表面质量的试验研究

通过超声振动钻磨与普通钻磨的对比试验,研究了缓进给超声振动钻磨对工件表面微观形貌和表面粗糙度的影响。结果表明,超声振动钻磨可明显地提高A l2O3工程陶瓷表面的质量,是陶瓷精密加工的一种新方法。     

旋转超声磨削加工中刀具结合剂类型与加工性能的关系

实验分析了硬脆材料旋转超声磨削过程中刀具结合剂类型对加工性能的影响以便提高加工精度和加工表面的完整性.首先,采用能谱分析研究了铁基、陶瓷基和青铜基3种超声振动刀具中结合剂与金刚石颗粒的把持形式,并根据相同加工工艺条件下刀具磨损形式确定了把持力大小.然后,结合超声振动刀具特性,通过旋转超声磨削加工实验研究刀具结合剂类型与切削力、刀具磨损量、加工表面完整性的关系,并对实验结果进行了分析.实验结果表明:相对于陶瓷基和青铜基结合剂超声振动刀具,铁基结合剂超声振动刀具把持力最大,Z轴切削力平均值最小(为46.8 N);加工18 000 mm3材料后,刀具轴向磨损量最小(为0.1 mm);而陶瓷基结合剂超声振动刀具加工表面质量最好,表面粗糙度最大值为21.79 μm.结果证实铁基超声振动刀具适用于粗加工,陶瓷基超声振动刀具则适用于精加工.     

Surface quality evaluation in ultrasonic drilling through the Taguchi technique

Ultrasonic drilling of commercially pure titanium and titanium alloy (Ti-6Al-4v) was investigated in this study. During the experiments, process parameters such as work piece, grit size, slurry concentration, power rating and tools were changed to explore their effect on the surface roughness. Taguchi’s technique was applied to obtain an optimal setting of ultrasonic drilling (USD) process parameters. Average surface roughness (Ra) was measured by using the Optical Profiling System. Two-dimensional and three-dimensional contour plots were obtained from the profiling system to quantify and visualize the surface roughness. From the experimental results and further analysis, it is concluded that the effect of slurry concentration and grit size have a significant effect on surface roughness more than other parameters. In addition, the surface roughness is apparently similar in two and three dimensions as visualized from contour plots. Ultrasonic drilling is established as a material removal process with good surface quality.