Active brazed ceramic cemented carbide compound drills for machining lamellar graphite cast iron

The optimum and efficient way of machining is linked to the choice of the most appropriate cutting tool and cutting tool material. High performance cutting ceramics are characterized by excellent hardness properties at elevated temperatures. For this reason, cutting ceramics meet the requirements for machining with high cutting speeds to increase process productivity. Whereas cutting ceramics are widely used in turning and milling operations, their use in drilling processes, using ceramic insert tipped tools, is limited to larger diameter applications due to design restrictions. Beyond small diameters, solid ceramic tools were of negligible interest for industrial applications owing to their excessive tool manufacturing costs. This paper presents a new tool concept which addresses this challenge and permits a more productive machining process for drilling small diameter holes using ceramics as the cutting material. An active brazed compound drill combines the advantageous properties of ceramics and cemented carbide as the cutting tool material and basic holder material, respectively. The investigations presented here describe the manufacturing chain as well as the application of a compound drill, and compares it to a widely used industrial reference tool.     

Prediction of chatter in NC machining based on a dynamic cutting force model for ball end milling

Ball end milling is one of the most widely used cutting processes in the automotive, aerospace, die/mold, and machine parts industries, and the chatter generated under unsuitable cutting conditions is an extremely serious problem as it causes excessive tool wear, noise, tool breakage, and deterioration of the surface quality. Due to the critical nature of detecting and preventing chatter, we propose a dynamic cutting force model for ball end milling that can precisely predict the cutting force for both stable and unstable cutting states because our uncut chip thickness model considers the back-side cutting effect in unstable cutting states. Furthermore, the dynamic cutting force model considers both tool runout and the penetration effect to improve the accuracy of its predictions. We developed software for calculating the cutting configuration and predicting the dynamic cutting force in general NC machining as well as single-path cutting. The chatter in ball end milling can be detected from the calculated cutting forces and their frequency spectra. A comparison of the predicted and measured cutting forces demonstrated that the proposed method provides accurate results.     

Machining characteristics and fracture morphologies in a copper-beryllium (Cu-2Be) alloy

The technology of materials removal is improved greatly by the introduction of advanced cutting tools like cubic boron nitride, ceramics, polycrystalline diamond and the more recent whisker-reinforced materials. In this paper, the influence of cutting temperature on machinability, mechanical properties, microstructure, and fracture morphology of Cu-2Be alloy using a polycrystalline diamond cutter is investigated. The information on machining, microstructure, and fracture morphology of Cu-2Be alloy are very useful to understand their fabrication characteristics and the basic mechanisms of its deformation and fracture. The machinability (in terms of surface finish) of Cu-2Be alloy is evaluated as a function of cutting temperature, resulting from wet and dry cutting. Machining is carried out on a Hardinge Cobra 42 CNC machine (Hardinge Inc., Elmira, NY), and the machining parameters used—cutting speed, depth of cut, and feed rate—are kept constant during both wet and dry cutting. The machined surface finish on Cu-2Be alloy is measured using a surface finish analyzer (Surftest 401, series 178) technique. The machined specimens are examined for their strength and hardness properties using a standard Universal Testing Machine and Rockwell hardness tester, respectively. Wet cutting (using coolants) produced a smooth surface finish when compared with dry cutting of the Cu-2Be alloy. The machined specimens are examined for their microstructural features using a Nikon optical microscope. The specimens are etched using a suitable etchant solution for revealing such microstructure constituents as grain size, phase proportions, and the possible overheated areas (especially in dry cutting). The fractured surfaces from the tensile and impact toughness tests are investigated for their fracture morphologies (dry and wet cutting) using a microprocessor-controlled scanning electron microscope (Jeol Model JSM 5910 LV). A detailed analysis is also made to understand and interpret the basic fracture mechanisms responsible for crack initiation and crack propagation. The Cu-2Be alloy showed relatively higher mechanical properties in wet cutting in comparison to dry cutting operations. Fracture studies demonstrated intergranular and ductile fractures as dominant modes of fracture mechanisms in Cu-2Be alloy.     

Analysis and influence of acetylene and propane gas during oxyfuel gas cutting of 1045 carbon steel

Many metal-manufacturing industries include oxyfuel cutting among their manufacturing processes because cutting and welding are often required in metal-cutting processes, specifically in the fabrication of pressure vessels and storage tanks. The oxyfuel cutting process uses controlled chemical reactions to remove preheated metal by rapid oxidation in a stream of pure oxygen. Previous research has demonstrated that metal cutting surfaces varied depending on the gas used for the combustion as well as the cutting speed (Vc) used during the process. In this research, AISI 1045 carbon steel was cut using an oxyacetylene and an oxypropane cutting process. Different tests, such as surface roughness, cut drag displacement, groove width, microhardness, and microstructure, were used to analyze the influence of the Vc and the combustion flame (oxyacetylene and oxypropane). The results showed, in general, better cut surfaces when using propane gas. Also, it was demonstrated that oxyacetylene cutting is almost 85% more expensive than oxypropane cutting.     

Cryogenic properties of some cutting tool materials

Cutting tool materials belong to a group of nonductile materials. Chipping and breaking of the cutting edge and fracturing of the tool are common types of tool failure even under conventional machining conditions. This leads to a concern about whether cutting tool materials are able to maintain their strength and toughness and withstand the low-temperature thermal shock during cryogenic machining. The objective of this investigation was to study the behaviors of these kinds of materials at cryogenic temperatures. The results will also serve as a basis in selecting the suitable cutting tool materials for cryogenic machining and in determining the cryogenic strategy and optimum cutting conditions. Several representative cutting tool materials, such as five grades of commercial carbide-cobalt alloys and M46 highspeed steel, are investigated in terms of microstructural observation, impact testing, transverse rupture strength measurement, and indentation testing. It has been shown that carbide tool materials generally retain their strength and toughness as the temperature decreases to liquid nitrogen temperature. The behaviors of carbide tool materials at cryogenic temperatures can be explained in terms of the temperature effects on the binder phase.     

Optimizing the use of dry cutting in rough turning steel operations

The main objective of using cutting fluids in machining operations is the reduction of temperature in the cutting region to increase tool life. However, the advantages offered by cutting fluids have been strongly debated because of their negative effects on the economic aspect, the environment and the health of workers using them. A trend to solve these problems is cutting without fluid, a method named dry cutting, which has been made possible due to technological innovations. This work aims to seek conditions in which dry cutting is satisfactory compared with the flood of fluid (called here wet cutting) usually used. Aiming at this goal, several experiments were carried out varying parameters such as cutting speed, feed, depth of cut and tool material in rough turning of ABNT 1045 steel in dry and wet cutting. The analysis of the results showed that wet turning is, as expected, better for tool life. The second conclusion is that dry cutting cannot be used with large depth of cut. But the main conclusion is that, if the tool material is changed to a more wear resistant one, dry cutting can be used with results very similar to those obtained with a flood of fluid.     

Active compensation for portal machines

The cutting performance of a machine tool is mainly determined by its static and dynamic behavior. During a cutting process high static and dynamic forces may occur, which result in instabilities of the cutting process. Especially, long protruding structure components, such as z-slider of a portal machine, represent a distinct weak spot concerning their structural behavior. The structure integrated compensation modules represent a new approach to compensate static and dynamic deformations of slider structures and help to achieve a considerable improvement of their compliancy behavior.     

基于Design Explorer的激光切割机横梁优化设计

以某型激光切割机横梁为研究对象,使用ANSYS Design Explorer优化设计模块,将激光切割机横梁的加强筋尺寸、壁厚、矩形孔作为主要的优化参数,在该横梁原强度和刚度不变的前提下对其进行轻量化设计。分别使用优化前后的2个横梁进行工件切割试验,试验结果表明:优化后该横梁的总变形、应力、应变最大值有所下降且分布得到改善,切割工件的切割质量得到提升,质量减少了10.5%。     

不同冷却喷雾场下硬质涂层刀具切削蠕墨铸铁性能研究

研究在复合喷雾油膜附水滴冷却时,3种不同结构喷嘴的喷雾场及在硬质涂层刀具切削蠕墨铸铁过程中的切屑流向,并分析刀具和喷射位置对切削力的影响。研究表明:与普通圆柱型和扁平型喷嘴相比,尖嘴型喷嘴的雾化效果更佳,无大液滴现象,喷雾集中,连续雾化稳定。在硬质涂层刀具切削加工蠕墨铸铁过程中,当喷雾场只作用于刀具前刀面时,普通圆柱型喷嘴和尖嘴型喷嘴有良好的断屑作用;而尖嘴型喷嘴和扁平型喷嘴对切屑流具有更好的导向性。相对干切削和冷风辅助切削,尖嘴型喷嘴与外冷复合喷雾条件下切削蠕墨铸铁时,切削力可减小30～60 N,其中喷雾场喷射在刀具前刀面时的切削力最低。不同硬质涂层刀具需要与外冷复合喷雾的喷射位置相互匹配以达到最小的切削力。      

Mechanics of machining of face-milling operation performed using a self-propelled round insert milling cutter

There has been a renewed interest in the technology of rotary tools because of their ability to perform more productive machining and the concurrent evolution of a number of new ‘difficult-to-machine’ materials. This paper presents an investigation into the application of rotary tools in a face-milling operation. The work involved analysis of cutting forces and chip characteristics, and the development of analytical as well as conceptual models to predict the cutting forces. It was evident that the proposed model predicts cutting force magnitude with a fair accuracy.     

Statistical analysis of the effects of machining parameters and workpiece hardness on the surface finish of machined medium carbon steel

The objective of this study is to ascertain the effect of machining parameters and workpiece hardness on surface roughness of machined components and to develop a better understanding of the effect of process parameters on the machined surface. Such an understanding can provide insight into the problems of controlling the finish of machined surfaces when the process parameters are adjusted to obtain a certain surface finish. The collected data were analyzed using parametric analyses of variance (ANOVA) with surface finish as the dependent variable and hardness of the workpiece material, cutting tool position from the surface of the clamping device (chuck), depth of cut, cutting velocity, and cutting feed as independent variables. The results showed that surface roughness is significantly affected by the workpiece hardness, cutting feed, cutting speed, depth of cut, cutting tool position from the chuck, and their interactions with each other. The results suggest that feed rate and cutting speed can be adjusted to produce a certain surface finish when the position of the cutting tool from the surface of a clamping device or the hardness of the workpiece is changed.     

PCD和CVD金刚石刀具切削性能对比及失效机理初探

通过切削实验,观察切削前后刀具的表面和刃口形貌、金刚石刀片组成成分、以及被加工工件表面粗糙度,比较两种刀具的切削性能,探讨其失效机理。结果表明:在同等条件下,CVD金刚石刀具的切削性能要明显优于PCD刀具。在车削过程中,PCD刀具的失效机理主要是结合剂与被加工材料中化学成分发生化学反应使结合剂流失,导致刀具结构疏松,从而导致磨粒团脱落。CVD刀具的失效机理为产生变质层磨损。切削过程中随着加工时间的进一步延长,切削区温度不断升高,当达到热化学反应温度时,就会在刀具表面形成变质层,从而带来切削过程中刀具的磨损;同时高温状态下CVD金刚石的晶界疲劳破坏,也可能会造成CVD金刚石刀具的磨损失效。     

An experimental investigation on effect of minimum quantity lubrication in machining AISI 1040 steel

The growing demands for high productivity of machining need use of high cutting velocity and feed rate. Such machining inherently produces high cutting temperature, which not only reduces tool life but also impairs the product quality. Application of cutting fluids changes the performance of machining operations because of their lubrication, cooling, and chip flushing functions. But the conventional cutting fluids are not that effective in such high production machining, particularly in continuous cutting of materials likes steels. Minimum quantity lubrication (MQL) presents itself as a viable alternative for turning with respect to tool wear, heat dissipation, and machined surface quality. This study compares the mechanical performance of MQL to completely dry lubrication for the turning of AISI-1040 steel based on experimental measurement of cutting temperature, chip reduction coefficient, cutting forces, tool wears, surface finish, and dimensional deviation. Results indicated that the use of near dry lubrication leads to lower cutting temperature and cutting force, favorable chip–tool interaction, reduced tool wears, surface roughness, and dimensional deviation.     

Effect of cutting parameters on pitting corrosion resistance of S32760 duplex stainless steel

To improve the performance in service of S32760 duplex stainless steel (DSS) in the marine environment, the influence of cutting parameters of S32760 DSS on the pitting corrosion resistance of the workpiece is studied. Cutting experiments are performed on S32760 DSS by varying the cutting parameters to investigate their effects on the surface morphology. The electrochemical experiments are conducted on the workpiece immersed in the 3.5 wt% sodium chloride solution to investigate how the cutting parameters affect the pitting corrosion resistance of S32760 DSS. The results indicate that the pitting corrosion resistance is influenced by the cutting speed and feed rate, which in turn affects the surface roughness. The cutting depth does not have a significant impact on the surface roughness but significantly affects the pitting resistance. The recommended cutting parameters are as follows: feed rate of 0.1 mm/r, cutting speed of 130 m/min, and cutting depth of 0.4 mm.     

基于需求分类遗传算法的Al/15% SiC_p复合材料电化学加工工艺参数的优化

电化学加工（ECM）是一种重要的非传统加工工艺,主要用于加工难加工材料和错综复杂的型材。作为一个复杂的过程,很难确定最优参数去改善切削性能。金属去除率和表面粗糙度是最重要的输出参数,决定切削性能。由于切削参数对金属去除率和表面粗糙度的影响不一致,从而没有简单的切削参数的最佳组合。用多元回归模型来表示输出与输入变量之间的关系,并用基于需求分类遗传算法（NSGA-II）的多目标优化方法来优化ECM过程,得到一个需求解集。     

二维超声加工淬硬钢的建模与参数优化

利用正交设计方法研究了硬质合金刀具二维超声加工(UEVC)淬硬钢Cr12Mo V时切削用量的三个因素对加工表面粗糙度和切削力的影响,并利用信噪比、方差及贡献率等方法对各因素间的相互作用进行了分析。以切削参数为独立变量,以切削力和表面粗糙度为响应,利用回归分析建立数学模型。实验结果表明:进给量是对表面粗糙度(Ra、Rz)影响最大的因数,贡献率分别为91.8%和88.8%;其次是切削深度,贡献率分别为3.72%和9.77%;对切削力(Fz)影响最大的二个因素是进给量和切削深度,贡献率分别为56.69%和38.46%;切削速度对表面粗糙度、切削力的贡献率均最小。此外,建立的回归方程对Ra、Rz和Fz均有很高的可决系数,分别为91.8%、94.3%和88.2%,说明所建线性回归模型的准确性。     

车床复合循环指令应用的若干问题及解决途径

应用数控车床复合循环指令时,使用不同的指令切削效率不同.G71指令的使用可能导致的零件加工误差、刀具寿命降低以及复合循环指令应用的换刀问题等,可以通过混合编程与切削参数的设定等措施来解决.只要合理使用复合循环指令,就能利用它的优势发挥作用.     

Quantification of the chip segmentation in metal machining: Application to machining the aeronautical aluminium alloy AA2024-T351 with cemented carbide tools WC-Co

The chip segmentation process has a significant effect on the cutting force fluctuation during machining which could affect tool vibration and tool wear. This paper deals with a quantitative analysis of the chip segmentation phenomenon in metal machining. The notion of intensity of the phenomenon has been introduced. Various parameters have been proposed for this purpose. These parameters are based on dimensional characteristics of the segmented chip and the strain distribution within the chip. A Finite Element based modelling has been developed to simulate the chip formation process in the case of machining aeronautical aluminium alloy AA2024-T351 with WC-Co based cutting tools. From the simulated chip morphologies, introduced chip segmentation parameters are assessed. The impact of the cutting speed and tool geometry on the chip segmentation intensity is clearly highlighted. The relevance of each parameter is discussed. Cutting force and contact length fluctuations with respect to the cutting speed variation when segmentation occurs are discussed and deeply analysed. A correlation between average cutting force reduction and segmentation intensity when the cutting speed increases as well as between chip formation process and cutting force oscillation has been established thanks to the introduced parameters, showing thus their usefulness.     

YW2切削AISIH13钢切屑形成的试验与数值研究

文章以YW2对AISIH13钢进行切削及数值模拟实验。扫描电子显微镜和能谱散射仪被用于切屑微观形貌观察及成份分析。实验结果表明,切削用量对切屑形态的影响显著;切削热促使切屑表面氧化。模拟结果显示切屑温度高达700℃左右,其应力应变分布有助于"卷曲"生长,呈螺旋状;切屑发生碰撞而折断,其临界断裂应力与应变分别为702MPa及1.65mm/mm。     

The influence of solid lubricant particle size on machining parameters in turning

Turning is one of the most fundamental and indispensable processes of metal removal in industry. The heat generated in the cutting zone during turning is critical in deciding the workpiece quality and tool life. Though cutting fluids are widely employed to carry away the heat in metal cutting, their usage poses threat to ecology and the health of workers. Hence, there arises a need to identify eco-friendly and user-friendly alternatives to conventional cutting fluids. Modern tribology has facilitated the use of solid lubricants. The present work features a specific study of the application of solid lubricant in turning. The process performance is judged in terms of cutting force, tool temperature, tool wear and the surface finish of workpiece, keeping the cutting conditions constant. The results obtained from the experiment show the effectiveness of the use of the solid lubricant as a viable alternative to dry and wet machining. The unique utility of solid lubricant is highlighted.