Selection of optimal material and operating conditions in composite manufacturing. Part I: computational tool

The Genetically Optimized Neural Network System (GONNS) is proposed as a human-like decision-making tool for the selection of optimum composite material and operating conditions. Multiple neural networks represent the characteristics of the system after a training process and genetic algorithms find the optimum operating conditions. The error of the GONNS was found to be less than 1% when the neural networks-represented analytical functions and genetic algorithms were used to select the optimal conditions. The GONNS is very promising for many complex optimization problems when analytical equations are not available to represent the characteristics of the system.     

Influences of chip serration on micro-topography of machined surface in high-speed cutting

Saw-tooth chip changes from macroscopically continuous ribbon to separated segments with the increase of cutting speed. The aim of this study is to find the correlations between chip morphology and machined surface micro-topography at different chip serration stages encountered in high speed cutting. High strength alloy steel AerMet100 was employed in orthogonal cutting experiments to obtain chips at different serration stages and corresponding machined surfaces. The chips and machined surfaces obtained were then examined with optical microscope (OM), scanning electron microscope (SEM), and white light interferometer (WLI). The result shows that chip serration causes micro-waves on machined surface, which increases machined surface roughness. However, wave amplitudes (surface roughness) at different serration stages are different. The principal factor influencing wave amplitude is the thickness of the sawed segment (tooth) of saw-tooth chip. With cutting parameters in this study, surface roughness contributed by chip serration ranges from 0.39 μm to 1.85 μm. This may bring on serious problems in the case of trying to replace grinding with high-speed cutting in rough machining. Some suggestions have been proposed to control the chip serration-caused surface roughness in high-speed cutting based on the results of the current study.     

Basic principles for the design of cutting edge roundings

Adapted cutting edge roundings lead to a performance increase of cutting tools. The optimal cutting edge design is determined by the thermomechanical process load and thus depends on the machined material. In this study, the external mechanical load is investigated in direct relation to material properties by means of microcinematography. It could be shown that load characteristics are mainly material independent, whereas the load level depends on the machined material. Finally, the findings were transferred into a model, which enables the design of cutting edge roundings based on material properties.     

Characteristics of high speed micro-cutting of tungsten carbide

In this study, experiments are carried out to evaluate the characteristics of high speed cutting of tungsten carbide material using a Makino V55 high speed machine tool with cubic boron nitride (CBN) tool inserts. The cutting forces were measured using a three-component dynamometer, the surface roughness of the machined workpiece was measured using a Mitutoyo SURFTEST 301, and the machined workpiece surfaces and the chip formation were examined using a scanning electron microscope (SEM). Experimental results indicate that the radial force F_x is much larger than the tangential force F_z and the axial force F_y. Two types of surfaces of the machined workpiece are achieved: ductile cutting surface and fracture surface. Continuous chips and discontinuous chips are formed under different cutting conditions. Depth of cut and feed rate almost have no significant effect on the surface roughness of the machined workpiece. The SEM observations on the machined workpiece surfaces and chip formation indicate that the ductile mode cutting is mainly determined by the undeformed chip thickness when the tool cutting edge radius is fixed. Ductile cutting can be achieved when the undeformed chip thickness is less than a critical value.     

Investigations of White Layer Formation During Machining of Powder Metallurgical Ni-Based ME 16 Superalloy

Surface integrity of machined parts made from the advanced Ni-based superalloys is important for modern manufacturing in the aerospace industry. Metallographic observations of the ME 16 alloy microstructure were made using optical metallography and a high-resolution scanning electron microscope with energy dispersive x-ray spectrometer (HR SEM/EDS). Tool life of cemented carbide inserts with TiAlN coating during machining (finishing turning operation) of ME 16 superalloy has been studied and wear patterns of the cutting tools were identified. Surface integrity of the machined part after completion of the turning operation was investigated. The morphology of machined parts has been examined and cross-sections of the machined surfaces have been analyzed. The formation of white layer on the surface of the machined part was studied for varied machining conditions. It was found that a 2-4 μm thick white layer forms during turning of the ME 16 superalloy. This layer was investigated using EDS and XRD. The studies show that the white layer is an oxygen-containing layer with a high amount of aluminum, enriched by chromium and tungsten. Under specific cutting conditions, the structure of white layer transforms into a γ-alumina. Formation of this thermal barrier ceramic white layer on the surface of the machined part negatively affects its surface integrity and cutting tool life.     

Experimental and numerical modelling of the residual stresses induced in orthogonal cutting of AISI 316L steel

Residual stresses in the machined surface layers are affected by the cutting tool, work material, cutting regime parameters (cutting speed, feed and depth of cut) and contact conditions at the tool/chip and tool/workpiece interfaces. In this paper, the effects of tool geometry, tool coating and cutting regime parameters on residual stress distribution in the machined surface and subsurface of AISI 316L steel are experimentally and numerically investigated. In the former case, the X-ray diffraction technique is applied, while in the latter an elastic–viscoplastic FEM formulation is implemented. The results show that residual stresses increase with most of the cutting parameters, including cutting speed, uncut chip thickness and tool cutting edge radius. However, from the range of cutting parameters investigated, uncut chip thickness seems to be the parameter that has the strongest influence on residual stresses. The results also show that sequential cuts tend to increase superficial residual stresses.     

The optimal cutting-parameter selection of production cost in HSM for SKD61 tool steels

The main purpose of this study was to construct an investigation of optimal cutting parameters for minimizing production cost on the rough machining of high speed milling operation. A machining model is constructed based on a polynomial network. The polynomial network can learn the relationships between cutting parameters (cutting speed, feed per tooth, and axial depth of cut) and tool life through a self-organizing technique. Once the material removal volume for machined parts and various time and cost components of the high speed milling operations are given, an optimization algorithm using a simulated annealing method is then applied to the polynomial network for determining optimal cutting parameters. The optimal cutting parameters are subjected to an objective function of minimum production cost with the feasible range of cutting parameters.     

Impact of the cutting dynamics of small radial immersion milling operations on machined surface roughness

This paper deals with a numerical and experimental study of the dynamics of flank milling operations at low cutting rates. It focuses on both properties of the cutting vibratory phenomena and their impacts on the roughness of the machined surface. The study is based on a one degree of freedom model of the mechanical machining system. The system is of the rigid cutter–flexible workpiece type. The cutting force model is based on the regenerative mechanism. The roughness of the surface machined at high speed revolutions has been studied for both forced vibrations occurring during stable cutting and self-excited vibrations occurring during unstable cutting. It is shown that forced vibrations have only a very slight impact (roughness remains quite similar to that obtained with a fully rigid mechanical system), while unstable cutting mainly impacts roughness. The stable milling zones can be shown on a roughness map. The study of the roughness shows that the boundary between stable and unstable cutting conditions, in the case of interrupted cutting, is a wide zone characterised by a doubling of the tooth passing period. In this zone, only one tooth over two is removing material due to the vibratory motion. A discussion explains the phenomenon.     

基于净切削比能的钛合金清洁切削加工表面完整性研究

目的 探究钛合金清洁切削过程中能量消耗的变化与加工表面完整性的关系，通过切削参数优化选择，以实现加工表面质量的控制，从而提高钛合金高效洁净制造零件的使用寿命和服役性能。方法 本文提出一种基于能量消耗的过程签名方法，来描述多工步清洁切削加工过程与加工表面完整性的相互影响。建立了净切削比能计算模型，结合钛合金两工步铣削试验，分析了粗加工参数变化对粗加工、精加工切削力，以及净切削比能的影响规律，并进一步对两工步加工过程中的净切削比能展开研究。本文研究了不同粗加工参数条件下粗加工和精加工表面残余应力及微晶尺寸的变化规律。结果 切削力和切削参数的变化均会影响净切削比能的大小。多工步切削加工过程中，粗加工和精加工切削参数的不同会改变净切削比能，进而引起表面完整性的变化。对切削比能影响最大的是径向切深，其次是进给量、切削速度。随着进给量和径向切深的增大，切削比能降低；随着切削速度的升高，净切削比能先增大后减小。净切削比能较大时，加工表面层残余应力较大，微晶尺寸较小。结论 在保证加工质量的前提下，从节能降耗的角度出发，选取合适的切削速度、较大的切削深度、进给量，从而降低净切削比能、减少能量消耗，提高加...     

Effect of tilt angle on cutting regime transition in glass micromilling

Recent development in mechanical micromachining technology has increased the realization of micromachining as a feasible manufacturing process of micro-scale components including glass-based devices. It has been found that glass can be machined in a ductile regime under certain controlled cutting configurations. However, favorable ductile regime machining instead of brittle regime machining in micromilling of brittle glass is still not fully understood as a function of cutting configuration. In this study, the effect of tilt angle along the feed direction on cutting regime transition has been studied in micromilling crown glass with a micro-ball end mill. Straight glass grooves were machined in water bath by varying the tool tilt angle and the feed rate, and the resulting surface was characterized using the scanning electron microscope and the profilometer to investigate the glass cutting regime transition. In characterizing the cutting regimes in glass micromilling, rubbing, ductile machining, and brittle machining regimes are hypothesized according to the undeformed chip thickness. It is found that a crack-free glass surface can be better machined in the ductile mode using a 45° tilt angle and feed rates up to 0.32 mm/min. During each milling pass, surface roughness was found to decrease from the entry zone to the groove bottom and then increase to the exit zone regardless of the cutting regime.     

基于RP技术陶瓷型精铸模具的应用与发展

介绍RP技术和陶瓷型铸造技术在模具设计、制造、工艺方面的特点及应用现状,从保证模具尺寸精度、降低表面粗糙度、缩短制造周期、降低生产成本等方面分析,指出将RP技术与陶瓷型精铸相结合,是模具制造业的发展方向之一,特别是对于形状复杂、难以进行机械加工成型的型腔曲面,效果更为明显,是适合我国技术现状和装备条件的模具成型新方法.     

Investigation of glass thickness effect on thermal slumping by experimental and numerical methods

Thermal slumping process is a high volume and low cost manufacturing method for fabricating aspherical and freeform glass mirrors with large dimensions. It has been aggressively tested for X-ray mirrors for space-based telescopes and for solar panels as well. In case a concave mold is used, the relationship between the upper surface contour of a slumped mirror and that of the mold becomes non-linear. On the other hand, the final surface contour of the slumped glass is a very important parameter which directly affects the optical performance of the mirror. In this research, experiments of thermal slumping glass plates on a parabolic concave mold were performed to study the thickness effect on the slumping process and the final surface contour of the upper surface of the glass plate. In addition, numerical simulation was conducted to ensure the internal stresses were removed at selected cooling rate and predict the corresponding surface contour. A comparison between simulation and experiments showed that the finite element method (FEM) simulation is adequate for predicting the surface contour if the glass was fully slumped. It was also discovered that under certain process conditions, thinner glass plates may not be fully slumped therefore proper remedies to the manufacturing process are necessary.     

Orthogonal cutting mechanisms of graphite/epoxy composite. Part I: unidirectional laminate

An experimental study of orthogonal cutting mechanisms was conducted in the edge trimming of unidirectional Graphite/Epoxy composite with polycrystalline diamond tools. The effects of tool geometry and operating conditions were evaluated from an analysis of chip formation, cutting force and machined surface topography. All aspects of material removal were found to be primarily dependent on the fibre orientation. Discontinuous chip formation was noted throughout this study, regardless of trimming parameters. Chip dimensions and force measurements depicted a change in chip formation with fibre orientation, and the presence of three distinct mechanisms in the edge trimming of fiber reinforced composite material. A combination of cutting, shearing and fracture along the fibre/matrix interface was observed.     

微铣刀制备技术与实验研究

微铣刀制备技术是微细铣削的关键技术之一,对微细铣削加工出的微小零部件的特征尺寸和表面质量有重要影响。从微铣刀具的材料与涂层及其制造工艺两方面,对微铣刀制备技术进行了介绍,并通过线电极电火花磨削方法制备了刀头直径为100μm的微铣刀,初步验证了基于自研μEM-200CDS2微细组合电加工机床开展微铣刀在位制备的能力。     

Dry machining of Inconel 718, workpiece surface integrity

In the machining of Inconel 718, nickel based heat resistant superalloy and classified difficult-to-cut material, the consumption of cooling lubricant is very important. To reduce the costs of production and to make the processes environmentally safe, the goal is to move toward dry cutting by eliminating cutting fluids. This goal can be achieved by using coated carbide tool and by increasing cutting speed.The present paper firstly reviews the main works on surface integrity and especially residual stresses when machining Inconel 718 superalloy. It focuses then on the effect of dry machining on surface integrity. Wet and dry turning tests were performed at various cutting speeds, with semi-finishing conditions (0.5 mm depth of cut and 0.1 mm/rev feed rate) and using a coated carbide tool. For each cutting test, cutting force was measured, machined surface was observed, and residual stress profiles were determined. An optimal cutting speed of 60 m/min was determined, and additional measurements and observations were performed. Microhardness increment and the microstructure alteration beneath the machined surface were analysed. It is demonstrated that dry machining with a coated carbide tool leads to potentially acceptable surface quality with residual stresses and microhardness values in the machining affected zone of the same order than those obtained in wet conditions when using the optimised cutting speed value; in addition, no severe microstructure alteration was depicted.     

微沟槽织构对切削力和表面粗糙度的影响

为研究微织构对切削过程中产生的切削力和已加工表面粗糙度的影响,在聚晶立方氮化硼(PCBN)刀片前刀面制备与主切削刃平行的宽度为32.6μm的微沟槽织构。分别用微沟槽刀具和无织构刀具在主轴转速为450、500、600 r/min的条件下切削淬硬钢GCr15,分析切削力和已加工表面粗糙度。试验结果表明:微沟槽改善了刀具的切削性能,主切削力、进给力和切深力均小于无织构刀具;进给力、切深力随着主轴转速的增加均变大,主切削力表现为先减小再增大;用微沟槽织构刀具切削的已加工表面粗糙度大于无织构刀具,表明微沟槽不利于获得表面质量较好的工件;随着主轴转速增加,微沟槽刀具和无织构刀具切削的表面粗糙度均减小。     

Surface characteristics of machined Inconel-718 nickel-base superalloy using natural and controlled contact length tools

The surface characteristics of machined Inconel-718 nickel-base superalloy were investigated using natural and controlled contact length tools, at various cutting speeds, and under both dry and lubricated conditions. Surface damage in the form of cavities and holes, fractured areas, and long and short straight grooves parallel to the direction of cutting was produced when machining was carried out at low cutting speeds and with tools having natural or controlled contact length, and at high cutting speeds with tools having natural contact lengths. The intensity of surface damage and total area affected decreased as the cutting speed was increased. The quality of the machined surface was drastically improved at high cutting speeds, when tools having controlled contact lengths were used. The application of lubricants was less effective for improving the surface quality. The results were interpreted in terms of the mechanics of chip formation, the interaction between the tool-nose region and freshly machined surface, and the tool forces resulting from the machining process.     

模具多轴数控加工技术的现状与发展

随着科学技术的突飞猛进,模具制造技术迅速发展,多轴数控加工、高速加工、电火花加工、快速模具制造等先进技术在模具制造中得到了广泛的应用。本文介绍了多轴数控加工技术的特点与应用现状,并指出了多轴数控加工编程技术存在的问题、以及实现多轴数控加工技术的难点,最后对多轴数控加工技术的发展趋势进行了展望。     

The effect on fatigue life of residual stress and surface hardness resulting from different cutting conditions of 0.45%C steel

The affected layer is generated within the machined surface layer through the cutting process. Cutting conditions such as the nose radius of the tool, feed rate and shape of cutting edge at the finishing operation affect the residual stress, surface hardness, and surface roughness. In this paper, it is shown that such machined surface property could be controlled by the setting of the cutting conditions to some extent. Then the effect of the machining conditions on the fatigue life was investigated through a fatigue test using the specimen finished under various cutting conditions. It was shown that it is possible to get longer fatigue life for machined parts than the virgin material or the carefully finished material without affected layer, only by setting the proper cutting conditions. Such a situation was realized when the generated residual stress was small and the induced surface hardness was high. A longer fatigue life for the machined components can be obtained by applying such cutting conditions as a low feed rate, a small corner radius and a chamfered cutting edge tool.     

The form error prediction in side wall machining considering tool deflection

In this research, an effective method for the form error prediction in side wall machining with a flat end mill is suggested. The form error is predicted directly from the tool deflection without surface generation by cutting edge locus with time simulation. The developed model can predict the surface form error accurately about 300 times faster than the previous method. Cutting forces and tool deflection are calculated considering tool geometry, tool setting error and machine tool stiffness. The characteristics and the difference of generated surface shape in up milling and down milling are discussed. The usefulness of the presented method is verified from a set of experiments under various cutting conditions generally used in die and mold manufacturing. This study contributes to real time surface shape estimation and cutting process planning for the improvement of form accuracy.