Model for surface-roughness parameters determination in a virtual machine shop environment

A virtual reality machine shop environment was developed and integrated with a graphical model for the calculation of quantitative data affecting the roughness of a machined surface. During the machining process simulation in the virtual environment, material removal and milling machine axes kinematics are visualized in real time and qualitative parameters related to the process feasibility are evaluated. The model determines the machined surface topomorphy as a cloud of points retrieved from the visualization system Z buffer and surface roughness is calculated. The current study is focused on the methodology for the verification of the quantitative data acquired by the system. Results were verified with data determined in cutting experiments and by another numerical model that was integrated into the system. The results were found to be in agreement with both the numerical model and the experiments.     

Influence of machining parameters on surface roughness in finish cut of WEDM

Surface roughness is significant to the finish cut of wire electrical discharge machining (WEDM). This paper describes the influence of the machining parameters (including pulse duration, discharge current, sustained pulse time, pulse interval time, polarity effect, material and dielectric) on surface roughness in the finish cut of WEDM. Experiments proved that the surface roughness can be improved by decreasing both pulse duration and discharge current. When the pulse energy per discharge is constant, short pulses and long pulses will result in the same surface roughness but dissimilar surface morphology and different material removal rates. The removal rate when a short pulse duration is used is much higher than when the pulse duration is long. Moreover, from the single discharge experiments, we found that a long pulse duration combined with a low peak value could not produce craters on the workpiece surface any more when the pulse energy was reduced to a certain value. However, the condition of short pulse duration with high peak value still could produce clear craters on the workpiece surface. This indicates that a short pulse duration combined with a high peak value can generate better surface roughness, which cannot be achieved with long pulses. In the study, it was also found that reversed polarity machining with the appropriate pulse energy can improve the machined surface roughness somewhat better compared with normal polarity in finish machining, but some copper from the wire electrode is accreted on the machined surface.     

Fuzzy-nets-based in-process surface roughness adaptive control system in end-milling operations

A fuzzy-nets-based in-process adaptive surface roughness control (FN-ASRC) system was developed to be able to adapt cutting parameters in-process and in a real time fashion to improve the surface roughness of machined parts when the surface roughness quality was not meeting customer requirements in the end-milling operations. The FN-ASRC system was comprised of two sub-systems: (1) fuzzy-nets in-process surface roughness recognition (FN-IPSRR); and (2) fuzzy-nets adaptive feed rate control (FN-AFRC) sub-system. To test the system, while the machining process was taking place, the FN-IPSRR system predicted the surface roughness, which was then compared to the desired surface roughness. If the desired surface roughness was not met, then, the FN-AFRC system proposed a new feed rate for the machining process. Once the feed rate was changed, and the cutting continued, the output of the surface roughness of the new feed rate was compared with the desired surface roughness. This proposed FN-ASRC system has been demonstrated to be successful using 25 experimental tests with 100% success rate.     

Optimization of drilling parameters on surface roughness in drilling of AISI 1045 using response surface methodology and genetic algorithm

Modeling and optimization of cutting parameters are one of the most important elements in machining processes. The present study focused on the influence machining parameters on the surface roughness obtained in drilling of AISI 1045. The matrices of test conditions consisted of cutting speed, feed rate, and cutting environment. A mathematical prediction model of the surface roughness was developed using response surface methodology (RSM). The effects of drilling parameters on the surface roughness were evaluated and optimum machining conditions for minimizing the surface roughness were determined using RSM and genetic algorithm. As a result, the predicted and measured values were quite close, which indicates that the developed model can be effectively used to predict the surface roughness. The given model could be utilized to select the level of drilling parameters. A noticeable saving in machining time and product cost can be obtained by using this model.     

超声纵扭辅助铣削高强铝合金表面润湿性能研究

针对超声辅助加工在工件表面形成微刻划表面可以提高高强铝合金表面的微结构性能的现象,进行了单激励旋转超声纵扭复合铣削表面微观结构的试验,基于水接触角理论和纵扭铣削运动学理论分析了加工参数对水接触角的影响;搭建了单激励超声纵扭铣削试验平台,采用正交试验法研究了不同加工参数对表面粗糙度、铣削力以及表面润湿性能的影响。结果表明：超声振幅为4μm时表面质量最佳,切削速度和进给量与表面粗糙度和水接触角呈正相关的关系;超声加工方式下的表面水接触角较普通方式更大,而在超声加工时低振幅加工比高振幅加工的表面水接触角大,当转速达到一定值时,高振幅和低振幅所加工的表面水接触角差别不大。合适的加工参数条件下超声纵扭加工方式可以降低加工表面的粗糙度,改变表面的润湿性。     

Spectral analysis of surface roughness features of a lapped ultraprecision single-point diamond machined surface

Single-point diamond turning of soft metals could provide a much shiny surface with an optimal feed rate; however, the machining mark would be left on the machined surface, which caused the roughness cannot be neglected. If the feed rate is too small, the roughness of the surface could be improved but the reflectiveness would be decreased because of damaging the profile. Therefore, it is necessary to develop a lapping method to reduce the roughness by removing the machining mark, while the reflectiveness can be kept at the original level simultaneously. In this study, the novel lapping method, using strands of wool fibers to deliver the abrasive slurry to rub against the lens, was proposed for removing the machining marks on the mold of a lenticular lens by lapping without damaging the profile of the mold. Even though the normal pressure applied by the wool strands onto the mold surface is very low, the coefficient of friction would be increased significantly with the application of the abrasive slurry. The combined effect was to provide a relatively large shear force to lap the surface with a minimal normal force. Therefore, the proposed method could theoretically avoid damaging the lens while effectively removing the irregularities that appeared on the surfaces. In order to evaluate the proposed lapping method, we firstly lapped the machining marks with different lapping parameters (speed, grit size, time, and pressure) to find out the relationship between these parameters and roughness with the same profile of the mold. Secondly, the optimal lapping parameters were designed based on the above lapping results to deduce the best lapping solution for processing the machining marks. Thirdly, the lapped surface profile of the mold was test by optical profiling system, and the features of the surface can be categorized into various spectral distribution groups. Finally, by comparing the variation of the spectral distribution groups, it is verified that based on our proposed methodology, selective removal of surface spectral groups of features becomes possible.     

INFLUENCE OF MACHINING PARAMETERS ON THE WHITE LAYER FORMATION PROCESS AND ITS CHARACTERISTICS IN TURNING OF HARDENED STEEL

This article contains results of experimental research activities of white layer formation (WLF) and its characteristics during a process of turning hardened steels (THS), which have been carried out in laboratories of DD Cimos TMD Ai Grada?ac. WLF. Characteristics during the THS process were analyzed from the aspects of influence caused by machining parameters as well as tool flank wear width. Experimental tests of tool wear have been performed. The tool used in experimental tool wear was ceramic cutting insert CNGA 120408T, catalogue mark IN22 Al2O3-TiCN. In accordance with achieved results, value of tool flank wear 220 µm has been set as the criterion of wear. In accordance with defined wear criterion, determination of level and type of influence that machining parameters have on WLF and its characteristics were carried out in accordance with planned experimental methodology. Experiments have shown that cutting speed and tool flank wear width (for all other machining conditions unchanged) can be used for control of WLF and its characteristics. Structural changes in surface layer of the working piece, during the cutting process of hardened material, except for the WLF are also presented through a transition zone, e.g., dark layer, which has lower hardness than the initial material. Hard WL can take over a protection role for a machined surface from abrasive actions, while softened zone (dark layer) can take over a function of WL solder with the initial material. Analysis of achieved results points to a possibility of controlling the WLF and its characteristics, and therefore a possibility of using WL in a positive context. The basis for the above mentioned is the effect of additional plastic deformation of WL (APDWL), which occurs only under certain machining conditions. The effect seen, if follows WLF, results in decrease of machined surface roughness compared to its expected value. Accordingly there is a possibility for identification of WL on a machined surface by measuring the roughness parameters without previous metallographic preparation of samples.     

Improving the surface quality in wire electrical discharge machined specimens by removing the recast layer using magnetic abrasive finishing method

This study explores the feasibility of removing the recast layer formed on aluminum alloy cylindrical specimens machined by wire electrical discharge machining (WEDM) by using magnetic abrasive finishing (MAF). The WEDM is a thermal machining process capable of accurately machining parts with high hardness or complex shapes. The sparks produced during the WEDM process melt the metal’s surface. The molten material undergoes ultra-rapid quenching and forms a layer on the surface defined as recast layer. The recast layer may be full of craters and microcracks which reduce service life of materials tremendously, especially under fatigue loads in corrosive environments. This investigation demonstrates that MAF process, can improve the quality of WEDM machined surfaces effectively by removing the recast layer. The present work studies the effect of some parameters, i.e., linear speed, working gap, abrasive particle size, and finishing time on surface roughness and recast layer thickness using full factorial analysis. Three-level full factorial technique is used as design of experiments for studying the selected factors. In order to indicate the significant factors, the analysis of variance has been used. In addition, an equation based on regression analysis is presented to indicate the relationship between surface roughness and recast layer thickness of cylindrical specimens and finishing parameters. Experimental results show the influence of MAF process on recast layer removal and surface roughness improvement.     

Effects of process parameters on surface roughness in abrasive waterjet cutting of aluminium

Abrasive waterjet cutting is a novel machining process capable of processing wide range of hard-to-cut materials. Surface roughness of machined parts is one of the major machining characteristics that play an important role in determining the quality of engineering components. This paper shows the influence of process parameters on surface roughness (R_a) which is an important cutting performance measure in abrasive waterjet cutting of aluminium. Taguchi’s design of experiments was carried out in order to collect surface roughness values. Experiments were conducted in varying water pressure, nozzle traverse speed, abrasive mass flow rate and standoff distance for cutting aluminium using abrasive waterjet cutting process. The effects of these parameters on surface roughness have been studied based on the experimental results.     

Influence of graphite and machining parameters on the surface roughness of Al-fly ash/graphite hybrid composite: a Taguchi approach

This paper presents an experimental investigation on the surface roughness of pure commercial Al, Al-15 wt% fly ash, and Al-15 wt% fly ash/1.5 wt% graphite (Gr) composites produced by modified two-step stir casting. The effect of reinforcements and machining parameters such as cutting speed, feed rate, and depth of cut on surface roughness, which greatly influence the performance of the machined product, were analyzed during turning operation. The optimum machining parameters were found in minimizing the surface roughness of the materials by using the Taguchi and ANOVA approach. Results show that the presence of the fly ash particles reduces the surface roughness of composites compared with pure Al. The inclusion of 1.5 wt% Gr in the Al-fly ash composite reduces the surface roughness considerably. A scanning electron microscopy investigation was carried out on the machined surfaces of the tested materials. Confirmation tests were performed to validate the regression models.     

Surface topography and roughness of high-speed milled AlMn1Cu

The aluminum alloy AlMn1Cu has been broadly applied for functional parts production because of its good properties. But few researches about the machining mechanism and the surface roughness were reported. The high-speed milling experiments are carried out in order to improve the machining quality and reveal the machining mechanism. The typical topography features of machined surface are observed by scan electron microscope(SEM). The results show that the milled surface topography is mainly characterized by the plastic shearing deformation surface and material piling zone. The material flows plastically along the end cutting edge of the flat-end milling tool and meanwhile is extruded by the end cutting edge, resulting in that materials partly adhere to the machined surface and form the material piling zone. As the depth of cut and the feed per tooth increase, the plastic flow of materials is strengthened and the machined surface becomes rougher. However, as the cutting speed increases, the plastic flow of materials is weakened and the milled surface becomes smoother. The cutting parameters (e.g. cutting speed, feed per tooth and depth of cut) influencing the surface roughness are analyzed. It can be concluded that the roughness of the machined surface formed by the end cutting edge is less than that by the cylindrical cutting edge when a cylindrical flat-end mill tool is used for milling. The proposed research provides the typical topography features of machined surface of the anti-rust aluminum alloy AlMn1Cu in high speed milling.     

Application of Taguchi and response surface methodologies for surface roughness in machining glass fiber reinforced plastics by PCD tooling

This paper discusses the use of Taguchi and response surface methodologies for minimizing the surface roughness in machining glass fiber reinforced (GFRP) plastics with a polycrystalline diamond (PCD) tool. The experiments have been conducted using Taguchi’s experimental design technique. The cutting parameters used are cutting speed, feed and depth of cut. The effect of cutting parameters on surface roughness is evaluated and the optimum cutting condition for minimizing the surface roughness is determined. A second-order model has been established between the cutting parameters and surface roughness using response surface methodology. The experimental results reveal that the most significant machining parameter for surface roughness is feed followed by cutting speed. The predicted values and measured values are fairly close, which indicates that the developed model can be effectively used to predict the surface roughness in the machining of GFRP composites. The predicted values are confirmed by using validation experiments.     

Influence of cutting speed on surface integrity for powder metallurgy nickel-based superalloy FGH95

Powder metallurgy (PM) nickel-based superalloy FGH95 has been widely used for components, which requires the greatest service performance. The surface integrity is becoming more and more important in order to satisfy the increasing service demands. However, the machined surface of FGH95 is easily damaged due to its poor machinability. The purpose of this paper is to investigate the effects of dry milling process parameters on the surface integrity of FGH95. Experiments were conducted on a CNC machining center under different cutting speeds. The machined surface is evaluated in terms of surface roughness, microhardness and white layer. Experiments results show milled surface integrity of FGH95 is sensitivity to the cutting speeds. The machined surface roughness decreases with increase of the cutting speed, but with further increase of cutting speed between 80?m/min to 100?m/min an increase in surface roughness appears. For microhardness, it can be seen that the machined workpiece surface hardens seriously. It can also draw the conclusion that cutting speed has the marginal effect on the white layer thickness generated in the machined subsurface.     

Dynamic surface generation modeling of two-dimensional vibration-assisted micro-end-milling

An integrated model is proposed to simulate the surface generation in two-dimensional vibration-assisted micro-end-milling (2-D VAMEM). The model includes the developed submodels as dynamic cutting force model, machining system response model, and machined surface generation algorithm. The effects of feed rate on cutting force and surface roughness are investigated through simulations. It is found that the cutting force increases while the surface roughness decreases with the increment of the feed rate when the feed per tooth is smaller than the tool edge radius. The trials have been carried out to evaluate and validate the proposed model and the simulation results. The integrated model contributes to the comprehensive understanding of the process of machined surface generation in 2-D VAMEM and will assist the machining operators to select optimal machining parameters.     

超声振动辅助磨削-脉冲放电加工表面粗糙度研究

通过多因素方差分析法分析了超声振动辅助磨削一脉冲放电复合加工参数（脉冲宽度、脉冲间隔、参考电压、超声振幅）对加工表面粗糙度的影响程度,建立了表面粗糙度的二次模型,并用响应曲面法预测一定切削参数范围内任意切削条件下的表面粗糙度值,方差分析结果和响应曲面法预测结果基本一致。研究结果对实际生产过程中加工参数的优化具有一定的指导作用。     

OPTIMAL MACHINING CONDITIONS FOR TURNING OF PARTICULATE METAL MATRIX COMPOSITES USING TAGUCHI AND RESPONSE SURFACE METHODOLOGIES

The present investigation focuses on the influence of machining parameters on the surface finish obtained in turning of LM25 Al/SiC particulate composites. The experiments are conducted based on Taguchi's experimental design technique. In this work, the effect of machining parameters on the surface roughness is evaluated and optimum machining conditions for maximizing the metal removal rate and minimizing the surface roughness are determined using response surface methodology. A second-order response surface model for the surface roughness is developed to predict the surface roughness. The predicted values and measured values are fairly close to each other, which indicates that the developed model can be effectively used to predict the surface roughness on the machining of Al/SiC-MMC composites with 95% confidence intervals within the ranges of parameters studied.     

OPTIMAL MACHINING CONDITIONS FOR TURNING OF PARTICULATE METAL MATRIX COMPOSITES USING TAGUCHI AND RESPONSE SURFACE METHODOLOGIES

The present investigation focuses on the influence of machining parameters on the surface finish obtained in turning of LM25 Al/SiC particulate composites. The experiments are conducted based on Taguchi's experimental design technique. In this work, the effect of machining parameters on the surface roughness is evaluated and optimum machining conditions for maximizing the metal removal rate and minimizing the surface roughness are determined using response surface methodology. A second-order response surface model for the surface roughness is developed to predict the surface roughness. The predicted values and measured values are fairly close to each other, which indicates that the developed model can be effectively used to predict the surface roughness on the machining of Al/SiC-MMC composites with 95% confidence intervals within the ranges of parameters studied.     

Wire electrical discharge machining of ASP30 tool steel

Wire electrical discharge machining is a non-traditional cutting process for machining of hard and high strength materials. This study analyzed the effects of the main input parameters of wire electrical discharge machining of ASP30 steel (high alloyed Powder metallurgical [PM] high speed steel) as the workpiece on the material removal rate and surface roughness. The input parameters included spraying pressure and electric conductivity coefficient of the dielectric fluid, linear velocity of the wire and wire tension. The machined surface quality was evaluated using SEM pictures. Results indicated that increasing the spraying pressure of dielectric fluid leads to a higher material removal rate and surface roughness and that increasing the wire tension, linear velocity of wire, and electric conductivity of the dielectric fluid decreases the material removal rate and surface roughness.

     

Improvement of EDM efficiency with a new adaptive control strategy

In most of the commercially available EDM systems, the control parameters such as the electrode jump height and the discharge machining time between two consecutive electrode jump actions are set manually to constant values which can ensure stable machining even under the worst machining conditions. It is beneficial to keep the machining process stable, but much time is consumed in the electrode jump process. In order to improve the EDM efficiency, a new adaptive control strategy which directly and automatically regulates the electrode jump height and discharge machining time has been developed in this paper. Experimental results show that the adaptive control system can obviously improve the machining efficiency regardless of the surface area, shape, and depth of the machined dies. Meanwhile, the accuracy and surface roughness of the fabricated dies can be well retained.