Finishing of Hardened Boreholes: Grinding or Hard Cutting?

The finishing processes of parts have been carried out mainly by abrasive grinding techniques. Grinding is a theoretically well-elaborated and widespread machining process. That is why its replacement by another metal removal technique, hard cutting, requires very careful examination. In this article, the possibilities are outlined for finishing internal cylindrical surfaces of hardened steels (i.e., boreholes, by employing hard cutting instead of grinding). The process characteristics, the surface quality, and some economic and ecological features of the process are compared theoretically and experimentally, and discussed.     

Highly Efficient and Precision Fabrication of Cylindrical Parts from Hard Materials with the Application of ELID (Electrolytic In-Process Dressing)

The ELID (Electrolytic In-Process Dressing) grinding process, which incorporates in-process dressing of metal bonded superabrasive wheels, was applied for efficient and precision grinding of hard materials such as ceramic, hard metals, and quenched steels. Addressed in this paper are some of the typical applications of ELID Grinding for cylindrical machining. The significant advantages, performances, and characteristics of mirror surface grinding for external surface, internal surface, and end-face Finish processes of cylindrical components are described.     

A novel magnetorheological honing process for nano-finishing of variable cylindrical internal surfaces

A novel magnetorheological honing process is designed and developed for nano-finishing of cylindrical internal surfaces with the help of permanent magnets. The radial movement of magnetic tool surface is adjusted as per the internal diameter of different cylindrical components and make it fixed before start of finishing so that it can maintain constant working gap while perform finishing. The present developed magnetic tool surface always constitutes higher magnetic field than the inner surface of ferromagnetic or non-ferromagnetic cylindrical workpiece. This is an important requirement to finish the internal surface of ferromagnetic or non-ferromagnetic cylindrical components because it ensures MR polishing fluid cannot stick on the workpiece surface while performing the finishing. Hence, present developed process is useful for finishing of ferromagnetic cylindrical molds, dies, hydraulic actuators, etc. for its better functional applications after the conventional honing or grinding process. The internal surface roughness of cylindrical ferromagnetic workpiece is dropped to 90?nm from its initial value of 360?nm in 100 minutes of finishing. Further scanning electron microscopy has also been done to understand the surface characteristics of finished workpiece. The results revealed that the developed magnetorheological honing process is capable to perform nano-finishing of internal surface of the ferromagnetic cylindrical components.     

Development of an integrated model for process planning and parameter selection for machining processes

The concept of ‘do it right the first time’ in the machining industry not only expects the best quality products but also at the best possible cost. The cost of machining depends on intelligent process planning and selection of machining parameters such as speed, feed, and depth of cut. The problem of machining parameter selection has received great attention by researchers and many techniques have been developed. A review of these techniques reveals that the selection of the machine and cutting tool is done before the process of cutting parameter selection and process sequencing, and often the selection is based on experience. The current research is an attempt to develop an integrated model (ExIMPro: Expert system based Integrated model for Machining Processes) which finds the sequence of operations with set of machines, tools, and other process parameters to minimise the cost of machining for a cylindrical part. This system consists of existing expert system Machining Parameter SELection (MPSEL) for machine and tool selection and a Microsoft Excel® and Visual Basic® based parameter selection model. The present model focuses on turning and cylindrical grinding operations but other processes can be incorporated with little modification to the software.     

旋转超声内圆磨削砂轮变幅器的设计与试验研究

砂轮变幅器是旋转超声内圆磨削谐振系统的关键部件,其设计质量直接影响超声磨削的工艺效果。但目前内圆磨削砂轮变幅器缺乏较为完善的理论分析模型。为提高砂轮变幅器理论分析模型的通用性,基于非谐振设计理论建立了纵向谐振砂轮变幅器的理论分析模型,并利用砂轮变幅器各振动单元间的力、位移连续条件与边界条件推导了其频率方程。然后,针对频率方程进行编程求解,并通过ANSYS有限元仿真分析进行验证。最后,加工制作了纵向谐振砂轮变幅器,并开展阻抗特性分析试验、超声谐振试验和振动位移测量试验,分析了其谐振特性。试验结果表明,所研制的砂轮变幅器的谐振试验频率与理论设计频率一致,其输出端振动位移的试验值与仿真值的相对误差为7.83%,符合旋转超声内圆磨削的要求,验证了理论分析模型求解的正确性。研究结果为旋转超声内圆磨削砂轮变幅器的设计提供了便捷且有效的方法。     

Magnetorheological finishing of ferromagnetic blind-hole type surfaces

Products having blind-hole type surfaces such as bottle caps are being manufactured in today’s industry and are of great use. Such products are made in permanent blind-hole type mold cavities. At present, these cavities are being finished by internal grinding operations. After grinding, surface defects such as deep-seated groove, cavity, axial scratch, and ploughed material are induced because of uncontrollable finishing forces applied by grinding pins onto the workpiece surface. To obtain a better quality on final-made products, the blind-hole type mold cavities should be made defect-free. In the present process, two different tools based on magnetorheological fluid are developed to finish the lateral and bottom surfaces of cylindrical blind-hole type mold cavities. The workpiece used for finishing is the hardened EN31 die steel. The finite element studies determined the variation in magnetic field within the working gaps. The change in surface roughness (R_a) values of both inner lateral and bottom surfaces reduced by 67.7% and 69.5%, respectively, and found significant improvement in surface characteristics as compared to the initial grind surfaces. The results revealed the usefulness of present process to finish the blind-hole type mold cavities in manufacturing industries for producing a better quality of final-made products.     

Recursive parameter estimation for categorical process control

Statistical process adjustment (SPA) is utilised prevalently in novel manufacturing scenarios. When quality characteristics rather than internal process variables are inspected for the purpose of quality control, data with different resolutions may be collected. This paper proposes a Bayesian framework for parameter estimation when only categorical observations are available. The proposed method incorporates categorical information recursively and updates parameter estimates in real time. Simulation results show that the framework is effective in utilising low-resolution information in parameter estimation, model building and process control.     

The development of a target‐focused process capability index with multiple characteristics

Within an industrial manufacturing environment, Process Capability Indices (PCIs) enable engineers to assess the process performance and ultimately improve the product quality. Despite the fact that most industrial products manufactured today possess multiple quality characteristics, the vast majority of the literature within this area primarily focuses on univariate measures to assess process capability. One particular univariate index, C_pm, is widely used to account for deviations between the location of the process mean and the target value of a process. While some researchers have sought to develop multivariate analogues of C_pm, modeling the loss in quality associated with multiple quality characteristics continues to remain a challenge. This paper proposes a multivariate PCI that more appropriately estimates quality loss, while offering greater flexibility in conforming to various industrial applications, and maintaining a more realistic approach to assessing process capability. Copyright © 2010 John Wiley & Sons, Ltd.     

Monitoring and evaluation of process parameters in a plunge grinding operation

Plunge grinding, like other grinding operations, is a complex process because of a large number of factors that are involved. This often makes it difficult to determine the optimal grinding parameters in pursuit of a certain product quality and cost, based upon the existing generic knowledge and experience about the process. However, the combined effect of the large number of factors and therefore, the performance characteristics of a given grinding system (including grinding wheel, component, grinding machine as well as workpiece holding system) can be learned by monitoring the grinding process. This can then help in the determination of optimal or near optimal grinding parameters. The paper describes a computerised system for the analysis of a plunge grinding operation based on the monitored power traces. This analysis yields data on important parameters such as grinding power (P), specific energy (E?s?), grinding force (F?t?), system deflection (Δy) and stiffness (K?s?). The paper also discusses the evaluation models used in the system, in particular, the model proposed for evaluation of system deflection and stiffness. The effect of the system stiffness on grinding process is analysed and a method to determine spark-out period, required to eliminate the system deflection, is proposed in the paper.     

基于改进田口方法的轮毂装配过程质量控制研究

针对风力机轮毂装配工序的质量控制问题，结合多品种小批量生产模式的特点，提出了一种面向定位布置的轮毂装配关键工序识别与监控的方法。综合考虑轮毂装配生产中的成本因素及相对质量损失，制定装配工序的质量特性损失标准，采用改进的质量损失函数识别轮毂装配关键工序；为解决统计过程控制（SPC）方法应用于小批量生产模式的瓶颈，引入基于直觉模糊集的工序相似性分析与评定方法，通过分析工序相似性的影响因素，构建轮毂装配成组工序相似性评判指标体系及评定模型，完成工序相似性的测度。最终使用SPC方法监控管理轮毂装配关键工序，确保轮毂的装配质量。该研究为小批量生产模式中运用SPC方法管理过程质量提供了理论依据。     

An investigation on machined surface quality and tool wear during creep feed grinding of powder metallurgy nickel-based superalloy FGH96 with alumina abrasive wheels

In this study, the machined surface quality of powder metallurgy nickel-based superalloy FGH96 (similar to Rene88DT) and the grinding characteristics of brown alumina (BA) and microcrystalline alumina (MA) abrasive wheels were comparatively analyzed during creep feed grinding. The influences of the grinding parameters (abrasive wheel speed, workpiece infeed speed, and depth of cut) on the grinding force, grinding temperature, surface roughness, surface morphology, tool wear, and grinding ratio were analyzed comprehensively. The experimental results showed that there was no significant difference in terms of the machined surface quality and grinding characteristics of FGH96 during grinding with the two types of abrasive wheels. This was mainly because the grinding advantages of the MA wheel were weakened for the difficult-to-cut FGH96 material. Moreover, both the BA and MA abrasive wheels exhibited severe tool wear in the form of wheel clogging and workpiece material adhesion. Finally, an analytical model for prediction of the grinding ratio was established by combining the tool wear volume, grinding force, and grinding length. The acceptable errors between the predicted and experimental grinding ratios (ranging from 0.6 to 1.8) were 7.56% and 6.31% for the BA and MA abrasive wheels, respectively. This model can be used to evaluate quantitatively the grinding performance of an alumina abrasive wheel, and is therefore helpful for optimizing the grinding parameters in the creep feed grinding process.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00305-2     

机床涂装工艺浅述

我国现阶段机床产品的涂装工艺仍以小批量、手工为主,随着机床零部件质量的提高以及规模化生产,原有机床涂装方式已不适合现代机床工业的生产.通过对机床产品特性的分析和方案比较,提出了机床产品涂装工艺设计和平面布置,并介绍了主要的涂装设备:水旋喷漆室、油漆烘干室、多功能喷涂打磨室.通过对机床涂装工艺合理的设计,使得工件可以按产品特性组织批量生产.     

An experimental investigation as to the effect of cutting parameters on roundness error and surface roughness in cylindrical grinding

This paper presents the results of an experimental investigation as to the effects of grinding parameters on roundness error and surface roughness in cylindrical grinding. Many variables including the wheel materials, wheel loading and dressing, workpiece metallurgy, work drive mechanisms, work holding methods, coolant types, feeds and speeds, machine stiffness and age, surface conditions, centre conditions, floor vibrations all influence the quality of ground parts. However, the composite sum of these grinding parameters creates static and dynamic forces. It is obvious that the roundness error and surface roughness are created by many parameters, but in this study, only the effects of the depth of cut, work speed and feed rate which create the grinding forces in cylindrical grinding are investigated. The grinding experiments were planned according to the principles of orthogonal arrays (OAs), developed by Taguchi, and were performed so as to understand the effects of these parameters on roundness error and surface roughness. The experimental data was analysed by using statistical tools: the percent contribution from an analysis of variance (ANOVA) and the correlation between machining parameters with roundness error (R) and also surface roughness (Ra). Roundness was found to be the most related with the cutting speed, grinding force and depth of cut, while surface roughness is related to feed rate and work speed.     

基于双盘直槽研磨的圆柱滚子自转运动研究

为了解决双盘直槽研磨方法实施过程中的关键技术问题,针对圆柱滚子在研磨状态下的自转运动展开相关研究。首先,对圆柱滚子在研磨状态下的自转运动进行理论分析,得到了其稳定自转的条件。然后,基于ADAMS （automatic dynamic analysis of mechanical systems,机械系统动力学自动分析）软件建立了圆柱滚子自转运动的动力学仿真模型,并以圆柱滚子与上、下研磨盘间的摩擦系数,下研磨盘V形槽半角,单个圆柱滚子所受研磨载荷及上、下研磨盘相对运动线速度为主要影响因素,以圆柱滚子的相对滑动率为评价指标,进行了计及因素间交互作用的正交试验。通过响应均值分析与方差分析,得到了可实现圆柱滚子稳定且连续自转的最优参数组合。最后,在自主设计的圆柱滚子自转运动试验平台上对最优参数组合的正确性进行了验证试验。试验结果表明,最优参数组合下圆柱滚子自转时的平均相对滑动率仅为0.30%,能够实现稳定且连续的自转,这充分证明了通过理论分析与正交试验得到的最优参数组合的正确性。研究结果证实了基于双盘直槽研磨的圆柱滚子自转运动的合理可行域,其对双盘直槽研磨方法的工程实践具有指导意义,为提高圆柱滚子批直径尺寸一致性奠定了基础。     

Experimental investigation of cutting parameters in machining of 100Cr6 with tangential turn-milling method

The turn-milling methods for machining operation have been developed to increase efficiency of conventional machines recently. These methods are used especially by coupling some apparatuses on the computer numerical control (CNC) machine to decrease the production time and machine costs, ensure the maximum production and increase the quality of machining. In this study, 100Cr6 bearing steel extensively used in industry has been machined by tangential turn-milling method. This paper presents an approach for optimization of the effects of the cutting parameters including cutter speed, workpiece speed, axial feed rate, and depth of cut on the surface roughness in the machining of 100Cr6 steel with tangential turn-milling method by using genetic algorithm (GA). Tangential turning-milling method has been determined to have optimum effects of cutting parameters on the machining of 100Cr6 steel. The experimental results show that the surface roughness quality is close to that of grinding process.     

纳米结构陶瓷涂层的外圆磨削力以及磨削表面精度的实验研究

使用功率计监测磨削加工的能量消耗，探讨了纳米结构陶瓷涂层的外圆磨削过程；对纳米陶瓷涂层和传统陶瓷涂层在磨削力和磨削表面精度方面进行了比较．磨削实验使用了外圆磨床和陶瓷结合剂金刚石砂轮．通过测量主轴功率获得切向磨削力，讨论了加工参数，如切深、进给率以及砂轮粒度对切向磨削力的影响．还对磨削后的涂层表面用粗糙度仪和扫描电镜进行了评估，揭示了表面粗糙度与加工参数的关系．     

Analysis of in-site grinding process using new equipment for calendar roll machines

Development in production technology has increased the need for high productive efficiency and effective utilization of machines. Tires, paper, rexin, and other rubber-based products are produced by using calendar roll machines. Web wrinkling, torn material, misaligned cutting, slitting, poor adhesion and laminate characteristics are the major errors in a calendar roll machine. The geometry, camber of rollers play a major role for most of the errors stated. This paper focuses on the experimental investigations carried out for cambering the rolls in-site (without removing), through grinding process with newly modeled equipment. The results obtained through in-site grinding are compared and discussed. It is observed that in-site grinding reduces the machine idle time by three-fourth of the normal roll grinding process and avoids the machine characteristic errors. New equipment comfortably eliminates the wrinkles and improves the quality of the rubber-coated fabric with the variation in thickness only between 1 and 2 µm.     

A new method for online monitoring when grinding Ti-6Al-4V alloy

This study proposes a grinding process from a control perspective to improve surface quality and precision in the machining process and speed up intelligent production. This method provides a cognitive decision-making process. On this basis, a new approach was developed to measure the amount of grinding wheel wear (GWW) and predict surface roughness (SR) in accordance with the compressed air measuring head and hybrid algorithms fuzzy neural networks (ANFIS)–Gaussian regression function (GPR) and Taguchi empirical analysis. A series of experiments were conducted in various processing conditions. The results showed the efficiency of the grinding process in measuring the amount of GWW and predicting the SR of the Ti–6Al–4V alloy accurately. The proposed model is able to predict SR values with 99.69% precision and 98% confidence interval. This study laid the foundation for monitoring GWW and SR in actual industrial environments.     

蜗杆砂轮磨齿机几何误差敏感度分析

为识别影响蜗杆砂轮磨齿机空间精度的关键几何误差项,提出一种基于旋量理论和Sobol法的几何误差敏感度分析方法。以YW7232型蜗杆砂轮磨齿机为研究对象,首先,基于旋量理论建立机床的几何误差模型;然后,采用Sobol法计算机床磨削过程中各几何误差项对空间误差分量的敏感度系数,并识别出关键几何误差项;最后,对机床的关键几何误差项进行修正,通过仿真分析对比修正前后机床的空间误差分量以及3种测量模式下球杆仪的杆长。仿真结果表明所提出的方法可有效识别出机床磨削过程中的关键几何误差,这可为提高机床精度提供理论指导。     

A variance change point estimation method based on intelligent ensemble model for quality fluctuation analysis

For multivariable production process, knowing the first time of process really changes (change point) will help to accelerate the location of assignable causes and make measures for process adjustment. So effective estimating the change point is an important way to analyse the quality fluctuation of process. In the present study, an intelligent ensemble model for quality fluctuation analysis is proposed to estimate the variance change point in multivariable process. With the method, the process is decomposed based on moving window analysis, then different types of kernel functions are combined together to form the multi-kernel support vector machine model, which has combined the feature mapping capability of each basic kernel in the new feature space. The particle swarm optimisation is considered to search the optimised multi-kernel parameters. After that, each sub-characteristic is regarded as a pattern to be recognised to determine the change point by using the optimised intelligent ensemble model. Finally, a case study is conducted to evaluate the performance of proposed approach. It reveals that the method could estimate the time of variance change point in continuous production process accurately.