自聚类神经网络在磨削烧伤辨识中的应用

本文选用磨屑热辐射流温度信号作为辨识信号源，提出了用自聚类神经网络辩识磨削烧伤的策略与方法。实验结果表明：自聚类神经网络可用于辨识磨削烧伤，辨识精度较高，且具有一个重要特点：网络训练是无师自学习的。     

磨床砂轮智能监测及修整系统

介绍一种具有较好通用性和实用性的砂轮智能监测及修整系统，该系统利用BP神经网络建立声发射(AE)信号、振动信号、砂轮电机功率信号与砂轮磨钝之间的非线性关系，能够根据传感器信号，自动在线监测砂轮磨钝，及时启动砂轮自动修整系统，并且通过采用CNC砂轮自动修整器，能够解决多种类型的成型砂轮的修整。     

基于粗糙集理论的磨削烧伤与砂轮磨钝在线监测

研究了基于粗糙集理论的在线辨识磨削烧伤和砂轮磨钝的新方法,以测取信号、计算敏感特征量、构造辨识砂轮磨损和磨削烧伤的知识表示系统、连续属性离散、分类模式的合并、属性约简、知识提取的顺序对获取的信息进行处理,提取判别规则,进而通过判别规则来辨识磨削烧伤和砂轮磨钝,辨识结果与实验数据相符,理论和实验表明,采用粗糙集理论来解决多品种、小批量生产方式中的分类辨识非常有用。     

砂轮天赋菜貌评定的方法

概率分布法是评定砂轮表面形貌的一种新的综合性方法，它能用于分析锋利砂轮和磨钝砂轮表面磨料切刃和容屑槽在径向上的不同分布特点，为磨削基本理论的研究提供一种有力的工具。     

砂轮磨钝监测及修整

利用声发射(AE）信号归原处理法对砂轮磨钝程度进行监测，在此基础上开发了砂轮磨钝监测及自动修整系统。该系统可以对小批量、多品种工件磨削过程中砂轮钝化进行有效的监测，采用的CNC砂轮自动修整器能够解决多种类型成型砂轮的修整，具有一定的通用性和实用性，能实现磨削砂轮监测、修整过程的自动化和智能化。     

加工多头蜗轮的单头滚刀设计

概率分布法是评定砂轮表面形貌的一种新的综合性方法，它能用于分析锋利砂轮和磨钝砂轮表面磨粒切刃和容屑槽在径向上的不同分布特点，为磨削基本理论的研究提供一种有力的工具。     

磨屑热辐射流信号用于磨削烧伤在线辩识的可行性研究

磨削烧伤在线辩识一直是机械制造领域所研究的重要课题，本文提出了一种新的用于辩识的信号源－磨屑热辐射流，并对其可行性进行了理论分析和实验验证。     

砂轮磨钝的在线监测与预报

本文在分析砂轮磨钝过程中各种指标变化情况的基础上，选择合理的砂轮磨钝判断标准，并对此判据实现在线监测和预报。一、砂轮磨钝标志的选择1．砂轮磨钝过程的试验研究试验在MS1320外圆磨床上进行，用白刚玉、棕刚玉、绿碳化硅等砂轮对45淬火钢、GCr15轴承钢等材料的试件进行切入磨削试验，试验中采用了不同的磨削用量组合，观察、记录了磨削过程中多种指标的变化情况。由试验结果得知，在不同的试验条件下，每一种指标在磨削过程中的变化规律基本相同。图1～图3所示是其中一组试验的记录。该组试验采用的砂轮为GB60ZR1AP400×50×203…     

金刚石砂轮的修整

随着工业生产的高速发展,使用硬质合金的机械零件部件、刀具和立方氮化硼刀具等越来越广,而磨削加工硬质合金、立方氮化硼的适宜磨料是金刚石砂轮,因此,金刚石砂轮的使用也越来越广泛。 金刚石砂轮和其它磨料的砂轮一样,使用一段时间以后,由于磨料失去锐角而变钝,或者磨屑嵌塞缝     

不锈钢细长薄壁管轴的磨削加工

不锈钢材料具有较大的韧性,进行磨削加工时砂轮表面容易被磨屑嵌塞和粘附,由于砂轮堵塞,使磨粒切削能力降低甚至丧失,导致磨削热增大,砂轮材料的导热性又差,从而导致磨削区的温度剧增,磨屑在高温高压的作用下与磨粒相互熔焊在一起。     

Image processing of grinding wheel surface

Identifying the situation of grinding wheel wear and loading is a very important issue for high efficiency grinding operations. This paper presents a new method that detects and identifies the chip loading and cutting edge wear of a grinding wheel using the image processing toolbox of MATLAB. The different optical characters of the metal chips and the abrasive grains are analysed. The Sobel operator is adopted to make edge detection. A sensitivity threshold based on the global condition is used to decrease the noise. Image dilation and erosion processes are used to ensure the edge of each loaded chip is covered by a continuous section. The ratios of chips are calculated and displayed to monitor the wheel surface working status.     

Image processing of the grinding wheel surface

Identifying the situation of grinding wheel wear and loading is a very important issue for high-efficiency grinding operations. This paper presents a new method that detects and identifies the chip loading and cutting edge wear of a grinding wheel using the image processing toolbox of the MATLAB package. The different optical characters of the metal chips and the abrasive grains are analysed. The Sobel operator is adopted to make the edge detections. A sensitivity threshold based on the global condition is used to lower the noise. Image dilation and erosion processes are used to ensure that the edge of each loaded chip is covered by a continuous section. The ratios of chips are calculated and displayed to monitor the wheel surface working status.     

杯状砂轮修整器对CBN砂轮的修形及磨削

研究杯状砂轮对陶瓷ＣＢＮ砂轮的修形,及修形后磨削高速钢和软钢的加工特性。通过研究得出,磨削高速钢时砂轮磨粒磨损和切屑附着、磨削软钢时砂轮表面发生堆积物熔着是砂轮磨耗的主要原因。     

A study on wear mechanism and wear reduction strategies in grinding wheels used for ELID grinding

Metal-bonded superabrasive diamond grinding wheels have superior qualities such as high bond strength, high stability and high grindability. The major problems encountered are wheel loading and glazing, which impedes the effectiveness of the grinding wheel. Electrolytic in-process dressing (ELID) is an effective method to dress the grinding wheel during grinding. The wear mechanism of metal-bonded grinding wheels dressed using ELID is different form the conventional grinding methods because the bond strength of the wheel-working surface is reduced by electrolysis. The reduction of bond strength reduces the grit-depth-of-cut and hence the surface finish is improved. The oxide layer formed on the surface of the grinding wheel experiences macrofracture at the end of wheel life while machining hard and brittle workpieces. When the wheel wear is dominated by macrofracture, the wheel-working surface is free from loaded chips and worn diamond grits. When the oxide layer is removed from the wheel surface, the electrical conductivity of the grinding wheel increases, and that stimulates electrolytic dressing. The conditions applied to the pulse current influence the amount of layer oxidizing from the grinding wheel surface. Longer pulse ‘on’ time increases the wheel wear. Shorter pulse ‘on’ time can be selected for a courser grit size wheel since that type of wheel needs high grinding efficiency. Equal pulse ‘on’ and ‘off’ time is desired for finer grit size wheels to obtain stable and ultraprecision surface finish.     

On the grindability of low-carbon steel under dry, cryogenic and neat oil environments with monolayer brazed cBN and alumina wheels

Grinding of low-carbon steel often exhibits severe wheel loading due to the formation of long chips and high adhering tendency of the work material with the grits. Conventional composite-type alumina wheels are commercially utilised for grinding low-carbon steel. However, the actual nature of grit wear cannot be truly understood in a composite wheel. The truing and dressing conditions also have some influences on the wear mechanism. Therefore, in order to explore the wear pattern on a single layer of grits, monolayer brazed cBN, white and grey Al₂O₃ wheels were used in the present study. The grindability of AISI 1020 steel was evaluated under dry, liquid nitrogen and neat oil environments. The surface profile of the workpiece after being ground in each environmental condition was traced with a surface profilometer to reveal the mechanism of grit wear. The post-grinding conditions of the wheels were observed using scanning electron microscopy. The cBN wheel was found to outperform the alumina wheels in terms of grinding forces and grit wear. The wear of the cBN wheel was remarkably arrested with the application of neat oil. On the other hand, large-scale adhesion and breakage of grits in white alumina wheel were observed under cryogenic environment. In fact, the beneficial role of liquid nitrogen could not be realised in reducing grinding forces and grit wear with all the three types of wheel. A lubricating agent like neat oil appeared to be more suitable than cryogenic cooling when grinding low-carbon steel.     

Diamond face grinding of WC-Co composite with spark assistance: Experimental study and parameter optimization

Electro-discharge machining (EDM) characteristics of tungsten carbide-cobalt composite are accompanied by a number of problems such as the presence of resolidified layer, large tool wear rate and thermal cracks. Use of combination of conventional grinding and EDM (a new hybrid feature) has potential to overcome these problems. This article presents the face grinding of tungsten carbide-cobalt composite (WC-Co) with electrical spark discharge incorporated within face of wheel and flat surface of cylindrical workpiece. A face grinding setup for electro- discharge diamond grinding (EDDG) process is developed. The effect of input parameters such as wheel speed, current, pulse on-time and duty factor on output parameters such as material removal rate (MRR), wheel wear rate (WWR) and average surface roughness (ASR), are investigated. The present study shows that MRR increases with increase in current and wheel speed while it decreases with increase in pulse on-time for higher pulse on-time (above 100 μs). The most significant factor has been found as wheel speed affecting the robustness of electro- discharge diamond face grinding (EDDFG) process.     

Experimental study of wheel wear in electrolytic in-process dressing and grinding

Profile accuracy of components ground with ultra-precision machine tools is primarily dependent on wheel wear. Quantitative analysis of wheel wear is therefore an important aspect for precision grinding with electrolytic in-process dressing (ELID). In this paper, wheel wear is measured from ELID grinding experiments with different dressing and machining parameters. The grinding forces and dressing current characteristics of the experiments are also compared. Based on the results, a benchmark function is defined for wheel wear rate. A relation for identifying insufficient dressing from sufficient dressing for particular machining conditions is also identified. It is found that insufficient dressing produces pitting and/or arcing on the wheel surface, and wheel wear can be linearly correlated to ELID grinding conditions when the wheels are sufficiently dressed.     

磨削力与砂轮磨损的关系

本文综述了国内外砂轮磨损检测技术的发展概况。重新建立了磨削力经验公式。通过对磨削力两分比值变化的分析与试验,提出院用磨削力两分力比值来评价砂轮磨损的方法。最后,用磨削力两分力比值的变化作为砂轮磨损的评价标准进行了利用Intel-8086微处理机监控磨削过程的试验,结果是令人鼓舞的。     

DEVELOPMENT OF AN OPTICAL SCANNER TO STUDY WEAR ON THE WORKING SURFACE OF GRINDING WHEELS

The efficiency of the grinding operation is highly dependent on the grinding wheel surface topography. Several methods for the evaluation of the grinding wheel surface have been developed in the last few years. In some of these methods, the grinding wheel has to be removed from the machine for an evaluation using a microscope or a profilometer. Some other methods are able to measure the topography at the grinding machine, but they do not give detailed information about grain distribution and wear. This paper shows a new method to map the grinding wheel surface. The proposed system is based on an optical scanner capable of measuring the light beam reflected from the wear flat areas on the abrasive grains over the whole wheel peripheral surface. The Mapping System for Grinding Wheels (MSGW) is able to acquire data with the wheel running at the work speed (30 m/s)and the measurement carried out on the grinding machine without stopping. The system is applied on a surface grinding operation where an Alj0₃grinding wheel is used. The results show that the system can be used to map the wear flats at the grinding wheel surface and also to analyze the wear phenomena efficiently.