Morphological evolution and grinding performance of vitrified bonded microcrystal alumina abrasive wheel dressed with a single-grit diamond

Dressing experiments under different conditions were carried out on a vitrified bonded microcrystal alumina abrasive wheel with a single-grit diamond dresser. The grinding performance of the as-dressed abrasive wheels was investigated. The dressing force, grinding force and the surface morphology of abrasive wheel and machined workpiece were studied to shed light on the relationship among the dressing processing vectors, morphology of abrasive wheel and the grinding performance. The results obtained show that the dressing forces increase with the increasing volume of the abrasive wheel material removed per unit time. The sensitive analysis reveals that the dressing feed speed take a greater effect than the single dressing depth on the dressing force. The self-sharpness of vitrified bonded microcrystal alumina abrasive wheel brings into some functions under certain dressing conditions, but a deep dressing depth would lead to an excessive abrasive self-sharpness, i.e. abrasive grits fall off and embed into the workpiece surface.     

Precision grinding using CBN wheels

The paper systematically reviews experimental research on the performance of cubic boron nitride (CBN) grinding wheels and discusses advantages and difficulties experienced in the application of CBN wheels particularly for internal grinding with fine-grain wheels.The hardness of CBN grains potentially increases re-dress life and improves dimensional stability. The problem is that increased re-dress life increases the importance of avoiding wheel loading, particularly for small-grain wheels. This paper highlights the importance of touch dressing for improved dimensional stability and other operational techniques to maintain an open surface topography of the wheel. The paper also demonstrates the benefit of an open-structured small-grain CBN wheel for precision grinding. Effects on grinding temperature are also illustrated.     

絮凝剂净化黄铜矿选矿尾矿回水的工业生产实践

在常规pH值条件下,使用定量絮凝剂APAM+助凝剂净化黄铜矿选矿尾矿回水,在工业应用中取得了良好效果,提高尾矿回水利用率20%~35%。使用净化后的尾矿回水浮选对精矿品位有明显提高,精矿金品位合格率提高2.55%,精矿铜品位合格率提高2.23%。既减轻了环保安全压力,又保证了生产指标,同时也提高了尾矿回水利用率,缓解了选矿厂季节性水资源短缺的问题。     

司家营铁矿选别流程的演变及技术改造

叙述了司家营铁矿自2007年10月投产以来多项重大选矿工艺改造。氧化矿选别系统：新建浮选厂房并增加新型浮选设备,过滤设备扩容、改型,中强磁前弱磁设备提高场强,增加强磁设备,重选增加扫选和重精控制筛分,三段磨矿“二对一”改造,循环水净化处理,沉降池改造,浮选药剂制度优化等。原生矿选别系统：磁选柱尾矿返回位置优化,增加尾矿回收系统,增加污水池,改造给排水系统,实现工业废水零排放。系统改造后提高了选矿技术水平以及精矿产量与质量,社会效益和经济效益显著。同时,提出了氧化矿选别系统降低尾矿品位,提高金属回收率的研究方向;原生矿系统磨前预选提高入选品位,以达到增产减排的目标。     

修整双滚道砂轮用滚轮工艺研究

如何开发高精度、高耐用度修整双滚道砂轮用滚轮 ,提出了一套研究方法 ,并进行了实验 ,得出了可行性结论     

Electrochemical discharge dressing of metal bond micro-grinding tools

Micromachining using miniature metal bond grinding tools is widely used in microelectromechanical systems. However, dressing of these micro-tools is time-consuming and likely to damage the abrasives. In this paper, a novel dressing technique called electrochemical discharge dressing (ECDD) is presented. A dull micro-end grinding bit and an auxiliary electrode are connected to the cathode and anode of a power supply, respectively. The auxiliary electrode is immersed in an electrolyte, and the grinding face of the tool is in contact with the electrolyte surface. During dressing, metal bond on the tool-electrolyte interface is progressively removed subjected to electrochemical discharge effect, thus creating grain protrusion. Experiments were conducted to evaluate the dressing performance of ECDD in terms of surface morphology of the tool, grinding force and surface roughness of the workpiece. Experimental results show that abrasive grains on the tool protrude without observable damage. The normal grinding force and the surface roughness of the workpiece are reduced by half after dressing.     

金属切削刀具变前角及其刃磨工艺的实验研究

主要探讨自动机床应用高速切削时的排屑和断屑问题,以及相应排屑槽的形状参数及其制造刃磨方法,为新型不重磨硬质合金刀片的研制提供参考数据。     

金刚石砂轮金属结合剂的气中单脉冲电火花放电去除机理

针对金属结合剂金刚石砂轮修锐困难的问题,提出采用气中电火花接触放电修锐的方法。为有效地实现微细金刚石砂轮的修锐,建立单脉冲电火花放电去除加工的试验系统,研究金属结合剂的气中和液中电火花放电去除机理。在试验研究中,主要分析无负荷电压和放电极性对脉冲放电电流、脉冲放电间隙、脉冲放电去除量、电极磨耗比等的影响。结果表明,正极性不易发生短路现象,而且气中的脉冲放电间隙小于液中的 ,适应于微细金刚石砂轮的修锐。此外,在气中放电中存在由绝缘破坏引起的火花放电向附有电弧柱的电弧放电转变的临界无负荷电压,且电火花放电的去除量可以明显小于电弧放电的去除量,但是当无负荷电压小于某一定值时电极消耗比会快速增加。修锐的试验结果显示,利用气中单脉冲电火花放电去除加工条件可以实现金属结合剂微细金刚石砂轮的修锐,产生较好的砂轮出刃形貌,改善磨削表面质量。     

The laser dressing of resin-bonded CBN wheels by a Q-switched Nd: YAG laser

Resin-bonded cubic boron nitride (CBN) grinding wheels are widely used in industry due to their good grinding ability. There is, therefore, a need to find a good method suitable for the dressing of these wheels. This paper presents a new method dressed by an acoustic-optic Q-switched Nd: YAG laser based on thermal interaction, which is unlike the conventional mechanical dressing methods based on force interaction. The mechanism of the selective removal of the bond was analysed. Experiments of a single pulse ablation on the resin bond and the CBN grains, and the laser dressing of resin-bonded CBN wheels with different dressing parameters have been carried out. The grinding force has been compared for the conventional mechanical dressed wheel and the laser dressed wheel. It is shown that the resin-bonded CBN grinding wheel is suitable for an acoustic-optic Q-switched Nd: YAG laser dressing with radial irradiation, which is better than a continuous wave (CW) laser dressing with radial irradiation and conventional mechanical dressing methods.     

齿轮形超硬修磨轮的设计与制作技术

论述了齿轮形超硬修磨轮的制造工艺 ,提出了基体轮的设计原则 ,分析了主要工序的技术要求 ,研制出了高质量的齿轮形超硬修磨轮 ,并用于对齿轮加工刀具和砂轮的修形上 ,为硬齿面齿轮多种高效精加工方法的应用提供了保证。