In-process wire electrical discharge dressing (IWEDD) of metal bonded diamond wheels

Electrical discharge dressing has been established as alternative for conditioning metal bonded diamond wheels, which will be exploited to develop in-process wire electrical discharge dressing (IWEDD). The main requirements for its successful implementation are first presented in this work. Small depth of dressing cuts was found to be feasible and high material removal rates were achieved without damaging diamonds. Dulled grains are finally removed by mechanical contact with the work piece. It was found that grinding forces can be kept constant over time while non-productive time is reduced, showing that IWEDD is a suitable conditioning method with great potential for future industrial applications.     

A hybrid process of raining co-deposition and rotary wire spark erosion in the development of a custom CBN tool for making a biochip injection mold

This study examines a hybrid process combining raining co-deposition and rotary wire spark erosion with one-off grinding to generate an array of microgrooves in the fabrication of biochip injection molds on NAK80 steel. A precision composite electroforming device that can create a rain like co-deposition effect to uniformly grow a Ni-based Cubic Boron Nitride (CBN) abrasive layer onto a wheel-blank substrate is proposed and employed. Slicing and dressing are conducted by using rotary wire spark erosion to make the co-deposited wheel-blank into a thin CBN wheel-tool with a grinding edge array that alternates between coarse and detailed. A multiple microgroove array on NAK80 steel is one-off generated by using the developed CBN wheel-tool array, swiftly creating a superior surface finish for biochip injection molding. A comprehensive examination of the quantitative and qualitative properties of the CBN wheel-tool was undertaken. Experimental results have been evaluated in terms of CBN grit content, accuracy of co-shaft machining, influence of grinding depth, shape of microgroove and tool wear as well as an estimation criterion for the CBN wheel-tool array.     

细粒度金刚石砂轮椭圆超声振动修整试验研究

针对硬脆材料精密加工中细粒度金属结合剂金刚石砂轮修整精度低、修整速度慢、成本高的难题,开发了基于局部共振设计方法的新型单驱动椭圆振动超声修整装置,设计了专用试验砂轮.修整试验结果表明:与普通机械修整方式比较,椭圆超声振动修整后的砂轮表面磨粒分布均匀、静态磨粒数增加;磨粒表面平滑完整,多个棱边有完整锋利的磨刃;同时,结合剂三角洲面积减小,磨粒突出高度增大,延性修整痕迹明显.随着修整切深增加,单位面积上砂轮突出磨粒数减少,砂轮的承载率下降,磨粒锋利性降低;随着修整导程增加,各截层的磨粒数逐步减少,但是承载率增加,磨粒变得锋利;砂轮转速增加,椭圆超声振动修整的效果减弱,砂轮磨粒锋利性降低,而超声功率增大有利于改善修整效果.选择合理参数,采用椭圆振动超声复合修整技术,可以实现细粒度金刚石砂轮的低成本快速修整.     

绕丝结构砂轮磨削沟槽结构化表面

为磨削出微沟槽结构化表面,设计一种将金刚石丝锯紧密缠绕在基体上的新型砂轮,提出相应的结构砂轮平面磨削沟槽结构的方法。首先,建立砂轮几何模型与数学模型并得出磨粒运动轨迹方程;其次,理论分析磨削沟槽表面的创成机理及磨削参数对沟槽形貌的影响;最后,通过仿真和实验验证新型砂轮磨削沟槽结构的可行性和不同磨削参数下的沟槽结构形态。研究结果表明:绕丝结构化砂轮可以平面磨削出结构化沟槽表面,且改变磨削用量能磨出不同尺寸的参数与排布的沟槽结构。      

三坐标数控磨轮修整器的无累积误差插补控制方法

本文从成型磨削特点出发,引出新型计算机数控成型磨轮修整概念,提出了平面三座标数控修整方法,为了提高修整精度,从原理上详细介绍和分析了无累积误差插补计算机控制方法。     

金刚石砂轮精密修整工艺研究

金刚石砂轮机械磨削是砂轮整形的传统方式。砂轮旋转速度以及工具砂轮的进给量是金刚石砂轮机械精密整形的主要工艺参数。通过在超硬材料砂轮整形机床上的大量实验和砂轮磨削力的分析,得到了金属结合剂和树脂结合剂金刚石砂轮精密整形的比较理想的工艺参数;确定了工具砂轮的线速度应在11 m/s左右,工具砂轮轴转速在1 050～1 800 r/min;金刚石砂轮轴转速设定在400～1 000r/min,金刚石砂轮的线速度为2.6～10.5 m/s。同时,分析比较了机械修锐和喷砂修锐的效果。     

Wire electrical discharge machining of metal bond diamond wheels for ceramic grinding

The application of cylindrical wire Electrical Discharge Machining (EDM) for profile truing of metal bond diamond wheels is presented. Instead of using the mechanical force to break the diamond and matrix in the grinding wheel, the wire EDM process uses the thermal energy or electrical sparks between the wire and rotating grinding wheel to remove the metal bond and form the wheel. The design and manufacture of a corrosion-resistant, precise spindle with the high-electrical current capability for wire EDM truing of grinding wheel is first introduced. Three truing configurations were designed to study effects of wire EDM process parameters and to investigate the level of form accuracy and corner radii achievable by the wire EDM truing of diamond wheels. Results show that the wire EDM process can efficiently generate the μm-scale precision form on the diamond wheels. The wheel, after truing, was used to grind the silicon nitride workpiece. Grinding forces and wheel wear rate were measured. In the beginning of the grinding, high wheel wear rate was identified. The subsequent wheel wear rate was considerably lower and stabilized.     

A fundamental study on the mechanism of electrolytic in-process dressing (ELID) grinding

Demands for high quality surface finish, dimensional and form accuracy are required for optical surfaces and it is very difficult to achieve these using conventional grinding methods. Electrolytic in-process dressing (ELID) grinding is one new and efficient method that uses a metal-bonded diamond grinding wheel in order to achieve a mirror surface finish especially on hard and brittle materials. However, studies reported so for have not explained the fundamental mechanism of ELID grinding and so it has been studied here by conducting experiments to establish optimal grinding parameters to obtain better surface finish under various in-process dressing conditions. In this research the results show that the cutting forces are unstable throughout the grinding process due to the breakage of an insulating layer formed on the surface of the grinding wheel; however, a smoother surface can be obtained using a high dressing current duty ratio at the cost of high tool wear. ELID grinding is efficient for feed rates of less than 400 mm/min, and surface cracks are observed when it exceeds this limit.     

Development of a New Turning Center for Grinding Ceramic Materials

A grinding center based on an NC turning center has been developed for efficient external, internal or cam grinding of ceramic mechanical parts. The grinding center is provided with not only various grinding wheels, but also an ultrasonic grinding attachment for reducing grinding force during coring or expanding holes. The grinding center is also equipped with an on-machine wire electro-discharge trueing/dressing unit for metal bond diamond wheels. All the other revisions necessary for grinding ceramic materials have been made on the turning center. The developed grinding center was confirmed to have expected abilities in efficient grinding and form grinding.     

成形砂轮高精度修整技术研究

介绍成形磨齿的原理与现状.分析数控插补修正砂轮中金刚石工具自身形状误差对砂轮修整精度的影响;并提出相应的解决措施,即在修整过程中,通过工具的旋转,以保持工具与砂轮间实际修整作用点不变,从而消除工具误差对砂轮修整精度的影响.并设计出具体修整装置.实践表明:采用该方法不仅可以保持高的工作精度,而且可以延长工具的使用寿命.     

Effects of electric discharge dressing parameters on polycrystalline diamond micro-tool surface topography and their micro-grinding performances

Polycrystalline diamond (PCD) micro-grinding tools are shaped by using different electro-discharge machining processes, among which wire electro-discharge grinding (WEDG) process is widely accepted due to its capability of producing highly precise, ultra-thin and dimensionally accurate tools. Observing the effects of different WEDG conditions on the tool surface and analyzing the tool's topographic features relevant to micro-grinding are of utmost importance. Current study deals with dressing of polycrystalline diamond tool blanks at different combinations of wire tension and discharge energy to observe the effects of dressing parameters on the tool surface morphology and statistics. Surface roughness, ridge type surface defects and diametrical error in the fabricated tool are analyzed with respect to discharge energy and wire tension. High wire tension produces tools with consistence surfaces and desired diameter. Binder material cobalt is efficiently melted and flushed out from the tool surface at high wire tension, which leads to proper segregation and protrusion of diamond abrasives from the surface. Static abrasive grit density measured by processing the 3D surface data of the tool is found to be ≈165–170 per mm, as compared to theoretically determined value of ≈200 per mm. Micro-slot grinding experiments are carried out on BK7 glass, to quantify the effects of the dressing parameters on the micro-grinding performances of the PCD micro-tools. Cutting forces for all the tools are found to be within 1 N whereas normal force exceeds beyond 1 N. Cutting forces are found to be higher for the tools dressed at high wire tension due to large diameter of the tool as compared to that of undersized tool obtained at low wire tension. Cutting nature is found to be mix of ductile-brittle for the machining conditions adopted in this paper.     

电火花线切割用镀层丝设计

分析了复杂多拐角工件电火花线切割加工中存在的问题,提出了有效的解决方案。从应用角度出发,设计了特殊的表层电极丝材料,优化了镀层丝的性能,满足了电火花线切割加工复杂多拐角工件的应用要求,提高了加工精度和表面质量。     

先进光学磨削中杯形修整技术开发及应用

对于金刚石砂轮修整,尤其是有高精度要求的圆弧金刚石砂轮,杯形砂轮修整技术可以获得较好的砂轮磨削性能以及修整效率。本文开发了配套超精密平面磨床使用的杯形修整器,分析了其机械误差影响,并完成了修整实验及砂轮表面测量及半径拟合处理,从宏观上考察了该修整器对砂轮磨削性能的提高,结果证明该修整器可以进行有效修整,提高了加工工具精度,能满足金刚石砂轮修整使用要求。     

Dressing process model for vitrified bonded grinding wheels

A holistic dressing process model for vitrified bonded grinding wheels was designed. It regards the dressing process as a tribological system subjected to a complex load collective. The intensive analysis of the input variables and their impact on the system function led to new knowledge about the acting mechanisms. The model enables a qualitative prognosis of the grinding wheel topography, the dressing forces and the thermal dressing process load.     

Grinding of microstructured functional surfaces: a novel strategy for dressing of microprofiles

For the grinding of microstructured functional surfaces called riblets, a novel dressing strategy using diamond profile rollers was introduced for the generation of microprofiles on vitrified grinding wheels. The purpose of the present study is to grind special designed riblets (microgrooves with a width of 40 μm and depth of 20 μm) on the surfaces of compressor blades with the purpose of drag reduction in turbulent flow. It is currently not possible to achieve the desired microprofiles on grinding wheels by profile dressing directly, due to the limited producible minimal profile tip geometry on the dressing roller. The new profile dressing strategy using a profile shift kinematic allows generating microscopic roof profiles with an ideal sharp profile tip. Compared with dressing using form rollers, the new dressing method using profile rollers offers a much higher dressing efficiency and process stability at dressing microprofiles.     

Influence of different grinding wheel and dressing roller specifications on grinding wheel wear

A targeted adjustment of the dressing results and the methodological influence of the dressing process on the non-stationary wear of a grinding wheel after dressing increases the productivity and the reproducibility of grinding processes. Despite the great economic importance of grinding processes with vitrified corundum grinding wheels and the great relevance of the dressing process for the application behavior of these grinding wheels, quantitative models are missing for the purposeful design of the dressing process. In previous studies, a dressing model was successfully developed which predicts the dressing force in the dressing process as well as the workpiece roughness and the grinding wheel wear behavior in a grinding process for a specific grinding wheel and form roller specification. However, a transferability of this model to other grinding wheel and form roller specifications is not possible because the influence of the grain size and the hardness of the grinding wheel as well as the dressing tool topography on the grinding wheel wear and thus on parameters of the dressing model are not known. The objective of this work was to extend the model to additional grinding wheel and form roller specifications to ensure a broad applicability of the model.     

金属结合剂金刚石砂轮表面微槽的激光修整技术

针对金属结合剂金刚石砂轮表面微槽修整困难的问题,采用红外纳秒激光器开展修整试验,探究激光功率、脉冲重复频率、激光烧蚀时间等因素对其材料去除的影响规律,并对U型和V型2种砂轮微槽提出梯度步进激光修整工艺。结果表明:修整后的砂轮微槽实际轮廓与设计轮廓对比,其顶部和底部实际宽度相对误差的绝对值最大为4.4%,实际深度相对误差的绝对值最大为9.6%。用修整后的砂轮V型微槽对直径为4英寸(10.16 cm)的蓝宝石晶圆边缘进行倒角,晶圆锐利的边缘被修整成规则形状,边缘轮廓对称度良好,且与激光修整后砂轮表面的微槽轮廓一致,验证了金属结合剂金刚石砂轮表面微槽激光成型修整的可行性。      

NURBS在微机控制球面轴承内套双沟一次磨削加工中的应用

球面内套双沟道一次磨削加工技术对保证对称球面加工精度、提高粗糙度水平和磨不镁粗利，是提高球面轴承等机械产品质量和生产效率的先进技术手段。本文介绍应用ＮＵＲＢＳ技术实现在对砂轮修整中的数字插补控制方法。     

Dressing of filigree fine-grained metal bonded grinding wheels

Metal bonded grinding tools offer a remarkable potential for micro grinding because of their favorable wear behavior. However, metal bonded grinding tools, especially dicing blades, are hard to dress by conventional dressing methods. Electro contact discharge dressing, which is presented in this paper, is a numerically controlled dressing process offering the possibility to create the geometry and topography of the grinding wheel simultaneously at negligible dressing forces. The power of an electric circuit thermally removes the metal bond of the grinding wheel during the dressing process. The quality of the created profiles and the influence of the dressing parameters on the specific material removal rate of the grinding tool as well as the wear of the electrode are investigated at fine-grained grinding wheels.     

基于磨削法的金刚石磨料工具精密修磨技术

对磨削法修磨复杂形面金刚石磨料工具的技术进行研究。使用光学影像磨床,采用形面组合法对典型复杂形面金刚石工具进行修磨应用试验;通过理论分析、试验以及对修磨形貌显微观察等手段分析修磨机理;对修磨基本工艺、修磨效率和修磨精度的影响进行试验研究,并确定其相关规律。研究结果表明:磨削法修磨去除机理是通过磨粒接触面内局部接触点产生的高应力使金刚石表面发生微破碎,因此采用基于磨削法的精密修磨技术具有高效率和高精度的优点;对修整效果的主要影响因素是修磨切深、修磨速度、修磨砂轮等;单一元素形面修磨精度可以达到0.002 5 mm,角度5′以内,整体形面轮廓精度可以达到0.005 mm以内,修整砂轮后采用切入磨削工件加工,其表面粗糙度可以达到0.120 μm以下。