PERFORMANCE OF BRAZED DIAMOND CUP-TYPE WHEELS WITH DEFINED GRAIN PATTERN IN GRINDING CEMENTED CARBIDE

A new cup-type grinding wheel of the brazed monolayer diamond is developed with a defined grain pattern on the wheel surface. Grinding performance of the brazed wheel in the surface grinding of cemented carbide is studied. Experimental results show that when continuous dry grinding is employed, grits of the brazed diamond grinding wheel fail mainly in attritious wear and fracture modes and no pull-out ones are found in conventional electroplated and sintered diamond wheels. It indicates the strong retention of brazing alloy to diamond grits and the longer service life of the wheel. In addition, the ground surface has good roughness. The theoretical surface roughness agrees well with experimental results.

New Vitrified Bond Diamond Grinding Wheel for Grinding the Cylinder of Polycrystalline Diamond Compacts

In this work, a kind of new vitrified bond based on Li2O-Al2O3-SiO2 glass ceramics was used to bond the diamond grains, which is made into grinding wheel and the cylindrical grinding process of polycrystalline diamond compacts （PDCs） by using the new vitrified bond diamond grinding wheel was discussed. Several factors which influence the properties of grinding wheel such as amount of vitrified bond and the kinds and amount of stuff in grinding wheel were also investigated. It was found that the new vitrified bond can firmly combine diamond grains, when there are only diamonds and vitrified bond in the structure of grinding wheel, the longevity of the grinding wheel is about 2.5-3 times as that of resin bond grinding wheel for processing PDCs. The grinding size precision of PDCs can be improved from 4-0.03 mm to 4-0.01 mm because of larger Young＇s modulus of vitrified bond than resin bond. The grinding time of a PDC product can be 1.75-2.0 min from 3.25-3.5 min, so this kind of grinding wheel can save much time for processing PDCs. Also, there is hardly noise when using this new vitrified bond diamond grinding wheel to process PDCs. The amount of vitrified bond in grinding wheel influences the longevity of grinding wheel. When the size of diamond grains is 90-107 μm, the optimal amount of vitrified bond in grinding wheel is 21% （wt pct）. When the amount of vitrified bond exceeds 21%, there are many pores in grinding block, which will decrease the longevity of grinding wheel. The existence of addition stuff such as Al2O3 or SiC can reduce the longevity of grinding wheel.

Precision Grinding of Reaction Bonded Silicon Carbide Using Coarse Grain Size Diamond Wheels

Reaction bonded SiC（RBSiC） is attractive for optical application because of its favorable properties and low fabrication cost. However, the difficultness and cost involved in RBSiC grinding limit its application. The investigation on high efficient and low-cost machining with good grinding quality is desired. Generally, high efficient machining for RBSiC is realized by using coarse grain size grinding wheels, but serious grinding damage is inevitable. In this paper, monolayer nickel electroplated coarse grain size diamond grinding wheels with grain sizes of 46 μm, 91 μm, and 151 μm were applied to the grinding of RBSiC. An electrolytic in-process dressing（ELID） assisted conditioning technique was first developed by using cup shape copper bonded conditioning wheels with grain sizes of 15 μm and 91 μm to generate the conditioned coarse grain size wheels with minimized wheel run-out error within 2 μm, constant wheel peripheral envelop as well as top-flattened diamond grains. Then, the grinding experiments on RBSiC were carried out to investigate the grinding performance and material removal mechanism. The experimental results indicate that the developed conditioning technique is applicable and feasible to condition the coarse grain size diamond wheels under optimal conditioning parameters, and the material removal mechanism involved in RBSiC grinding is the combination of brittle fracture and ductile deformation to generate smooth ground surface. This research is significant for the high efficient and low-cost precision grinding of RBSiC with good ground surface quality.

RESEARCH ON PARALLEL GRINDING METHOD OF NON-AXISYMMETRIC ASPHERIC LENS

In order to resolve the problems of machining non-axisymmetric aspheric lens,which is short of flexibility in mould grinding and needs high accuracy CNC machine center in globediamond wheel grinding, a new parallel grinding method that utilizes common arc diamond wheel isput forward. Base on the approach calculation of machining locus, the advantages of parallelgrinding that machines non-axisymmetric aspheric lens by 2.5-axis CNC machine center have beenobtained. The results of grinding experiment show the new method can meet the need of grinding highaccuracy non-axisymmetric aspheric lens.

High Efficiency Axial Deep Creep-Feed Grinding Machining Technology of Engineering Ceramics Materials

Axial deep creep-feed grinding machining technology is a high efficiency process method of engineering ceramics materials, which is an original method to process the cylindrical ceramics materials or hole along its axis. The analysis of axial force and edge fracture proved the cutting thickness and feed rate could be more than 5-10 mm and 200 mm/min respectively in once process, and realized high efficiency, low-cost process of engineering ceramics materials. Compared with high speed-deep grinding machining, this method is also a high efficiency machining technology of engineering ceramics materials as well as with low cost. In addition, removal mechanism analyses showed that both median/radial cracks and lateral cracks appeared in the part to be removed, and the processed part is seldom destroyed, only by adjusting the axial force to control the length of transverse cracks.

Material Removal Behavior and Surface Integrity in Grinding of UltrafineGrained WC-Co Materials

Due to the excellent combination of wear resistance and fracture toughness,the ultrafine-grained WC-Co composites can significantly improve the durability and reliability of industrial tools.However,the grinding of ultrafine-grained WC-Co remains a challenge.In order to provide an experimental basis for improving grinding quality of ultrafine-grained WC-Co,a series of surface grinding experiments on ultrafine-grained WC-Co hardmetals were conducted by diamond wheel under various grinding conditions,and the material removal behavior and surface integrity in grinding of ultrafine-grained WC-Co materials were characterized by means of scanning electron microscopy(SEM),X-ray microstress analyzer and surface roughness analyzer in this paper.The results indicate that the material removal behavior in grinding of ultrafine-grained WC-Co materials is determined not only by the abrasive grain size on the wheel,but also by the depth of cut.The roughness values of ground surface increase with increasing grit size of diamond wheel,and increase initially,then decrease with increase in depth of cut.Grinding causes the residual compressive stress in the surface layer of ground cemented carbides under various grinding conditions;the magnitude of residual surface stress increases with increasing grit size of diamond wheel,and isn't changed obviously along with the change of depth of cut.

金刚石砂轮与金刚石滚轮磨削接触的声发射监测

为了实现金刚石砂轮磨削加工金刚石滚轮过程的自动化,需要对磨削接触状态进行准确识别。由于磨削过程中材料去除率较小导致声发射信号幅值变化不显著,仅用有效值对磨削接触状态识别的准确性受噪声影响很大。针对此问题,通过模态分解和相关性分析相结合的方法对采集的声发射信号进行处理,再计算各分量的有效值和方差值完成特征提取,最后利用支持向量机对磨削接触状态进行识别。实际应用发现:该方法对滚轮的磨削接触状识别准确率达到了98.3%,准确实现了对磨削接触状态的识别。

粗粒度金刚石砂轮的放电赋能磨削修整试验研究

针对粗粒度金刚石砂轮磨粒出刃形貌难以控制的问题,提出了放电赋能磨削修整技术,旨在实现出刃磨粒的等齐性。系统研究了该复合修整技术的材料去除机理,建立脉冲放电传热数值模型,以金刚石热软化深度作为磨削深度,最大限度发挥放电赋能磨削的修整优势。探究了机床运动参数(待修砂轮转速、刀具轮转速、进给速度、磨削深度)对砂轮修整精度和刀具轮损耗深度的影响规律,并优化了工艺参数以实现粗粒度砂轮的高效高精修整。磨粒粒度为180目的金刚石砂轮修整后轮廓误差PV值为11.97μm。修整砂轮表面形貌检测结果表明,放电赋能磨削修整可将磨粒部分去除,使得砂轮表面磨粒具有较好的等齐性。磨削的碳化硅陶瓷工件表面粗糙度达412 nm,表明了修整砂轮具有优异的磨削性能。

超精密晶圆减薄砂轮及减薄磨削装备研究进展

在芯片制程的后道阶段,通过超精密晶圆减薄工艺可以有效减小芯片封装体积,导通电阻,改善芯片的热扩散效率,提高其电气性能、力学性能。目前的主流工艺通过超细粒度金刚石砂轮和高稳定性超精密减薄设备对晶圆进行减薄,可实现大尺寸晶圆的高精度、高效率、高稳定性无损伤表面加工。重点综述了目前超精密晶圆减薄砂轮的研究进展,在磨料方面综述了机械磨削用硬磨料和化学机械磨削用软磨料的研究现状,包括泡沫化金刚石、金刚石团聚磨料、表面微刃金刚石的制备方法及磨削性能,同时归纳总结了软磨料砂轮的化学机械磨削机理及材料去除模型。在结合剂研究方面,综述了金属、树脂和陶瓷3种结合剂的优缺点,以及在晶圆减薄砂轮上的应用,重点综述了目前在改善陶瓷结合剂的本征力学强度及与金刚石之间的界面润湿性方面的研究进展。在晶圆减薄超细粒度金刚石砂轮制备方面,由于微纳金刚石的表面能较大,采用传统工艺制备砂轮会导致磨料发生团聚,影响加工质量。在此基础上,总结论述了溶胶–凝胶法、高分子网络凝胶法、电泳沉积法、凝胶注模法、结构化砂轮等新型工艺方法在超细粒度砂轮制备方面的应用研究,同时还综述了目前不同的晶圆减薄工艺及超精密减薄设备的研究进展,并指出未来半导体加工工具及装备的发展方向。

偏转激光切向修整凹形面金刚石倒角砂轮的研究

为了减小凹形面金刚石砂轮的激光修整误差,建立激光遮蔽效应和激光斜面分散效应误差模型,分析了激光切向修整凹形面金刚石砂轮的误差来源,提出了偏转激光修整凹形面成形砂轮法,并通过理论分析和实验验证,探索了修整参数对凹形面砂轮轮廓精度和圆弧半径的影响。结果表明,在1°~1.5°的偏转角范围内,斜边轮廓修整精度为8μm;在合适的偏转角度下,圆弧半径误差小于10μm;在修整凹弧半径为0.2 mm和0.5 mm、补偿半径分别为0.03 mm和0.06 mm时,凹弧半径误差分别缩小0.02 mm和0.03 mm。偏转激光修整法有效地提高了修整精度,减小了修整误差,为凹形面金刚石修整提供了新思路。

陶瓷磨削用多层钎焊金刚石砂轮的研制

为解决传统树脂、电镀金刚石砂轮磨削陶瓷材料时存在的磨削寿命短、砂轮易堵塞烧伤等问题,分析利用钎焊金刚石技术制备陶瓷磨削用多层钎焊金刚石砂轮的可行性。结合钎料组分优选,制备具有开槽结构的多层钎焊金刚石砂轮,并对99.9%高纯度的Al_(2)O_(3)陶瓷进行磨削性能试验。结果表明:树脂、电镀金刚石砂轮分别存在磨削效率低和磨削寿命不足的问题,单层钎焊金刚石砂轮磨削效率较高但磨削寿命有限,多层钎焊金刚石在保持高磨削效率的同时磨削寿命优势明显,较单层钎焊金刚石磨轮提升约60%。在陶瓷材料磨削过程中,多层钎焊金刚石砂轮磨削效果显著,虽磨粒出露高度有限,但开槽设计的排屑效果显著,砂轮表面不易发生陶瓷粉末黏结、堵塞。

激光修整青铜金刚石砂轮预测模型与优化研究

为了根据实验规律获得更多激光修整青铜金刚石砂轮的工艺参数,采用反向传播(BP)神经网络和粒子群遗传混合优化算法(PSO&GA),建立了激光修整青铜金刚石砂轮的预测模型。首先通过分析激光修整的原理得出砂轮型面角度、激光偏转角度、入射角度和光斑重叠率为主要影响参数,并以砂轮型面角度误差和峰谷(PV)值为评价指标修整了192组工艺实验数据;建立了4×9×2的3层BP神经网络预测模型,通过PSO&GA混合优化算法对预测模型进行训练优化;最后选取16组实验数据测试BP神经网络预测模型,预测结果比较准确;并对比了梯度下降法(GD)、粒子群优化算法(PSO)和遗传算法(GA)的BP神经网络的训练效果。结果表明,经PSO&GA-BP预测模型角度误差预测偏差在0.2°以内,PV值预测偏差在1.6μm以内,相较于其它优化算法,收敛速度更快、精度更高。该研究为激光修整青铜金刚石砂轮提供了良好的预测模型。

弧形金刚石砂轮机械修整研究进展

弧形金刚石砂轮因特有的弧形轮廓,常用于陶瓷、光学玻璃、硬质合金等难加工材料光学元件的精密超精密磨削加工。然而,在光学元件磨削加工过程中,由于砂轮与工件表面间的相互作用,砂轮表面受到挤压破坏,长时间磨削后会产生砂轮堵塞、砂轮磨损、砂轮尺寸和形状精度下降等问题,进而降低了磨削后光学元件的表面粗糙度、面形精度和损伤厚度等。修整弧形金刚石砂轮是解决上述问题的有效途径之一,机械修整因具有修整效率高、便于实现等特点,仍是弧形金刚石砂轮在位修整的主要应用方法。对弧形金刚石砂轮的机械修整方法进行了综述,探究了不同修整方法的修整机理与特点,分析了修整效果的评价方法,并对弧形金刚石砂轮机械修整的发展方向进行了展望。

不同造孔剂树脂金刚石砂轮对硬质合金球阀的精密研磨

为改善硬质合金球阀的加工效果,在树脂金刚石砂轮中引入造孔剂,对其力学性能、微观形貌及磨削性能进行分析,研究空心玻璃球和塑料球造孔剂对树脂金刚石砂轮性能的影响。结果表明:随着造孔剂体积分数增加,树脂砂轮的抗折强度逐渐下降,且2种造孔剂对抗折强度的影响基本一致;砂轮的硬度随造孔剂体积分数的增加亦逐渐下降,但空心玻璃球造孔剂对砂轮硬度的影响显著大于塑料球的;加入造孔剂明显提升了砂轮的锋利性,空心玻璃球体造孔剂体积分数为15%和塑料球造孔剂体积分数为20%的砂轮综合性能最好,且后者的综合性能优于前者的。

一种树脂金刚石复合材料的分子动力学模拟

本文研究一种用于制备微细砂轮的树脂金刚石复合材料,该复合材料由丙烯腈-丁二烯-苯乙烯(ABS)作为基体,聚氯乙烯(PVC)作为混料,邻苯二甲酸二辛酯(DOP)作为加工助剂,与金刚石磨粒混合而成。对5种不同配比的共混体系进行分子动力学模拟,结果显示:提高ABS的质量比,复合材料分子间作用力逐渐增强,密度逐渐降低,延展性和柔性先减小后增加,ABS和PVC的相容性先减小后增加,复合材料最佳配比为62.5wt%ABS、18.6wt%PVC、8.3wt%DOP和10.6wt%金刚石磨粒。

金刚石砂轮的磨削整形法研究

为研究金刚石砂轮修整的工艺,采用绿碳化硅砂轮对金刚石砂轮进行磨削整形法修整。通过改变修整量、修整速比、切削进给量、工作台速度得出修整参数对砂轮磨削性能的影响规律。研究结果表明,工件表面粗糙度随着修整量增加而增大,修整量增加到一定次数时粗糙度变化不大;修整速比增大时,工件表面粗糙度值增大;切削进给量增大时,工件磨削表面粗糙度增大;工作台速度增大时,工件表面粗糙度增大。所得结论为绿碳化硅砂轮修整金刚石砂轮的工艺参数选取提供了切实有效的参考价值。

Ni-Cr合金Ar气保护炉中钎焊金刚石砂轮的研究

用活性钎料钎焊单层金刚石砂轮与传统电镀砂轮相比具有磨削锋利、寿命长等优异性能。利用 Ar气保护炉中钎焊的方法 ,用 Ni-Cr合金粉末做钎料 ,适当控制钎焊温度、保温时间和冷却速度 ,实现了金刚石与钢基体的牢固连接。利用扫描电镜和 X射线能谱 ,结合 X射线衍射结构分析 ,发现在钎焊过程中 Ni-Cr合金中的 Cr元素分离出在金刚石界面形成富 Cr层并与金刚石表面的 C元素反应生成 Cr3C2 和 Cr7C3,这是实现合金层与金刚石有较高结合强度的主要因素。重负荷磨削实验表明金刚石为正常磨损 。

脆性材料超精密磨削时影响表面质量因素的研究

首先从理论上分析了脆性材料在超精密磨削过程中影响表面质量的各种主要因素。然后针对影响脆性材料已加工表面质量的各种主要因素作了大量的试验研究。研究结果表明，对于脆性材料，砂轮的平均磨粒尺寸对已加工表面质量的影响很大。试验证明：当采用超精密磨床并在Ｖｓ＝１２００ｍ／ｍｉｎ、ｆ＝０—２００μｍ／ｒ、ａｐ＝０．１—１０μｍ的磨削条件下进行磨削时，只有当金刚石砂轮的平均磨粒尺寸小于 ２０μｍ，才能在塑性磨制模式下加工出高质量的超光滑表面。

超硬磨料砂轮的激光修锐技术研究

介绍激光修整超硬磨料砂轮的原理 ,利用 Nd:YAG固体脉冲激光器进行激光修锐青铜结合剂和树脂结合剂超硬磨料砂轮的试验 ,用扫描电镜观察了激光修锐前后砂轮表面的微观形貌 ,对激光作用下砂轮表面不同结合剂材料的去除机理进行分析 ,通过磨削陶瓷试验 ,研究激光修锐的金刚石砂轮的磨削性能 ,并与普通砂轮磨削法修锐的金刚石砂轮进行对比。结果表明 ,采用试验所确定的激光参数可选择性地去除砂轮表面的结合剂材料 ,而不损伤超硬磨粒 ,激光修锐的砂轮可获得较大的容屑空间和磨粒突出高度 。

陶瓷磨削的表面/亚表面损伤

磨削是目前工程陶瓷的主要加工方法 ,本文主要对国内外在陶瓷磨削后工件表面 /亚表面损伤 (主要是微裂纹和表面残余应力 )方面所作的研究成果进行了总结、分析和讨论 ,提出了一些有待研究的问题及其研究思路 .同时就作者所承担项目“纳米结构材料精密磨削及其预报”研究中的临界砂轮磨粒切深 (dc)和被磨工件临界损伤深度 Cr(临界中位裂纹长度 )的预测模型进行了分析 ,并建立了临界砂轮磨粒切深 (dc)理论模型 .