干式磨抛用钎焊金刚石磨抛盘制备与试验

为解决传统树脂砂轮片干式磨抛高强度钢存在的磨抛效率低、火花大、粉尘多、安全性低等问题,分析了利用钎焊金刚石技术的优势制备新型磨抛盘的可行性,并提出了解决对策。结合新型金刚石磨料排布工艺,利用Ni-Cr合金焊料,真空钎焊制备了钎焊金刚石磨抛盘。对AH36船用高强度钢进行了干式磨抛对比试验。试验表明:与传统树脂砂轮片相比,钎焊金刚石磨抛盘磨削效率提高40%左右,磨削寿命是前者的12倍以上;磨屑平均体型较大且种类多,无熔融状磨屑存在,磨粒表面基本无磨屑粘附,证明了新型磨抛盘干式磨削时可有效控制磨削温度。     

黏弹性阻尼结构对钎焊金刚石磨抛盘磨抛性能的影响

针对钎焊金刚石磨抛盘在磨抛过程中存在振动大、噪声大、手感不佳等问题,结合黏弹性阻尼材料减振降噪原理及磨抛盘整体结构,设计了自由约束结构的橡胶衬垫结构。利用ANSYS模态仿真分析此结构下的固有模态以校核临界转速,并与树脂砂轮片、钎焊磨抛盘进行了磨抛对比试验。试验证明,同等磨抛条件下,带有黏弹性阻尼结构的磨抛盘噪声仅比角磨机空转噪声值高0.6 d B,振动较钎焊磨抛盘降低48%,磨抛效率2倍于市场上常见的树脂砂轮片。     

高温钎焊工艺对磨抛盘基体性能的影响研究

对磨抛盘基体高温钎焊前后的抗弯性能、显微硬度以及材料金相组织进行试验对比分析,研究高温钎焊工艺对磨抛盘基体性能的影响。结果表明,加钎料层基体焊后抗弯性能增强;基体焊后组织更为均匀,材料的强韧性更好,结合界面处组织致密;基体焊后材料显微硬度值降低了40HV0.05,焊后结合界面区域的显微硬度较高,验证了自行设计的磨抛盘基体的选材及结构设计能够满足要求。     

基于磨粒轨迹均匀性的钎焊金刚石磨抛盘地貌优化设计

磨粒轨迹均匀性是衡量钎焊金刚石磨抛盘加工表面质量的重要指标。基于磨粒有序排布方式设计了矩形阵列、同心圆、螺旋线和叶序4种磨粒有序排布地貌,利用MATLAB软件得到不同地貌下磨粒的运动轨迹仿真结果,发现矩形阵列与叶序排布方式的磨粒轨迹均匀性较优。采用轨迹分布非均匀性来定量评价磨粒轨迹的均匀性程度,对比分析了磨粒有序排布与随机排布地貌的磨粒轨迹均匀性,得出结论：有序排布地貌的磨粒轨迹均匀性优于随机排布,且叶序排布方式为最佳地貌;提高磨抛盘转速、减小磨抛盘进给速度均能够提高钎焊金刚石磨抛盘磨粒轨迹均匀性。通过磨抛实验对仿真结果进行验证,结果表明：相对于随机排布,地貌优化后的钎焊金刚石磨抛盘材料去除率高,加工表面质量好,加工性能得到提高。     

机械电解抛磨曲面的工具设计和试验研究

设计和制造了专用曲面抛磨工具,对抛磨过程进行了运动仿真,并通过机械电解复合加工工艺试验,验证了工艺的可行性,具有加工效率高、质量好的优点.     

钎焊金刚石磨盘磨抛低合金高强度钢Q345的试验研究

为提高低合金高强度钢Q345的磨抛效率和磨抛工具的使用寿命,设计、制备了2种粒度的钎焊金刚石磨盘。用钎焊金刚石磨盘进行了低合金高强度钢Q345的磨抛性能试验,并与传统的树脂砂轮片进行了对比研究。试验结果表明,钎焊金刚石磨盘的磨抛效率高于树脂砂轮片,不同粒度的钎焊金刚石磨盘磨抛效率有所差异,钎焊金刚石磨盘的磨抛温度低于树脂砂轮片,金刚石磨粒的磨损量小,服役寿命长。     

基于最大熵原理的平面研抛工艺参数优化

提高光学零件研抛加工精度的关键是优选工艺参数。对此提出一种基于最大熵原理的平面研抛工艺参数优化方法。建立了工件研抛信息熵的数学表达式并给出了相关的物理解释,并对定偏心平面研抛工艺参数优选进行了数值模拟计算。研究结果表明,在定偏心平面研抛中,选择工件与研抛盘同方向等速转动可以使工件表面材料去除均匀,选择较大的偏心率可以提高加工效率,同时应实时修整研抛盘以减小研抛盘磨损对工件加工精度的影响。     

机器人磨抛加工接触稳态自适应力跟踪研究

磨抛加工作为复杂曲面制造的最后关键工序,直接决定着零件的轮廓精度与表面质量。机器人具有运动范围大、通用灵活与智能化等优势,结合砂带磨抛工艺被广泛应用于大型复杂曲面零件的加工。但机器人多轴耦合、末端响应速度慢与定位精度低等弊端导致磨抛加工接触力精准控制困难,难以实现机器人柔顺力控加工。针对机器人磨抛加工接触稳态力跟踪问题,在阻抗控制与基于环境参数估计的参考轨迹自适应生成方法上,提出采用遗传算法对位置误差引起的接触力误差进行补偿。结果表明,所提出的方法提高了机器人磨抛加工接触力的跟踪精度,接触稳态力跟踪误差降低约85.7%,具有较好的稳定性与可靠性,可以实现机器人在未知环境下的柔顺自适应加工。     

4+2自由度叶片抛磨专用机器人轨迹规划方法研究

砂带抛磨作为复杂曲面叶片精密加工的最后一道工序,其加工质量直接影响叶片的服役性能和寿命。传统6自由度机器人多关节串联具有明显的弱刚性,在末端夹持大型叶片时抗变形能力欠佳。为此,文章自主设计研发了4+2自由度叶片抛磨专用机器人系统,并开展复杂曲面叶片抛磨轨迹规划方法研究。首先基于D-H法建立该机器人运动学模型,进行机器人运动学的正、逆解的求解;其次给出了综合考虑抛磨工具与工件曲率的干涉、刀路轨迹行距和轨迹点密度对残留高度的影响规律的轨迹规划方法,建立了2个单元的协同运动模型保证叶片的加工实现;最后通过叶片抛磨轨迹数控程序验证了所获得的抛磨轨迹的正确性。     

叶片抛磨表面粗糙度优化预测模型及实验研究

抛磨作为提高叶片表面质量的最后一道工序,能够显著提高叶片表面完整性,表面粗糙度是衡量叶片抛磨后表面完整性最重要的技术指标。采用六自由度机器人+百叶轮弹性磨具对叶片进行抛磨加工,首先采用单因素实验法分析了影响叶片表面粗糙度的主要工艺参数,接着采用正交试验得出了叶片抛磨加工的优化工艺参数区间,最后采用非线性回归模型对表面粗糙度进行了预测。实验验证结果表明,影响叶片表面粗糙度的主要工艺参数依次为百叶轮目数、接触压缩量、抛磨循环次数和机器人进给速度,采用川崎RS20N机器人抛磨某型号精铸汽轮机叶片,优选区间为百叶轮目数（200～600）#之间,接触压缩量为（0.2～1.2）mm,抛磨循环次数为（2～4）次,进给速度为（0.1～0.4）mm/s,在优选工艺区间进行加工,表面粗糙度均低于0.4μm,预测模型和实际抛磨结果误差率低于10%,表明该预测模型能够为实现叶片抛磨工艺参数在线控制和调整提供理论依据。     

单层钎焊金刚石砂轮的修整实验研究

为满足单层钎焊金刚石砂轮高效精密加工的性能要求,对磨粒有序排布单层钎焊金刚石砂轮的修整进行了实验研究。采用磨粒有序排布的钎焊金刚石修整工具对钎焊砂轮进行了修整,该修整方法通过修整工具粒度的变化以及修整速比的调整来控制砂轮形貌,从而使氧化锆的磨削表面粗糙度达到了精密加工的水平。对砂轮形貌进行了观测统计,数据表明,砂轮磨粒的等高性得到明显改善且避免了磨粒端部的严重钝化。     

微波铁氧体基片高效磨削技术研究

针对微波铁氧体基片的功能要求、材料特性和磨削工艺特点,通过大量实验分析了铁氧体基片ELID磨削与普通磨削的磨削力对比结果和形成原因,以及磨削力随工艺参数的变化规律,在此基础上,对ELID磨削效率、表面质量及磨削中出现的问题和解决途径进行了深入研究。实验结果表明,ELID磨削方法适用于微波铁氧体基片的高效磨削,保证了表面加工质量,将ELID磨削技术与平行研抛工艺结合起来,能够形成微波铁氧体基片精密高效的批量生产能力。     

Development and performance of monolayer brazed CBN grinding tools

CBN grinding tools have been broadly utilized in machining difficult-to-cut materials in recent years. Grains of the conventional grinding tools, however, are held in the tool matrix just through the mechanical incrustation effect induced by the electroplated or sintered metal, which results in the stochastic grain distribution and limited grain protrusion, in addition to the easy grain pullout and premature tool failure by the strong impact forces generated during machining. These properties and shortcomings of the electroplated or sintered tools have restricted the potential of CBN superabrasive grains. Therefore, a new technology has been developed and introduced in this paper to fabricate successfully monolayer CBN grinding tools, in which the highly protruding grains could be planted in the required uniform pattern through the brazing effect among CBN grains, filler alloy and tool substrate at elevated temperature. Finally, comparative grinding tests performed with the conventional electroplated and newly-developed brazed CBN tools have indicated that highly increased efficiency and prolonged tool lives, as well as low fabrication and use cost could be achieved by applying the brazed CBN grinding tools.     

Investigation and development of a molding process for the production of micro-hairs

Cubic boron nitride (cBN) is a unique synthetic material on account of its high hardness, high wear resistance, excellent cutting edge stability and relative chemical inertness compared to diamond. The introduction of monolayer electroplated cBN wheels replaced the complex pre-grinding wheel preparation work (truing and dressing) of composite cBN wheels and thereby extensively facilitating the application in high-efficiency deep grinding, creep feed grinding, etc. The present work has aimed at developing a precisely controlled brazing technique suitable for bonding the cBN grits to a steel substrate in monolayer form with higher bond strength, larger grit protrusion and more uniform grit distribution compared to that in the currently used galvanically bonded wheels. Experimental investigation have clearly demonstrated the potential of the newly developed brazed wheels under varying grinding conditions for processing materials like bearing steel. Improved capability of these wheels over galvanically bonded wheels could be better recognised during dry grinding at high material removal rate and for large stock removal when galvanically bonded wheels were found to suffer from severe wheel loading in grinding bearing steel and from unusual increase in grinding forces due to grit pullout. Creation of wider inter-grit spaces with strong bonding and uniform grit spacing happened to be the essence of the present brazed cBN wheel.     

天线罩CNC修磨机床磨削轨迹计算

为了完成天线罩类大型复杂型面硬脆材料工件内廓型的测量与精密磨削，研制了天线罩CNC修磨机床；依据测量得到的天线罩内廓型离散数据和曲面上要求的各点去除量，经复杂数据处理后在计算机控制下，由电镀球形金刚石砂轮进行天线罩内廓型的精密磨削；根据天线罩内廓曲面的特点和加工要求，提出了一种刀具轨迹计算方法；在满足指定精度的情况下实现天线罩内廓曲面的高效率加工，使天线罩达到设计规定的性能指标。     

异型石材加工中心磨抛砂轮创新改造设计研究

对石材数控机床磨抛砂轮现状进行了分析,研究了现有的加工方法和磨头结构,针对异型石材加工中心在工作过程中,对于复杂曲面磨抛时存在的问题,应用技术创新方法中ARIZ85算法流程寻求解决方案,进行了自动加工磨抛砂轮的创新改造设计。在对实际问题分析的基础上,完成了系统功能分析及原因分析,通过对创新原理应用,使用了技术矛盾分析,维数变换和分离方法的等算法,确定了异型石材加工中心磨抛砂轮设计方案,解决了在加工中心上无法实现复杂曲面磨抛的问题。     

软体磨具新技术

零件曲表面的磨光,抛光技术是精密加工技术领域的难题,传统的磨具难以直接对不规则的曲面进行加工。作者研究的软磨具,是一种体内均匀含磨料的新型高分子复合材料、磨料和抛光粉为加工要素,聚氨酯基网链状高分子材料为连接剂并为抛光要素。新型软磨具为三维柔软的弹性体,能适应任意曲率的零件（金属或非金属）表面的磨光和抛光要求。本文包括新型软磨具的生成理论,制造技术和曲面零件抛光的工艺性能试验研究。     

Efficient microspark erosion-assisted machining of a monocrystalline microdiamond stylus using a heat-avoidance path

Monocrystalline diamond possesses covalent bonding making diamond extremely hard and difficult to machine. In this study, a microdiamond stylus typically used in measuring surface roughness is machined to exemplify the proposed ‘microspark erosion-assisted machining with heat-avoidance path’ technique. Based on the high thermal conductivity and weak electrical conductivity of boron-doped monocrystalline diamond, high-frequency pulsed discharge plasma is employed to efficiently perform microspark erosion machining on an extremely hard monocrystalline diamond blank. It was found that the pulse-on time and servo voltage respectively affect erosion plasma length and the erosion gap during diamond machining. Also, the safety distance and safety height of the erosion path dominate heat transfer to filler metal. These factors all affect the firmness of the brazed diamond blank on the substrate. Three mechanisms for removing carbon atoms from the diamond blank surface were observed. They are vaporization, melting, and graphitization of carbon atoms. This graphitized carbon atoms have weak electrical conductivity, which is conducive to inducing the wire-electrode to generate a greater electric field and secondary discharging, facilitating removal of additional carbon atoms. Experimental results indicate that a microdiamond stylus prototype with a tip of 10 μm can be safely formed using a ‘microspark erosion-assisted machining with heat-avoidance path’ technique, creating 93.7% repeatability of the minimum residual stylus diameter. The tangential micro-grinding facilitates the stylus tip to receive grinding from the grinding wheel's maximum tangential speed and create the precision microdiamond stylus with 1 μm in tip-radius. The applied microspark erosion-assisted machining had a diamond material removal rate that was 54% more efficient than conventional grinding of a commercial microdiamond stylus. The formed microdiamond stylus was inspected by Raman spectroscopy and verified by the surface roughness standard gauge to be up to industry standards.     

金刚石表面的膜层沉积处理及其感应钎焊的研究

将热丝化学气相沉积(HFCVD)处理的金刚石作为磨料感应钎焊制作金刚石工具。HFCVD处理试验中,混合气为H2和CH4(体积流量比为100∶1.5),炉内压力为2.0kPa,700℃下处理45min后,在金刚石表面沉积了一层非晶碳膜。感应钎焊HFCVD处理的金刚石显示,出露部分的金刚石棱边能保持良好的锋利性;浸没在钎料层下面的金刚石表面形成了有均匀孔隙且形状不规则的铬碳化合物,液态钎料充填这些化合物孔隙之间,能够增强钎料对金刚石的把持强度。3种金刚石磨料感应钎焊制作的金刚石磨盘的高效重负荷石材磨削试验显示,HFCVD处理的金刚石的整体破碎率和脱落率最低。