薄片工件磨削加工的工艺改进

分析了薄片工件在磨削加工中的特点,介绍了对薄片工件常用的加工方法。通过对薄片工件磨削措施的改进,成功地实现了对薄片工件的精度控制,总结出在磨削加工薄片工件时应注意的事项,为制订同类薄片零件的磨削加工工艺方法提供了新的思路。     

一种半圆弧面支架加工工艺

为有效解决车削加工工件两侧圆弧时,工件需转换二次装夹,导致定位精度不高和加工偏差,达不到工件工艺要求的形位公差,以及加工工件尺寸不稳定等问题,制作了专用工装装夹,将工件扣装在工装上,控制夹具体厚度,在工件装夹后,两圆弧面构成一整圆弧面进行车削加工。通过应用该工装,改两次装夹为一次装夹,实现对圆弧侧面的加工,提高了加工精度,保证了产品质量。     

旋转磁场在微小工件磁力研磨加工中的应用

微小工件在工业产品中的应用日益增多,相对于其他工件的加工,微小工件由于在加工过程中装夹困难,至今缺少高效的加工手段。磁力研磨加工中使用旋转磁场被认为是解决微小工件加工困难的有效手段。介绍了磁力研磨技术在应用领域的最新成果,总结了产生旋转磁场几种的方法,分析了磁力研磨加工的加工原理和技术特点。讨论了影响磁力研磨加工质量的几个因素,解释了影响因素的作用原理。最后指出了在磁力研磨加工存在的问题,展望了旋转磁场在微小工件磁力研磨加工中的发展前景。     

CFRP薄壁圆筒零件的精密加工与测量技术

介绍了用于精密加工、测量CFRP薄壁圆筒工件的技术。通过合理的工艺规划、夹具设计,克服了工件的加工难点,实现了工件的精密测量。根据实际加工情况改进了工艺流程与夹具设计,进一步提高了工件加工质量,基本满足设计要求。     

某薄形工件的磨削方法的探讨

分析了薄形工件在平面磨削加工中的难点,并通过对一种薄形工件磨削加工的试验、验证,继而得出了薄形工件磨削加工中的几点建议。     

面向加工特征的工件制造过程能耗预测方法

在工件的制造过程中,具有多个特征的工件在加工时,其加工特征的能耗属性不同,为了研究在工件不同的加工特征对能耗的影响,创建了面向加工特征的工件制造过程能耗预测模型。首先,将工件看成单个加工特征的集合体,其次对工件特征切削功率的分析,创建有关切削功率的能耗数学模型;然后采用GM(1,1)模型完成工件加工时其切削功率的灰色建模,实现整个工件能耗的预测过程,最后通过对冲床顶支座的加工过程为例,说明了该模型的准确性。     

细长工件加工精度影响因素及控制措施

针对细长工件加工中存在问题,通过分析影响加工精度主要因素,提出了更具针对性精度控制对策,通过实践应用所制定精度控制对策取得了良好效果,提升了工件加工精度升,降低了工件粗糙度也有所降低,确保了工件加工效率,值得进一步推广应用。     

各种轴向对刀量仪在数控外圆磨床上的应用

在数控端面外圆磨床或数控内、外圆磨床上,大部分都配备了端面对刀量仪和内、外圆测量量仪,使工件在磨削加工中,形成了一个闭环反馈,控制了磨床的加工精度.在磨削加工过程中,对加工工件的尺寸变化,量仪检测器进行在线检测,其结果随时向数控系统发出各种信号,例如粗磨、精磨、光磨信号,系统能自动改变加工程序,从而达到控制加工精度的一致性,提高了工件加工精度和工作效率,预防了废品的产生.对于一些加工带轴肩的外圆工件来说,为了纠正工件中心孔深浅的不一致而引起端面轴向位置的偏差,应用了轴向对刀量仪装置来检测加工工件的端面位置,从而使工件端面能正确定位.这样在数控磨床上加工多台阶工件带来可能和方便.     

机械加工零件表面的质量控制措施

为了确保进行机械加工时更好地控制工件表面质量,通过实例分析法,结合硬铝合金工件在实际铣削加工过程中不同参数情况下工件表面质量情况,进行分析与研究。结果表明:铣削加工硬铝合金工件的作业过程中,随着切削深度值逐步增大,加工工件的粗糙度也有所增加;设定的径向进给量参数值越小,加工工件的表面粗糙度也会进一步的减小;进给速率参数逐步增加,工件粗糙度相应也会随之增。通过实验得出了不同因素对于工件表面质量影响的规律,为工件加工中具体参数确定提供了参考与依据。     

虚拟加工过程薄壁工件铣削变形模型研究

在薄壁工件的切削加工中,工件的受力变形是影响加工过程的一个主要因素,文中针对薄壁工件侧面的立铣加工,建立了不同复杂度的切削过程模型,以仿真工件薄壁在加工中受到切削力发生的变形,虚拟实现受到工件变形影响下的切削过程。通过仿真创成的工件表面形貌与实际切成的工件表面的比较,对文中各模型进行了验证。     

BTA深孔加工系统中工件的振动分析

将深孔加工中的工件简化成两端固定支撑的旋转梁,建立工件的动力学模型,运用梁理论得到工件的自由振动方程,利用MATLAB拟合分析在不同切削位置、不同主轴转速和不同进给量情况下工件的振动偏移量。分析结果表明,加工到工件的不同位置时,工件的偏移量不同,中心处工件偏移量最大;增大刀具的进给量,工件的振动偏移量增大;转速的变化对工件的振动影响较小。     

夹紧方案的数学建模及夹紧力的优化设计

夹紧变形有两大产生原因:由夹紧副变形导致的工件位置误差以及由夹紧力导致的工件变形。本文主要建立了夹紧副变形与工件位置误差的关系模型;并基于该模型,以最小工件位置误差为目标,实现了夹紧力的优化设计。     

Numerical study on the dynamics of an electrical discharge generated vapor bubble in EDM with different shapes of the tool and the workpiece

In this paper, the effect of the shapes of the tool and the workpiece on the dynamic behavior of an electrical discharge generated vapor bubble in the process of EDM (Electrical Discharge Machining) is investigated. The boundary integral equation method is employed for numerical simulation of the problem. Results show that in the case of the concave tool and workpiece the lifetime of the electrical discharge generated vapor bubble is longer than the case of the flat tool and workpiece. By increasing the concavity of the shapes of the tool and the workpiece, the lifetime of the bubble increases. Results also show that in the case of the convex tool and workpiece, the lifetime of the electrical discharge generated vapor bubble is shorter than the lifetime of the bubble in the case of the flat tool and workpiece. In this case also, by increasing the convexity of the shapes of the tool and the workpiece, the lifetime of the bubble decreases. Numerical results show that in the case of the concave tool and workpiece the rate of pressure drop on the surface of the workpiece is higher than the rate of pressure drop on the workpiece in the cases of the flat and convex tool and workpiece. The high rate of pressure drop on the surface of the workpiece leads to the ejection of more molten material from the crater and consequently leads to more material removal rate.     

Machining fixture layout design using ant colony algorithm based continuous optimization method

In any machining fixture, the workpiece elastic deformation caused during machining influences the dimensional and form errors of the workpiece. Placing each locator and clamp in an optimal place can minimize the elastic deformation of the workpiece, which in turn minimizes the dimensional and form errors of the workpiece. Design of fixture configuration (layout) is a procedure to establish the workpiece–fixture contact through optimal positioning of clamping and locating elements. In this paper, an ant colony algorithm (ACA) based discrete and continuous optimization methods are applied for optimizing the machining fixture layout so that the workpiece elastic deformation is minimized. The finite element method (FEM) is used for determining the dynamic response of the workpiece caused due to machining and clamping forces. The dynamic response of the workpiece is simulated for all ACA runs. This paper proves that the ACA-based continuous fixture layout optimization method exhibits the better results than that of ACA-based discrete fixture layout optimization method.     

基于线性不等式方程组解的存在性及其通解的工件可达/可离性分析算法

工件的可达/可离性反映了将工件安装到/脱离出夹具装夹布局的可能性,分析可达/可离性有助于在工件上正确选择装夹表面和装夹点。为此依据工件与装夹元件的实际接触或装配情况,利用泰勒定理提出了工件可达/可离性模型。通过将工件安装到/脱离出装夹布局的可能性等价于可达/可离性模型的解的存在性,借助任意数可表达为两个非负数之差这一数学技巧作为桥梁,将工件可达/可离性模型的解的存在性问题转化为线性规划问题,提出了工件可达/可离性的判断方法。尤其是在判断可达/可离性模型有解的情况下,继而考虑了工件安装到/脱离出装夹布局的方向性。在此基础上,进一步将可达/可离的方向性转化为可达/可离性模型的通解,由此构建了求解线性不等式方程组的Γ-算法。这个“先有解-再求解”的算法仅涉及到装夹元件在工件表面处的位置与单位法矢量信息,不仅适用于形状复杂的工件,而且避免了可达/可离性模型无解情况下依旧求解的局限性,同时也拓展和丰富了自动化夹具设计的理论基础。     

COMPUTER SIMULATION OF BELOW-CENTER AND ABOVE-CENTER CENTERLESS GRINDING

Centerless grinding of ceramic components in the conventional above-center mode under aggressive conditions often results in workpiece spinning. One way to avoid workpiece spinning is to use below-center grinding, but this can lead to problems with part rounding and lobing. The present investigation was undertaken to develop a practical simulation to assist in the selection of acceptable set-up conditions for centerless grinding. From the initial workpiece profile and set-up conditions as input, the simulation predicts workpiece spinning and the progressive change in the workpiece profile for both above-center and below-center grinding. Simulation results for workpiece lobing were found to be consistent with experimental results obtained for below-center grinding of zirconia specimens.     

液动压悬浮抛光中磨粒与工件表面作用的数值模拟研究

针对液动压悬浮抛光固-液两相流中固相磨粒与工件表面撞击的过程中,对磨粒以不同的速度和不同的角度撞击工件表面后残余应力沿工件深度方向的分布规律进行了研究,利用ABAQUS软件建立了单颗磨粒撞击工件表面的三维有限元模型。对磨粒流撞击工件表面时的速度场进行了输出,利用PFC/3D软件建立了磨粒流撞击工件表面的三维离散元模型。研究结果表明:随着撞击角度和速度的增大,在工件表层形成的压应力场会增大,沿深度方向残余应力值急剧下降,磨粒流中磨粒间的撞击对磨粒撞击工件表面的速度场影响不大。     

Selections of working conditions for creep feed grinding. Part(I)–thermal partition ratios

A thermal model focused on the heat transfer to the fluid, workpiece and grain is developed for creep feed grinding. In this model, the conduction effect in the moving direction of the workpiece is considered which is found to be very significant especially for creep feed grinding. Moreover, the thermal partition ratios to the workpiece, fluid and grain are well defined and discussed. The results reveal that the cooling effect of the fluid is more crucial especially at larger grinding depth and smaller workpiece speed. Furthermore, the promotion of the wheel speed is helpful to reduce the fraction of heat entering the workpiece. Also, the workpiece thermal partition ratio is greatly influenced by the workpiece speed. Its value is even less than 5% as the workpiece speed is smaller than 4 mm/s. Comparing the thermal partition of wet grinding to that of dry grinding, the abrupt increase of heat entering the wheel and workpiece due to the occurrence of boiling in the fluid is verified.     

偏心件车削加工方法

针对偏心工件车削加工特点,分别介绍了三爪卡盘车削、四爪卡盘车削、两顶尖车削和专用夹具车削加工方法.说明了三爪卡盘加工偏心工件时垫片厚度与偏心距的计算、修正方法以及相互之间的关系.探讨了偏心工件车削加时需要注意的事项.     

MODELING WORKPIECE DYNAMICS USING SETS OF DECOUPLED OSCILLATOR MODELS

During the machining of thin-walled components, the dynamic behavior of the workpiece has a significant influence on the machining process and on the quality of the machined surfaces. In this article, a hybrid simulation concept for modeling regenerative workpiece vibrations is presented, which couples a geometric workpiece model with sets of decoupled harmonic oscillators to take the workpiece dynamics into account.