基于制造资源能力的装夹工艺分层设计技术

为发展创成式的计算机辅助工艺设计,研究了计算机辅助工艺设计系统中工件装夹规划的自动生成算法.基于扩展有向图,建立了零件的公差信息和基准-加工特征关系的数学表示模型,基于公差分析和制造资源能力模型,建立了从单件层到多件层的工件装夹工艺生产算法.该数学模型和算法可自动识别工件的加工特征、装夹基准,并根据制造资源能力和公差分析对装夹进行优化分组,实现装夹分组对工件加工精度的影响最小化,进而生成装夹规程.最后以实例证明了该方法的可行性.     

基于UG NX的数控车削编程及加工

针对数控车削加工中两次装夹零件的特点,根据加工工艺,基于UG NX,对加工工件坐标系及加工轮廓进行定义,实现在一个CAD/CAM文件中完成两次装夹零件的数控车削编程,编程与加工工艺紧密衔接,编程过程清晰,结果直观.基于编程结果,进行了数控车削加工实践,并对类似特征的车削零件开展数控车削加工.     

一种基于工件几何特征优化的能耗模型及应用

制造过程中能耗的影响因素很多,加工工艺、工艺路线、工件加工特性等都会影响制造系统能耗。针对工件加工制造过程能耗优化问题,首先在工件加工特征层面,提出特征能耗单元概念,并建立特征能耗单元模型。然后利用物元法,结合工件几何特征类树,构建了以特征能耗单元为基础的工件几何特征能耗物元模型。从该模型中提取能耗影响因子k,优化工件几何特征,直观地达到控制工件特征来优化加工制造过程能耗的目的,为控制需加工实现的工件几何特征的目标能耗提供理论参考。最后,以轴类工件外圆特征车削加工为例验证分析了该模型的有效性。     

基于参考功率曲线的大型工件加工进度状态信息的自动采集新方法

大型工件是大型装备制造业生产过程中常见的加工件,管理和调度人员掌握现场大型工件加工进度信息,对加工任务的按时完成,提高加工效率,优化生产过程管理,支持动态优化调度等具有多方面的重要意义。大型工件加工时间长,且许多情况是单件加工,因此加工进度状态信息的自动采集比较困难。基于此,提出一种利用机床主传动系统功率信息进行大型工件加工进度状态信息采集的方法。该方法通过所事先测得的机床主传动系统启动功率和空载功率数据库,以及工件加工工艺所确定的切削用量、加工材料和过程时间等参数,可获得虽不十分精确但足够反映出形状特征的工件加工过程的参考功率曲线;加工中对工件加工过程的机床主传动系统功率曲线进行实时采集,将采集到的功率曲线与参考功率曲线进行形状特征上的定性比较和时间过程的定量比较,可获取该工件的加工进度状态信息。在某冶金装备制造车间大型工件加工过程的应用验证表明,上述方法具有很好的应用前景。     

基于递归分析的混流生产模式机械加工过程能效分析和状态监测

针对混流生产模式下机械加工过程的能量效率研究问题,提出一种基于递归分析和图像处理技术的能量效率分析与状态监测方法.通过对各类工件分别进行多次加工试验,采集加工过程功率数据,应用聚类算法分析功率的时域特征并找出聚类中心,基于此建立各工件加工过程的参考功率数据库;在混流加工过程中,通过递归分析和图像匹配算法判断实时加工功率...     

宝钢连轧管机组机架的加工工艺

介绍了宝钢 140mm连轧管机组机架的加工工艺和加工过程中的注意事项。该加工工艺适用于对串孔同心度与同轴度精度要求高的工件的加工。     

基于永磁体的抗磁性材料磁流变抛光装置研究

针对现有磁流变抛光技术的加工精度难以提高,加工过程中抛光热不容易控制等问题,对磁流变抛光工艺,以及抗磁性材料工件在抛光过程中的工作间隙的磁通量密度进行了研究。对永磁体抛光刀具刀尖表面模型,以及铜合金工件表面之间的关系和模型进行了归纳,提出了一种基于永磁体的抗磁性材料磁流变抛光方法;利用Maxwell对抛光装置工作间隙磁通密度进行了仿真,并进行了相关试验。研究结果表明:基于磁流变抛光液,利用永磁体组成的抛光刀具对抗磁性材料工件进行加工,工件表面质量有了明显提高,实现了纳米级别的加工精度。     

机床调整尺寸的计算

一批零件加工前,必须调整机床。加工中,还必须根据点图或(?)-R控制图,对机床进行必要的重新调整。调整的目的是使工件的尺寸分散范围全部包容在公差范围之中。机床调整尺寸的计算分两种情况讨论。 1.对于稳定的工艺过程 加工过程中主要受随机性误差的影响,点图上的点子波动幅度不大,这时质量稳定,该工艺过程是规定的工艺过程。这时最理想的调整尺寸是使尺寸分散中心(?)与公差带中心A_m重合。本文所讨论的问题是所有尺寸都还未加工出来,利用随机误差的特征来判断当前调整好的情况下,今后加工所得的尺寸分布是否都能包容在规定的公差范围内。通过试切工件所得的尺寸,对今后尺寸分布情况进行判断。在稳定的工艺过程中,工件尺寸是服从正态分布的。     

一种基于动态时间弯折和功率信息的在线加工工件自动识别和监控方法

针对目前车间工件加工进度信息主要靠人工统计、且在混类加工时经常出现统计出错以及工人为加快加工进度擅自改变加工参数造成浪费等现象,在分析数控机床主轴功率特性的基础上,提出一种基于动态时间弯折技术和功率信息的在线加工工件自动识别和监控方法。该方法首先将各种工件加工时可能的主轴功率信息经过特征矢量的选取、特征序列的形成及其时间规正和匹配距离计算以及K均值法的聚类等处理过程,形成特征模板库;在工件加工时实时采集功率信息并进行处理形成特征矢量序列,将该序列与特征模板库中的模板进行时间规正和匹配距离计算等处理,根据匹配距离的大小以及所设定的门限值,判断加工工件的类别或监控加工过程加工参数的正确性。在某装备制造车间的应用验证表明,上述方法能很好地识别加工工件的类别,并起到监控加工过程的作用。     

面向制造特征的STEP-NC非线性工艺路线激励生成方法

为解决STEP-NC非线性工艺路线生成中处理加工约束困难的问题,根据STEP-NC面向制造特征的特点,提出一种对制造特征进行激励选择排序的非线性工艺路线规划方法。利用加工方案选择原则确定制造特征的加工方案,根据已确定的制造特征加工方案,对具有多个加工操作的制造特征进行特征分解。针对制造特征相交可能存在的加工遮挡问题,提出基于制造特征划分的刚性优先约束判断方法。利用制造特征集合划分方法表达刚性优先约束以及装夹与刀具的柔性约束,并通过对不同制造特征集中制造特征的激励、选择、可行制造特征动态更新等操作,实现非线性工艺路线的生成。结合实例验证了所提非线性工艺路线激励生成方法的可行性与有效性,并表明该方法较好地解决了工艺约束及其知识的表示问题。     

挤出平模头自动抛光技术研究

为了提高挤出平模头的工艺稳定性、产品的一致性及生产效率,本文对挤出平模头自动化抛光技术进行了初步研究。简要地介绍了课题研究的背景和意义;从抛光机理出发,针对挤出模具钢进行了可加工性试验研究;研究结果表明,采用化学机械抛光的方法茄工所获得的加工表面能够达到平模头产品的粗糙度要求。最后,根据平模头的尺寸要求和工艺要求,研制出了一种能够实现大尺寸工件自动抛光的装置。     

Chatter prediction utilizing stability lobes with process damping in finish milling of titanium alloy thin-walled workpiece

Machining chatter often becomes a big hindrance to high productivity and surface quality in actual milling process, especially for the thin-walled workpiece made of titanium alloy due to poor structural stiffness. Aiming at this issue, the stability lobes are usually employed to predict if chatter may occur in advance. For obtaining the stability lobes in milling to avoid chatter, this article introduces an extended dynamic model of milling system considering regeneration, helix angle, and process damping into the high-order time domain algorithm which can guarantee both high computational efficiency and accuracy. Via stability lobes, the reasonability and accuracy of the proposed method are verified globally utilizing specific examples in literature. More convincingly, the time-domain numerical simulation is also implemented to predict vibration displacement for partial stability verification. In this extended model, process damping is well-known as an effective approach to improve the stability at low spindle speeds, and particularly, titanium alloy as typical difficult-to-machine material is generally machined at low spindle speeds as well due to its poor machinability. Therefore, the proposed method can be employed to obtain the 3D stability lobes in finish milling of the thin-walled workpiece made of titanium alloy, Ti-6Al-4V. Verification experiments are also conducted and the results show a close agreement between the stability lobes and experiments.     

工件材料切削加工相对性指标初探

针对工件材料切削加工性问题,提出了相对切削力的概念,在相同加工条件下,用以比较不同工件材料切削力的大小。通过试验测量出一组切削力数据,计算出加工几种常用材料时的相对切削力,并对其切削加工性进行了分析讨论？     

Performance comparison of conventional and wiper ceramic inserts in hard turning through artificial neural network modeling

Hard turning with ceramic tools provides an alternative to grinding operation in machining high precision and hardened components. But, the main concerns are the cost of expensive tool materials and the effect of the process on machinability. The poor selection of cutting conditions may lead to excessive tool wear and increased surface roughness of workpiece. Hence, there is a need to investigate the effects of process parameters on machinability characteristics in hard turning. In this work, the influence of cutting speed, feed rate, and machining time on machinability aspects such as specific cutting force, surface roughness, and tool wear in AISI D2 cold work tool steel hard turning with three different ceramic inserts, namely, CC650, CC650WG, and GC6050WH has been studied. A multilayer feed-forward artificial neural network (ANN), trained using error back-propagation training algorithm has been employed for predicting the machinability. The input?Coutput patterns required for ANN training and testing are obtained from the turning experiments planned through full factorial design. The simulation results demonstrate the effectiveness of ANN models to analyze the effects of cutting conditions as well as to study the performance of conventional and wiper ceramic inserts on machinability.     

工件材料可切削加工性评价的图示法研究

在分析影响工件材料切削加工性的主要因素的基础上,提出了用图示法直观地描述和评价工件材料的切削加工性的新的表达方法。该切削加工性图与工件材料的机械性能和物理性能直接关联,图上5根轴分别代表了材料的5种物理机械性能。在对材料的性能量化的基础上,通过和参考材料性能的比较,得到其他材料的切削加工性图。该切削加工性图可以帮助工程技术人员了解材料在切削过程中的表现,通过比较不同材料的切削加工性图,在新材料或未知材料的切削加工过程中指导选择切削刀具、切削参数及其他切削条件。     

A method for identification of geometrical tool changes during machining of titanium alloy Ti6Al4V

There exists an increasing demand for cost and time-efficient cutting tests for describing the performance of different combinations of cutting tools and workpiece materials in the cutting process both in industry and academia. Cutting tools are expected to withstand the heat and the pressure developed during the machining of difficult-to-machine materials such as Ti6Al4V. This article introduces a new test method which may be used in order to analyze both the machinability of a workpiece material as well as the cutting tool behavior. The experiments were performed by using a predefined sequence of feeds, a so-called Stepwise Increased Feed Test. A gradually increased load on the cutting edge was thus applied up to the point where plastic deformation of the cutting edge was obtained. The limit for the initial change in tool geometry was identified through analysis of measured cutting forces.     

数控加工仿真中毛坯数据模型

在NC仿真中,毛坯的三维图形处理是一项关键技术.一方面要实现几何造型的显示功能,另一方面还要求三维图形具有可加工性,加工成品的信息具有可记录性.设计了一种能够记录毛坯(工件)形状变化信息的数据结构,有效地实现了NC仿真中毛坯形状动态数据管理.     

Cutter path orientations when high-speed finish milling inclined hardened steel

The use of high-speed milling (HSM) for the production of moulds and dies is becoming more widespread. Critical aspects of the technology include cutting tools, machinability data, cutter path generation and technology. Much published information exists on cutting tools and related data (cutting speeds, feed rates, depths of cut, etc.). However, relatively little information has been published on the evaluation of cutter paths for this application. Most of the research focuses on cutter path generation with the main aim on reducing production time. Work concerning cutter path evaluation and optimisation on tool wear, tool life and relevant workpiece machinability characteristics are scant. This paper investigates and evaluates the different cutter path orientations when high-speed finish milling inclined hardened steel, at a workpiece inclination angle of 75°. The results demonstrate that employing a vertical downward orientation achieved the longest life. However, in terms of workpiece surface roughness, vertical upward orientation is generally preferred.     

Modeling and analysis of workpiece stability based on the linear programming method

After being located on a machine bed, a workpiece will be subject to gravity and cutting forces during the machining operation. In order to keep the locating precision as well as the production safety, it is necessary to maintain the workpiece stability. In this paper, a linear programming method is proposed for stability analysis of the workpiece. Based on the linear approximation of the friction cone, a quantitative criterion is established to verify the workpiece stability in association with the rationality of the clamping sequence, magnitude of clamping forces and clamping placement. This criterion allows designers to plan reasonably the clamping sequence, magnitude of clamping forces as well as clamping placement. Compared with existing methods, the main advantage of this approach lies in that the sophisticated computing of contact forces between fixture elements and the workpiece is avoided. In this work, both friction and frictionless cases can be easily taken into account in stability analysis. Mathematical formulations of the method are given and some numerical tests are finally demonstrated to validate the proposed method.     

Digraph and matrix method to evaluate the machinability of tungsten carbide composite with wire EDM

Machinability aspect is of considerable importance for efficient process planning in manufacturing. Machinability of an engineering material may be evaluated in terms of the process output variables like material removal rate, processed surface finish, cutting forces, tool life, specific power consumption, etc. In this paper, graph theoretic approach (GTA) is proposed to evaluate the machinability of tungsten carbide composite. Material removal rate is considered as a machinability attribute of tungsten carbide to evaluate the effect of several factors and their subfactors. Factors affecting the machinability and their interactions are analyzed by developing a mathematical model using digraph and matrix method. Permanent function or machinability index is obtained from the matrix model developed from the digraphs. This index value helps in quantifying the influence of considered factors on machinability. In the present illustration, factors affecting machinability of tungsten carbide are grouped into five broad factors namely work material, machine tool, tool electrode, cutting conditions, and geometry to be machined. GTA methodology reveals that the machine tool has highest index value. Therefore, it is the most influencing factor affecting machinability.