浅析零件中心孔对质量的影响及修研方法

各种精密工件的加工中,顶尖夹持是常见的定位夹紧方式。顶尖夹持误差在生产加工中,对产品质量的影响也是无法避免的,工件的装夹误差是影响加工精度的一个显著因素。通过分析中心孔本身形状误差和位置误差与齿圈径向跳动、齿距累积误差、齿向误差、齿厚偏差和工件圆度的关系,论述了当中心孔位置误差造成工件回转轨迹发生变化时,对齿圈径向跳动、齿距累积误差、齿向误差造成的影响;当中心孔孔口尺寸不一致时,对齿厚的影响;中心孔形状误差对工件圆度的影响等的工作机理,探讨了顶尖夹持定位时,提高中心孔本身形位误差的有效修研方法,并进行了归纳和总结。     

一面双销定位的概率计算法(下)

二、从保证角向定位精度探讨工件销孔中心距加工允许偏差±△g 的计算当两销孔直径为最大尺寸,两定位销直径为最小尺寸,销孔中心距与定位销中心距相同时,可能产生最大的角向定位误差。工件的最大角向定位误差 tga_(max)(见图6)为:     

电机座孔同轴度测量

我厂加工的电机机座前端和后端止口内孔的同轴度要求如图1所示,以一端内孔轴线为基准,求另一端内孔轴线与基准轴线的同轴度误差.由于工件尺寸较大,用常规的检测方法无法进行测量.如果按照上述基准进行测量就会产生以下两种相反的测量结果,且测量重复性差,检测数据不可靠.下面以单个截面圆来讨论同轴度误差的测量.     

钻床夹具精度分析的新方法—实态法

在钻床上使用夹具加工工件时,被加工孔的位置精度,会受到诸多因素的影响。其影响因素有工件定位误差T_D,夹具制造误差T_z,夹具安装在机床上的安装误差T_A,由于被加工件的变形、夹具定位件、导向件、刀具的磨损、以及刀具的偏斜引起的随机误差T_S等。当被加工孔的位置精度有一定要求时,要用尺寸链原理综合分析各误差的累积关系,使所设计的夹具能保证工件的加工精度要求.在误差尺寸链的各环中,工件被加工孔的仕置精度T_0为封闭环,影响加工精度的各误差T_1为组成环。由于各误差的性质、工件或夹具元件的加工批量和加工方法的不同,使得尺寸分     

箱体孔加工误差对齿轮传动精度的影响

齿轮的轴是安装在箱体孔内的,箱体孔的加工误差必然导致齿轮副的传动误差。多年来,箱体孔的中心距偏差和轴线的平行度误差,一直是借用齿轮副的中心距偏差和轴线平行度误差。直到颁布了JB/GQ1071-85《机床圆柱齿轮箱体孔中心距偏差和轴线平形度公差》标准后,箱体孔的加工才有了单独的标准可以遵循,本文就箱体孔中心距偏差和齿轮副的中心距偏差的关系,箱体孔轴线平形度误差对齿轮副轴线平行度误差的影响,以及这二者对齿轮传动精度的影响进行讨论。     

径向槽回转切削运动学及加工误差分析

提出采用无分度运动的回转切削方法加工径向槽,建立了刀尖相对于工件的运动轨迹方程和两种理论加工误差模型(轮廓倾斜误差模型和轮廓周向误差模型),结合实例分析了中心距、刀具半径等参数对理论加工误差的影响.结果表明,采用回转切削方法加工径向槽不仅可以提高自动化程度和生产效率,而且通过合理选择中心距和刀具半径等参数,可将理论加工误差控制在允许的范围内.     

孔中心距公差标准

在孔及孔组的加工中,不仅要规定孔的尺寸公差,还要规定孔与孔之间中心距公差,以保证装配及互换性。控制孔中心距公差的方法有两种:一种是用尺寸公差控制;另一种是用位置度公差控制。两者相比,我们认为用位置度公差控制孔中心距更为合理。现将两种控制方法的标注形式、优缺点、应用范围叙述如下。 一、标准形式 1.用尺寸公差控制孔中心距公差 此法有下列两种标注形式: (1)链式标注(图1)此种标注中,相邻两孔中     

一种用于数控车床的新型端面拔动顶尖

本文论述了一种用于数控车床的新型端面拔动顶尖，它适用在数控车床上进行轴类零件的加工。该顶光刚性强、定位精度高、能补偿由于被加工轴的中心孔误差所引起的轴向尺寸误差。工件在一次装夹中即可完成粗、精车、提高了工件的加工精度和生产效率。     

一种用于数控车床的新型端面拨动顶尖

本文论述了一种用于数控车床的新型端面拨动顶尖，它适用在数控车床上进行轴类零件的加工。该顶尖刚性强、定位精度高，能补偿由于被加工轴的中心孔误差所引起的轴向尺寸误差。工件在一次装夹中即可完成粗、精车，提高了工件的加工精度和生产效率。     

接料臂加工误差分析与工装设计

料臂类零件的内孔与轴由键槽定位,键槽中心与工作面有相对位置尺寸.加工料臂时,应先加工键槽,以键槽为基准加工工作面.工作面到内孔中心的距离是键槽到内孔距离的几倍,键槽配合面较小的误差反映到工作面上则误差会成倍增大.为了避免人为因素引起的加工误差,应减小同一批料臂的相对误差,采用工装定位加工.     

Multi-point location theory, method, and application for flexible tooling system in aircraft manufacturing

To solve problems in aircraft manufacturing, flexible tooling system with “Forming-Machining” process is presented. Pointwise degree of freedom is defined on aircraft large-scale thin-wall workpiece during its machining process where traditional six-point location principle is not suitable, and base on which adaptive multi-point location method used for this kind of workpieces is described. Furthermore, multi-point location/support algorithm is developed to solve positions of location/support spheres of flexible tooling system to construct envelope surface of workpiece and avoid machine tool interference. Test data of sample workpiece show that flexible tooling system meets the requirements of aircraft large-scale thin-wall workpiece machining with manufacturing error and cycle decreased.     

履带趾转动耳孔的一种批量加工方法

102寸美国履带趾,装配状态是一件单转动耳孔插入另一件双转动耳孔中间,耳孔中再穿入一根转动轴,形成一串长链带.每两两能摆动一定的角度.其工件的加工难点是孔及孔同轴度有要求,工件互换性强.本文介绍了用特定的设备,通过特制的工装定位完成该履带趾的批量加工的一种方法.     

定位误差与尺寸链的关系

分析了定位误差的构成与尺寸链之间的关系及相似性 ,结合实例介绍了尺寸链算法在分析计算定位误差和加工误差时的应用。     

Modelling of Metal Removal in Reverse Zones in the Process of Internal Grinding

The removal of metal during reverse motion of the grinding wheel at extreme cross sections of holes in the workpiece during internal grinding is considered. In a single double pass of the wheel, the vibration of the contact area and the cutting forces are found to be significantly different in reverse motion within input and output holes. That disrupts the stability of metal removal and the machining precision over the length of the hole being machined. Approaches to the modeling of internal grinding with reverse motion of the grinding wheel are considered.     

漏斗形分布深孔系组合夹具

机械加工过程中,加工折线孔需将工件分两次装夹,如有多个不同角度方位的折线孔(通称"漏斗形分布孔系"),需多次装夹,操作繁琐,且难以保证精度。使用本组合夹具能快速、精确、批量地加工多个不同角度方位的折线孔,大大提高了生产质量和效率。     

The effect of starting hole geometry on borehole quality and tool life of twist drills

This paper reports about the relationship between starting hole geometry and twist drill performance, which is determined by the location error and diameter of the drilled borehole as well as the tool life of the employed twist drills. The experimental results lead towards the conclusion that the type of starting hole has a significant effect on borehole quality. This, however, is not as commonly assumed attributed to a variation in the location error of the different starting holes themselves, but to how a starting hole allows the subsequent twist drill to engage in the cutting process. Although twist drills that drill straight into the workpiece material achieved the longest tool life due to a gentle engagement, a deep starting hole (‘pilot hole’) results in the most satisfying overall twist drill performance.     

Research on ECM process of micro holes with internal features

Micro holes with internal features are widely used as spray holes and cooling holes nowadays, which are usually required to be with high aspect ratio and shape accuracy, as well as good surface quality. An electrochemical machining (ECM) process is presented to machine these micro holes with diameter <200 μm. A quantitative relation between micro-hole diameter and machining parameters including voltage, duty ratio and feedrate is obtained through orthogonal experiments. According to the designed shape of internal features, change rules of machining parameters for varied diameters in different depth are obtained, and then micro holes with internal features are shaped precisely. Taking reverse tapered hole as an example, ECM experiments by varying parameters of voltage, duty ratio and feedrate (called varying voltage machining, varying duty ratio machining and varying feedrate machining, respectively) are carried out. Micro holes with inlet diameter of 178 μm and taper angle of 1.05° are shaped on a 1.0 mm-thick workpiece of 18CrNi8. The deviation of inlet is <3 μm and the taper-angle error is <0.1° in varying voltage machining. The corresponding dimensional accuracy of taper angle is improved by 51% than that of varying duty ratio machining under the same efficiency. The machining efficiency of varying voltage machining is increased by 36% compared to the efficiency in varying feedrate machining. In addition, the micro holes with complex features of funnel shape and bamboo shape are machined.     

动叶可调风机轮毂轴孔的加工

本文对地铁、矿井、电站等领域应用的动叶可调轴流通风机轮毂零件轴孔(与轴之间采用带键过渡配合性质)的加工,提出并实施了一种新的以车床代替磨床的工艺方法.该方法解决了轮毂零件外形尺寸偏大,轴孔加工部位结构尺寸小;精度要求高并且为非连续加工表面的技术难点.为类似特殊异形工件的精确加工,提供了一个新的工艺借鉴.能使企业以低投资,制造高技术含量、高质量、高回报的产品.     

虚拟加工中的加工误差分析与预测

分析了影响虚拟环境下复杂曲面产品数字化端铣加工误差产生的主要因素,综合考虑刀具和工件的柔度,同时考虑加工表面的变形敏感度,讨论面向虚拟制造的加工尺寸误差预测模型总体框架,提出了一个端铣加工过程表面加工尺寸误差预测模型。所给出的表面误差预测模型较全面地考虑了端铣加工过程,适于多种加工条件,能够反映端铣加工过程由切削力导致的系统变形对加工误差所造成的影响。最后给出了一个仿真实例。     

万吨桨油孔和起吊孔的加工

在分析了万吨桨起吊孔和油孔的加工特点后,给出了使用小万向钻和特殊钻头以及间歇进给和退出的办法进行万吨桨油孔的深孔加工;使用小万向钻和专用工装采用先钻后镗,分层切削,逐渐去除余量,扩大孔径直到设计尺寸.经过实际生产的检验,所设计的方案取得良好的效果,可以满足万吨桨加工需要.