异形截面工件的成形原理与分析

工件的轴线与车床主轴线重合,刀具卡于与刀架固联的卡刀夹具上。装卡后刀具相对工件应满足:工件旋转轴线与刀具旋转轴线相交于刀具的前端面上并相夹一个任意方向的角度β(加工中β大小和方向不变)。对于刀具,其前端面的正投影的形状和     

立式车床结构的发展

立式车床结构发展,主要应体现扩大工艺性能,提高控制的自动化水平、加工效率和精度,以及使用上的可靠性。除了为某些具体厂家加工特定的零件而去生产高效率的专用立式车床外,还应继续生产万能立式车床。但为提高柔性,减少加工新零件的专用工艺装备及安装调整时间应在万能立式车床上增加数控装置、多用途刀架、自动换刀及换毛坯装置、高精度直线和角度定位的进给拖动装置,以及在机床上直接检验零件尺寸的检测装置。这样作的结果,使一台万能立式车床变成了多功能机床。本文着重研究立式车床某些部件的结构变化及扩大了工艺性能的有关装置的结…     

刀具的调整装置

一种直接在机床上调整多刃刀具(镗刀、铣刀)用的装置取得了专利权。此装置装有几个百分表,其特点是备有百分表测杆精确轴向移动机构和用蜗杆传动的能精确调整测杆轴线和刀具轴线相对位置的回转机构,此机构可保证在调整尺寸前,使百分表和刀具的轴线严格保持垂直状态。供车床用的类似带表装置已为人们所熟悉,此类装置安装在车床刀架上并按如下方法固定在一定位置上:即表的零位读数应同测杆接触平面与主轴轴线的吻合情况相一致。因此这类装置是专用的,只适于于车床使用。     

编制自动换刀程序需要解决的几个问题

在微电脑控制车床技术中,编制自动换刀程序是实现自动换刀从而提高加工效率、使产品质量稳定可靠的重要环节。下面结合我们用TP801-Z80单板机改造的车床,对编制自动换刀程序需要解决的几个问题作简要介绍。一、刀架旋转角度的确定在零件加工过程中,使用的刀具不断变换,若将所需要的刀具准确地旋转到加工位置,关键是正确     

用于车削加工的数控补偿刀架

为提高机床的加工精度,我们研制了在线测量柔性补偿系统,并已应用在卧式多轴自动车床上。该系统是将主动测量仪测得的已加工零件的尺寸误差经微机处理后,送给补偿刀架来补偿待加工零件的加工误差。它不仅能补偿确定性误差,还能补偿热变形、刀具磨损及随机因素引起的误差。这套系统包括主动测量仪、控制用微机软硬件及接口装置、补偿刀架三部分。前两部分已在《机床》 1987年第 5期和1988年第1期发表,这里只介绍数控补偿刀架部分。 一、结构特点及工作原理 如图1所示,刀夹11和底座14分别用螺栓固定在多轴车床纵刀架的装刀平面上。当步进电机1…     

六角自动车床前刀架的改进

一、改装设想普通C1325、C1356等型号单轴六角自动车床设计有四个刀架,可同时装夹十多把刀具,能完成内孔、外圆、台肩、平面、螺纹等多种加工工序,是一种自动化程度较高的机床。但美中不足的是四个刀架都只能作单一的轴向或径向进给运动。机床的回转刀架由于结构的限制所装刀夹一无微调,二无抬刀机构,至使加工外圆时,不但工件尺寸难调整,而且带有退刀纹。采用前后刀架径向切削时又受到机床和零件的刚度限制不能满足零件加工工艺的要求,限制了机床功能的发挥。最近,我们根据前刀架的结构特点,及回转刀架的空间位置,探索设计了一种可装在前刀架上的专用     

可调自动进刀钻孔夹具

由车床上卡盘1卡住工件旋转(图2),方刀架5卡住夹具4,偏心内锥套2孔中安装钻头或其它刀具(图1),经大拖板作纵向自动进给,对工件进行切削加工。二、结构特点(图1)1.由原来手动进刀钻孔变成机械自动进刀钻孔。2.结构简单、合理、制造容易、使用方便,是车床经常要用到的通用性的夹具。     

宽刃超声波切割刀的研究与设计

针对传统切割方法对大尺寸脆性、粘性食品切割时,会产生碎屑、挤压变形等问题,对用于食品的20 kHz宽刃超声波切割刀的模型设计、刀具横向振动等方面进行了研究。根据复合变幅杆设计理论,确定了切割刀基本尺寸,通过在刀具特定位置上开槽的方法抑制了刀具横向振动。依照优化流程图,在ANSYS环境下对刀具进行了模态分析,得出了刀具模型最优解,使刀具在20 kHz频率左右刃口振动主要以纵向振动为主,刀具整体振型均匀;利用激光位移传感器对刀尖进行了振幅测量,发现刀具振型稳定;对上述宽刃超声波切割刀进行了面包切割实验。实验结果表明:该宽刃超声波切割刀进行食品切割时整体振型均匀,不会产生碎屑、挤压变形等问题。     

加工内球面夹具

内球面车夹具安装在车床刀架上(附图),刀具安装在刀座4里,根据需要变动伸出长度 L,来调整所需的工作半径 R,再用螺钉5紧固。车刀伸出长度 L=R-H(H 对给定的夹具是个定数)。这样,用同一把刀能加工不同半径的球面。     

夹具定位尺寸公差与配合的制订(三)

7.根据工件尺寸精度制订车床夹具的定位尺寸除用上述方法外,还可根据工件尺寸精度制订。如工件用毛坯面定位或留有加工余量的工序尺寸,自由尺寸公差或公差较大等情况,夹具定位尺寸均无需修正,可直接取基本值或中点坐标值。对于在平面与斜面上钻孔,且钻孔轴线对加工面不垂直时,其尺寸没有公差要求或公差较大时(包括距离尺寸和角度),亦可直接取基本值或中点坐标值。     

硬泡棉鞋垫斜边专用数控切削设备的研制

研究了硬泡棉鞋垫斜边专用数控切削设备的工作原理、机械结构和控制系统软硬件结构,介绍了用AutoCAD绘制硬泡棉鞋垫轮廓曲线并提取坐标点的方法,研究了用PLC控制二维数控平台实现鞋垫斜边平面曲线的方法,论文研究了用Z轴电机控制刀具切削方向以切削出硬泡棉鞋垫均匀光滑斜边的方法.     

A model for cryosectioning based on the morphology of vitrified ultrathin sections

Electron microscopy of vitrified ultrathin sections allows cell ultrastructure to be studied in the hydrated state. Sectioning of the frozen material is, however, a limiting step, since the cutting forces cause severe mechanical deformation. In order to address this problem, we have investigated the surface of cryosections. It is shown that cryosections have two fundamentally different surfaces. One surface is rough, deformed by cutting-induced deformation lines which are orientated perpendicular to the cutting direction. The other surface, in comparison, is not affected by those deformation lines. Except for knife marks it is smooth. In order to explain the observations, the following model is proposed. The rough relief corresponds to the former block face. Its roughness originates from material that is squeezed out of the section plane when the section is compressed in the cutting direction and bent away from the specimen block. The smooth section surface is the surface in contact with the knife during the sectioning. This contact keeps the surface smooth while imprinting the knife marks.     

Cutting teeth in the SEM

An SEM was used to observe and record dental tissues as they were being cut. Sound human deciduous and permanent teeth were stored in 70% ethanol until required, then soaked in water, superficially dried and screwed to the SEM specimen stage through small drill holes made when they were wet. Many specimens were frozen and studied at cryogenic temperatures so that they would not become dehydrated. Edges used to cut the teeth included steel and tungsten carbide fashioned to resemble clinical cutting instruments, and diamond ultramicrotome knives and burs. The cutting tools were held either in a micromanipulator or a rigid tool post clamped to the specimen stage. The finest control was obtained by moving the specimen with the usual stage controls. SEM was conducted at 3 or 5 kV using TV speed scanning on the uncoated samples. All experiments were video-taped. 3-D control was difficult with a mono image and a real-time stereo system was therefore developed. Continuous, flowing sections of enamel could be obtained using diamond knives to cut the prism-free, surface zone tangentially. Thin sections of dentine, cement and bone curled up as they were cut, thus demonstrating permanent deformation. Subsurface enamel always fractured as it was cut, either locally as the tissue passed over the knife edge or tore out beneath the plane of the knife or by larger fragments cleaving off at larger distances ahead of the knife. Appearances were characteristic of prism orientation with respect to cutting direction. No anisotropy of cutting behaviour was found with dentine or bone: These tissues only fractured when thicker sections were taken. The SEM methods employed here can be usefully applied in the study of other materials.     

A new sawing machine by diamond wire

Diamond wire is widely used for stone cutting; it is typically employed to extract a block in quarry and to square the block in a machining company. In particular, the frames to square or to cut the blocks present many technological limits, such as the high costs of the diamond wire, the frequent break of the diamond wire during cutting, the poor quality of cut surfaces, and the dangerous process and productivity lower than that of the same tool used in a quarry. The present work shows an innovative prototype machine to cut by a diamond wire which overcomes the aforementioned technological limits. The developed machine has a bridge frame among which two pulleys move the diamond wire as regards the stone block according with the feed speed. The diamond wire moves on the two pulleys with a cutting speed. A tensile force is applied to the wire that twists it during the contact with the stone, instead of keeping it along a straight direction parallel to the foundation of the machine. The twisting of the diamond wire makes the use of the wire itself more productive and safer, since the wear of each single bead during cutting is more uniform. Moreover, the resulting specific pressure acts on each bead along the arc of contact with the cut block and increases along the cutting direction from the entrance to the exit of the contact with the stone. The increasing of the specific pressure causes a bending of the diamond wire during the contact with the stone. The developed prototype was provided with a sensory system to measure both the cutting power and the tensile force of the diamond wire during experimental tests. In this way it was possible to verify the functionality of the prototype plant and, in the same time, to evaluate the productivity of the implemented cutting process.     

基于线锯高效切割的复杂直纹面模型建立及仿真

针对天然石材、人工晶体等材料复杂曲面加工中，初始毛坯与最终产品形状差别较大，粗加工材料去除量大，导致加工效率低、刀具磨耗严重的问题，提出了一种基于线锯加工和点加工协同去除的高效粗坯加工的解决思路。根据线锯加工特点，提出了对最终产品的数字化模型进行分层处理，利用多边形对各层二维外轮廓曲线进行包络，将层与层之间的多边形进行顺序拟合得到相应直纹面模型的建模思路。分析了不同包络多边形边数、连接方式所构建的不同直纹面模型对粗坯加工时间的影响。仿真结果表明，虽然增加多边形的边数或者通过层间旋转可以减小剩余未加工材料体积，但整体粗坯加工时间反而有所增加，从而不利于提高效率。粗坯加工时间可作为综合评价指标来优化构建直纹面模型。     

Effect of reciprocating wire slurry sawing on surface quality and mechanical strength of as-cut solar silicon wafers

This paper investigates reciprocating wire slurry sawing for photovoltaic (PV) silicon wafering and compares the resulting wafer surface quality and its mechanical strength to that obtained in unidirectional wire sawing. It is found that wire reciprocation creates two significantly different morphological or cutting zones on the wafer surface. The zone width varies with the distance travelled by the wires, the cutting location on the wafer surface, and direction of wire motion. The size of the morphological zone created during forward motion of the wire is larger than that created during its backward motion. The zone width is found to decrease along the wire cut direction. In addition, there appears to be greater kerf loss and increased surface roughness in the forward cutting zone. In general, results suggest a higher material removal rate during forward motion of the wire than during backward motion. Notwithstanding the surface morphology variations, the fracture strengths of reciprocating wire sawn wafers are found to be quite similar to that exhibited by wafers produced by unidirectional wire sawing.     

一种隐函数NC刀具轨迹的绘制方法

一般的数控编程软件,都是基于参数曲面的,但参数函数表达式在许多方面不如隐函数表达式.把隐函数的优势应用到数控加工编程中,即对于截面法的数控加工,求出刀具切削平面与隐函数曲面的加工轨迹,再用正负法绘制刀具轨迹曲线.首先对单调NC轨迹曲线进行绘制,进一步用不求极值点坐标而实现自动控制变向的方法,求出NC加工轨迹;该方法简单、快速,能够实现隐函数曲面的数控加工编程,具有很好的实际应用价值.     

Cutting of polished single-crystal silicon by wire electrical discharge machining

Smoothly polished single-crystal silicon plates were cut by wire electrical discharge machining (WEDM) in water and in oil in order to investigate the effect of WEDM on the polished surfaces. For cutting in water, polished surfaces near cut sections have chips and cracks, and are extremely rough; the rough regions are upheaved. Examinations suggest that the upheaved region is silicon dioxide and results from oxidization of the surfaces by WEDM. Moreover, the polished surfaces far from the cut section are somewhat rough. For cutting in oil, polished surfaces near a cut section are smooth and almost flat although they have chips and cracks. These findings indicate the WEDM in oil is better than that in water for cutting polished single-crystal silicon to obtain high-quality surfaces.     

精密外沟槽精车工艺分析

针对液压活塞工件外矩形槽的槽底表面粗糙度要求达到Ra 0.8μm的精密加工问题,采用在普通数控车床上精车的办法,从刀具选择、刃磨到进刀方式以及防止车刀产生积屑瘤等,制订了周密的工艺过程,结果使工件稳定地达到了技术要求,为类似工件的加工提供了成功借鉴。     

Modeling and analysis of white layer depth in a wire-cut EDM process through response surface methodology

A white layer is considered a major flaw on a workpiece surface machined with wire-cut electrical discharge machining (WEDM). In this paper, an attempt has been made to model the white layer depth through response surface methodology (RSM) in a WEDM process comprising a rough cut followed by a trim cut. An experimental plan for rotatable central composite design of second order involving four variables with five levels has been employed to carry out the experimental investigation and subsequently to establish the mathematical model correlating the input process parameters with the response. Pulse on time during rough cutting, pulse on time, wire tool offset, and constant cutting speed during trim cutting are considered the dominant input process parameters whilst the white layer depth is the response. An insignificant lack of fit term indicated a curve with a good fit. Also, an extensive analysis of the influences of all the individual input parameters on the response has been carried out and presented in this research study.