PLC模块控制回转工作台在三轴数控铣床铣削螺旋伞齿轮中的应用外文文献翻译正文.doc

PLC模块控制回转工作台在三轴数控铣床铣削螺旋伞齿轮中的应用外文文献翻译正文 PLC模块控制回转工作台在三轴数控铣床铣削螺旋伞齿轮中的应用S. Mohsen Safavi & S. Saeed Mirian & Reza Abedinzadeh & Mehdi KarimianReceived: 25 November 2008 / Accepted: 23 November 2009 # Springer-Verlag London Limited 2009摘要 当今,数控机床在机电一体化领域中得到了日益广泛的应用。机械、电气和数据处理系统与数控技术相结合,引领了新的生产加工理念。近年来,数控技术的发展已将非线性校正技术在切削弧齿锥齿轮中的应用变为可能。在本文中,我们将尝试采用带有外加PLC模块分度台的三轴数控铣床,运用带有索引工作界面的通用铣床的传统连续多重切削方法来加工制造出这个螺旋伞齿轮。该研究包括a弧齿锥齿轮的几何建模,b运用CAD/CAE系统进行传统或新型非传统方案的模拟仿真,c数控加工工艺的设计与PLC编程,d通过三轴数控铣床的实验切削来探索新方案的正确性。结果表明,开发的螺旋伞齿轮实验切削方案不仅与先进数控加工相比成本更低,而且相比传统切削,加工齿轮的时间也较短。因此,在螺旋伞齿轮加工领域,这是一个很经济的方案。关键词:齿轮加工,螺旋伞齿轮,CAD/CAM/CAE,数控技术,PLC,交流电动机,逆变,接近传感器,光电传感器,旋转编码器1 引言 齿轮是工业机械领域中重要的精密机构,在平行轴、横向交叉或非交叉轴之间用于传递机械功率和机械运动。虽然有时会看不见,但齿轮仍是我们工业文明中最重要的机械元件之一。在各式各样的条件下,齿轮会以几乎达到无限的速率运转。得到发展的齿轮加工设备与工艺流程已经非常先进与成熟。无论大批量生产还是小批量生产,无论在小型车间还是分批处理的加工车间,加工齿轮的流程按顺序都需要以下四步操作:下料切齿热处理研磨根据它们的类型、应用范围及强度和刚度要求,通常经过铸造、挤压、锻造、粉末冶金、注塑加工和滚齿加工来完成齿轮的加工制造。在这一系列加工流程中,螺旋伞齿轮是最复杂的一种齿轮,在成角度的横轴之间,它用来传递回转运动。 沿齿长方向,螺旋伞齿轮有径向弯曲的齿廓曲线。这类齿轮之所以能够保证与配合齿轮有光滑的啮合,主要是因为它们有胜过直齿轮的曲型齿廓,这样它们同一时间接触并啮合的齿数会更多。螺旋伞齿轮的设计与制造仍然是一个热门的研究课题,在直升机运输齿轮系、摩托车齿轮减速器及其他工业分支中都得到十分重要的应用。对于制造而言,这种齿轮通常由一种特殊机床加工而成,如滚齿机、成型机。目前,基于轮齿加工的特种数控加工机床已运用于工业实践中。这也许就是轮齿加工的相关文献在公开的研究领域稀少的原因所在。最近,基于齿轮加工的数控加工机床已得到长足发展并逐渐运用于工业实践。然而,它们的运动结构与工业数控铣床还是有着内在的差异,前者是为一种特种刀具而设计的。 先前对齿轮的研究主要涉及齿轮的设计和分析。在对其几何特征与设计参数进行研究的同时,Tsai和Chin基于切面方向上的齿轮传动和渐开线齿轮几何学,提供了一个关于锥齿(直齿轮、螺旋伞齿轮)的数学曲面模型。后来,这个方案与A-daccak等人和Shunmugan等人基于精密球面渐开线的齿轮曲面模型进行了比较,从而得出了一个截然不同的模型。依据标称偏差,其精确度(相比运用特种机床加工的螺旋伞齿轮)得到了验证。 对于冠齿轮,一些结论是可行的。Litvin和Kim通过改良直齿轮的基圆提出了运用范成法获得渐开曲线。运用斜齿轮传动误差的修正测定值,Umeyama在节圆上设计了一个标准剖面,在面齿轮的上下表面设计了一个改良剖面。Tamura等人对采用平面齿形的锥齿轮研究得出了一个点接触模型。这些研究都与专为加工齿轮而特殊设计的那些特种齿轮加工机床(如滚齿机、成型机)返程齿剖面有关。Suh等人对螺旋伞齿轮加工的雕刻面加工方法的可行性做了研究,并验证了运用带有回转摆动升降台的四轴数控铣床生成加工轨迹的可能性。同时,一种螺旋伞齿轮基于模型的验证法也得以提出。 在本文中,对于螺旋伞齿轮我们将尝试采用一种新的加工流程,加工时运用带有可用于控制分度台的PLC模块的三轴铣床。很明显,这种加工方法的生产率不及特种加工机床。可除了生产率,这种加工方法的优点有以下几个方面:1传统加工方法需要消耗大量投资成本来获得各种特种机床,所选用刀具加工的齿轮种类、尺寸和几何形状也非常有限;2运用这种新的加工方法,各种类型的齿轮都可通过工业三轴数控铣床加工而成;3相比运用特种加工机床,采用该方法加工更为经济。一个不同于先前的工作重点是,为了模拟全部加工过程并获得加工参数,需要开发自动计算机模型。所有先前的研究都在计算复杂的数学方程组和设计几何模型。鉴于上述情况,我们的重点在于螺旋伞齿轮的加工实验检验,而不在于提供螺旋伞齿轮的几何或数学模型。这是第一次同时运用机电一体化机床和数控铣床来加工特殊齿轮,甚至一个机械元件。2 螺旋伞齿轮的几何规格 通常,一个齿轮的几何参数都由工程图给出。对于定义其几何形状而言,有些参数(主要参数)是必须有的。为此,我们采用名为“GearTrax”的驱动元件开发软件来算得这些主要参数。 螺旋伞齿轮的设计要求高精度的数学计算,并且生产这种齿轮传动机构不仅需要高质量的设备和加工此类齿轮传动机构的机床,而且还需要拓展适当的机床参数设置。这样的设置虽然不合乎标准,但也需要由能够保证符合高质量齿轮传动要求的每种情况的设计(根据齿轮传动的几何参数和展成工具)来确定。3 加工螺旋伞齿轮 由引言中的讨论,我们知道所有类型的齿轮都能通过加工手法来获得所需要的所有规格,其中高精度齿轮的加工手法仍然非常卓越的。成型铣削是加工任意类型齿轮的最常见的加工工序。所使用的道具都具有类似相邻轮齿间隙的相同形状。标准刀具通常用于齿轮的成型切削。在美国,这些刀具的每个径节都是原来的8倍,用于加工标准表上指示的多齿齿轮。格利森公司基于为补充冠齿轮范成原理而产生的锥齿轮范成的普遍概念:相互啮合的大小齿轮可分别考虑,运用了表面滚齿的加工手法。 由公式1可知,表面滚齿加工的速率比应取决于工具齿轮与展成齿轮的齿数比: (1)其中,和分别为工具齿轮与展成齿轮的扭转角速度;和分别为工具齿轮和展成齿轮的齿数。 展成齿轮与工具齿轮的基圆半径由公式2、3确定: (2) (3)其中,s为机床径向设定值。 范成的冠齿轮可考虑为螺旋角为90度的特殊斜齿轮。因此,出现了“形齿轮”这个通用术语。当已生成的大小齿轮的配合吃面共轭时,可以考虑对范成冠齿轮的概念进行补充。在实践中,为了使失配的轮齿表面得以匹配,形齿轮的大小齿可能互不相同。形齿轮的旋转由戟齿轮上的摇架旋转体现。 用三轴数控铣床加工螺旋伞齿轮,我们首先应该对开发的CAD/CAM系统的几何建模和仿真模块尽享程序测试。运用商业软件Solidworks创建CAD模型和MSC。运用Visual NASTRAN 4D软件(运用3D模型的CAE机械运动分析系统)模拟齿轮加工并得到分析结果。 对于机床的结构而言,很明显,螺旋伞齿轮的数控机床上,工件的回转运动史必要的。基于其切削的性能分析,通过一步安装,螺旋伞齿轮的数控加工至少也可达到四轴控制的要求。因此,对于三轴铣床具备回转工作台是必要的。成型切削或成型铣削都会在测试中用到。刀具从齿轮毛坯中心想要得到的齿高径向进给,然后穿过齿面,而回转工作台绕其中心旋转工件来获得所需的齿宽。当加工完成一个齿间时,刀具后退,分度头指示齿轮毛坯,继续切削下一个齿间。从根本上说,这种方法是一种简易而灵活的螺旋伞齿轮加工方法。所需的设备和刀具都相对简单,并且只运用标准三轴数控铣床。然而,防止出现任何的工件损坏,就每一工步为短程的刀具进给而言,我们有必要做到谨慎考虑。 我们在GearTrax环境下创建螺旋伞齿轮用以模拟操作工序并估算一些加工参数,如端铣刀的原始高度、接近传感器的位置、电动机转矩、电动机转速及转动频率。例如,在Solidworks环境下,端铣刀与螺旋伞齿轮的齿顶间距为14.7mm,这是我们沿Z轴用来垂直定位主轴的。 同时,根据我们使用的CAE系统所提供的图形报告,电动机的角速度和转矩分别为1rpm和48Nm。 Mastercam是一种可以生成刀具加工轨迹的机械专业软件。根据齿轮的总深度和表面宽度,在我们的切削程序中可设计出加工轮廓线为矩形的刀具轨迹。 其它加工参数和刀具的规格也应录入软件的刀具轨迹菜单。在加工轮廓线窗口,我们要用到以下两个选项:考虑到对切削量的较大控制,在多通道口允许刀具多工步进给。 2、在没有额外的几何尺寸条件下,在入口/出口位置变动之前,导入/导出拉长的或缩短的刀具轨迹,这样有助于我们控制加工补偿,并能使短时间编制固定加工轮廓线变为可能。 虽然这种齿轮的成型切削一般运用万能铣床上的分度头来完成,但其加工过程缓慢并需要技术熟练的工人师傅和操作者。刀具安装在刀柄轴上,运用分度头来旋转(切削轮齿)并指示齿轮毛坯。工作台设置在螺旋角为35度的角度上,并且分度头也应与工作台的纵向丝杠相适应,以便使齿轮毛坯得以纵向回转运动。 针对上述提供的方法,我们采用了连接了蜗轮蜗杆变速箱的交流电动机。蜗轮蜗杆变速箱用来减小交流电动机的输出速度,并将齿线也节圆锥面间的角度设置为螺旋角大小。 只要刀具轨迹编制与蜗轮蜗杆变速箱输出轴的旋转运动间的同步性达到要求,机电一体化系统便可同时控制四根轴(一轴用于工作台的回转运动,三轴用于刀具的切削运动)。 同时,在机电一体化系统中我们运用梯形图和通用编程语言来操作PLC。 基于梯形图,PLC的操作步骤如下: 第一步 读取外部输入信号,例如传感器与旋转编码器的地址。 第二步 根据第一步中的输入信号值,计算输出信号并将其传送给变频器(反相器),从而驱动交流电动机正反转或通过旋转编码器使电动机旋转一定的角度(齿距)。配置数控铣床的同时,所有系统的程序按以下五个阶段完成: 第一阶段 成型刀抵达第一个接近传感器,传感器一旦检测到成型刀,就向PLC发送一个+5V的信号,正如前面提到的,PLC接收信号并向变频器发送一个输出信号来驱动电动机正转。 第二阶段 以Mastercam中生成的刀具加工轨迹用成型刀加工旋转的工件。 第三阶段 刀具抵达第二个接近传感器,传感器通过检测刀具来向PLC传送第二个信号,同时PLC接收并向变频器发送一个停止指令。 第四阶段 铣刀从停止的工件退刀并回到起始位置。同时,变频器驱动电动机反转直到输出轴回到第一工位,在这个位置,光电传感器的接收器可可通过输出轴的纵向裂纹接收传输光线。 第五阶段 重复一至四阶段直到第一个齿间切削完成。PLC根据运行上述四阶段的次数计数直到达到加工程序中的预设次数。然后,PLC向变频器发送信号指示齿轮毛坯达到加工直径尺寸,接着上述所有阶段重复运行。加工直径由1024脉/转的旋转编码器测定。 在本次创新的加工方法的有利体现里,加工时间是主要关注的指标之一。例如,加工完成一个齿间只需2分钟。相比较,运用传统方法加工同样的齿间需要花费半个多小时。 在本次创新关于手工切削的深远有利体现里,切削刀头的瞬间角度补偿是在跳转程序结束之前立即设置的。4 加工策略 工件为木料,通过车削加工将坯料预加工为锥状(齿顶锥角)。用于实验的5号标准刀安装在机床主轴上,齿轮毛坯安装在蜗轮蜗杆变速箱的输出轴上。随后,刀具向齿轮毛坯的中心进给以达到所需齿深(围绕30条加工程序以避免次品出现)。加工完成一个齿间,退刀;根据已编译的程序由交流电动机指引齿轮毛坯接着切削下一个齿间。5 结论 在本文中,我们尝试运用三轴数控铣床通过成形铣削的方法加工螺旋伞齿轮。为了达到这一目的,我们对CAD/CAM模具的切削步骤和刀具轨迹算法做了研究。运用复杂的数学程序,所有的预先工作都与设计息息相关,并没有依靠经验加工理论。从根本上说,成形切削用于加工齿轮简单而灵活。所需的设备和刀具相对简单、廉价,一台标准数控铣床即可。因而,并不需要技术熟练的操作者来创建加工系统。与运用专业机床加工齿轮的常规方法相比,本文所采用的加工方法用于加工各种规格的螺旋伞齿轮或其它类型的齿轮,改进起来也很容易。与手动切削加工相比,这种加工方法又是一个全自动的,因为所有的加工参量都通过电脑模块得到。这种加工理念同时也是一个多变的系统(运用机电一体化和数控系统),并且会源源不断地发展下去。参考文献1. De Garmo EP, Black JT.材料与工艺制造. Prentice?Hall, New York. 19572. Shigley JE. 机械工程设计. McGraw-Hill, New York. 19863. Maitra GM. 齿轮设计手册. McGraw-Hill, New York. 19944. Tsai Y, Chin P. 垂直表面几何学与螺旋伞齿轮. ASME J Mech Trans Autom Des 1094:443?449. 19875. Al-daccak M, Angeles J, Gonzalez-Palacios M.精确球面渐开线的锥齿轮模具. ASME J Mech Des 116:364?368. 19946. Shunmugam M, Narayana S, Jayapraksh V. 轮齿几何平面的创建与正态偏差: 第一部分?圆柱齿轮. J Mech Mach Theory 335:517?524. 19987. Shunmugam M, Rao B, Jayaprakash V. 轮齿几何平面的创建与正态偏差: 第二部分?锥齿轮. J Mech Mach Theory 335:525?534. 19988. Litvin F, Kim D. 带有定位支架连结的改良渐开线直齿轮啮合范成与仿真及传动误差的折算标准. ASME JMech Des 119:96?100. 19979. Umeyama M.斜齿轮副传动误差的齿面改质效应与优化. Trans Jpn Soc Mech Eng C 61582:8?15. 199510. Tamura H, Tanaka K. 基于拟补偿冠齿轮的螺旋伞齿轮切削方法. Trans Jpn Soc Mech Eng C 58547:202?208. 199211. Tamura H et al. 基于拟补偿冠齿轮的直齿锥齿轮切削方法. Trans Jpn Soc Mech Eng C 63606:259?264. 199712. Suh S, Ji W, Chung D. 运用数控铣床的螺旋伞齿轮的曲面加工. Int J Mach Tools Manuf 41:833?850. 200113. Suh S, Lee E, Kim H. 运用STEP-NC的虚拟齿轮模具测量弧齿锥齿轮的几何误差. Int J Mach Tools Manuf 42:335?342. 200214. Krenzer TJ. 表面铣削与表面研磨, AGMA. 技术文献, 90 FTM 1315. Pitts LS, Boch MJ. 运用表面研磨方法的锥齿轮与准双曲面齿轮的设计与开发. No. 4332, 格林森公司. 199716. Suh S, Kang J. 自由表面的多轴数控加工过程设计. Int J Prod Res 33:2723?2738. 199517. Dudley DW. 达力齿轮手册, 齿轮的设计、制造与应用. McGraw-Hill, New York. 196218. Jaeschke R. 电力传输控制系统. Penton/IPC, Cleveland, pp 210?215. 197819. Campbell S. 固态交流电机控制. Marcel Dekker, New York, pp 79?189 ISBN 0-8247-7728-X. 1987 Use of PLC module to control a rotary table to cut spiral bevel gear with three-axis CNC millingS. Mohsen Safavi & S. Saeed Mirian & Reza Abedinzadeh & Mehdi KarimianReceived: 25 November 2008 / Accepted: 23 November 2009 # Springer-Verlag London Limited 2009Abstract CNC machining nowadays makes more use of Mechatronics increasingly. Combining numerical control with mechanic, electric, and data processing systems can lead to new methods of production. In recent years, the development of CNC has made it possible to perform nonlinear correction motions for the cutting of spiral bevel gears. In this paper, we attempt to manufacture the spiral bevel gear using a three-axis CNC milling machine interfaced with an additional PLC module based on traditional discontinuous multi-cutting method accomplished by using a universal milling machine interfaced with an indexing work head. This research consists of a geometric modeling of the spiral bevel gear, b simulating the traditional and our new nontraditional method using a CAD/CAE system, c process planning for CNC machining and PLC Programming, d experimental cuts with a three-axis CNC milling machine were made to discover the validity of the presented method. The results demonstrate that invented experimental cutting method of SBGs not only is less expensive than advanced CNC machining but also produces gears in a shorter time in comparison with the traditional cutting. Thereby, it is an economical method in manufacturing of SBGs.Keywords:Gear manufacturingSpiral bevel gear .CAD/CAM/CAECNCPLCAC motorInverter .Proximity sensorsPhotoelectric sensorsRotary encoder1 Introduction Gears are important and precision mechanisms for industrial machinery as a means for mechanical power or motion transmission between parallel, intersecting and nonintersecting cross-axis shafts. Although hidden from sight, gears are one of the most important mechanical elements in our civilization. They operate at almost unlimited speeds under a wide variety of conditions. The machines and processes that have been developed for producing gears are among the most existing ingenious ones. Whether produced in large or small quantities, in cell, or job shop batches, the sequence of processes for gear manufacturing requires four sets of operations: 1. Blanking 2. Gear cutting 3. Heat treatment 4. GrindingDepending on their type and application or required strength and resistance, gears are manufactured by casting, extruding, forging, powder metallurgy, plastic molding, gear rolling, and machining. Among these processes, machining is more frequently used for high-precise gears. Among the various types of gears, the spiral bevel gears SBG are the most complex type and are used to transmit the rotational motion between angularly crossed shafts. SBGs have teeth curved longitudinally along the length of the teeth. The main advantage of these gears over the straight-toothed varieties lies in the fact that more teeth are in contact at the same time because of the curve-shaped contour of the teeth and so a smoother meshing action between the mating pair is ensured. The design and manufacturing of spiral bevel gears is still a hot topic of research that is vital for application of such gears in helicopter transmissions, motorcycle gears, reducers, and in other branches of industry. As far as manufacturing is concerned, the gears are machined by a special type of machine tools, such as gear hobbing and shaping machines. Recently, special CNC-based gear manufacturing machine tools are used in industrial practice. This may be why literature on gear manufacturing is sparse in the open research domain. Recently, CNC-based gear manufacturing machine tools have been developed and increasingly used in industrial practice. However, their kinematic structure is still inherently different from the industrial CNC milling machine, as the former is designed for a special type of cutter. Previous studies on gears have been mainly concerned with the design and analysis of gears. The geometric characteristics and design parameters of gears have been studied. Tsai and Chin presented a mathematical surface model for bevel gears straight and SBGs based on basic gearing kinematcis and involute geometry along the tangent planes. Later, this method was compared with another model based on exact spherical involute curves by Al-daccak et al. Shunmugan et al. presented a different model, and its accuracy compared with the spiral bevel gear manufactured by special machine tools was verified in terms of nominal deviation For crown gears, a few results are available. Litvin and Kim suggested a generation method for an involute curve from a modified base circle for a spur gear. Umeyama designed a standard profile at the pitch circle and a modified profile at the top/bottom face gear with a determination of the modification value for transmission error of helical gear. Tamura et al. studied a point contact model for a bevel gear using a flat surface tooth. These studies are concerned with the generation of the tooth profile for special gear machines, such as gear hobbing and shaping machines, which are specially designed for manufacturing gears. Suh et al. investigated the possibility of a sculptured surface-machining method for the manufacture of spiral bevel gears and verified the possibility by presenting tool-path generation using a four-axis CNC milling machine interfaced with a rotary-tilt table. A model-based inspection method for the spiral bevel gears was also presented In this paper, we attempt to present a new manufacturing procedure of SBGs by using a three-axis milling machine interfaced with a PLC module which operates as an indexing table. In terms of production rate, it is obvious that this method will be lower than that of the special machine tool. Other than production rate, this method is advantageous in the following respects: 1 the conventional method requires a large investment for obtaining various kinds of special machinery and cutters dedicated to a very limited class of gears in terms of gear type, size, and geometry; 2 by this method, various types of gears can be manufactured with the industrial three-axis CNC milling machine; 3 this method is more economical than using the special machine tool. One of the main points which separate our work from previous ones is developing an automatic computer model in order to simulate the process entirely and obtain machining parameter. All previous studies have been engaged in calculating complicated mathematical equations and designing geometric models. In view of the above, special attention is given to experimental tests rather than presenting geometrical or mathematical model of SBGs. This is the first time that mechatronic tools and a three-axis CNC milling machine are being used simultaneously in manufacturing a special gear and even a mechanical element.2 Geometric specifications of the spiral bevel gears Most of the time, the geometric parameters of a gear are provided with an engineering drawing. Some parameters principal parameters are required for defining the geometry. To calculate these parameters, we have used “drive component development software” called GearTrax The design of spiral bevel gear requires high-accuracy mathematical calculations, and the generation of such gear drives requires not only high-quality equipment and tools for manufacturing of such gear drives but also the development of the proper machine-tool settings. Such settings are not standardized but have to be determined for each case of design depending on geometric parameters of the gear drive and generating tools to guarantee the required quality of the gear drives.3 Manufacturing the SBG As it was discussed in the introduction, by machining, all types of gears can be made in all sizes, and machining is still unsurpassed for gears having very high accuracy. Form milling is one of the most common machining processes used to manufacture any types of gears. The cutter has the same form as the space between adjacent teeth. Standard cutters usually are employed in form-cutting gears. In the USA, these cutters come in eight sizes for each diametral pitch and will cut gears having the number of teeth indicated in standard tables. Gleason works used the face hobbing process that is based on the generalized concept of bevel gear generation in which the mating gear and pinion can be considered respectively, generated by the complementary generating crown gears As it is shown in Eq. 1, velocity ratio of face hobbing process depends on tooth number of tool and generating gear: (1)where, wt and wc denote the angular velocities of the tool and generating gear; Nt and Nc denote the number of the blade groups and the tooth number of the generating gear The radii of the rolling circles of the generating gear and the tool are determined by Eqs. 2 and 3: (2) (3)where s is the machine radial setting. The generating crown gear can be considered as a special case of a bevel gear with 90 pitch angle. Therefore, a generic term “generating gear” is used. The concept of complementary generating crown gear is considered when the generated mating tooth surfaces of the pinion and the gear are conjugate. In practice, in order to introduce mismatch of the mating tooth surfaces, the generating gears for