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2008-03-10 15:15:44 作者： 来源：互联网 浏览次数：353
简介：毕业设计（论文）开题报告 1． 结合课题任务情况，根据所查阅的文献资料，撰写1500～2000字左右的文献综述。 1 机床的数控化改造有关资料表明，目前我国机床总拥有量为378万台，其中数控机床只有8万多台，远远低于美国、日本、德国、韩国等制造业发达国家机床数控化率20%以上的水平"主要表现在设备老化陈旧、自动化水平低、技术水平落后、劳动生产率低，严重影响了生产力的发展"采用先进的工艺设备，逐步增加数控机床所占比重，已经成为我国制造技术发展的总趋势，也是企业走出困境提升水平，实现跨越式发展的必由之路"提高。机床数控化有两个途径: 1)购买新的数控机床 2)把普通型的旧机床改造成数控机床平均测算，购买一台数控车床12万左右，数控改造一台只需3万元左右"考虑到我国企业的经济状况，靠投入大量资金购买更新数控机床不太现实"如何少投资多收益，利用有限的设备改造资金引进数控技术，笔者认为第2种方法比较适合我国企业的实际情况，普通机床的数控改造应成为我国企业数控技术推广应用的基本做法。普通机床的数控改造，是指将普通机床配置上数控系统，并对机床的某些部位做一定的改造，使机床具有数控加工能力"改造的项目随机床种类和精度要求而不同，现以经济型数控车床为例说明。 1.1数字控制系统进口数控系统有日本系统、德国系统、美国-8051系统等：国产数控系统主要有华中数控系统、广州数控系统等"这些数控系统均具有直线插补、圆弧插补、车公/英制螺纹、刀具补偿、间隙补偿、刀具自动转位等功能，性能稳定、价格适中"操作面板简单直观，主要有起动键、暂停键、单段/连续开关、连续进给键、急停键、键盘、显示屏等"不但控制弱电，对主轴变速、刀架转位、主轴起停与换向及其他一些辅助性动作也能通过指令控制。 1.2 滚珠丝杠螺母副改造普通车床的进给丝杠都是滑动丝杠，即丝杠与螺母之间的摩擦为滑动摩擦"为了更好地消除丝杠与螺母之间的转动间隙，保证机床的加工精度，需要将原机床的滑动丝杠螺母副改换成滚珠丝杠螺母副"此项改造不属于必改项，对机床精度要求不高时，可以通过预紧原螺母的方法消除转动间隙。 1.3 步进电机选用车床进给传动部分改造一般是拆除原机床的机械传动机构，用步进电机经齿轮或同步带机构，减速驱动丝杠，带动刀架纵向或横向移动"纵向步进电机固定在床身上，横向步进电机固定在床鞍上。 1.4 减速驱动机构在机床改造中，步进电机和丝杠传动副之间装有减速机构，其主要目的是为了得到所需的脉冲当量和增大驱动力矩，一般采用齿轮传动机构或同步带传动机构"此项改造不属于必改项，在步进电机的转矩足够大，结构许可的情况下，也可以不用减速驱动机构，由步进电机直接与丝杠副相连。 1.5 自动刀架安装刀架改造是数控改造的重要内容，即将原普通车床的手动转位刀架替换成自动转位刀架"卧式车床自动转位刀架最常见的型式是螺旋型四转位刀架，拆除小拖板后将刀架调整好高度安装在中拖板上，由数控系统直接控制，效率高、工艺性能可靠。 1.6 光电编码器加工螺纹时为了保证步进电机进给与主轴的旋转相配合，切削出固定螺距、固定起点、多头螺纹等量分度的螺纹，通常在主轴尾部安装增量式光电编码器"切制螺纹时，编码器与主轴同步旋转，同时发出与主轴转角相对应的脉冲信号，控制刀架纵向移动。 1.7 导轨改造普通车床均为滑动导轨，这种导轨的缺点是静摩擦系数大，低速时易产生爬行现象，影响运动平稳性和定位精度"为了克服这一缺点，数控改造时，一种是将原导轨贴塑，使其成为贴塑导轨：另一种是将原滑动导轨换成滚动导轨"当机床精度要求不高时，一般不做导轨改造，以降低数控改造成本。 1.8 主轴变速机构主轴变速改造一般采用交流异步电动机变频调速系统，由控制变频器，变频器驱动交流异步电动机，实现自动无级变速在自动化程度要求不高的情况下，机床主轴变速部分可不做改动，仍采用原手动变速机构，这样可大大降低改造成本。 2 数控设备新发展数控系统是数控机床和数字化设备的核心，经过50多年的发展，数控系统已由原来传统的封闭体系结构系统发展到了采用微型计算机的开放式结构数控系统，并且进一步与网络技术、信息技术和控制技术相结合，向网络化、集成化和智能化方向发展。企业在激烈的市场竞争中要生存和发展，技术更新必须走在前列数控技术作为高新技术产物，其先进生产力作用直接带动了世界范围机械制造业的革命性变化为了使数控技术走向企业，我们需要对各环节依靠新技术、新成果、新方法进行改进，从而实现企业的跨越式发展普通机床数控改造是综合性很强的一门机电一体化技术，该技术如想更好成果应用于企业，需要不断地跟踪学习并应用新持术成果。
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目 录
前 言··························································································································· - 0 - 1 设计方案····················································································································· - 1 - 1.1系统运动方式的确定······························································································· - 1 - 1.2 伺服系统的选择····································································································· - 1 - 1.3 执行机构传动方式的确定······················································································· - 1 - 1.4 计算机的选择········································································································ - 1 - 2 经济型数控机床进给伺服系机械部分计算与校核····································· - 2 - 2.1设计方案的确定································································································· - 2 - 2.2 机械部分设计与计算························································································ - 2 - 2.4步进电机选择··································································································· - 14 - 3 进给伺服系统机械部分结构设计·································································· - 22 - 3.1纵向进给伺服系统总图设计··········································································· - 22 - 3.2进给伺服系统的装配图··················································································· - 22 - 4 经济型数控车床数控系统硬件电路图························································ - 24 - 4.1系统的功能······································································································· - 24 - 4.2 CPU存储器及I/O接口··················································································· - 25 - 4.3 I/O接口电路··································································································· - 25 - 4.4 步进电机的软件控制及转程序设计······························································ - 26 - 4.5 点比较法直线插补·························································································· - 29 - 4.6 其他辅助电路·································································································· - 32 - 5机床的加工程序编制····························································································· - 33 - 参考文献························································································································ - 35 - 附 录····························································································································· - 37 -
前 言
数控技术是以数字量编程实现控制机械或其他设备自动工作的技术。 有关资料表明，目前我国机床总拥有量为378万台，其中数控机床只有8万多台，远远低于美国、日本、德国、韩国等制造业发达国家机床数控化率20%以上的水平"主要表现在设备老化陈旧、自动化水平低、技术水平落后、劳动生产率低，严重影响了生产力的发展"采用先进的工艺设备，逐步增加数控机床所占比重，已经成为我国制造技术发展的总趋势，也是企业走出困境提升水平，实现跨越式发展的必由之路"提高。 这种数控系统由于功能适宜，价格便宜，用它来改造车床，投资少、见效快，成为我国“七五”、“八五”重点推广的新技术之一。 经济型数控车床，对于保证和提高被加工零件的精度，主要依靠两方面来实现：一是系统的控制精度；二是机床本身的机械传动精度。数控车床的进给活动系统，由于必须对进行位移的位置和速度同时实现自动控制，所以数控车床与普通卧式车床相比，应更有更好的精度，以确保机械运动系统的传动精度和工作平稳性。 十几年来，随着科学技术的发展，经济型数控技术也在不断进步，数控系统产品不断改进完善，并且有了阶段性的突破，使新的经济型数控系统功能更强，可靠性更稳定，功率增大，结构简单，维修方便。由于这项技术的发展增强了经济型数控的活力，根据我国国情，该技术在今后一段时间内还将是我国机械行业老设备改造的很好途径。对于原有老的经济型数控车床，特别是80年代末期改造的设备，由于种种原因闲置的很多，浪费很大；在用的设备使用至今也十几年了，同样面临进一步改造的问题通过改造可以提高原有装备的技术水平，大大提高生产效率，创造更大的经济效益。
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