普通立式铣床的数控改造

摘 要

本次设计主要是普通立式铣床的经济型数控改造设计，在本设计中，采用AT89C51、2764、6264、8155等芯片扩展成简单的开环单片机控制系统，通过铣削参数的计算确定步进电机。软件采用模块式，主要包括主程序模块、键盘显示模块、串行通信模块、凸轮程序处理模块、报警中断模块等。有键盘输入用户加工程序，存入外部程序存储器（2764），根据加工程序内容控制步进电机驱动工作台的径向（X向）和周向（Y向）联动，从而加工出相应的凸轮轮廓。同时，设计中也考虑到系统的精确性和稳定性，采用双片齿轮错齿法调整滚珠丝杠的轴向间隙，选用光电隔离电路去除强电干扰，选择大功率场效应晶体管斩波驱动电路实现脉冲的放大。

本设计造价低、适应能力强、应用范围广。采用本机床加工可大幅度降低工人劳动强度，有效提高加工生产率和提高工件精度。

关键词：数控技术，数控改造，单片机，，机床改造，凸轮加工

ABSTRACT

The design is General economic vertical milling machine design of NC, in this design, use of AT89C51, 2764,6264,8155, and other chip expansion into simple open-loop control system microcontroller, through the milling parameters Calculation determine stepper motor. Use of modular software, including the main program modules, keyboard modules, serial communication module, Cam process of the module, the police interrupted module. A keyboard input users processing procedures, into the external program memory (2764), in accordance with procedures for processing the content control of the stepper motor-driven table radial (X to) and the Zhou (Y to) linked to processing the corresponding cam Contour. At the same time, also taking into account the design of the system accuracy and stability of a dual-gear tooth wrong ball screw adjustment of the axial gap, the choice of optoelectronic circuits to remove segregation-interference, select high-power field-effect transistor chopper Driver circuit pulse amplification.

The design of low cost, strong adaptability and wide application. Using this machine tool workers can be significantly reduced labor intensity, effectively enhance the productivity and improve processing accuracy of the workpiece.

Keywords: NC, NC transformation, SCM, machine transformation,

processing Cam

目 录

第1章 绪论 ···················································································· 1

1.1 课题背景 ············································································································· 2

1.2 现实意义 ·············································································································· 2

1.3 设计任务 ·············································································································· 2

1.4 总体设计方案分析 ······························································································ 2

1.5 总体设计方案确定 ······························································································ 2

1.5.1 伺服系统 ··········································································································· 2

1.5.2 控制信号 ··········································································································· 2

1.5.3 辅助功能 ··········································································································· 2

第2章 步进电机的确定 ·································································· 1

2.1 步进电机的选用 ································································································· 2

2.1.1 铣削用量 ··········································································································· 2

2.1.2切削层参数 ········································································································ 2

2.1.3 铣削力和功率 ··································································································· 2

2.1.4计算 ···················································································································· 2

第3章 消隙方法与预紧 ·································································· 2

3.1 消隙方法 ·············································································································· 2

3.1.1 偏心轴套调整法 ···························································································· 2

3.1.2 锥度齿轮调整法 ···························································································· 2

3.1.3 双片齿轮错齿调整法 ···················································································· 2

3.2 预紧 ······················································································································ 2

第4章 步进电机接口电路及驱动 ····················································· 1

第5章 数控系统设计 ······································································ 1

5.1 确定机床控制系统方案 ····················································································· 2

5.2 主要芯片配置 ······································································································ 2

5.2.1 主要芯片选择 ································································································ 2

5.2.2 主要管脚功能 ································································································ 2

5.2.3 EPROM的选用 ···························································································· 2

5.2.4 RAM的选用 ································································································· 2

5.2.5 8031存储器及I/O的扩展 ············································································ 2

5.2.6 8155工作方式查询 ······················································································· 2

5.2.7 状态查询 ········································································································ 2

5.2.8 8155定时功能 ······························································································· 2

5.2.9 芯片地址分配 ································································································ 2

5.3 键盘设计 ·············································································································· 2

5.3.1 键盘定义及功能 ···························································································· 2

5.3.2 键盘程序设计 ································································································ 2

5.4 显示器设计 ·········································································································· 2

5.4.1 LED的显示原理 ··························································································· 2

5.4.2 LED显示器与8155的连接 ········································································· 2

5.4.3 显示缓冲区 ···································································································· 2

5.5 光电隔离电路 ······································································································ 2

5.6 越界报警电路 ······································································································ 2

5.6.1 主要电子器件 ································································································ 2

5.7 总体程序控制 ······································································································ 2

5.7.1 数据处理程序 ································································································ 2

5.7.2 串行通信的软件设计 ···················································································· 2

5.7.3 加工程序的设计 ···························································································· 2

5.7.4 流程图 ············································································································ 2

5.7.5 总程序 ············································································································ 2

结论 ································································································· 1 参考文献 ························································································· 1 致谢 ································································································· 1

第1章 绪论

1.1 课题背景

在美国、日本和德国等发达国家，它们的机床改造作为新的经济增长行业，生意盎然，正处在黄金时代。由于机床以及技术的不断进步，机床改造是个"永恒"的课题。我国的机床改造业，也从老的行业进入到以数控技术为主的新的行业。在美国、日本、德国，用数控技术改造机床和生产线具有广阔的市场，已形成了机床和生产线数控改造的新的行业。在美国，机床改造业称为机床再生(Remanufacturing)业。从事再生业的著名公司有：Bertsche工程公司、ayton机床公司、Devlieg.Bullavd(得宝)服务集团、US设备公司等。在日本，机床改造业称为机床改装(Retrofitting)业。从事改装业的著名公司有：大隈工程集团、岗三机械公司、千代田工机公司、野崎工程公司、滨田工程公司、山本工程公司等。

我国目前机床总量380余万台，而其中数控机床总数只有11.34万台，即我国机床数控化率不到3％。近10年来，我国数控机床年产量约为0.6～0.8万台，年产值约为18亿元。机床的年产量数控化率为6％。我国机床役龄10年以上的占60％以上；10年以下的机床中，自动/半自动机床不到20％，FMC/FMS等自动化生产线更屈指可数（美国和日本自动和半自动机床占60％以上）。可见我们的大多数制造行业和企业的生产、加工装备绝大数是传统的机床，而且半数以上是役龄在10年以上的旧机床。用这种装备加工出来的产品普遍存在质量差、品种少、档次低、成本高、供货期长，从而在国际、国内市场上缺乏竞争力，直接影响一个企业的产品、市场、效益，影响企业的生存和发展。所以必须大力提高机床的数控化率。

1.2 现实意义

机床改造可以减少投资额、交货期短，同购置新机床相比，一般可以节省60％～80％的费用，改造费用低。机械性能稳定可靠，改造后的机床性能高、质量好，可以作为新设备继续使用多年。熟悉了解设备、便于操作维修，改造可以精确地计算出机床的加工能力；另外，由于多年使用，操作者对机床的特性早已了解，在操作使用和维修方面培训时间短，见效快。可充分利用现有的条件, 可以充分利用现有地基，不必像购入新设备时那样需重新构筑地基。可以采用最新的控制技术,可根据技术革新的发展速度，及时地提高生产设备的自动化水平和效率，提高设备质量和档次，将旧机床改成当今水平的机床。

1.3 设计任务

本次设计要求把普通立式铣床改造成加工凸轮的数控铣床，包括在机械本体上加装数控工作台和数控系统的设计。数控工作台包括径向和回转方向的联动。本设计主要针对数控系统的硬件和软件部分进行设计。在硬件部分的设计中，从经济性考虑，整个系统采用单片机进行控制，工作台两个方向的驱动分别采用两台步进电机实现。软件部分包括凸轮数据处理程序、加工程序等控制程序。

本设计具体为将一台X502型普通立式铣床改造成加工凸轮的数控铣床，改造目的主要是利用数控方法加工凸轮。要求原铣床的改动尽可能少，希望保留原来操作机构，以便数控部分发生故障时仍能手工半主动操作。

X502型立式铣床其主电动机1转速为1450r/min，功率为2.2kW，通过带传动经变速传动齿轮链将运动传给主轴X。主轴有8级不同的转速，即47.5r/min、67r/min、95r/min、132r/min、190r/min、265r/min、375r/min、530r/min。主轴上传动功率为1.45kW。该主轴不能进行升降运动。工作台的升降只能通过轴7手动操作，纵向的机动时通过万向接头2将运动传给VIII轴实现。而横向和纵向那个手动操作时手柄5和手轮4进行的。

1.4 总体设计方案分析

本课题的主要任务是通过对普通立式铣床改造，实现凸轮的数控加工。在数控系统中对任意直线、圆弧或其他复杂曲线轮廓的加工都是通过插补实现的，一般的插补如直线插补和圆弧插补都是基于直角坐标系，在凸轮的铣削加工中，由于凸轮零件的型面的特殊性，如图1.1，一般插补算法很难实现加工。因此这里采用了基于极坐标的脉冲计数法，也称极坐标插补法。通过对工件回转方向和径向进给方向的联动实现凸轮型面的加工。

图1.1 凸轮示意图

由于原有机床的主运动机构仍然能够满足铣削加工的要求，在改造中可以不予改变。为了实现工作台的两轴联动，必须进行数控工作台的设计。数控工作台的设计工作包括机械本体的设计和控制部分的设计。在机械部分，回转运动方向步进电机经过齿轮降速，通过涡轮蜗杆传动驱动转台的转动；径向方向步进电机通过滚珠丝杠传动拖动工作台沿径向导轨做径向进给运动。在控制部分，主要是对控制信号、伺服系统以及系统的辅助功能进行软硬件的设计。

1.5 总体设计方案确定

1.5.1 伺服系统

伺服系统是数控装置和机床主体联系的纽带,是数控机床的重要组成部分,是将数控指令转变为进给运动的执行机构。数控机床的精度、响应速度、稳定性、有无爬行、调速范围等技术指标以及加工质量和生产率都主要取决于伺服系统。该机床伺服驱动的特点是低速、小扭矩。

在进行总体方案设计时,首先要作工艺方案的可行性分析和必要的工艺试验。结构设计时,既要考虑整机和各模块的精度要求、伺服轴的零位设置要求以及工艺性要求等,而且还要特别注意提高工艺系统的静、动刚度,伺服驱动传动链要尽可能短,并采取有效的减振消振措施。进行惯量匹配时,应综合考虑机械传动部件的惯量、阻尼和刚度对系统的影响,以获取良好的动特性。从而提高机床的工作稳定性、可靠性和精度保持性。

在本文中，我们采用步进电机做伺服电机，步进电机是一种离散运动的执行装置，

它和现在数字控制系统有着内在的联系，因此很容易和其他数字器件进行接口。另外，步进电机进给量和步进脉冲成严格的比例关系，没有累积误差，在停止时具有天生的自锁能力，可以组成结构较为简单而又具有一定精度的开环控制系统。基于步进电机的以上几个优点，在我们的伺服系统中，采用了开环控制系统。如图1.2所示。

图1.2 步进电机的开环控制

1.5.2 控制信号

在步进电机控制系统中，控制信号经过控制器处理，通过功率放大器放大驱动步进电机的运转。

在数字控制系统中，控制信号的产生有两种方案：

第一种，采用PLC控制。PLC控制是对开关量的控制，无法实现对轨迹控制，所以不予考虑。

第二种，采用微型计算机。微型计算机功能强大，用途广泛，但是成本太高，从经济性考虑，所以也不能予采用。

第三种，采用单片机控制。此种控制方案开发周期长，但成本低，能实现凸轮加工数控功能，应用单片机来实现是比较现实和经济的。

在本次设计中，采用第三种控制，即单片机控制。

1.5.3辅助功能

在数控系统中，除了要实现 主要功能以外，还需要一些辅助功能，例如，数据的采集、系统复位，工作台回原位、报警及处理等。这些功能的实现将在后面章节里进行详尽的描述。

参考经济型铣床改造的有关技术资料，对比单片机控制和PLC控制后，确定总体方案如下：