机械工程专业英语翻译

53 Industrial Robots

There are a variety of definitions of the term industrial robot. Depending on the definition used, the number of robot installations worldwide varies widely. Numerous single-purpose machines are used in manufacturing plants that might appear to be robots. These machines can only perform a single function and can not be reprogrammed to perform a different function. Such single-purpose machine is do not fit the definition for industrial robots that is becoming widely accepted.关于工业机器人的定义有很多。采用不同的定义，全世界各地机器人的数量就会发生很大的变化。在制造工厂中使用的许多单用途机器可能会看起来像机器人。这些机器人只有单一的功能，不能通过重新编程的方式去完成不同的工作。这种单一用途的机器人不能满足被人们日益广泛接受的关于工业机器人的定义。

An industrial robot is defined by the International Organization for Standardization (ISO) as an automatically controlled, reprogrammable, multipurpose manipulator, which may be either fixed in place or mobile for use in industrial automation applications.

国际标准化组织(ISO)对工业机器人的定义为：一种能够自动控制的、可重复编程的多功能操作机，它可以是固定式的，也可以是移动式的，应用于工业自动化领域。

there exist several other definitions too, given by other societies, , by the Robot Institute of America (RIA), the Japan Industrial Robot Association (JIRA), British Robot Association (BRA) , and others. The definition developed by RIA is: A robot is a reprogrammable multifunctional manipulator designed to move material, parts, tools, or specialized devices through variable programmed motions for the

performance of a variety of tasks.

其他的一些协会，例如美国机器人协会( RIA)，日本工业机器人协会(JIRA)、英国机器人协会(BRA)等，都对工业机器人提出了各自的定义。由美国机器人协会提出的定义为：机器人是一种用于移动材料、零件、工具或者专用装置的，通过可编程序动作来执行多种任务并具有可重复编程能力的多功能操作机。

All definitions have two points in common. They all contain the words reprogrammable and multifunctional. It is these two characteristics that separate the true industrial robot from the various single-purpose machines used in modern manufacturing firms.

在所有的这些定义中有两个共同点，即“可重复编程”和“多功能”这两个词，正是这两个特征将真正的机器人与现代制造工厂中使用的各种单一用途的饥器区分开来。

The term "reprogrammable" implies two things: The robot operates according to a written program, and this program can be rewritten to accommodate a variety of manufacturing tasks.

“可重复编程”这个词意味着两件事：机器人根据编写的程序工作．并可以通过重新编写程序来使其适应不同种类的制造工作的需要。

The term "multifunctional" means that the robot can, through reprogramming and the use of different end-effectors, perform a number of different manufacturing tasks. Definitions written around these two critical characteristics have become the accepted definitions among manufacturing professionals.

“多功能”这个词意味着机器人能通过重复编程和使用不同的末端执行器，来完成不同的制造工作。围绕着这两个关键特征所撰写的定义已经变成了被制造业的专业人员所接受的定义。

The first articulated arm came about in 1951 and was used by the U, S. Atomic Energy Commission. In 1954, the first industrial robot was designed by George C. Devol. It was an unsophisticated programmable materials handling machine.

第一个关节式手臂于1951年被研制出来供美国原子能委员会使用。在1954年，第一个可以编程的机器人由乔治C.沃德尔设计出来。它是—个不复杂的，可以编程的物料搬运机器人。

The first commercially produced robot was developed in 1959. In 1962, the first industrial robot to be used on a production line was installed in the General Motors Corporation. It was used to lift red-hot door handles and other such car parts from die casting machines[l] in an automobile factory in New Jersey, USA. Its most distinctive feature was a gripper that eliminated the need for man to touch car parts just made from molten metal. It had five degrees of freedom(DOF). This robot was produced by Unimation

第一个商业化生产的机器人在1959年研制成功。通用汽车公司在1962年安装了第一个用于生产线上的工业机器人。它在位于美国新泽西州的一家汽车厂中用来从压铸机中取出红热的车门拉手以及诸如此类的汽车零件。它最显着的特点是通过采用手爪，避免由人去接触那些刚刚由熔化的金属形成的汽车零件。它有五个自由度。它是由万能自动化公司

( Unimation)生产的。

A major step forward in robot control occurred in 1973 with the development

of the T3 industrial robot by Cincinnati Milacron.[2] The T3 robot was the first commercially produced industrial robot controlled by a minicomputer. Figure shows a T3 robot with all the motions indicated, it is also called jointed-spherical robot.

在1973年，辛辛那提米拉克龙( Milacron)公司研制出T3工业机器人，在机器人的控制方面取得了重大的进展。T3机器人是第一个商业化生产的采用小型计算机控制的机器人。T3机器人和它的所有运动如图所示，它也可以称为关节式球面机器人。

Since then robotics has evolved in a multitude of directions, starting from using them in welding, painting, in assembly, machine tool loading and unloading, to inspection.

从那时起，机器人技术在很多方面都得到了发展，这包括焊接、喷漆、装配、机床上下料和检测。

Over the last three decades automobile factories have become dominated by robots. A typical factory contains hundreds of industrial robots working on fully automated production lines. For example, on an automated production line, a vehicle chassis on a conveyor is welded, painted and finally assembled at a sequence of robot stations.

在过去的30年中，机器人在许多汽车制造厂中占据了主要地位。在一个工厂中，通常有数以百计的工业机器人工作在全自动生产线上。例如，在一条自动生产线上，车辆底盘装在输送机上，在通过一连串的机器人工作站时进行诸如焊接、喷漆和最后的装配等项工作。Mass-produced printed circuit boards (PCBs) are almost exclusively assembled by pick-and-place robots, typically with SCARA manipulators,[3] which pick tiny

electronic components, and place them on to PCBs with great accuracy. Such robots can place tens of thousands of components per hour, far surpassing a human in speed, accuracy, and reliability

在印刷电路板的大批量生产过程中，装配工作几乎完全是通过抓一放型机器人进行的。通常采用平面关节型装配机器人( SCARA)，它可以抓取微小的电子元器件并以非常高的精度将其放到印刷电路板上。这类机器人每小时可以放置成千上万个元器件，其速度、精度和可靠性都远远超过了人类。

A major reason for the growth in the use of industrial robots is their declining cost. Since 1970s, the rapid inflation of wages has tremendously increased the personnel costs of manufacturing firms. In order to survive, manufacturers were forced to consider any technological developments that could help improve productivity. It became imperative to produce better products at lower costs in order to be competitive in the global market economy. Other factors such as the need to find better ways of performing dangerous manufacturing tasks contributed to the development of industrial robots. However, the fundamental reason has always been, and is still, improved productivity.

工业机器人成本的降低是促进它们的使用量增长的一个主要原因。从20世纪70年代开始，工资的快速增长大大增加了制造业中的人工费用。为了生存，制造厂商被迫考虑采用一切能够提高生产率的技术。为了在全球性市场经济的环境中具有竞争能力，制造厂商必须以比较低的成本，生产出质量更好的产品。其他的因素，诸如寻找更好的方式来完成带有危险性的制造工作，也促进了工业机器人的发展。但是，其根本原因一直是，而且现在仍然是提高生产率。

One of the principal advantages of robots is that they can be used in settings that are dangerous to humans. Welding and parting are examples of applications where robots can be used more safely than humans. Most industrial robots of today are designed to work in environments which are not safe and very difficult for human workers. For example, a robot can be designed to handle a very hot or very cold object that the human hand cannot handle safely.

机器人的主要优点之一是可以在对于人类来说危险的环境中工作。采用机器人进行焊接和切断工作是比由人工来完成这些工作更为安全的例子。大部分现代机器人被没计用在对人类来说不安全和非常困难的环境中工作。例如，可以设计一个机器人来搬运非常热或非常冷的物体，这些物体如果用人工搬运，则存在不安全因素。

Even though robots are closely associated with safety in the workplace, they can, in themselves, be dangerous. Robots and robot cells must be carefully designed and configured so that they do not endanger human workers and other machines. Robot workspaces should be accurately calculated and a danger zone surrounding the workspace clearly marked off. Barriers can be used to keep human workers out of a robot's workspace. Even with such precaution it is still a good idea to have an automatic shutdown system in situations where robots are used. Such a system should have the capacity to sense the need for an automatic shutdown of operations.

尽管机器人与工作地点的安全密切相关，它们本身也可能是危险的。应该仔细地设计和配置机器人和机器人单元，使它们不会伤害人类和其他机器。应该精确地计算出机器人的工作空间，并且在这个工作空间的四周清楚地标出危险区域。可以通过设置障碍物来阻止工人进入机器人的工作空间。即使有了这些预防措施，在使用机器人的场地中设置一个自动停止工作的系统仍然不失为一个好主意。这个系统应当具有能够检测出是否有需要自动停

止工作要求的能力。

50 Computer Numerical Control

Today, computer numerical control machine tools are widely used in manufacturing enterprises. Computer numerical control is the automated control of machine tools by a computer and computer program.

今天,计算机数控机床广泛应用于制造企业。计算机数控机床的自动控制是计算机和计算机程序。

The CNC machines still perform essentially the same functions as manually operated machine tools，but movements of the machine tool are controlled electronically rather than by hand. CNC machine tools can produce the same parts over and over again with very little variation. They can run day and night，week after week，without getting tired. These are obvious advantages over manually operated machine tools，which need a great deal of human interaction in order to do anything.

数控机器仍执行相同的函数作为手动机床,但机床控制电子的运动,而不是用手。数控机床可以产生相同的部分,一次又一次变化很少。他们可以日夜不停地运转,一周又一周,没有累了。这些明显的优势在手动机床,需要大量的人工交互为了做任何事。

A CNC machine tool differs from a manually operated machine tool only in respect to the specialized components that make up the CNC system. The CNC system can be further divided into three subsystems：control，drive，and feedback. All of these subsystems must work together to form a complete CNC system.

数控机床不同于一个手动机床只有在尊重专业的组件构成的数控系统。数控系统可以进一步分为三个子系统:控制、驱动,和反馈。所有这些子系统必须共同努力,形成一个完整的数控系统。

1. control system 控制系统

The centerpiece of the CNC system is the control. Technically the control is called the machine control unit（MCU），but the most common names used in recent years are controller，control unit，or just plain control. This is the computer that stores and reads the program and tells the other components what to do.

数控系统控制的核心。技术控制称为机控制单元(MCU),但近年来最常用的名字是控制器,

控制单元,或者就是简单的控制。这是计算机存储和读取程序,告诉其他组件该做什么。

2. Drive system. 驱动系统。

The drive system is comprised of screws and motors that will finally turn the part program into motion. The first component of typical drive system is a high-precision lead screw called a ball screw（）. Eliminating backlash in a ball screw is very important for two reasons. First，high-precision positioning can not be achieved if the table is free to move slightly when it is supposed to be stationary. Second，materials can be climb-cut safely if the backlash has been eliminated. Climb cutting is usually the most desirable method for machining on a CNC machine.

螺丝和汽车的传动系统是由部分程序,最终将变成运动。第一个组件的典型的驱动系统是一种高精度丝杠称为滚珠丝杆。消除反应在滚珠螺杆是非常重要的两个原因。首先,不能实现高精度定位如果表是免费的移动略当它应该是固定的。第二,材料可以安全地同向如果反弹

已经消除。爬上切割通常是最可取的方法在数控加工机器。

Drive motors are the second specialized component in the drive system. The turning of the motor will turn the ball screw to directly cause the machining table to move. Several types of electric motors are used on CNC control systems，and hydraulic motors are also occasionally used.

驱动电机驱动系统中的第二专业组件。电动机的转动将滚珠螺杆直接导致加工表。几种类型的电机是用在数控控制系统和液压马达也偶尔使用。

The simplest type of electric motor used in CNC positioning systems is the stepper motor（sometimes called a stepping motor）. A stepper motors rotates a fixed number of degrees when it receives an electrical pulse and then stops until another pulse is received. The stepping characteristic makes stepper motors easy to control.

最简单的类型的电动机用于数控定位系统是步进电机(有时称为步进电机)。步进电机旋转固定数量的度当它收到一个电脉冲,然后停止,直到接收到一个脉冲。步进特性使步进电机容易控制。

It is more common to use servomotors in CNC systems today. Servomotors operated in a smooth ，continuous motion—not like the discrete movements of the stepper motors. This smooth motion leads to highly desirable machining characteristics，but they are also difficult to control. Specialized hardware controls and feedback systems are needed to control and drive these motors. Alternating current（AC）servomotors are currently the standard choice for industrial CNC machine tools.

这是今天使用伺服电机在数控系统中更为普遍。伺服电机运行在一个光滑、连续的活动,

如离散运动的步进电机。这光滑的运动导致高度理想的加工特点,但他们也难以控制。需要专门的硬件控制和反馈系统控制和驱动这些汽车。交流电伺服电机目前工业数控机床的标准选择。

3. Feedback System 反馈系统

The function of a feedback system is to provide the control with information about the status of the motion control system，which is described in Figure .

反馈系统的功能是为控制提供运动控制系统的状态信息,如图所示。

The control can compare the desired condition to the actual condition and make corrections. The most obvious information to be fed back to the control on a CNC machine tool is the position of the table and the velocity of the motors. Other information may also be fed back that is not directly related to motion control，such as the temperature of the motor and the load on the spindle—this information protects the machine from damage.

控制可以比较所需的条件的实际条件和改正。最明显的信息反馈给控制数控机器上工具的位置表和汽车的速度。其他信息也可以反馈,不是直接关系到运动控制,如电动机的温度和负载信息保护机器免受损坏。

There are two main types of control systems：open-loop and closed-loop. An open-loop system does not have any device to determine if the instructions were carried out. For example，in an open-loop system，the control could give instructions to turn the motor 10 revolutions. However，no information can come back to the

control to tell it if it actually turned。All the control knows is that it delivered the instructions. Open-loop control is not used for critical systems，but it is a good choice for inexpensive motion control systems in which accuracy and reliability are not critical.

主要有两种类型的控制系统:开环和闭环。一个开环系统没有任何设备来确定指令进行。例如,在一个开环系统,控制可以给指令将电动机10革命。然而,任何信息可以回到控制告诉它,如果它实际上控制知道是它的指示交付。开环控制不用于关键系统,但这是一个不错的选择廉价的运动控制系统的精度和可靠性并不是最关键的

Closed-loop feedback uses external sensors to verify that certain conditions have been met. Of course，position and velocity feedback is of primary importance to an accurate CNC system. Feedback is the only way to ensure that the machine is behaving the way the control intended it to behave.

闭环反馈使用外部传感器验证某些条件已经满足。当然,位置和速度反馈是最重要的一个精确的数控系统。反馈是唯一的办法,以确保机器的行为控制计划的行为方式。

32、机械加工精度基础

加工是通过最简单和最廉价的方式将原材料转变为有用的产品。因此，只为了加工某些原材料和获得预期的产品，这样还不够。事实上，通过采用最简单、最快以及最高效的方法来实现预期的目标是非常重要的。如果采用的技术不够高效，所得零件的成本将会很高，并且这样的零件会在和其他制造商生产的类似零件的竞争中失去优势。同时，产品的生产时间应尽量短以使厂家占据更大的市场份额。

可以通过不同的方式对现代工业进行分类。其分类方式可以是按加工过程，按产品类

型也可以按产量和差异程度分类。按加工过程分类可以用铸造行业和冲压行业以及类似的

行业来印证。当按产品分类时，产业可以分为汽车行业，航空航天产业以及电子产业。第

三种方式，即按产量分类，可以分为三种类型，大批量生产，单件小批量生产和中批量生产。以下让我们简要介绍每一类的特点。

大批量生产的主要特点是相同或相似零件产量高，时间周期较长。年产量不高于5万

件就不能认为是大批量生产。正如你所期望的那样，产量是基于一个预设的销量并且其不

直接受每日或每月订单量的影响。典型的大批量生产行业就是汽车行业。

单件小批量生产是基于小批量的销售订单。每一小批可以同20到200或更多类似零件组成，取决于消费者的需求。很明显，这类产业主要适用于二级承包商，他们主要生产类

型多变的零件以供应不同类型的行业。其使用的机器必须可调节以使其配置满足订单零件

的需要，因为订单零件种类通常是变化的。同时，为了完成各种不同的任务，工人应该经

验丰富，因为制造不同的零件，其任务通常是有差异的。

中批量生产介于单件小批量生产与大批量生产之间。其产量范围是1万件到2万件之间，其采用的机床主要是可调机床和多功能机床。由于用户定制生产量的增加，此类产业

也正在逐渐流行。

制造中一个非常重要的事实就是在加工零件时几乎不可能使零件获得理想的公称尺寸。这通常是由于一些不可预期的，尽管非常小的机床固有偏差和各种复杂的因素，如工件的

弹性变形和回复，或者是由于加工过程中的安装、温度，甚至有时还包括工人的技术等因素。由于分析和完全消除此类因素的影响非常困难，建立一个偏差容许度对于基本尺寸会

更可行，只要这样的偏差不会以有害的方式影响到零件的正常工作。从基本尺寸到每一侧

的尺寸偏差（即正负偏差）决定了分别决定了尺寸的上下极限，并且此上下极限的差值即

为公差。公差是一个正值。你可能会想到，公差大小取决于基本尺寸，公差大小是一个有

数字字母的符号，称为公差等级。在ISO标准体系中，公差有18个标准等级，公差可以通过公式计算得到或者从ISO公布的手册中查到。很明显，在制造零件过程中，越小的公差就越需要高精度的机床，因此也增加了成本。

在零件装配前，配合面的尺寸关系必须明确。换句话说，必须建立两配合面好偏差所参考的零位线的位置。这实际上决定了配合面相对运动的松紧度和自由度。在配合的分类主要有三种，即间隙配合、过渡配合、和过盈配合。在所有的间隙配合中，轴的上极限总是小于配合孔的下极限。这在过盈配合中是不成立的，过盈配合中，轴的下极限必须大于配合孔的上极限。正如其名字所表示的那样，在过渡配合中，其属于中间配合。根据ISO 标准，轴的制造总是参照内部零件，即轴的配合面是以孔为参照的。相应地，从配合位置看，键是以轴为参照的，键槽是以孔为参照的。

说明配合的类型的方式有两种，基轴制和基孔制。参照零位线的公差带是通过一个字母说明的，通常对轴用小写字母，对孔用大写字母，而公差等级是用一数字说明的，如先前提到的。因此一个配合方式可以表示为H7/h6，F6/g5，或者其他类似的方式。

当一个灯泡坏了的时候，你仅仅会买一个灯泡并且换掉原来的灯泡就行了。这个简单的操作并不需要一个装配工和一个机械师，但是如果没有两个重要的概念，互换性和标准化，这样的操作是不可能实现的。互换性即同一个零件必须可以互换，即是说这个零件可以替换其他的每一个零件，不管是在装配还是在维修过程中，都不需要任何配合操作。你很容易明白，互换性是通过建立一个可接受的公差来实现的，任何超出基本尺寸的偏差都是不允许的。

48 Process Planning

Process planning is the determination of how a particular part will be manufactured in the shop. It consists of breaking manufacturing process for the

part into small steps，and then determining the optimum method of achieving that manufacturing step. This includes determining the type of Manufacturing process to use，as well as the machining parameters for that particular process. It also includes determining a sequence of operations for the individual manufacturing actions that attempts to optimize a combination measure of manufacturing time and cost.

工艺设计是确定如何制造一个特定部分的商店。它包括生产过程的部分分解成小步骤,然后确定最优方法制造的实现步骤。这包括确定生产过程使用的类型,以及加工参数对这个特定的过程。它还包括确定个人的操作序列生产行动,试图优化相结合的制造时间和成本。

The essence of the process planning task can be reduced to five basic steps. First，the required operations must be determined by examining the design data and employing basic machining data （such as that square parts cannot be made on lathes ）.

流程规划任务的本质可以概括为五个基本步骤。首先,所需的操作必须由检查设计数据和使用基本的加工数据(如广场部分不能在车床)。

Second，the machines required for each operations must be determined. This selection depends on knowledge of machine factors，such as availability，machining rate ，size，power，and torque.

第二,必须确定每个所需的机器操作。这个选择取决于机器的知识因素,如可用性、加工速度、大小、功率和扭矩。

Third，the required tools for each identified machine must be determined.

第三,必须确定每个确定机所需的工具。

Fourth，the optimum cutting parameters for each selected tool must be determined. These parameters include feed rate ，cutting rate ，depth of cut，and so forth. This determination depends on design data, such as material and surface roughness specifications，and on tool-cutting behavior.

第四,最优切削参数为每个选定的工具必须确定。这些参数包括加料速度、切削速度、深度减少,等等。这决心取决于设计数据,材料和表面粗糙度等规范行为。

Finally，an optimal combination of these manufacturing process must be determined. The optimum is the process plan that minimizes some measure of manufacturing time and cost. This provide a detailed plan for the economical manufacture of the part.

最后,必须确定这些生产过程的最优组合。最优过程计划,最大限度地减少一定的制造时间

和成本。这提供了一个详细的计划经济生产的部分。

Traditionally process planning is performed manually by highly experienced process planners who possess an in-depth knowledge of the manufacturing process involved and the capabilities of the shop floor facilities. Because of the experience factor involved in process planning and in the absence of standardization of the process, conventional process planning has largely been subjective. Moreover，this activity is highly labor intensive. Rather than carrying out an exhaustive analysis and arriving at optimum values which could be time consuming，process planners often tend to play safe by using conservative values and this situation would invariably lead to no-optimal utilization of the

manufacturing facilities and longer lead times.

传统工艺设计是由经验丰富的手动执行过程计划拥有深入的知识生产过程和车间设备的功能。因为经验因素参与过程的计划和在缺乏标准化的过程中,传统的工艺设计在很大程度上是主观的。此外,这个活动是高度劳动密集型的。而不是进行详尽的分析和到达最优值可以耗费时间,过程规划者往往玩安全使用保守的价值观,这种情况总是会导致生产设施的利用率和较长的交货期。

The need for shorter lead times，satisfying varied customer demands on the product variety and the optimum use of manufacturing facilities prompted research organizations and industries to automate many functions in the manufacturing process. Harnessing the power of the computer is extremely advantageous in process planning since vast amount of data needs to be used for making the right decision for planning the manufacturing operations.

需要更短的交货期,满足不同客户需求的产品种类和生产设备的最佳使用促使研究组织和

工业自动化生产过程的许多功能。利用计算机的力量是极其有利的过程规划以来,大量的数据需要用于制造业务的计划做出正确的决定。

Computer-aided process planning（CAPP）involves the use of computers to automate this process. The design data would typically be the finished part design file from the CAD system . As part of the realization of the gains of CIM，the CAM process are designed to start with this CAD design file as their input. This insures a continuity of information flow from design engineering to manufacturing engineering. It also provides an exactly accurate and well-structured form of input to manufacturing with no additional cost to design engineering . It is this

well-structured input that allows for the use of computer-aided processes in manufacturing engineering.

计算机辅助工艺规划(CAPP)涉及到电脑的使用自动化这个过程。设计数据通常是完成部分设计文件从CAD系统。作为实现的收益的一部分CIM,凸轮设计过程开始与这个计算机辅助设计文件作为输入。这确保连续性信息流从工程设计到制造工程。它还提供了一个完全准确、结构形式的输入制造没有额外成本设计工程。正是这种结构良好的输入允许使用计算机辅助制造工程流程。

There are two basic approaches to computer-aided process planning ，. variant or generative，which are briefly discussed below.

计算机辅助工艺设计有两种基本方法,即。变体或生成,下面简要讨论。

The first of these is variant or retrieval method. In this method，the computer makes a search through its store of number of standard or partially completed process plans that have been previously developed by human planners. Using the current design data supplied by the CAD system，it searches for a plan that was based on a part of similar design. This search can make effective use of group technology design coding to simplify the search for similar code numbers，and hence for similar part designs. This original plan is then modified or completed by the human planners to suit the exact requirements of the current part design. The use of a computer and group technology to search for the most similar past design，and to retrieve the process plan for that design ，significantly reduces the work required of the process planners. Their task becomes one of modifying the exist plan to suit the particular dimensions of the current part. They are required to

perform the entire process planning method only in the case of a completely new part design.

第一个是变体或检索方法。在这种方法中,计算机搜索的商店数量的标准或部分完成过程的计划,已经被人类以前开发的规划者。使用当前设计CAD系统提供的数据,搜索一个计划,

是基于类似的设计的一部分。这个搜索可以有效利用成组技术设计编码简化搜索相似的代码数量,从而为类似的部分设计。这个原计划然后修改或完成人类的规划者,以适应当前的确切需求部分的设计。使用计算机和组技术来寻找最相似的设计,和检索流程规划设计,显着减少所需的工作流程的规划者。他们的任务成为修改计划以适应当前的特定维度存在的部分。他们只需要执行整个过程规划方法的一个全新的部分设计。

The second method of computerized process planning is the generative method. In this method，a process plan is automatically generated on the basis of the same logical procedures that would be followed by a traditional process planners in making that particular part. However，the generative method is complex because it must contain comprehensive and detailed information of the part shape and dimensions ；process capabilities；selection of the manufacturing methods ，machinery ，and tools；and the sequence of operations to be performed.

计算机化工艺规划的第二个方法是生成方法。在这种方法中,一个过程的计划的基础上自动生成相同的逻辑程序,紧随其后的是一个传统工艺规划师在这个特定的部分。然而,生成方法是复杂的,因为它必须包含全面和详细的信息部分的形状和尺寸,过程能力;制造方法的

选择,机械,工具,操作的顺序被执行。

The generative method is capable of creating a new plan instead of having to use and modify an existing plan（as the variant method must）. Although generally

used less commonly than the variant method，this method has such advantages as （a）flexibility and consistency for the process planning for new parts and （b） higher overall planning quality.

生成方法能够创建一个新计划而不是使用和修改现有计划(如变异方法必须)。虽然通常使

用一般低于变异方法,该方法具有灵活性(a)和一致性的过程规划新部件和(b)质量更高的

总体规划。

40、机床精度

现代机床是近乎完美的奇迹。考虑一个车床生产一个公差为50μm圆块，这是预期的

性能,它意味着机器要保持滑动工具和旋转工件每边差25μm得关系,同时要做一遍又一遍。那个维度是不到一半的一根头发的厚度。

去车转一个一边宽差25μm圆快,工具必须先被调整,使之有μm准确的尺寸。这样的

一个微小数额是无法看见的,而现在的机器有夸大展示微小粗细视觉的操作。当金属被巨大的力在不同深度切割时,这台机器必须引导工具沿着一条确定的导轨并保持工件稳定，以便使工具和工件互不偏离超过μm——这是不密切的工作。小于微米的公差在某些操作中举行。

在运行中的错误是由机械工件引起的，如(a)不准确施工,(b)偏斜,(c)穿,(d)热膨

胀,(e)污垢,(f)操作人员失误。好的设计和机器工具的操作取决于遵守使误差小的原则。这些原则被发现于构件、轴承、直学位和旋转运动,测量装置、标准建设良好的机器工具。

对于自动化机床用于控制误差的设计尤其重要,如数控就比那些操作者可以弥补错误

如简单的手动机器人更注意控制误差的设计。

对于构件，一个明显的特征是各机床工具的刚性。许多标准机床组件常被cast？,但

是一些,尤其是特殊单元,则是通过钢板和部分焊接在一起建立的。

机床设计弹性元件的刚度特性的一个目的是保持和维护真实小挠度的队列。在机械原理表明,机器构件的挠度与立方体它的深度方向的载荷成反比。因此（机部工具分是深的方向和重肋的主要力量,采取其他部队和宽的时刻）。

机床部件设计不仅要求坚硬的,而是有更多的刚性与尽量少的重量。第一个显着的原因是机器必会被移动,至少从是产地的地方移动到使用它的地方。第二个原因是刚性而又质量小能避免振动,这能提高机器生产力。第三个原因则是移动的零件如果惯性小就比较容易精确控制, 在自动控制中特别重要。

对一个简单的情况下,任何一个单自由度的物体有一个自然频率即W n= k/m。因素m 指的是构件的质量，而k则是与刚度成正比。因此,加强刚性与减小质量,能提高其固有频率。一个高固有频率是需求的,因为它不易被常规干扰影响。

导轨的制造对机械工具要求很高。导轨的要求是精度高，表面粗糙度低，摩擦力低价值和低磨损率

导轨的类型可分为存在滑动摩擦力的导轨也称为抗磨导轨和存在滚动摩擦的导轨也称为耐磨导轨。

有许多传统的导轨被用于机床上。它们是V型滑槽,平面滑槽,燕尾槽。

反摩擦导轨在滑动构件之间涉及中间滚动构件（滚珠或滚柱）,从而减少摩擦。

旋转工件或机床刀具被称为主轴。今天大多数机床工具主轴以滚动轴承运行。滚子轴承，通常是锥形的，用于在低速和中等速度时承重。球轴承运行自如,能承受高速,并适合于低重承载。球轴承的精度最高，预装和匹配套的选定都要尽量减少跳动。加压气体的高刚性，低摩擦滑动轴承用于高转速主轴。