stored in the satellite‘s buffer before being collected at the central computer. 当需要时卫星计算机发送指令程序到每个独立机床中。来自机床的反馈数据在电脑中央存储接受之前存储在卫星内存中。
（2）Computer numerical control计算机数字控制
Since the introduction of DNC, there have been dramatic advances in computer technology. 由于DNC 技术的介入，在计算机技术上得到了很大的发展。 The physical size and cost of a digital computer have been significantly reduced at the same time that its computational capabilities have been substantially increased. 计算机在尺寸和成本显著减少的同时，计算机的能力却有很大的提高。 In numerical control, the result of these advances has been that the large hard-wired MCU of conventional NC have been replaced by control units based on the digital computer. Initially, minicomputers were utilized in the early 1970s. 在数控中，这些发展使得由硬件布置的MCU变为数字电脑控制的控制单元。最早，小型机在1970 年使用。 As further miniaturization occurred in computers, minicomputers were replaced by today‘s microcomputers. 随着计算机进一步小型化，小型机被当今的微型机取代。
Computer numerical control is an NC system using dedicated microcomputer as the machine control unit. 计算机控制也是一种数字控制，它采用微型计算机作为控制单元。Because a digital computer is used in both CNC and DNC, it is appropriate to distinguish between the two types of system. There are three principal differences: 由于数字电脑用于CNC 和DNC 中，只近似区分两种类型。有三个区分原则：
? DNC computers distribute instructional data to, and collect data from, a large number of machines. CNC computers control only one machine, or a small number of machines. DNC 电脑接受和发送指令数据都是来自许多机器，CNC 电脑控制只是一个机器或多个机器。
? DNC computers occupy a location that is typically remote from the machines under their control. CNC computers are located very near their machine tools. DNC 电脑占有一个位置通过控制来实现机器的旋转。CNC 电脑要非常靠近车床。
? DNC software is developed not only to control individual pieces of
production equipment, but also to serve as part of a management information system in the manufacturing sector of the firm. DNC 软件的发展不经可以控制生产设备的每个单独零件，还可以在生产坚固性方面提供主要控制信息。 CNC software is developed to augment the capabilities of a particular machine tool. CNC 的提高可以提高特殊车床的能力。
The general configuration of a computer numerical control system is pictured in Fig.2.5. 电脑数控系统的大体配置如图2.5 所示。As illustrated in the diagram, the controller has a tape reader for initial entry of a part program. 如图中所示，最初进入控制器的是磁带播放机。In this regard, the outward appearance of a CNC system is similar to that of a conventional NC machine. 这样，CNC 的外部系统与传统的NC机相似。However, the way in which the program is used in CNC is different. 似。然而CNC 中的程序使用方法是不同的。With a conventional NC system, the punched tape is cycled through the tape reader for each workpart in the batch. The MCU reads in a block of instructions on the tape, executing that block before proceeding to the next block. 与传统的数控系统比，纸带通过纸带阅读机对每个批次的工件循环。MCU读取磁带上的指示块，执行该块，然后进行下一个块。In CNC, the entire program is entered once and stored in computer memory.在数控中，整个程序一旦进入并储存在电脑的存储器中。 The machining cycle for each part is controlled by the program contained in memory rather than from the tape itself.每个零件的加工周期控制在内存中，而不是来自磁带本身的程序。
Control algorithms contained in the computer convert the part program instructions into actions of the machine tool (or other processing equipment). 在计算机中的控制算法转换成机床（或其他加工设备）的行动的一部分程序指令。Certain functions are carried out by hard-wired components in the MCU. MCU中进行硬连接组件的某些功能。For example, circular interpolation calculations are often performed by hard –wired circuits rather than by stored program. Also, a hardware interface is required to make the connections with the machine tool servo systems. 例如，圆弧插补计算往往是通过硬连接的电路，而不是由存储程序执行。另外，硬件接口需要与机床伺服系统连接。
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(3) Features of CNC control CNC的控制特点
In previous the important features and functions of the machine control unit in numerical control were described. 在前面，对数控机床控制单元的重要特征和功能进行了描述。CNC has made possible additional features beyond what is normally found in a conventional hard-wired MCU. Some of these features include the following: 数控已经超出了通常在传统的硬连线的单片机中可能发现的附加功能。其中一些功能包括以下内容：
1) Storage of more than one part program. 存储多个零件程序With improvements in computer technology, many of the newer CNC controllers have a large enough capacity to store more than a single program. 随着计算机技术的改进，许多新的CNC控制器有一个足够大的容量来存储大于一个单一的程序。This translates into the capability to store either one very large program or several small and medium-sized programs.这能力意味着存储成功其中一个非常大的程序或几个小型和中型项目。
2) Use of diskettes. 使用软盘There is a growing use of floppy disks for part programs in manufacturing. The capacity of an 8-in. 有越来越多的软盘制造业中的部分程序使用，8合一的能力。 diskette is the approximate equivalent of 8,000 ft of punched tape. Because of this more modern storage technology, many CNC controllers have the optional capability to read in programs stored on disks as well as punched tape. 软盘是大致相当于8000英尺纸带。因为这更现代的存储技术，许多CNC控制器可选的阅读能力在磁盘上以及纸带存储方案。
3) Program editing at the machine tool site.机床网站编辑计划 To deal with the mistakes in part programming, CNC systems permit the program to be edited while it is in computer memory. 为了解决部分编程的错误，数控系统允许程序编辑，而它是在计算机内存中。 Hence, the process of testing and correcting the program can be done entirely at the machine site rather than returning to the programming office in the shop to make the tape corrections. 因此，完全可以在机器网站中测试和纠正计划的过程，而不是去店里的编程办公室进行磁带更正。In
addition to part program corrections, editing can also be done to optimize the cutting conditions of the machining cycle. 除了部分程序更正，编辑也可以进行对切削条件下加工周期的优化。 After correcting and optimizing the program, a tape punch can be connected to the CNC controller in order to obtain a revised version of the tape for future use. 纠正和优化方案后，纸带穿孔机可以连接到CNC控制器，以获得供将来使用的磁带的修订版本。
4) Fixed cycles and programming subroutines. 固定周期和编程子程序The increased memory capacity and the ability to program the control computer in CNC provides the opportunity to store frequently use machining cycles in memory that can be called by the part program Instead of writing the instructions for the particular cycle into every program, a code is written into the program to indicate that the cycle should be execute. 增加内存容量和能力，在数控编程控制计算机提供了机会来存储经常使用在记录中的加工，而是写入到特定周期的指令，每一个程序的一部分程序，可以称为周期，写入代码到程序表明周期应当执行。Some of these cycles require the definition of certain parameters in order to execute. 这些周期需要通过某些参数的定义来执行。An example is a bolt hole circle, in which the diameter of the bolt circle, the spacing of the bolt holes, and other parameters must be specified. In other cases, the particular machining cycle used by the shop would not require parameter definition. 例如螺栓孔圆形，螺栓圈的直径，其中必须指定螺栓孔和其他参数的间距。在其他情况下，特别是加工店使用的周期并不需要参数的定义。
5) Interpolation.插值 Some of the interpolation schemes are normally executed only on a CNC system because of the computational requirements. 一些插值计划通常仅由于数控系统计算的要求而执行。Linear and circular interpolation are often hard-wired into the control unit.直线和圆弧插补往往很难连接到控制单元。 Helical, parabolic, and cubic interpolations are usually executed in a stored program algorithm.螺旋线，抛物线，立方插值通常作为存储程序的算法。
6) Positioning features for setup. 定位功能设置Setting up the
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machine tool for a certain job involves installing and aligning the fixture on the machine tool table.机床设定了一定量的工作，包括安装和对准夹具在机床的工作台上。 This must be accomplished so that the machine axes are aligned with the workpart. 这必须完成使机器轴与工件对齐。The alignment task can be facilitated using certain features that are made possible by software options in a CNC system. 使用某些功能，可能是数控系统软件的选项，可以促进对齐任务的完成。Position set is one of these features. With position set, the operator is not required to position the fixture on the machine table with extreme accuracy.位置设置是这些功能之一，通过位置设置，操作者并不需要极高的精度与定位夹具上的机械表格。 Instead, the machine tool axes are referenced to the location of the fixture by using a target point or set of target points on the work or fixture.相反，机床轴可通过目标点或工作和夹具上的目标点来参考夹具的位置。
7) Cutter length compensation. 刀具长度补偿This is similar to the preceding feature but applies to tool length and diameter.这是类似上述的功能，但适用于刀具长度和直径。 In older-style controls, the cutter dimensions had to be set very precisely in order to agree with the tool path defined in the part program.在老式的控制中，刀具尺寸设置非常精确，以完成在零件程序中刀具路径的定义。 Other methods for ensuring accurate tool path definition have been incorporated into newer CNC controls. One method involves manually entering the actual tool dimensions into the MCU. 确保刀具路径定义的其他方法已纳入新的数控系统。其中一种方法涉及到手动输入刀具的实际尺寸到MCU中。These actual dimensions may differ from those originally programmed. 最初的编程时这些实际尺寸可能会有所不同。Compensations are then automatically made in the computed tool path. 通过补偿，然后自动计算刀具路径。Another more recent innovation is to use a tool length sensor built into the machine. In this method, the cutter is mounted in the spindle and brought into contact with the sensor to measure its length. 另一个更加新近的创新是使用机器内置的刀具长度传感器。在此方法中，刀具安装在主轴和传感器之间来测量其
长度。This measured value is then used to correct the programmed tool path.然后用此测量值纠正编程路径。
8) Diagnostics. 诊断Many modern CNC machines possess an no-line diagnostics capability which monitors certain aspects of the machine tool and MCU operation to detect malfunctions or signs of impending malfunctions. 许多现代的数控机床具有无线诊断监控机床某些方面的能力和通过MCU操作检测到故障或即将发生故障的迹象。When a malfunction is detected, or measurements indicate that a breakdown is about to occur, a message is displayed on the controller‘s CRT monitor. Depending on the seriousness of the malfunction, the system can be stopped or maintenance can be scheduled for a nonproduction shift. 当检测到故障，或测量表明即将发生故障时，控制器的CRT显示器上会显示一条消息。根据故障的严重性，该系统可以停止或维修，可定为非生产性转移。Another use of the diagnostics capability is to help the repair crew determine the reason for a break down of the machine tool.诊断能力的另一个用途是帮助维修人员确定机床出问题的原因。 One of the biggest problems when a machine failure occurs is often in diagnosing the reason for the breakdown. 一台机器发生故障时最大的难题经常就是如何诊断故障原因。By monitoring and analyzing its own operation, the system can determine and communicate the reason for the failure.系统可以通过自身的运行的监测和分析，判断和通报失败的原因。
9) Communications interface. 通讯接口With the trend toward interfacing and networking in plants today, most modern CNC controllers are equipped with a standard communication interface to allow the particular machine tool to be linked to other computers and computer-driven devices. 在现时，树状网络中的网络接口和走向与趋势，最先进的CNC控制器配备了一个标准的通信接口，以允许特定的机床被其他计算机和计算机驱动装置。 11
Unit 3数控编程 Unit 3 Programming for Numerical Control A program for numerical control consists of a sequence of directions that causes an NC machine to carry out a certain operation, machining being the most commonly used process. Programming for NC may be done by an internal programming department, on the shop floor, or purchased from an outside source. Also, programming may be done manually or with computer assistance.数控编程由一系列方向构成，这些方向导致数控车床执行某种操作，加工是最常用的进程。数控车床编程由内部编程部门来完成，在车间里，或者从外部源购买。编程还可以手动或者在计算机辅助下来完成。 The program contains instructions and commands. Geometric instructions pertain to relative movements between the tool and the workpiece. Processing instructions pertain to spindle speeds, feeds, tools, and so on. Travel instructions pertain to the type of interpolation and slow or rapid movements of the tool or worktable. Switching commands pertain to on/off position for coolant supplies, spindle rotation, direction of spindle rotation, tool changes, workpiece feeding, clamping, and so on. 程序包括指令和命令。几何指令涉及刀具和工件间的相对移动。进程指令涉及主轴速度，进给以及道具等。行动指令涉及插值的类型以及刀具或者工作台的缓慢和快速移动。切换命令涉及到开/关冷却液供给状况，主轴旋转，主轴方向，换刀，工件进给，夹具固定等等。 (1) Manual programming. Manual part programming consists
first of calculating the dimensional relationships of the tool, workpiece, and worktable, based on the engineering drawings
of the part, and manufacturing operations to be performed and
their sequence. A program sheet is then prepared, which consists of the necessary information to carry out the
particular operation, such as cutting tools, spindle speeds,
feeds, depth of cut, cutting fluids, power, and tool or workpiece relative positions and movements. Based on this information, the part program is prepared. Usually a paper tape is first prepared for trying out and debugging the program. Depending on how often it is to be used, the tape may be made of more durable mylar. （1）手工编程。手工编程包括根据部分工程图纸首先算出刀具，工件以及工作台的尺寸关系，继而决定执行的操作和工序。那么一个包括执行特定操作所需必要信息的程序表就准备好了，例如刀具切削，主轴转速，进给，切削深度，切削液，以及刀具或者工件间的相对位置或者移动。根据这些信息，部分程序就准备好了。通常一
个纸带首先被准备好用于试用和调试程序。根据纸带被使用多久，纸袋通常用更耐用的聚酯薄膜制成。 Manual programming can be done by someone who is
knowledgeable about the particular manufacturing process and is able to understand, read, and change part programs. Because they are familiar with machine tools and process capabilities, skilled machinists can do manual programming with some training in programming. However, the work involved is tedious, time-consuming, and uneconomical consequently, manual programming is used mostly in simple point-to-point applications. 手工编程可以由那些具有特定制造工艺知识和能够理解，阅读以及更改部分程序的人来完成。因为他们熟悉机床刀具和工艺流程，熟练的机械师可以做一些手工编程的编程培训。然而，所涉及的工作
是乏味的，费时的，因此不合算。手工编程大多数用于简单的点对
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