Chapter 4 Lesson 1.ppt

1、Chapter 4 CNC MachinesLesson 1 The Fundamentals of CNC,Lesson 1 The Fundamentals of CNC,Part 1 New words and phrases in conjunction with 一起，连同，与协力 CNC (computer numerical control) 计算机数字控制 drill press 钻床 drill chuck 钻夹头 belt pulley 带轮 quill lever 主轴控制杆 intervention n 干涉 介入 tediousness n 沉闷 potential

2、a 潜在的 可能的 conventional machine 普通机床,Lesson 1 The Fundamentals of CNC,equivalent n 等价物：a 相等的 相当的 同意义的 CNC machining center 数控加工中心 CNC drilling & tapping center 数控钻削攻丝中心 over-simplify 过分简单化 commonality n 共性 公共 imply vt 暗示 意味 complexity n复杂 复杂的事物 axes n 主轴 accessory n 附属 零件 附加物 full-blown a 盛开的 张满的 成熟的

3、 tool magazine 刀具库,Lesson 1 The Fundamentals of CNC,Part 2 CNC stands for Computer Numerical Control and has been around since the early 1970s. Prior to this, it was called NC, for numerical control. While people in most walks of life have never heard of this term, CNC has touched almost every form

4、of manufacturing process in one way or another. If youll be working in manufacturing, its likely that youll be dealing with CNC on a regular basis. CNC代表计算机数字控制，自20世纪70年代以来一直受到人们的关注。此前它被称NC，即数字控制。虽然大多数其他行业的人从来没有听说过这个词，但CNC以这样或那样的方式几乎触及每一种形式的制造过程。从事制造业工作的人，很可能经常与CNC打交道。,Lesson 1 The Fundamentals of C

5、NC,While there are exceptions to this statement, CNC machines typically replace (or work in conjunction with) some existing manufacturing processes. Take one of the simplest manufacturing processes, drilling holes, for example. 尽管以上表述不尽如此，但数控机床显然替代（或参与）了现有的一些制造过程。举最简单的制造过程钻孔为例。,Lesson 1 The Fundamen

6、tals of CNC,A drill press can of course be used to machine holes. A person can place a drill in the drill chuck that is secured in the spindle of the drill press. They can then (manually) select the desired speed for rotation (commonly by switching belt pulleys), and activate the spindle. Then they

7、manually pull on the quill lever to drive the drill into the workpiece being machined. 台式钻床当然可以用于加工孔。操作者可以将钻头装在钻夹中，钻夹固定在台钻的主轴里；接着可以（手工）选择所需的转速（通常通过切换皮带改变主轴转速），并且启动主轴旋转，然后操作钻轴手柄，将钻头钻入被加工的工件。,Lesson 1 The Fundamentals of CNC,As you can easily see, there is a lot of manual intervention required to use

8、a drill press to drill holes. A person is required to do something almost every step along the way! While this manual intervention may be acceptable for manufacturing companies if a small number of holes or workpiece must be machined, but as quantities grow, so does the likelihood for fatigue due to

9、 the tediousness of the operation. And do note that weve used one the simplest machining operations (drilling) for our example. 显而易见，使用台式钻床钻孔，需要许多人为的干预。几乎全过程的每一步都需要人参与！如果只有数量不多的孔或工件要加工，这种人为干预对制造厂来说可能是可以接受的，但是，随着生产数量的增加，由于操作乏味而产生疲劳的可能性也增大了。务必注意我们只是举了最简单的操作之一（钻削）为例.,Lesson 1 The Fundamentals of CNC,Th

10、ere are more complicated machining operations that would require a much higher skill level (and increase the potential for mistake resulting in scrap workpieces) of the person running the conventional machine tool. (We commonly refer to the style of machine that CNC is replacing as the conventional

11、machine). 还有更加复杂的加工方式，对普通机床操作员的技能水平要求非常高（技能要求高，意味着操作失误的可能性也增大，易导致废品的产生）。（我们通常称被CNC替代的这种机床为普通机床。）,Lesson 1 The Fundamentals of CNC,By comparison, the CNC equivalent for a drill press (possibly a CNC machining center or CNC drilling & tapping center) can be programmed to perform this operation in a mu

12、ch more automatic fashion. See fig 2-2. Everything that the drill press operator was doing manually will now be done by the CNC machine, including: placing the drill in the spindle, activating the spindle, positioning the workpiece under the drill, machining the hole, the turning off the spindle. 相比

13、较起来，替代台式钻床的数控机床（可能是数控加工中心或数控钻削中心）可以通过编写程序完成这种操作，自动化程度极高。一度由台钻操作员做的各种操作现在都由数控机床完成，包括：将钻头装进主轴里、启动主轴、将工件定位在钻头下方、钻孔、停止主轴。,Lesson 1 The Fundamentals of CNC,As you might already have guessed, everything that an operator would be required to do with conventional machine tools is programmable with CNC machi

14、ne. Once the machine is setup and running, a CNC machine is quite simple to keep running. In fact CNC operators tend to get quite bored during lengthy production runs because there is so little to do. With some CNC machines, even the workpiece loading process has been automated. Lets look at some of

15、 the specific programmable functions. 也许你已经做出猜想：普通机床需要操作员做的每一件工作，在数控机床上都是由程序控制。一旦机床装夹完毕并且运行，数控机床容易保持自动运行状态。实际上，由于无事可做，数控操作员在冗长的生产运行过程中会感到很无聊。在有些数控机床上，甚至工件装夹的过程都是自动化的。让我们来看一下具体的可编程功能。,Lesson 1 The Fundamentals of CNC,Motion control 运动控制 All CNC machine types share this commonality: They all have two

16、or more programmable directions of motion called axes. An axis of motion can be linear (along a straight line) or rotary (along circular path). One of the first specifications that imply a CNC machines complexity is how many axes it has. Generally speaking, the more axes, the more complex the machin

17、e. 所有的数控机床都有一个共同点：它们都有两个或两个以上的可编程运动方向，称之为轴。轴运动可以是直线的（沿直线），也可以是旋转的（沿圆周轨迹）。表征数控机床复杂程度的首要指标之一是它有几个轴。一般说来，轴数越多，机床越复杂。,Lesson 1 The Fundamentals of CNC,The axes of any CNC machine are required for the purpose of causing the motions needed for the manufacturing process. In the drilling example, these (3)

18、axes would position the tool over the hole to be machined (in two axes) and machine the hole (with the third axis). Axes are named with letters. Common linear axis names are X, Y, and Z. Common rotary axis names are A, B, and C. 任何数控机床的轴是为了产生加工过程所需要的运动，在钻削的例子中，这些(三个)轴将刀具定位在待加工孔的上方两轴运动，然后加工孔。轴用字母命名，常

19、用的直线轴名称为X，Y，Z，常用的旋转轴名称为A，B，C。,Lesson 1 The Fundamentals of CNC,Programmable accessories可编程附件 A CNC machine wouldnt be helpful if all it could only move the workpiece in two or more axes. Almost all CNC machines are programmable in several other ways. The specific CNC machine type has a lot to do wit

20、h its appropriate programmable accessories. Again, any required function will be programmable on the full-blown CNC machine tools. Here are some examples for one machine type (machine centers). 如果数控机床只能进行两个方向以上的运动，则这种运动没有多少优势。几乎所的数控机床在很多方面都是可编程的，具体的数控机床与其配置的可编程附件很有关系。而且，在全数控机床上，任何需要的功能都是可编程的。下面是一种机床(加工中心)的一些可编程功能的例子。,Lesson 1 The Fundamentals of CNC,Automatic tool changer 自动刀具交换装