2. Unit Four Unit Four Passage Two Machining Centers

3. Learning Targets T o understand the whole passage T o know how to express types of machining centers and parts of the CNC Machining Center in English

4. Step A: Lead in Step B: Passage Understanding Step C: Structural Analyzing Step D: Assignment Teaching Procedures

5. Do you know? 1.What are the types of machining centers? 2. What are the parts of CNC Machining Center ? You can find the answer after fast reading. Passage Understanding

6. Types of machining centers 卧式加工中心 horizontal spindle type

7. Passage Understanding 立式加工中心 Types of machining centers vertical spindle type

8. Passage Understanding Parts of the CNC Machining Center bed saddle column table 床身 溜板 立柱 工作台

9. Passage Understanding servo system spindle tool changers MCU Parts of the CNC Machining Center 伺服系统 主轴 刀具交换装置 机床控制单元

10. Passage Understanding 托盘 梭子 滑鞍 导轨 参数 pallet shuttle saddle bedway specification

11. Sentences Structure The vertical spindle machining center is a saddle- type construction with sliding bedways which utilizes a sliding vertical head instead of a spindle movement. 主句的表语后面有较长的后置定语，在翻译时 把 with sliding bedways 转换成前置定语，而 把定语从句作为一个单句来处理。 立式加工中心是一种带有滑动床身导轨的溜板型结构，它 是利用垂直方向的床头的滑动来代替主轴的移动。

12. Sentences Structure The bed is usually made of high-quality cast iron which provides a rigid machine capability of performing heavy-duty machining and maintaining high precision. 这一句比较长，在翻译时应转化为两个短句。 定语从句中,provides 的宾语是 capability 。 床身通常由优质铸铁制成, 铸铁为刚性机床提供了执行 重载加工任务和保持高精度加工的能力。

13. Sentences Structure The servo system, which consists of servo drive motors, ball screws, and position feedback encoders, provides fast, accurate movement and positioning of the XYZ axis slides. 主语： the servo system 谓语： provides 定语从句： which consists of servo drive motors, ball screws, and position feedback encoders 伺服系统包括伺服电机、滚珠丝杠和位置反馈编码器，它提 供快速而准确的 XYZ 轴的移动和定位。

14. Sentences Structure Tool changers are usually bidirectional, which allows for the shortest travel distance to randomly access a tool. which 指代的是前面整个句子。做这种用法时， which 可以替换成 as. 刀具交换装置通常是双向的，这样就允许以最短的路径任 意地存取刀具。

15. Structural Analyzing Part one: para1- 4 Part two: para 5- 13 Part three: para 14 Types of machining centers Parts of the CNC machining center Machine axes

16. Exercises Put the following into Chinese and recite them. NC: numerical control NC machine tools 计算机数控 CNC: computerized numerical control 数字控制 MCU: machine control unit 机床控制单元 数控机床

17. Exercises Put the following into Chinese and recite them. a DC motor incremental positioning 步进电机 a stepper motor 直流电机 absolute positioning 绝对定位 相对定位

18. Exercises Try to identify the subject, predicate, object and attribute of the following sentences and to underline them separately. 1.The bed is usually made of high-quality cast iron which provides a rigid machine capability of performing heavy-duty machining and machining high precision. The bed is usually made of high-quality cast iron which provides a rigid machine capability of performing heavy-duty machining and machining high precision.

19. Exercises Try to identify the subject, predicate, object and attribute of the following sentences and to underline them separately. 2. New MCUs are becoming more sophisticated, making machine tools more reliable and the entire machining operations less dependent on human skills. New MCUs are becoming more sophisticated, making machine tools more reliable and the entire machining operations less dependent on human skills.

20. Assignment Answer the following questions according to the text. 1. What are the types of machining centers? 2. What are the parts of CNC Machining Center? 3. What is the five-axis machining center?