问题 问答题 简答题

主轴的驱动方式有哪些?各有什么特点?分别适用于什么场合?

答案

参考答案:

(1)齿轮传动:结构简单紧凑,能传递较大转矩,线速度不能过高。适用于变转速、变载荷场合。

(2)带传动:靠摩擦力传动(除同步齿形带),结构简单,制造容易,成本低,过载打滑。适用于中心矩较大的两轴传动,高速传动,不适用于速比要求准确的场合。

(3)电动机直接驱动:主轴部件刚度高,噪声和振动小,调速范围宽,有较大的驱动功率和转矩。适用于精密机床、高速加工中心和数控车床。

阅读理解

任务型阅读(10分)

It is very important to have good friends. 1)拥有许多朋友的一种生活是有趣且丰富多彩的。A life without a friend is a life without a sun.2)Having good       can       us in lots of different ways. People with a lot of friends usually feel happier than people with no friends. Everything we do will be more fun if we have friends with us to share our adventures(经历). When we are feeling sad or worried, our friends will give us advice and help us out of difficulties.

We should not only have good friends but also be good friends. We need our friends as much as they need us. We should be willing to help friends when they need help.

1. 回答下面问题

What will friends do when we are feeling sad or worried?

                                                                   

2. 在2)句的空白处填入适当的词使句意完整、上下文通顺:                

                                                                     

3. 将1)句译成英语:____________________________________________________

4. 写出文中与下列句子意思相近的句子:

If friends need our help, we should be glad to help them.

_____________________________________________________________________

5. 找出文中最能表达该短文主题的句子:                                

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