问题 问答题 论述题

叙述自动进给调节系统作用及要求?

答案

参考答案:

电火花成型加工的自动进给调节系统,主要包含伺服进给系统(自动进给调节系统)和参数控制系统。伺服进给系统主要用于控制放电间隙的大小。电火花加工中,电极与工件必须保持一定的放电间隙。由于工件不断被蚀除,电极也不断地损耗,故放电间隙将不断扩大。如果电极不及时进给补偿,放电过程会因间隙过大而停止。反之,间隙过小又会引起拉弧烧伤或短路,这时电极必须迅速离开工件,待短路消除后再重新调节到适宜的放电间隙。

伺服进给系统(自动进给调节系统)一般有如下要求:

(1)有较广的速度调节跟踪范围。在电火花加工过程中,加工规准、加工面积等条件的变化都会影响其进给速度变化,伺服进给系统应有较宽的速度调节范围,以适应各种加工的需要。

(2)有足够的灵敏度和快速性。放电加工的频率很高,放电间隙的状态瞬息万变,要求伺服进给系统根据间隙状态的微弱信号能相应地快速调节。

(3)有较高的稳定性和抗干扰能力。电蚀速度一般不高,所以伺服进给系统应有很好的低速性能,能均匀、稳定地进给,超调量要小,抗干扰能力要强。

填空题
单项选择题

Social control refers to social processes, planned or unplanned, by which people are taught, persuaded, or forced to conform to norms. In every society, some punishments or negative sanctions are established for deviant behavior. Without deviant behavior there would not be need for social control and without social control there would not be a way of recognizing the boundary between the acceptable and the unacceptable.

Social control may be either formal or informal. Informal mechanisms include expressions of disapproval by significant others and withholding of positive rewards for disapproved behavior. Most people internalize norms in the course of socialization. This is any group’s most powerful protection against deviance, in that the individual’s own conscience operates as an agent of social control. When informal sanctions fail, formal agents of social control may be called upon. In contemporary society, such formal agents and agencies include psychiatry and other mental health professions; mental hospitals; police and courts of law; prisons; and social welfare agencies. All these formal agents function to limit, correct, and control violation of norms. Conflict theorists would also point out that social control agents and systems tend, in any society, to serve the interests of powerful groups and to enforce the norms most beneficial to those who make the rules and who, therefore, define unacceptable behavior.

Social control, whether formal or informal, has a dual function. First, it punishes the wrongdoer and reaff’irms the boundaries of acceptable behavior. Second, and less recognized, it regulates the manner in which deviants are treated.

The purpose of formal agents is to ().

A. make beneficial rules

B. preserve social orders

C. control violation of norms

D. define acceptable behavior