问题 问答题 简答题

简述加工中心的主要加工对象。

答案

参考答案:

加工中心主要适用于加工形状复杂、工序多、精度要求高的工件。

1、箱体类工件这类工件一般都要求进行多工位孔系及平面的加工,定位精度要求高,在加工中心上加工时,一次装夹可完成普通机床60%~95%的工序内容。

2、复杂曲面类工件复杂曲面采用普通机械加工非常困难,有的甚至无法加工。

3、异形件异形件是外形不规则的零件,大多需要点、线、面多工位混合加工。加工异形件时,形状越复杂,精度要求越高,使用加工中心越能显示其优越性。

4、盘、套、板类工件这类工件包括带有键槽和径向孔,端面分布有孔系、曲面的盘套或轴类工件。

5、特殊加工在加工中心上还可以进行特殊加工。如在主轴上安装调频电火花电源,可对金属表面进行表面淬火。

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单项选择题

Narrative crept back into art through a side door marked fashion photography. In April 1967, French Vogue published a spread by Bob Richardson, the American photographer, that soon became a legend Informally christened " the Greek trip " by Richardson’s admirers, the spread featured Donna Mitchell, a striking brunet model, hanging out on the Aegean island of Rhodes with a male companion.

Of course, narrative never disappeared—it just went to the movies, and stayed, and stayed. But what had caused stories to be exiled from high art The idea of essence, and the equation of essence with goodness. Can you imagine Visual art is essentially composed of form, color, materials. Anything to do with content is extraneous and therefore to be associated with badness; therefore to be eliminated. Moreover, content, says this line of thought, is controlling. This means that a rose is the Virgin Mary (depending on what the meaning of " is " is). And art, like society, must be liberated from such hierarchically imposed values. What this argument overlooked, of course, is that narrative is a form in itself, not just a vehicle for content. Indeed, the ideology of formalism originated, in Soviet Russia, with the analysis of old folk tales. Narrative form, the analysis went, typically proceeds from an initial state of equilibrium through a series of destabilizing episodes, concluding with a heightened state of equilibrium at the end. Think Indiana Jones. You can plug whatever content you want in there as long as it creates the form. Each episode simply has to do with the work of creating disequilibrium.

A narrative does not, in other words, tell a story. A story is told to give listeners the pleasure of the narrative form. If you were to isolate the form of disequilibrium from the specifics of plot, you might arrive at something resembling the collected work of Cindy Sherman. Initially modeled after movie stills, Sherman’s pictures are not, of course, abstract. Over the years, in fact, their content has become increasingly elaborate. I see this as a form of generosity as well as a sign of advanced technical skills. Not since Giuseppe Arcimboldo (1527-1593), perhaps, has an artist contrived to turn the human figure into a more bountiful cornucopia for the eye.

Yet even the most visually splendid of Sherman’s images are minimalist, in that they reduce the narrative down to the precise moment when the center of gravity shifts. Perhaps some unheard word is spoken. A floorboard squeaks. From upstairs comes a thump. And a tentative state of equilibrium gives way to anxiety or dread. That moment, too, represents essence. What more do you need to know

According to the author, " narrative " is to " story " what()

A. " picture " is to " movie still "

B. " goodness " is to " badness "

C. " form " is to " content "

D. " color "is to " visual art "