為了減少系統(tǒng)的早期失效，機床制造廠可以對控制元件進(jìn)行篩選，即使每臺元件在實際使用條件下連續(xù)工作一定次數(shù)，把失效產(chǎn)品排除，以減少裝到系統(tǒng)中的元件早期失效。元件進(jìn)入耗損失效期以后，失效率將明顯上升。為了防止這種情況影響系統(tǒng)的可靠性，可以在有效壽命（或偶然故障期）將結(jié)束時，不管元件是否損壞，也進(jìn)行更換。采用篩選和預(yù)防性更換，可以保證系統(tǒng)中的元件工作在偶然失效期內(nèi)，在這個前提下才可以用元件的偶然失效率來計算系統(tǒng)的失效率。

在選擇方案時，應(yīng)考慮盡量減少控制元件數(shù)、接點數(shù)和焊點數(shù)，以降低系統(tǒng)的失效率。采用可編程控制器（PC）來代替由繼電器等組成的控制柜可以提高系統(tǒng)的可靠性。在比較可編程序控制器和繼電器控制柜兩種方案時，除了購置價格以外，還應(yīng)充分估計前者在提高可靠性、縮短開發(fā)周期和減小工作量以及節(jié)省維修時間等有利因素。

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