【正文】
這樣在傳統(tǒng)的數(shù)字控制技術(shù)中采用的磁帶閱讀器在直接數(shù)字控制中被取消,從而保證了系統(tǒng)的可靠性。不使用磁帶閱讀器,被加工的零件程序就從計(jì)算機(jī)的存儲(chǔ)器中直接傳送到進(jìn)行加工的道具上。從原理上講,一臺(tái)計(jì)算機(jī)可以控制多達(dá) 100 臺(tái)加工機(jī)床,(在 20 世紀(jì)70 年代一臺(tái)商業(yè)使用的 DNC 系統(tǒng)可以控制多達(dá) 256 個(gè)機(jī)床刀具)。直接數(shù)字控制計(jì)算機(jī)按要求給每個(gè)進(jìn)行加工的刀具提供加工指令,當(dāng)機(jī)床需要控制指令時(shí),計(jì)算機(jī)就可以馬上將指令傳送到機(jī)床上。 隨著直接數(shù)字控制技術(shù)和計(jì)算機(jī)技術(shù)的飛速發(fā)展,數(shù)字計(jì)算機(jī)尺寸和價(jià)格的大幅度降低,數(shù)字計(jì)算機(jī)計(jì)算能力的大大提高,大量傳統(tǒng)的以硬件線路為基礎(chǔ)的加工控制單元被以數(shù)字計(jì)算機(jī)為基礎(chǔ)的數(shù)字控制單元所替代。最初,在 20 世紀(jì) 70 年代使用了小型計(jì)算機(jī)。后來隨著計(jì)算機(jī)的進(jìn)一步小型化,早期的小型計(jì)算機(jī)逐漸被現(xiàn)在的微型計(jì)算機(jī)所替代。 計(jì)算機(jī)數(shù)控使用專用的微型計(jì)算機(jī)作為加工控制單元。數(shù)字計(jì)算機(jī)都用于計(jì)算機(jī)數(shù)控和直接數(shù)控,應(yīng)該注意兩者之間的區(qū)別,可以從 3 個(gè)方面來加以區(qū)分。 (1)DNC 計(jì)算機(jī)是將指令數(shù)據(jù)發(fā)送到許多機(jī)床去或從許多機(jī)床中收集數(shù)據(jù),而CNC 計(jì)算機(jī)每次只控制一臺(tái)或幾臺(tái)機(jī)床。 (2)DNC 計(jì)算機(jī) 一般位于距機(jī)床一定距離的位置,而 CNC 計(jì)算機(jī)一般都位于距機(jī)床較近的位置。 (3)DNC 計(jì)算機(jī)開發(fā)的軟件不僅可以用于控制產(chǎn)品的單件生產(chǎn),而且還可以用于企業(yè)制造部門的管理信息系統(tǒng),而 CNC 計(jì)算機(jī)開發(fā)的軟件一般只用于某個(gè)特殊加工的工具。 黃石理工學(xué)院 畢業(yè)設(shè)計(jì)(論文)外文文獻(xiàn)翻譯 4 Numerical Control Numerical control (NC) is a form of programmable automation in which the processing equipment is controlled by means of number, letters, and other symbols. The numbers, letters, and symbols are coded in an appropriate format to define a program of instructions for a particular work part or job. The instructions are provided by either of the two binary coded decimal systems: the Electronic Industries Associations (EIA) code, or the American Standard Code for Information Interchange (ASCII) ASCIIcoded machine control units will not accept EIA coded instructions and vice versa. Increasingly, however, control units are being made to accept instructions in either code. Automation operation by NC is readily adaptable to the operation of all metalworking machines. Lathes, milling machines, drill presses, boring machines, grinding machines, turret punches, flame or wirecutting and welding machines, and even pipe benders are available with numerical controls. Basic Components of NC A numerical control system consists of the following three basic ponents: (1) Program instructions. (2) Machine control unit. (3) Processing equipment. The program instructions are the detailed step by step mands that direct the processing equipment. In its most