机械专业英语文章中英文对照.doc

英语原文
ＮＵＭＥRＩCＡL ＣＯNTＲＯＬ
Nuｍerｉｃal coｎtｒｏｌ（Ｎ／C)iｓ　ａ form　oｆ pｒｏgｒammaｂlｅ　ａutoｍａｔｉoｎ ｉn wｈiｃh　tｈe ｐrocessing ｅqｕiｐmeｎt is ｃonｔｒoｌled ｂｙ meanｓ ｏf nｕmbers, 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.　When tｈｅ ｊob　chａnges,　tｈe　prｏgrａm ｏf ｉnｓｔｒucｔioｎs　is changeｄ． Thｅ cａｐabｉlitｙ tｏ　chaｎgｅ tｈe proｇｒam　is　ｗhat makes　N/C　ｓuitaｂlｅ　ｆｏr low－ａnd　mｅｄium-voｌｕme　proｄuｃｔion. Iｔ　is mｕch ｅasｉer tｏ wrｉtｅ proｇｒamｓ ｔｈan　tｏ ｍake ｍaｊoｒ　alteｒations　oｆ tｈe ｐroceｓｓing eqｕｉｐmｅnt．
Ｔｈere arｅ twｏ bａsic typeｓ oｆ　numericａlly　cｏntrｏｌｌｅｄ　mａchｉｎe　ｔｏｏｌs:ｐｏｉｎt—ｔo—ｐoｉｎt ａnd　ｃoｎtinuoｕs—pａth(ａlsｏ ｃａｌled　coｎｔouring）.Ｐoint—ｔｏ—poinｔ machines ｕｓｅ ｕnsｙｎchｒonｉzｅd ｍoｔｏrｓ, wｉtｈ　tｈe　reｓｕｌｔ thaｔ thｅ positｉｏn oｆ　tｈe machｉning hｅａd Caｎ ｂｅ　ａsｓureｄ　ｏnｌｙ ｕpｏn cｏｍpｌｅｔｉon of ａ movｅｍenｔ, or whｉｌe　onｌy oｎe mｏｔｏr ｉs ruｎninｇ.　Macｈines　of　this tｙpｅ arｅ pｒiｎｃｉｐalｌｙ used ｆｏｒ ｓtｒaｉｇht—liｎｅ　cｕts oｒ　for ｄriｌliｎｇ　oｒ bｏriｎｇ．
Ｔｈe Ｎ／C syｓtem conｓiｓｔs of　the fｏｌlｏwｉnｇ comｐｏnents:dａtａ inｐut,　tｈe　tａpｅ　rｅaｄeｒ wｉｔh ｔhe　cｏｎtrｏｌ ｕnｉｔ, ｆeedｂacｋ　ｄｅviceｓ,　ａnd thｅ　meｔal—ｃutｔing machiｎｅ ｔool or other　type of Ｎ/C equiｐｍｅｎt.
Ｄatａ inpｕｔ, alｓo　ｃａｌlｅd “ｍan—ｔo—conｔｒoｌ　link”, maｙ ｂe pｒoviｄｅd tｏ　ｔｈe machinｅ ｔｏol ｍanuaｌｌy, ｏｒ enｔirｅｌy by auｔｏmａtic ｍeａnｓ. Maｎual　ｍｅｔhodｓ　when usｅd ａs tｈｅ ｓolｅ　ｓouｒｃe ｏf　inpuｔ data aｒe　ｒesｔｒｉcｔｅd　to　a　ｒelａｔivｅ