机电专业英语 教学课件 作者 杨寿智 刘水平 机电专业英语.Lesson 6.ppt

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1、Lesson6OperatingtheMachineControlsTextBeforeusinganymachine,youmustbeabletousethecontrolsproperly,knowwhattheyarefor,andunderstandhowtheywork.Youmustalsobeawareofthepotentialhazardsthatexistforyouandthemachineifitismishandled.Thisunitpreparesyoutooperatelathes

2、.Mostlatheshavesimilarcontrolmechanismsandoperatinghandlesforfeedsandthreading.FeedcontrolleversThecarriageismovedalongthewaysbymeansoftheleadscrewwhenthreading,orbyaseparatefeedrodwhenusingfeeds.Onmostsmalllathes,however,aleadscrew-feedrodcombinationisused.In

3、ordertomakeleft-handthreadsandreversethefeed,thefeedreverseleverisused.Thisleverreversestheleadscrew.Itshouldneverbemovedwhenthemachineisrunning.Thequick-changegearbox(Figure6.1and6.2)typicallyhastwoormoreslidinggearshifterlevers.Theseareusedtoselectfeedsorthr

4、eadsperinch.Onthoselathesalsoequippedwithmetricselections,thethreadsareexpressedinpitches(measuredinmillimeters).Thecarriageapron(Figure6.3)containsthehandwheelforhandfeedingandapowerfeedleverthatengagesaclutchtoageardrivetrainintheapron.Handfeedingshouldnotbe

5、usedforlongcutsastherewouldbelackofuniformityandapoorfinishwouldresult.Whenusingpowerfeedandapproachingashoulderorthechuckjaws,disengagethepowerfeedandhandfeedthecarriageforthelast1/8in.orso.Thehandwheelisusedtoquicklybringthetoolclosetotheworkbeforeengagingth

6、efeedandforrapidlyreturningtothestartofacutafterdisengagingthefeed.Afeedchangeleverdivertsthefeedeithertothecarriageforlongitudinalmovementortothecrossfeedscrewtomovethecrossslide.Thereisgenerallysomeslackorbacklashinthecrossfeedandcompoundscrews.Aslongastheto

7、olisbeingfedtoonedirectionagainsttheworkload,thereisnoproblem,butifthescrewisslightlybackedoff.Thereadingswillbeinerror.Becauseofthebacklash,noactualmovementofthecrossslidewilltakeplaceeventhoughthemicrometerdialreadinghasbeenchanged.Whenitisnecessarytobackthe

8、toolawayfromthecutafewthousandthsofaninch,backofftwofullturnsandthencomebacktothedesiredpositiononthemicrometerdial.Crossfeedsaregeareddifferentlythanlongitudinalfeeds.Onmostlathes