模具外文翻译外文文献英文文献注塑模.pdf

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TheInjectionMolding
1、Theinjectionmolding
Injectionmoldingisprincipallyusedfortheproductionofthethermoplastic
parts,althoughsomeprogresshasbeenmadeindevelopingamethodforinjection

moldcavityfromareservoirofmeltedmaterialhasbeenextremelydifficulttosolvefor
thermosettingplasticwhichcureandhardenundersuchconditionswithinafew
-
processconsistsoffeedingaplasticcompoundinpoweredorgranularformfroma

coolingperiod,-molding
:(ⅰ)ahighmoldingspeed
adapterformassproductionispossible;(ⅱ)thereisawidechoiceofthermoplastic
materialsprovidingavarietyofusefulproperties;(ⅲ)itispossibletomold
threads,undercuts,sideholes,andlargethinsection.
2、Theinjection-moldingmachine

commonlyusedsysteminthelargermachinesisthein-linereciprocatingscrew,asshown
inFigure2-
plasticisfedtotherotatingscrew,itpassesthroughthreezonesasshown:
feed,compression,,thescrew-flightdepthisgradually
reduced,
,itforcesthescrew
back,trippingalimitswitchthatactivatesahydrauliccylinderthatforcesthescrew

plasticunderpressurefromescapingbackintothescrewflight.
Theclampingforcethatamachineiscapableofexertingispartofthesizedesignation
-of-thumbcanbeusedtodeterminethetonnagerequired
1:.

,thismayhavetogotothreeor
fourtons.
Manyreciprocating-screwmachinesarecapableofhandingthermosettingplastic


therangeof375°C~410°

coursethemoldmustbeheatedratherthanchilled,aswiththermoplastics.
3、BasicUnderfeedMould
AsimplemouldofthistypeisshowninFigure3-1,andthedescriptionofthedesign
,namely:the
movinghalf,thefloatingcavityplateandthefeedplaterespectively.
ThemovinghalfconsistsofThemovingmouldplateassembly,supportblock,backing
plate,
identicalwiththemovinghalfofbasicmoulds.
Thefloatingcavityplate,whichmaybeoftheintegerorinsert-bolsterdesign,is
locatedonsubstantialguidepillars(notshown)
mustbeofsufficientlengthtosupportthefloatingcavityplateoveritsfullmovement
andstillprojecttoperformthefunctionofalignmentbetweenthecavityandcorewhen

floatingcavityplaterespectively.
Themaximummovementofthefloatingcavityplateiscontrolledbystoporsimilar



spaceprovideforshouldbe65mmjustsufficientforanoperatortoremovethefeed
systembyhandifnecessary.
Thedesireoperatingsequenceisforthefirstdaylighttooccurbetweenthefloating

2:.
,springsmaybeincorporatedbetweenthefeedplate


normalpracticetomountthespringsontheguidepillars(Figure3-2)andaccommodate
theminsuitablepocketinthecavityplate.
Themajorpartofthefeedsystem(runnerandsprue)isaccommodatedinthefeed
platetofacilitateautomaticoperation,therunnershouldbeofatrapezoidalformsothat

isused,halftherunnerisformedinthefloatingcavityplate,whereitwouldremain,andbe
preventedfromfallingorbeingwipedclearwhenthemouldisopened.
Nowthatwehaveconsideredthemouldassemblyinthesomedetail,welookatthecycle
ofoperationforthistypeofmould.
Theimpressionsarefilledviathefeedsystem(Figure3-1(a))andafterasuitable
dwellperiod,
thecompressionsprings,whichcausethefloatingcavityplatetomoveawaywiththe

,itisarrestedby
,havingshrunk
ontothecores,
therunner(Figure3-1(b)).
Thespruepuller,beingattachedtothemovinghalf,ispulledthroughthefloating
cavityplateandtherebyreleasethefeedsystemwhichisthenfreetofallbetweenthe

ejectorsystemisoperatedandthemoldingsareejected(Figure3-1(c)).Whenthemould
isclosed,therespectiveplatesarereturnedtotheirmoldingpositionandthecycleis
repeated.
4、FeedSystem
Itisnecessarytoprovideaflow-wayintheinjectionmouldtoconnectthenozzle(of
theinjectionmachine)-wayistermedthefeed
,
3:.
equallytotheflow-wayitself,andtothemoldedmaterialwhichisremovefromthe
flow-wayitselfintheprocessofextractedthemolding.
Atypicalfeedsystemforafour-impression,twoplate-typemouldisshownin
Figure4-,mainrunner,branchrunner

whichgoingthroughthesprueandrunner,theviscositywillrise;however,theviscosityis

desirabletokeepthedistancethatthematerialhastotraveldowntoaminimumtoreduce

theimpressionlayoutgate’sdesign.

Asprueisachannelthroughwhichtotransfermoltenplasticinjectedfromthe
,whichisaseparatepartfrom
themold.

Arunnerisachannelthatguidesmoltenplasticintothecavityofamold.


followingfunction:restrictstheflowandthedirectionofmoltenplastic;simplifies
cuttingofarunnerandmoldingstosimplifyfinishingofparts;quicklycoolsand
solidifiestoavoidbackflowaftermoltenplastichasfilledupinthecavity.

Thepurposeofthecoldslugwell,shownoppositethesprue,istheoreticallyto
receivethematerialthathaschilledatthefrontofnozzleduringthecoolingandejection

thespruebushforejectionpurposes.
Thesprue,,the
runnerandthegateareimportantitemsthataffectthequalityorthecostofparts.
5、Ejection
Amoldingisformedinmouldbyinjectingaplasticmelt,underpressure,intoan
4:.
,all
thermoplasticmaterialscontractastheysolidify,whichmeansthatthemoldingwillshrink
.
Facilitiesareprovidedontheinjectionmachineforautomaticactuationofanejector
system,,themould’sejector
systemwillbemosteffectivelyoperatedifplacedinthemovinghalfofthemould,

moldingfromthecoreanditthereforefollowsthatthecore,too,willmostsatisfactorilybe
locatedinthemovinghalf.
Theejectorsysteminamouldwillbediscussedunderthreeheadings,namely:(ⅰ)
theejectorgrid;(ⅱ)theejectorplateassembly;and(ⅲ)themethodofejection.
、Ejectorgrid
Theejectorgrid(Figure5-1)isthatpartofthemouldwhichsupportsthemould
plateandprovidesaspaceintowhichtheejectorplateassemblycanbefittedand

convenientlyshaped“supportblocks”.
Theejectorplateassemblyisthatpartofthemouldtowhichtheejectorelementis
,formedbytheejectorgrid,directlybehind
(Figure5-2)consistsofanejectorplate,aretainingplateand



rodpassesthroughanejectorrodbushfittedinthebackplateofthemould.
、Ejectiontechniques
Whenamoldingcools,itcontractsbyanamountdependingonthematerialbeing
,forexample,asolidrectangular
block,themoldingwillshrinkawayfromthecavitywalls,therebypermittingasimple
,whenthemoldinghasinternalform,the
molding,asitcools,willshrinkontothecoreandsomepositivetypeofejectionis
necessary.
5:.
Thedesignerhasseveralejectiontechniquesfromwhichtochoose,butin
general,
ejectiontechniquesareasfollows:(ⅰ)pinejection(ⅱ)sleeveejection(ⅲ)stripper
plateejectionand(Ⅳ)airejection.
Figure2-1a
Figure2-1b
6:.
7:.
Figure3-1
8:.
Figure3-2
Figure4-1a
9:.
Figure4-1b
10
:.
Figure5-1
11:.
Figure5-2
12:.
注塑模
1、注塑模
尽管成型某些热固性材料的方法取得了一定的进步,但注塑模主要(还是)用
来生产热塑性塑件。(这主要是因为)热固性塑料熔体在很短的时间内就固化和硬
化,在从料斗想模具型腔注入热固性塑料熔体的过程中,也会出现这种情况,这个
问题一直非常难解决,注塑成型原理和铸造十分相似。注塑成型的工艺包括:首先
把料斗中的粉状或粒状的塑料混合物依次输送发哦计量区和溶化区,然后再注射到
模具的型腔中,经过短时冷却后,开模,推出成型塑件,注塑机分为手动、半自动
及全自动操作。注塑模具有以下优点:(ⅰ)较高的成型速度使大批量生产成为可
能;(ⅱ)为成型具有不同使用性能的热塑性材料提供了较宽的选择;(ⅲ)可以
成型带有螺纹的塑件、侧向凹陷的塑件、带有侧孔的塑件以及较大的薄壁件。
2、注塑机
熔融塑料进入模具中通常有几种方式。在大型注塑机上常带采用螺杆式的注入
方式,如图2-1所示。螺杆同时具有注射和塑化的功能。树脂原料进入旋转的螺杆时,
要经过图示的三个区域:喂入区、压实区和计量区。经过喂入区后,为压实树脂原
料,螺杆螺旋部分的深度逐渐降低,同时传递树脂原料间因剪切作用而产生的热量,
使原料呈半流动状态。在计量区,螺缸表面的加热装置对熔体进一步加热。当熔体
充满螺杆前部区域时,螺杆在熔体压力的作用下后退,触动限位开关使液压缸工作,
在液压力的作用下推动螺杆向前运动,将熔融塑料注射到闭合的模具型腔中。防倒
流阀能够阻止受压熔体倒流进螺杆的螺旋区。
注塑机的锁模系统做提供的锁模力由(塑件在分型面的投影)尺寸决定,锁模
力以吨位单位。通常靠经验来决定塑件所需要的锁模力总吨数,一般在塑件投影面
积上每平方英寸需要作用两吨锁模力。如果熔体流动困难或塑件较薄,锁模力应提
高到三到四吨。
许多往复螺杆式注塑机能生产热固性塑料。以前,热固性塑料由挤出模具或传
13:.
递模具生产。热固性塑料熔体在模具内固化或发生聚合反应,并在温度357℃~410℃
范围内推出。热塑性塑料熔体必须在模具内冷却成型,以保证推出时不发生变形,
这种热固性循环速度很快。当然,生产热塑性塑料时,模具必须被加热,而不是冷
却。
3、模具基本结构
这种简单的模具结构如图3-1所示,模具设计和开模顺序将在以下的篇幅中论
述。模具由三个基本部分组成,分别是动模部分、浮动型腔板和定模板。
动模部分包括动模板组件、支撑块、支撑板,推出机构和顶杆推出系统。这样
设计的动模部分与最基本的模具结构中的动模部分相同。
浮动型腔板通过导柱(图中没有示出)固定在定模板上,设计形式可以是整体
式,也可以是镶拼式。导柱必须有足够的长度,(以便磨具工作时)支撑浮动型腔
板完成开合动作,并在模具合模时完成对型腔和型芯的找正作用。导套分别安装在
动模板和浮动型腔板上。
浮动型腔板的最大运动距离由限位钉或类似装置控制。在动模板的适当位置钻
孔,以便安装限位钉。