mold.docx

mold.docx

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mold

1、A.MoldComponets

Moldsusedininjectionmoldingconsistoftwohalves;onestationaryandonemovable.Thestationaryhalfisfasteneddirectlytothestationaryplatenandisindirectcontactwiththenozzleoftheinjectionunitduringoperation.Themovablehalfofthemoldissecuredtothemovableplatenandusuallycontainstheejectormechanism.Therearemanypossiblemolddesigna,includingmultiplepiecemoldsforcomplicatedparts.Onproductionmoldingequipmentmanyarticlesmaybeshotatthesametimebytheuseofmultiplecavitymolds.Theuseofabalancedrunnersystemcarriestheplasticfromthespruetoeachindividualcavity.Atthispointthematerialpassesthroughagateintothecavity.Thegateisarestriction,smallerthentherunner,toprovideforevenfillingofthemoldcavityandtoallowtheproductstobeeasilyremovedformtherunnersystem.Withmostinjectionmoldingsystem,thearticlescanbesnappedawayfromtherunnerorspruewithoutadditionaltrimming.Prouductsthathavebeeninjectionmoldedcanusuallybeidentifiedbyfindingwherethegatewasbrokenoff.Thegatewillusuallybelocatedattheedgeorpartinglineofanobjectorinthecenterofcylindricalproduct.

Moldsareexpensive,asarethemachines.Yet,oncetheproducthasbeendesigned,moldsmade,andproductionstared,articlescanbeproducedinquantityatlowcost.Virtuallyallthermoplasticscanbeinjectionmoldedthroughvariationsinmoldandmachinedesign.

Mold（anddie）partsthataremass-producedandstandardizedinshapeanddimensionarereferredtoas“standards”（or“standardparts”）.Specializedoperatorsofmillingmachines,lathes,lathes,electronicdischargemachining（EDN）equipmentandgrindersproducemoldcomponentsindependentlyofeachother,followingdetaiedmoldpartdrawings.Finally,alltheseitemscometogetherwiththestandardmoldbaseandhardwareandareassembledbythemoldmaker.Today,standardcomponentsforthemoldmakingindustryaremarketedbyanumberofcompanies.Fig.3.1.1illustratethestandardcomponentsforMolds.

Table3.1.1Statusofstandardization（1998）componentsfor

Compression,Injection,andDie-CastMold

Pos.No.

Denomination

Standard

DIN

ISO

1

Plate,plain

16760-1

6753-2

2

Plat,drilled

V16760-2

/

3

Supportpillar

DINISO10073

10073

4

Centringsleeve

16759

9449

5

Locatingguidepillar

16761

8017

6

Locatingguidebusch

16716

8018

7

Ejectorpin,cylindricalhead

1530-A

6751

8

Shoulderedejectorpin,cylindricalhead

1530-C

8694

9

Ejectorpin,conicalhead

1530-D

/

10

Flatejectorpin

1530-F

8693

11

Ejectorsleeve

16756

8405

12

Spruepullerinsert

16757

/

13

Spruebushing

16752-1

10072

14

Anglepin

/

8404

15

Locatingunit,roundandfalt

/

8406

16

Locatingring

16763

10907-1

10907-2

17

Thermalinsulatingsheet

16713

15600

18

Coolingconnectors

16766

/

BMoldConstruction

Theconstructionofthemoldforinjectionmoldingbeginswiththeworkingdrawing.Fromitthetequirementsforthemoldcanbespecified.Thesewouldincludethematerialfromwhichthemoldshouldbemade,theavailabilityofequipmentformachiningthemold,andthemoldcapacityofthediesetonthemachine.

Coldrolledsteelisanidealmaterialforlaboratorymolds,sinceitmachineswell,isfairlyinexpensive,andholdsupwellfornozzlepressureandwear.Itsmajordisadvantageisthatitwillrustquicklyunlessprotectedbymoldteleaseorwaxduringstorage.Complicatedmoldcavitiesneedspecializedmachiningandpolishing,therefore,circularcavitieswhichcanbeturnedandpolishedonthelatherequirelessequipmentandmachiningskill.

Similarmoldsmayalsobemachinedfromaluminum,andtheyhavetheadvantageofnotrusting.Excessiveweardevelopsonthesprueduetothehighnozzlepressureonthesoftaluminum,butthiscanbeovercomebytheuseofasteelcoverplateonthetopofthemold.

Anothermethodofmoldconstructionisbythecastingprocessusinganaluminumfilledepoxyresin.Thistypeofmoldisparticularlysuitedtoproductsofintricatedesignandproductsthataredifficulttomachine.Thecastepoxyisstrongandgivesgoodsurfacedetail,however,itisbrittleandshouldhaveasteeltopplateattachedtoabsorbthewearofthenozzle.Apatternoftheproductmustbesecuredormadeandplacedonamoldplate.Thedragofasmallsteelflaskisplacedaroundthepatternandtheepoxyresinispouredtofillthemoldhalf.Whenthishalfofthemoldhasbeencured,thecopeisplacedoveritandtheremainderofthemoldpoured.Uponcuring,theflaskisremoved,allsurfacesmachinedsmooth,dowelpinholesdrilled,anddowelsinserted.Asteelcapplateshouldbeboltedtothetophalvesandthesprue,runners,andgatesmachined.Instructionsformixing,pouring,andcuringthealuminumfille