How To Prevent Mold Inaccuracies

Theprocessofproducingmoldsgenerateslargevolumesoffinechipsofmetalthat, iftheyarentpromptlyremoved, willlodgeinprecisionequipmentandmakeitimpossibletomeetclosetolerancesrequired.

Toolsusedinmachiningcentersandengraverstotypicallyproducemolds, areautomaticallymovedintoandoutofthemachinespindlesduringeachmachiningcycle, asrequiredtoperformspecificoperations.

Eachtimeatoolchangeoccurs, boththeoldandnewtoolsareexposedtochipsandotherparticlesfromthecuttingbed.

Ifanyoftheseparticlesweretosticktotheshank, thetoolwouldnotruntruewheninsertedintothespindle.

Thismightmakeitimpossibleforthemachinetomeetthelevelofprecisionrequiredinproducingmolds.

AirProblemsTopreventthisfromhappening, boththespindleandtoolareblastedwithcompressedaireachtimeatoolischanged.

Insomecases, thespindleandtoolarecleanedautomaticallybythecompressedairserviceinstalledinthemachinewhileothermachinesspindlesarecleanedmanually.

Theprobleminmanyplantsisthattheairusedtocleanthespindlescontainswaterthatcollectsinthecompressedairlineswheneverhumidityishigh.

Inthehotsummermonths, theairlinecanlookjustlikeagardenhose.

Theresultisthatwaterissprayedintothespindlealongwiththeair, causingrustthatcreatesthesameaccuracyproblemsasthechipsthattheairwasdesignedtoremove.

Sometimesspindlesneedtoberebuiltorscrapped, andinothercasesexpensiverepairstothemachinetoolmayberequired.

Thepresenceofwaterinairlinescancauseothermaintenanceproblemsaswell.

Mostplantsuseairmotorsinawiderangeoftoolssuchaspneumaticdrills.

Ifwatercontaminatesthecompressedairservice, thesemotorsmayrusttothepointthattheystopfunctioningafterjustafewweeksofservice.

Rebuildingthemotorstypicallytakesaboutfivehoursandcostsabout$500inparts.

PreventionThereareanumberofpotentialsolutionstothisproblem.

Refrigerateddryersarerelativelyinexpensivetopurchase, butconsumeaconsiderableamountofelectricityandalsorequireregularmaintenanceforthemotorsandothermovingparts.

Ontheotherhand, compressedairdryersbasedonthemembraneseparationprinciplecostslightlymorefromaninitialpurchasestandpoint, buthavenomovingpartsanddonotrequireanymaintenanceexceptforchangingthefiltereveryyear.

Dryersthatusethemembraneseparationprincipleworklikethis:FIrst, thecompressedairpassesthroughhighefficiencycoalescingfilters.

Thesefiltersremoveoilandwaterdropletsandparticulatecontamination.

Then, theairmovesintothedehydrationmembranes, whichconsistofbundlesofhollowmembranefibers, eachpermeableonlytowatervapor.

Asthecompressedairpassesthroughthecenterofthesefibers, watervaporpermeatesthewallsofthefiber, anddryairexitsfromtheotherend.

Asmallportionofthedryairisredirectedalongthelengthofthemembranefibertocarryawaythemoisture-ladenairthatsurroundsit.

Theremainderofthedryairispipedtotheapplication.

Thesedryersaredesignedtooperatecontinuously24/7.

Anelectricalsupplyisnotrequiredtousethesedryers.

Theonlymaintenancerequiredischangingtheprofiteercartridgeamaximumofonceayear.

Thetimerequiredtochangetheprofiteercartridgeisapproximatelyfiveminutes.

Forthesereasons, mostmoldmakerscalculationsshowthatmembraneseparationcostsconsiderablylessoverthelongrun.

(SelecedfromMoldmakingTechnologyMagazine) .

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