橡胶按键的designguide

©N.V.PhilipsIndustrialActivities2001SILICONEKEYPADDESIGNGUIDEP.CLAESVersionStatusDateAuthorModification(s)0.11999-09-2PCLDocSavedP/Creation/know-how/keymatsDate:1999-12-09Status:Author:PaulClaes10-Jan-012SCOPE.Thisdesignguidehastheaimtobea‘bible’foryourdesignofrubberkeypadsinthefuture.Itwillguideyouthroughthedifficultworldofdesigningandproducingkeypads“FIRSTTIMERIGHT”.Somerecommendationsaremadetoimprovethequalityofourkeymatdesign.Pleasetrytofollowtheserecommendationsinordertoreceiveexcellentproducts.Itwillhelpdesigninganddevelopinghighqualitykeymats.Incombinationwiththeplasticcasingthesekeymatswillfunctiontroublefree.Alsoabriefexplanationofoursuppliers'needsandprocessesisgiven.IexperiencedthattheearlierinaprocessadeveloperinvolvestheKH-basketholderand/orsupplier,thegreaterthebenefitswillbeintermsofquality,cost,designeffectivenessandeaseofproduction.POSITIVEPOINTS/POSSIBILITIES.-TheKH-basketisaneasy-to-usemanual.-Itprovidestechnicalinformationforeveryonewithlimitedexperienceindesigningsiliconekeymats.-Thepracticaltipsandkeymatspecificationsarealsousefulformoreexperienceddevelopers.-Effectivelyworkingwithsiliconekeymatsismadeeasier.NEGATIVEPOINTS/LIMITATIONS.-Abetterandreliablerelationwiththesupplierisnecessarytosolvetheproblemswithhighfalloffratesofsomekeymats.Thereforethecommunication(persontoperson)inthebeginningoftheprojectneedstobeimproved(EarlySupplierInvolvement).Mass-productionproblemsshouldalsobediscussedwiththesupplier.Moredirectcontactsarenecessarywithfollowingsharedbenefits:-leadtimereduction-optimaldesignwithminimalofchanges-goodproducebility,qualityandcosts10-Jan-013OVERVIEW1.GENERALMATERIALPROCESS2DESIGNMATERIALTOOLDESIGNGUIDES3COSTPRICE4CONCLUSIONS10-Jan-0141.GENERAL1.A.MATERIALSILICONERUBBER(K1763)isasyntheticrubber(elastomer)withasmainagentasilicone-oxygenskeleton.CH3CH3||O-Si-O-Si-O||CH3CH3Thesemacromoleculesgiveaverystablematerialwithfollowingproperties:+Environmentaldurability.Superiorresistancetohighandlowtemperature(-55°Cto+250°C)eveninheavyhumidity.+Highresistancetoageing.+Goodmechanicalandelectricalpropertiesevenathightemperatures.+Goodresistancetooilsandoxidation+Easytocolourandprint+Variousshapesofknobscanbeobtainedwithacomfortabletouchandclickfeeling.-Poorresistancetofuels-Lowstrength-Highcostprice(10Hfl/Kg-6timesmoreexpensivethennaturalrubber)DuetothesepropertiesSILICONERUBBERisextensivelyusedinthemanufacturingofkeypads.Alsowhenacompleteresistancetoweatherandfluidsisrequired.1.B.MOULDINGPROCESS1.B.1.COMPRESSIONMOULDINGApieceofuncuredrubberoftherightsizeisplacedbetweentwoheatedhalves(150°)ofamould.Thismouldisclosedinapress(1ton/sq.inch)andtherubberisforcedinthemouldcavity.Therubbergainsheatfromthemouldand‘cures’.Aftercuringthemouldcanbeopenedandthepartscanberemoved.Cycletimedependsonthevolumeofthepiece:3-10minutesAllcolourscanbeachievedfrommatttosemihigh-gloss.Itisarelativelysimpleprocessanditisoftenusedforcomponentsrequiredinfairlylowquantities.10-Jan-0151.B.2.TRANSFERINJECTIONAheatedmouldisclosedinapressandtherubberwillbeinjectedinthecavities.Thisisdonewithahydrauliccylinderincorporatedinthepress(orsometimesinthemould).Thismethodcanproducehigh-precisionpartsinmoderatequantitieswithouthightoolingcosts.1.B.3.DIRECTINJECTIONTwosiliconeliquidcomponents(catalyst+maincomponent)aremixedina1:1ratio.Ascrewinjectionsystemdeliversthislowviscosityliquidintotheclosedmould.Becauseofthevacuuminthecavities,onlyaverylowpressureisneededtoinjecttheliquidsiliconerubberandaveryfastcuringoccurs.Thedirectinjectionmouldshavenormallyonecavitysideandtwocoresides.Onecoreisusedformoulding,whilemouldedproductscanbetakenoutoftheotherone.Thisprocessisgenerallyusedformulty-cavitymouldsandfornotfrequentlychangeofmaterialbecauseoftheamountofrubberinthesystem.1.B.4.COMPARATIONOFCOMPRESSIONVERSUSINJECTIONMOULDINGCompressionmouldinganddirectinjectionarethetwomostfrequentlyusedproductionprocesseseachwiththeirownapplication.TocomparethetwoprocessestheRC01-keypadisused:(base38mmx32mm12knobs∅5mmheight8mm)COMPRESSIONINJECTIONToolingToolLeadtimeNumberofCavitiesToolingcostMaterialpriceProductpriceMinimumOrderCycletimeCapacity400x400mm6weeks48200000BFR186BFR/Kg4,5BFRNIL6minutes165000/month450x500mm10weeks22300000BFR222BFR/Kg3,9BFR150000/order2minutes285000/monthTherestrictionsofinjectionmouldingare:-material,onecolourblackortranslucentspecialcolourwillhaveadoublematerialprice-onehardnessforallkeys(between45and60shoreA)-keyheightmaximum10mm-onlyconductiveprintingpossible-highvolume3,5millionkeypads/year4yearsrun3shifts/day-keypadswithsmallshortbuttons,allsameshapeandheightPreferableusedforcomputerkeyboards10-Jan-0162.DESIGNIMPORTANTPOINTSTOGETAGOODQUALITYPRODUCTARE:MATERIAL(hardness)MOULDDESIGNRULES10-Jan-0172.A.MATERIALHARDNESSRawsiliconerubberisamilky-whitesyntheticrubberproducedbyapproximatelyfivesuppliersworld-wide:SHIN-ETSUDOW-CORNINGTORRAYTOSHIBABAYERAnimportantparameteristhehardnessthatcanvarybetween30and80shoreA.Forkeypads,thehardnessnormallyliesbetween:50shoreAX60shoreAOurgoalisahardnessof55shoreA±5shoreforallkeym