EMI EQUIPMENT MANUFACTURERS INC. www. EMI-INC.com White Paper Series Providing an authoritative guide that is intended to inform our readers concisely about complex technical issues. This white paper is meant to help our readers understand an issue, solve a problem, or make a better decisions. CONSIDERATIONS FOR MANUAL & AUTOMATIC GREEN SAND EXPANSIONS
11
Embed
CONSIDERATIONS FOR MANUAL & AUTOMATIC GREEN SAND …
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
EMI EQUIPMENT MANUFACTURERS INC.www.EMI-INC.com
White Paper SeriesProviding an authoritative guide that is intended to inform our readers concisely about complex technical issues. This white paper is meant to help our readers understand an issue, solve a problem, or make a better decisions.
CONSIDERATIONS FOR MANUAL & AUTOMATIC GREEN SAND EXPANSIONS
CONSIDERATIONS FOR MANUAL & AUTOMATIC GREEN SAND EXPANSIONS
WHITE PAPER TAKEAWAYS • Jolt Squeeze Machines • Automation Matchplate Molding •Gravity-fillmachinesvsBlow-fillmachines • Horizontal Tight Flask Molding Systems • In-line vs Cross-Loop vs Pallet Index Lines
Foundries,guidingtheirbusiness,havetosurvivethroughthevariouseconomiccyclesaswellasemergingmarketpressures,arewellawareofthecontinuousneedtoreinvestinequipmenttoincreaseproductivity,anddecreasethemanualcontentofcastingproduction,whilestillproducing consistent castings economically in a very demanding market. From their position, themoldingmachinemanufacturershavetoprovidetheproperlydevelopedequipmentand/ormoldingprocesstomeetthesedemands,whileatthesametimeimprovingcastingqualityandmaintainingasafeworkingenvironment.
Green sand molding remains an attractive casting production method for two main reasons:
1. Green sand production is and will always be less expensive, as the price of chemicalbinderscontinuestorisefasterthannormalinflation.
2. Green sand foundries are not as labor intensive. Oneobstaclepreventingfoundriesfrommovingintogreensandmoldingisthehigh capitalcostofevenasimplemechanizedplant.However,foundriesshouldrealizethat theincreasedproductivitythatgreensandmoldingofferswilloffsetthesecostsovertime andhavethepotentialforhigherrevenues.
a. Whatarecurrentmoldproduction/Futuremoldproductionrequirements? b. Iscurrentcastingqualityconsistentandreliable? c. Isscrapistoohigh? d. Aremyleadtimedeliverydatestoolongforlargevolumes?
Standard Jolt Squeeze Machines Tominimizetheinitialgreensandinvestment,standardmoldingmachinesofferamajor advantagebecauseafoundrycanmechanizeforgreensandmoldingwithreasonable initialexpense,andthebalanceofthemoldhandingcanbebuiltovertime.These machinescanbethesmall212/214joltmachines,upthroughthe722&730joltmolding machines. These machines can use almost any standard green sand match plate and copeanddragpatternequipment.Anumberofflasksizescanbecanbeemployedon thesamemachine,givingflexibilityofproductionandproductrange.
Astandardmoldingmatchplatesolutioncanbefoundwherecopeanddragareformed simultaneously.Theoveralloperatingefficiencyofthesemachinesisverymuchdependent ontheoperator’sabilitytocontinuallycarryoutthesemachinesmanualfunctions.By implementing mechanized mold handling systems, as previously stated, the machines can provide more productivity.
Automatic Horizontal Flaskless Molding (Matchplate) Afterthedevelopmentofthejolt,rap,andsqueezemoldingtechnology,thefocusofthemachineryforgreensandmoldproductionwasputintohandling systems designed to reduce the reliance on labor to achieve a morereasonableproductionrate.Automatichorizontalflasklessmoldingmachines,sometimesknownasautomaticmatchplatemoldingmachines,weredesignedandfirstintroducedtofoundriesintheUSAinthemid1960’s.Thesemachineshaveprobablyhadamorerapidgrowthintheirusethananyotherinnovationtogreensandmoldproductioninthelast60years.
Theseautomatichorizontalmatchplatemachinesarearelativelyeconomicformofmoldingmechanization. The machine produces a complete mould in one cycle and only requires one machineoperatorwhocansetcoresasnecessary,thusremovingsomeoftherelianceonmanuallabortomakethemold.Productionratescanbeover200moldsperhourun-cored.Ifcoredworkisrequired,thefoundryislimitedtoautomaticcoresettingifitwishestomaintainmaximum production, although automatic core setting is really a misnomer, since a man is required to put the core or cores into the setting unit.
Two methods of filling are used in flaskless molding:
Withblowmachine,thepatternplateistrappedinbetweenthecopeanddragflaskswhicharethentippeduponedgesothatthepatternisvertical.Sandisthenblownstraightdownfromapairofblowslotstofilltheflasksfromabove.Thismeansthatsand,whichistravelingataveryhighvelocity,mustmakearightanglechangeofdirectioninordertofilldeepergreensandpocketsormoldcavities.Consequently,therearefrequentlyproblemsfillinganddrawingdeepergreensandpocketsandcavities.Gravityfill&squeezemachineshaveshowntogivemore consistent mold quality and are more suited to deep and complicated pattern shapes.
Blowingamoldatthetypical40or50psipre-compactsthesandbeforeitissqueezed.Thismakesitnecessaryforblow-fillmachinestosqueezeharderinattempttoforcethesandintopocketsonthepattern.Thisoftenresultsinamoldthatisharderthandesirableontheflatareasandthepartingline,buttoosoftindeeperpocketsandmoldcavities.Thesehighersqueezepressuresrequirethickerandmoreexpensivepatternstoavoidpatternflexingandbreakage.Ifagreensandpocketisnotcompletelyfilledduringtheblowcycle,itisvirtuallyimpossible to squeeze hard enough to correct this problem.
Aluminumfoundriesdonotwanttomakeamoldthatistoohardbecauseofgasproblemscausedbythereducedpermeabilityofhardermolds.Blow-fillmachinessometimeshaveproblemsinthisareaduetothefactthattheymustsqueezehardertogetanacceptablemolddensity in deeper pockets. The important point is that mold hardness alone is not necessarily good;uniformdensityandrepeatabilityis!
As previously mentioned, any large projections or obstructions on the pattern plate make it difficulttogetanadequatelydensefillofthemoldonthesideofthemoldoppositetheblowslot.Thiscauseswhatiscommonlyknownasthe“shadoweffect”whichisasoftspotinthemold.Thesesoftspotspreventthemoldfrombeinguniformlydenseandareatroublesomesourceofcastingdefectsandscrap.Thisiswhyblowtypemachinesaregenerallylimitedtodoingsmallercastingswithoutanydeepordifficultpatternshapes.
Squeezingthemoldfrombothsidesrequiresthatbothhalvesofthemoldbefilledwithsanduniformly,andthesqueezepressuresonbothcylindersbeperfectlybalanced.Otherwise,theresultwillbeadamagedorbrokenpatternplate.Usersofblow-typemachinesmustbeverycarefultoadjustthemachine’soperatingprogramduringeverypatternchange.Attemptingtomakeamoldthatisnottallenoughforaparticularpatterncaneasilybreakordamagethepatternplate.Highsandcompactabilitywhenmakingamoldorablowthatisshortofsandcan also break the pattern.
Large asymmetrical castings such as cooking pots or brake drums inherently cause the biggestproblemsforthesemachines.Onesidewithalargecavitywillrequiresignificantlymoresandandalongerstroketosqueeze.Theothersidewithalargeflatsurfaceontheprojectionwillrequirelesssandandonlypermitashortsqueezestroke.Thisisverydifficulttobalanceandcontrolwiththeblow-fillmachineslimitedabilitytoconsistentlyfillandsqueezedeep pockets to an adequate and consistent mold density.
Anythingthatissetonthepatternand/orinvestedinthemoldisaproblemfortheblowmachines.Thisincludesram-upcores,chills,filters,chaplets,facingsand,exothermicsleeves,insulatedorevenopenrisers,etc.Theblowfillprocessprecludesalloftheseoperations,sincethesandrushinginandpatterntippingupverticallyduringthemoldingprocesswoulddislodge anything placed on the pattern.
Thedevelopmentofhighpressuremoldingusingflasks,tookplaceintheUSAinthemid195O’s.Thesehandlingsystemswereanaturalprogressionawayfromheavymanuallabor,and the reliance on labor to meet production targets.
TheCROSS-LOOParrangementhastwomouldinglines, one to produce the drag and the other to produce the cope, as they span the mold conveyor loop. This arrangementisnormallyusedforflasksizesabove36”x24”,and/orwhereheavycoresareplacedinthedrag,asinacylinderblock,forexample.ProductionratesontheCROSS-LOOPareslowerthantheIN-LINE,normallybetween260/300moldsperhour.
Thebenefitswhichthesetwosystemsofferaretheinfiniteflexibilityinuse,highproductivityandadaptationtoalltypesofcastings,especiallythoserequiringcoreswherethetightflasksystemisfoundtobemoreefficientand economical. This is because more castings can beproducedwithinthesamegivenmoldareawhencomparedtoflasklessmolds.
TheIN-LINEandCROSS-LOOPsystemsofferthefoundrythemostproductiveandflexibleapproachtomechanizedmoldingforcastingsrequiringcoresatahighproductionrateof+250mph.Thecostpermouldislessthanwithanyothersystem,calculatinginitialcapitalcost, against productivity and running costs.
Usingthisinformation,somemachinemanufacturershavedevelopedvariousmeansofcompactingthemoldinsidetheflask.ThatisBlowSqueeze,IMPACTmoldingwithsqueeze,vacuummolding,orevensqueeze(topandbottominsomecases)withcompensatingpeenfeet,allinordertoreducetheoperatingnoiseofthemachinebyeliminatingtheprovenjoltandrapmoldingmethodology.Inpracticehowever,allofthesemachineshavelimitations,astowhattypeofcastingstheycanproduceandtheyareextremelysusceptibletovaryingsandconditions. Inconsistent mold hardness is also common.
Sincethesetypesofhighpressureautomaticproductionsystemsrequirethefoundrytouseflasks,therearecostsandmaintenancetoconsider.Flasksforhighpressureautomaticmoldingareexpensive,asarepallets/moldcars.Flasksrequiremaintenancecleaningandroutineplannedpinandbushingreplacement.However,theyshouldlastatleasttentofifteenyears, so cost is expensed over a long period.
Thesesystemsrequirehandlingequipmentthroughthevariousstagesofmoldandcastingproduction. The most important job they do is to ensure parting line accuracy. They support themoldthroughitsvariousstagesofmovementandassistinresistingthemetalheadpressure,allowingasoftermoldtobemadethanisnecessaryforaflasklessone.Becausethegreenstrengthrequirementisless,soistheclaycontent.Thisreducesthecostofsandpreparationandincreasesmouldpermeability.Theyalsoallowatleast8O%ofthemouldareatobeused,whereonly6O%canbeusedeffectivelywithoutflasks.
ThehighercapitalcostofahighpressureIN-LINE,CROSS-LOOPorPALLETINDEXsystemdoestosomeextentlimittheirmarket,howeverwithlifespansover25years,thisinvestmentneedstobeweighedagainstthedemandandproductivitycapacitythesesystemscreate.Theheartofthehighspeedsystemsandthepartwhichkeepsitproducingmouldsinexcessof300perhour,isthemoldingmachine.Beinghighpressurejoltsqueezeunits,poweredhydraulically,theycanbecostly,butfromexperienceandknowledgebuiltupovermanyyears,certaincriteriaarenecessarytoincludeinafourpostmoldingmachinetoproducemoldsofconsistent high quality.
a. Rigidstructuretowithstandtheforcesdevelopedbythemachine. b. Sandhoppertoevenlydistributethecorrectamountofsandintotheflask. c. Aeratortofluffthesandasitfallsintotheflask. d. Upsetframetogiveaheadofsandabovetheflaskforsqueezing. e. Pre-joltactiontocompactthesandbeforesqueezing. f. Optionofsimultaneousjoltingwithsqueezingtoimproveeffectivesqueezeforces.
Asmostfourpostmoldingmachinesincorporateapatternshuttleforrapidchangeofpattern,thisunitcanbeusedalsoforproducingcopeanddraghalfmoldsalternatively,making it possible to have only one molding machine in the system. This immediately cuts theproductioncapacityinhalf,butalsoreducesthecapitalcostsignificantly.Itispossibletoachieveupto100/120moldsperhourusingasinglemachinewithinanIN-LINEarrangement.
Itisfairlyreasonabletoforecastthatgreensandwillcontinuetobethemostimportantmediumformakingmolds,wellintotheforeseeablefuture.Thedemandforcastingsinthedevelopedcountrieswilldecreasefurther,andalternativemethodsandmaterialswillbeadopted.Thefoundrieswhichsurvivethemarketchangesthatwilltakeplaceduringthistransitionwillhavetomechanizemoreeffectivelyandeconomicallyasbasiclabor,willeitherbe too expensive or unobtainable.
Forquestionsorcommentsfeelfreetocontacttheauthor,JerrySenkat: 216-651-6700 or by email at [email protected]