Variables as Production Cost Factors

Transcription

1 Geschäftsbereich Kunststfe ATI 6 Anwendunstechnische Process Variables as Production Cost Factors Information in Injection Moldin Thermoplastics: Melt, Mold and Demoldin Temperature, Prozeßrößen beim Spritzießen von Cycle Time, p-v- diarams Allemein Thermoplasten als Produktionskostenfaktoren Schmelze-, Werkzeu-, Entformunstemperatur, Zykluszeit, p-v--diaramme in Anlehnun an den Vortra Die Temperierun im Werkzeu anläßlich des Fachseminars Wirtschafliches Produzieren mit optimaler Werkzeutemperierun beim Spritzießen, SKZ Würzbur, Dezember, Vortraender Dipl.-In. Olaf Zöllner, Bayer AG, Leverkusen) Contents Inhalt Introduction. Einführun Melt. Melt durin molded part fillin. Schmelzetemperatur. Melt in holdin pressure and. Schmelzetemperatur während coolinder phases Formteilfüllun Heat a molten plastic 6. content Entformunstemperatur s tk = In π aeff References. Zykluszeit Wärmeinhalt einer Kunststfschmelze. Zusammenfassun. Literaturverzeichnis Die vorstehenden Informationen und unsere anwendunstechnische Beratun in Wort, Schrift und durch Versuche erfolen COV76/Pae elten jedoch nur als unverbindliche Hinnach bestem Wissen, weise, auch in bezu auf etwaie Schutzrechte Dritter. Die Beratun befreit Sie nicht von einer eienen Prüfun unserer Edition 6- Beratunshinweise und unserer Produkte im Hinblick auf ihre Einun für die beabsichtiten Verfahren und Zwecke. W M W π E W Druck p E Summary 7. Kühlzeit. spezifisches Volumen v. Schmelzetemperatur in der The coolin rmoplastic melts, Nachdruckund in der Kühlphase rmodynamic state curve. Influence ambient. Abkühlun derpressure Schmelze von. Influence coolin rate Thermoplasten, rmodynamischer Zustands Meltinverlauf. Einfluß des Umebunsdrucks State durin injection moldin. curve Einfluß der Abkühleschwindikeit 6 Demoldin and coolin time. Schmelztemperatur 7 Coolin time. Zustandsverlauf beim Spritz Cycle time ießen α>α>α)s,g Glas αg R αs freies p Volumen αg αg Anwendun, Verwendun und Verarbeitun unserer Produkte und der aufrund unserer anwendunstechnischen Beratun von Ihnen herestellten Produkte erfolen außerhalb unserer Kontrollmölichkeiten und lieen daher ausschließlich in Ihrem Verantwortunsbereich. Der Verkauf unserer Produkte erfolt nach Maßabe unserer Allemeinen Verkaufs- und Lieferbedinunen. Einfrierlinie x Wanddicke s p Schmelze αs αs p GO G G Temperatur S

2 Introduction When rmoplastics are injection moulded, ranules are melted in a screw COV76/Pae and conveyed into screw antechamber. Edition 6- The injection moldin rmoplastics is a form process in in which hihly complex physical processes take M = p ρ c p place. M = Mean increase in melt p = Pressure differential pressure loss) in a flow section The rmoplastic to be processed first has to be melted, runner/ate system before bein injected at hih pressure into a cold mold. ρ = Melt density Since mold is cooler than compound, shaped c p = Specific heat capacity. plastic part cools down and can be removed from mold Introduction once it has solidified. The particular sinificance this equation stems from fact that it can describe process independently The injection mouldin rmoplastics is a form processin in The individual process staes meltin, Once injection injection and coolin affect quality subsequent sinal has eometry, been be melt quite, pronounced, forms wall over and iven, molded screw part. moves forwards rheoloical and cross-section material values. As flow has channel already as been a mentioned, which hihly complex physical processes take place. both machine nozzle presses molten plastic throuh re result is no allowance elimination made for heat exchane via heat The control system mold plays a central with and cold mould mold. wall. Fiure shows a typical runner/ate system into cavity. The prile a flowin plastic role in quality-conscious and cost-efficient production The mouldin compound to be processed first has to be melted, before hih level mechanical and rmal fillin process frequently imposes a melt in a cooled injection mould. injection-molded parts. This control system is known to Lookin more closely at melt as influence decisive quality features, such as surface appearance and warpae. very considerable influence on melt. molded part is bein filled, it is seen that coolin can have a bein injected at hih pressure into a stressin on melt. The chief Riht next to mould wall, melt cold mould. Since mould is cooler parameters that affect this stress are has already solidified, ivin rise to a A prile, which can be quite pronounced, forms than compound, shaped plastic : frozen ede layer. The thickness Efficient mold control also helps to cut costs, over cross-section flow channel as a result part cools down and can be removed this layer will be a function however, since coolin time, and hence cycle time as dissipation heat via mold wall. Fiure shows a typical from mould once it has solidified. Nozzle/ate eometry processin conditions injection time, well, can be optimized in this way. prile a flowin plastic melt in a cooled Wall thickness moulded part melt and mould wall injection mold. The individual process staes Fillin rate ). In centre flow meltin, In order injection to fully and appreciate coolin affect importance coolin in an Mouldin compound channel, re is a uniformly hih quality injection mold, subsequent it is wise moulded to take a look at rmo dynamic Riht next to mold wall, melt has already solidified, Mould wall distribution. Peaks such part. processes that prevail durin injection moldin process. ivin rise to a frozen ede layer. The thickness this layer as those shown on diaram can will be a function processin conditions injection The stress actin on melt as it develop between centre The This n supplies control system answers to followin questions: time, melt and mold wall ). In flows can lead to internal friction processes, which n cause melt to that shear stress actin on melt channel and mould wall. It is here mould plays a central role in center flow channel, re is a uniformly hih distribution. quality-conscious What sort and cost-efficient chanes heat occur up. in molten plastic at injection-moulded individual staes parts. process, and what happens can develop heat between is enerated center throuh channel internal and mold is reatest Peaks and such hence as those here shown that most in diaram production This inside control a polymeric system melt is known as it cools? to Experimental What is difference investiations into wall. different a semi-crystalline ates and different plas- materials It is here friction. that shear stress actin on melt is influence between decisive an amorphous quality features, plastic and reatest [] and hence here that most heat is enerated such tic. as surface appearance and have shown that mean throuh internal The friction. prile can vary at dif- increase Δ M can be ferent points cavity close to warpae. described in approximate terms The as a ate, remote prile can from vary ate). different Hence, points an Efficient Melt mould control function pressure cavity loss Δp, close increasinly to ate, lare far from frozen ate). ede Therefore, layer an increasinly to be no lare can cause frozen ede maximum layer can cause maximum also helps to save costs, however, whereby re is assumed since. Melt coolin time, and durin hence molded exchane part fillin heat with mould peaks in Fi. ) ) to toshift towards center channel. This situation is depicted in cycle time as well, can be optimised in adiabatic => Q. ab = ). shift towards centre channel. this way. When rmoplastics are injection molded, ranules are Fi.. This situation is depicted in Fi.. melted in a screw and conveyed into screw antechamber. Δ In order to fully appreciate M = Δp ρ c importance Once injection coolin in sinal an injection has been iven, screw p moves Polystyrene mould, forward it is wise and to presses take a look molten at plastic Δ M throuh = mean both increase M = C W = C rmodynamic machine nozzle processes and that runner/ate prevail system in into melt cavity. C durin The fillin injection process mouldin frequently process. imposes Δp a = hih pressure level differential mechanical and rmal stress on melt. pressure The chief loss) in a flow. This parameters n supplies that affect answers this stress to are : section runner/ate followin questions: m system s 6 Nozzle/ate eometry ρ = melt density V x γ. What Wall sort thickness molded chanes part c p = specific heat capacity. s. occur Fillin in rate molten plastic at individual Moldin staes compound process, and The particular sinificance this what happens Mold wall inside a polymeric melt equation stems from fact that it can. as it cools? What is difference describe process independently between The stress an amorphous actin on plastic melt and as ait flows eometry, can lead to internal melt, semi-crystalline friction processes, plastic. which n cause wall melt to heat up. and rheoloical material values. As has already... mm. Experimental investiations into different been mentioned, ates and different re is no allowance Direction shear y shown that prile in a flowin plastic melt [] M can be described in approximate cold terms mould. as a function. Melt pressure loss durin Fi. : Temperature prile in a p, whereby re is assumed to be no moulded exchane part heat fillin flowin plastic melt [] with mold adiabatic Lookin => Qmore ab = ). closely at tem-. Melt materials [] have mean made for exchane increase heat with Fi. : Temperature perature melt as moulded part is bein filled, it is seen that coolin can have a very considerable influence on melt. A prile, which can Velocity V x

3 . Melt in holdin pressure and coolin phases Once mold has been trically filled, holdin pressure phase commences. In course this phase, melt is conveyed into mold cavity for as lon as possi ble, in order to fset tric contraction. Since flow melt is very small by comparison to flow that prevails durin fillin phase, re is no furr increase in tempera ture as a result internal friction. The melt experiences a steady fall. Immediately after holdin pressure phase comes residual coolin phase. Durin this phase, molten plastic, which has now almost completely soli dified, falls to demoldin. Fi. shows computed priles over crosssection a molded part durin coolin phase panel s = mm, material ABS). The prile flattens out increasinly with time. After approximately 6 s, in middle has fallen to demoldin. It is evident from what has just been said that melt is subject to constant chane durin injection moldin process. Apart from processin parameters injection time, injected compound and runner/ate system, mold coolin system also has a major influence on melt. The coolin mold, in particular, larely determines how uniformly and how rapidly heat is eliminated from plastic in order to permit demoldin. What happens in a plastic melt as it cools? At what does it freeze? How hih is its heat content, i.e. how much heat enery is required to heat or cool plastics? The answers to se questions will be provided in section that follows. x = 66 x mm = 66 mm x = x = mm mm x = x = mm mm. Melt. temp Melt pressure a Once Once mou th trically trically filled, f phase phase comme this phase, this phas me mould mould cavity ca fo order order to fset to o Since Since flow comparison to durin durin filli th furr furr increai a result a result inteo perature perature th steady steady fall. fa Immediately af phase phase comes c phase. phase. Durin D perature perature has now has almos now falls to falls to dem th Fiure Fiure shows priles priles over t.. mm mm.. moulded moulded part d Direction Direction shear shear y y panel panel s = s m p Fi. : Fi. Temperature : Temperature prile prile at different at different flow locations flow locations at time when time when Fi. : Temperature creasin moulded prile part at is different full [] flow locations at time when creasinly wi moulded part is full [] molded part is full [] ximately ximately 6 s, middle middle has fal h. Melt = Melt = C C s s It is evident It is evid fro s s said said that tha subject subject to cons to injection injection mould processin s s time, time, tempera compound compoun an runner/ate sy perature perature cont s s major major influence 6 s 6 s melt. The melt. c particular, particula lar s s uniformly uniforml and eliminated s eliminate from s s permit s permit demould What What happens cools? cools? At wha A w = C w = C freeze? H w = C Thickness molded part [mm] w = C freeze? How h Thickness molded part [mm] i.e. how i.e. much how heat or heat cool or pl c Fi. : Fi. Temperature : Temperature priles priles in a coolin a coolin rmoplastic rmoplastic melt at melt different at different Fi : Temperature priles in a coolin rmoplastic melt at different se se question points points time in computed) time computed) points in time computed) section section that fol th Temperature [ C] Temperature [ C] Polystyrene Polystyrene M = M = C C W = W C = C pt) xz pt) = 7 xz = bar/s 7 bar/s C C t F =. t F = s. s V x =. V x = m/s. m/s COV76/Pae Edition 6-

4 rmoplastic melts Thermodynamic state curve fluid The coolin When rmoplastic heat is eliminated melts, from rmodynamic a state curve polymeric melt, chains lose ir mobility, and sement after sement is free When heat captured is eliminated by from neihbourin a polymeric secondary valence and sement fields. The after melt sement becomes melt, chains. The coolin Glassy state Supercooled Fluid lose ir mobility, rmoplastic is melts captured fluid by neihbourin hihly viscous. amorphous secondary valence Thermodynamic fields. state melt curve becomes hihly viscous. The free ory When fers heat is eliminated a from V G a) semi-crystalline polymeric melt, chains lose ir The free particularly ory appropriate fers a particularly physical appropriate interpretation mobility, and sement after sement V TK ) is p = konst. partial free physical interpretation polymeric polymeric captured melt melt by coolin. coolin. neihbourin Accordin secondary V K ) crystalline to this ory, Accordin it is possible to this to ory, view a it valence polymeric is possible fields. The melt becomes melt as a to view a polymeric melt hihly as a viscous. amorphous vacancysaturated fluid Fi. ). V G ) semi-crystalline vacancy-saturated fluid Fi. ). The free ory fers a particularly appropriate physical interpretation polymeric melt coolin. f V K ) crystalline V = V m + f V TK ) T G = Tp E =const. = konst. T K partial K V V = Overall = V m + V Accordin to this ory, it is possible Temperature T V V m = Partial = overall molecules to view a polymeric melt as a vacancysaturated molecules fluid Fi. ). Fi. : Pressure-- diaram p-v- diaram) V oscillation m = partial expansion ) oscillation expansion ) V f = Free vacancy ) T G = T T K K V f = free vacancy V E = V) m + V f Temperature T V = overall The bottom curve in Fi. is prile tallisin point. Apart from semicrystalline domains, re are amor- V m = partial molecules Fi. : Pressure-- diaram p-v- diaram) for a purely crystalline material. At oscillation expansion ) Fi. : Pressure-- diaram p-v-θ diaram) V crystallisation, T K, phous domains present too. Once f = free vacancy ) material becomes The bottom fully curve crystallised. in Fi. prile tallisin point. falls Apart below from T semicrystalline domains, re behavior are amor- G, se The for a middle purely crystalline curve shows material. At / The free is n zero. In assume lassy state. The free is smaller than falls below for purely T G, se amor- crystallisation a semi-crystalline, material. T K, In phous this class domains present material, too. some Once furr course material process, becomes fully only crystallised. polymer chains are lined up closely in parallel durin oscillation expansion The free is n underoes any chane. crystalline lume is smaller crystallites. than for purely amor- zero. In phous assume materials lassy on state. account The free vo- V m coolin furr course and form process, submicroscopically only component. Inside oscillation expansion crystallites, almost under-completoes any chane. crystalline component. phous materials order prevails, on account with V m exception a few defects. In case amorphous rmoplastics top curve), In case melt amorphous is seen to rmo- for amorphous The superposition and semi-crystalline state curves The superposition state curves V f V By plastics contrast top curve), to purely melt crystalline is seen to for suffer undercoolin as rmoplastics materials, amorphous se and semi-crystalline that is materials f shown on have suffer a undercoolin crystallization as interval falls. Once has fallen diaram instead rmoplastics means a crystallizin that is shown that is point. on falls. Once has fallen diaram means that re is a a certain certain > below lass Apart transition amount time at in > below from lass transition semicrystalline domains, amount time re at each are amorphous TG, in TG, specific domains specific falls present less falls too. less which Once which attendant specific falls be- sharply straiht low sharply T straiht lines have a low can develop. The coolin or heatin G, se lines assume have a low lassy can develop. state. The The free coolin or is heatin radient). At below lass transition rate, and also ambient pressure, radient). At below smaller than lass for transition purely amorphous material is in rate, have and materials a also major influence ambient on account on pressure, state lassy crystalline material state a supercooled is component. in fluid. have curve. a major influence on state The free that exists at lassy state a supercooled fluid. curve. lass transition is frozen The free The superposition that exists at state curves for amorphous and in and remains virtually constant in. Influence ambient pressure lass transition semi-crystalline lassy state. is rmoplastics frozen that is shown in diaram in and remains means virtually that constant re is in a certain.amount Influence If a plastics time melt ambient at is subjected each pressure to pressure and n cooled, lower specific Fi. : Free- model The middle curve shows / accordin to [] lassy state. in which respective specific can behaviour a semicrystalline The material. coolin In this or class heatin If a plastics perature. rate, and melt The also lass is subjected ambient to pres- in s will result at each tem- develop. Fi. : Free- Fi. model : Free- accordin to [] model The overall VThe G is middle obtainedcurve pressure, material, shows some have a / major polymer influence chains sure and on case n state cooled, amorphous curve. lower rmoplastics) and crystallisation tem- specific accordin to [] from sum partial are lined up closely in parallel durin behaviour a semicrystalline partial s will result at each perature. plastics) The will be lass shifted towards hiherin molecules The overall V m oscillation V, expansion G is obtained or free material, V f. The chane some. almost Influence complete polymer order ambient chains prevails, pressure with s. case amorphous rmo- molecules V The overall V G is obtained from sum m oscillation expansion coolin and form submicroscopically perature semi-crystalline rmo- molecules) and vacancymaterial. small crystallites. In this Inside class crystallites mole cules) from and vacancy sum, partial in or free melt are V f. that The lined results up closely exception in parallel a few durin defects. plastics) and crystallisation to pressure semi-crystalline and n cooled, rmo- from a chane in can be Fiure 6 shows correlation between specific and chane in molecules V m oscillation melt that results expansion from a coolin chane and form If a plastic submicroscopically melt is subjected illustrated by means a pressure- means vacancy a pressure- diaram small crystallites. p-v- lower terials, Inside specific se materials s crystallites have will a crysplastics) result at at different will each be. pressures shifted towards for both The an hiher By contrast to purely crystalline ma- in tem perature can be molecules) illustrated and by -, or diaram free p-v- diaram) V f. diaram) The Fi. chane ). Fi. ). almost complete lass tallisation order interval prevails, instead in with a case crys- s. amorphous plastic rmoplastics) a and few defects. crystallization semi-crystalline left) and a semiin melt that results exception The bottom from curve a chane in Fi. in is prile for can a purely be crystalline material. illustrated At crystallization by means, a pressure- T K, By contrast mate- to purely crystalline matween specific and rmoplastics) shift to hiher Fiure s. 6 shows correlation berial becomes - fully crystallized. The diaram free p-v- is n terials, zero. se Fiure materials 6 shows have a correlation crys- different between pressures specific for both and an In furr diaram) course Fi. ). process, only oscillation tallisation interval instead at different a crys-pressures amorphous for both plastic an left) amorphous and a semiexpansion underoes any chane. plastic left) and a semicrystalline plastic riht). The Fiure illustrates differences that prevail between two In case amorphous rmoplastics top curve), classes material as transition from molten state melt is seen to undero undercoolin as to solid phase. The specific is enerally lower for falls. Once has fallen below lass transition T G, specific falls less sharply plastics on account crystallizin component semi-crystalline materials than for amorphous rmo- straiht lines have a low radient). Below lass transition, material is in lassy state structure. a super cooled fluid. The free that exists at lass tran sition is frozen in and remains virtually constant in lassy state. COV76/Pae Edition 6-

5 .pdf.. :6 lass R α >α >α ) S,G freezin line α G α G α G melt α >α >α ) S,G < p <.pdf.. : melt free α S freezin line melt α S lass α >α α >α ) S,G G α S α G freezin line α G lass G R G α G G S G p p α S semi-crystalline phase α S p < p < p melt < p < p melt α S α S >α S >α S α S >α S >α S solidification line solidification line α S p free < p < p α free S p α S melt α S >α S >α S α S semi-crystalline solidification line phase p < p < p α S p < p < p α p S α S α S p α S α S α S semi-crystalline R S p R K K K K S phase S α S p p α Fi. 6: p-v-θ Fi. diaram 6: p-v- a Diaram slowly Fi. coolin 6: a p-v- slowly amorphous Diaram coolin left) G amorphous a slowly and semi-crystalline coolin left) and amorphous semi-crystalline riht) left) plastic and riht) source: semi-crystalline plastic IKV) Source: riht) IKV) plastic Source: IKV) α G With semi-crystalline materials, curve displays a sharp Since molecules are endeavourin to attain a state kink. This sudden chane in specific is due to start internal equilibrium, it is possible for a reduction to occur in crystallization. crystalline plastic The point crystalline riht). The discontinuity plastic Fiureriht). rates. The The Fiure time that rates. is available The time for that anis Fiure available 7 shows for an Fiure shift 7 in shows lass transition to develop sition for an amorphous for an amorphous shift in lass tran- R marks G G excessively S lare R free K subsequent K to production. S illustrates differences illustrates that prevail differences internal that state prevail equilibrium internal state to develop equilibrium crystallizin point between two K. Below classes between this, Temperature material two classes at each material reduction individual as This will occur all more rapidly, Temperature hiher service at each individual be-temperaturcomes molten reduced shorter. stateit is rcomes already shorter. impossible It is already At impossible hiher finished freezin At hiher component freezin a is key word: a post- material two be-different material coolin at two rates. different coolin rates. in specific transition from is due transition molten not only state from to mal oscillation to solid phase. molecules, to The Fi. specific solid 6: phase. p-v- but also Diaram The for specific and a state primarily) a slowly equilibrium coolin for to a state amorphous to develop shrinkae. equilibrium at left) larer and to develop semi-crystalline free at larer is frozen riht) free plastic in, which Source: is frozen IKV) in, which is enerally lower is for enerally semi-crystalline lower for hih semi-crystalline increasin crystallization. When both s. se are superimposedplastics this leads on account to plastics parabolic crystallisin on account curve prile crystallisin for As coolin rate increases, no furr increase comes hih s. means that overall means that in overall in materials than for materials amorphous than rmo- for amorphous rmo- solid phase is reater. solid phase is reater. semi-crystalline component phase. structure. component structure. about in specific, however, and re is no furr crystalline plastic riht). The Fiure rates. The time that is available slow isobaric coolin slow for. isobaric Fiure C/scoolin 7. shows C/s shift in lass transition chane in lass transition. The specific With semi-crystalline With illustrates materials, semi-crystalline differences materials, that prevail internal state equilibrium rapid isobaric coolin rapid to develop. isobaric d C/scoolin. d C/s for an amorphous curve displays a curve between sharp displays two kink. This a classes sharp kink. material This as at each individual and lass transition becomes shorter. ume and It. is already lass transition impossible At hiher freezin strive towards a limit a material. two different The coolin specific rates. vol-. Influence sudden chane coolin in sudden specific rate chane transition in isspecific from molten is state. due to start due to crystallisation. to solid start phase. The crystallisation. The specific The for a state value. equilibrium to develop at larer free is frozen in, which point discontinuity point is enerally marks discontinuity lower for semi-crystalline marks hih s. means that overall in The specific that cm crystallisin point cm crystallisin materials results than at room is similarly a function coolin K. Below point for this amorphous K. Below rmoplastics rate. on this solid phase is reater. bar bar reduction in specific account In reduction case in crystallisin specific amorphous rmoplastics, is lass due component not transition only to is due structure. not only to will move towards reduced hih values rmal at reduced hih oscillation coolin rmal rates. oscillation The time that is slow isobaric Pressure coolin. p C/s.. K K molecules but also molecules With semi-crystalline and primarily) but also toand primarily) materials, to rapid isobaric coolin. d C/s available for an internal state equilibrium to develop at increasin crystallisation. curve increasin displays When crystallisation. a sharp kink. WhenThis each individual both se are both sudden superimposed, becomes se chane are this superimposed, in shorter. specific It is this already is. im possible leads for to a state parabolic leads due equilibrium curve to to prile parabolic start for to develop crystallisation. curve prile at hih forthetem- peratures. G Δv Δv Δ Δ semi-crystalline point phase. semi-crystalline discontinuity phase. marks cm G crystallisin point K. Below this bar reduction in specific. Fi. 7 shows shift in.lass Influence transition is coolin due not rateonly to for. an. Influence coolin rate amorphous material at two reduced different rmal coolin oscillation rates. At hiher freezin The specific that results at. K The specific molecules that a results larer but free also and at primarily) is frozen to in, room increasin crystallisation. similarly When a room is similarly a C which means that overall C function both se coolin are in superimposed, rate. solid In phase casethisis function coolin rate. In case reater. leads amorphous to parabolic rmoplastics, curve prile for amorphous rmoplastics, Δv lass transition will move Fi. 7: Comparison slow and rapid isobaric coolin Δ semi-crystalline phase. G an amorphous lass transition will move Fi. 7: Comparison slow and rapid isobaric coolin an amorphous towards hih values at hih coolin rmoplastic Source: IKV) towards hih values at hih coolin rmoplastic Source: IKV). Influence coolin rate. The specific that results at room is similarly a function coolin rate. In case amorphous rmoplastics, lass transition will move towards hih values at hih coolin Fi. 7: C Fi. Comparison 7: Comparison slow and slow rapid and rapid isobaric isobaric coolin coolin an amorphous an amorphous rmoplastic rmoplastic Source: source: IKV) IKV) COV76/Pae Edition 6-

6 Fi. shows correlation between specific at RT, in a normal atmosphere, and coolin rate and pressure durin coolin phase. Since molecules are endeavourin Since to attain molecules a state are internal endeavourin equilibrium, to attain it is possible a state for a internal reduction equilibrium, to occur it is in possible excessively for a reduction lare free to occur in subsequent excessively to production. lare free This will subsequent occur all to more production. rapidly, This hiher will occur service all more rapidly, hiher finished component service is key word: finished post- component is key word: post- As coolin rate increases, no furr increase coolin rate comes increases, about in no specific fur- As r, increase however, comes and about re in specific is no furr chane however, in and lass re is transition no fur-, r. chane in The specific lass transition and. lass transition The specific strive and lass towards transition a limit value. strive Althouh specific becomes larer shrinkae. as coolin rate increases, it relatively soon strives towards shrinkae. a limit value. This means that, with standard coolin rates > C/s that are encountered in practice, a constant increase in can be expected. In case semi-crystalline plastics, a reater towards a limit specific value. is similarly seen with hiher coolin rates. The crystalli zation conditions deteriorate. The deree crystallization is lower and specific becomes phase. larer. At an elevated coolin rate, however, crystallization phase. remains virtually constant. With se hih coolin rates, it must be born in mind that post-crystallization and hence a sub sequent reduction in specific can occur. This is frequently cause warpae and dimensional deviations in molded expected. parts. Efficient, uniform mold coolin is thus essential in case semicrystalline plastics. The properties molded part are determined by processin operation in mold. If, for instance, identical coolin rates are achieved in all areas molded part, throuh identical coolin conditions, n this will mark a major step in direction identical molded part properties. Meltin It is clear from p-v- diaram that rmoplastics do not possess a meltin point in sense a specific at which material chanes its areate state melt -> solid). Thermoplastics have a meltin rane or a freezin rane. This transition, or start chane from molten phase to solid phase, is known as lass transition or freezin for amorphous rmoplastics. The value this 6 is a function coolin rate and ambient pressure see Fis. 6 and 7). In case semi-crystalline rmoplastics, 6 reference is made to crystallization. This crystallization is a function pressure and is hardly affected by coolin rate Fi. ). There can, however, be differences in coolin and meltin semi-crystalline rmoplastics. Fi. shows difference between slow isobaric coolin and heatin at ambient pressure, and at bar, for a polypropylene rade. It is only when crystallization established in slow coolin test has been surpassed by a considerable marin that straihtline curve for melt is attained. The point contact characterises crystallite meltin, and is denoted as crystalline meltin point KS. COV76/Pae 6 Edition 6- cm cm.. K K 6 bar 6 bar Fiure shows correlation between specific at RT, in a Fiure shows correlation between specific at RT, in a normal atmosphere, and coolin rate and pressure durin coolin normal atmosphere, and coolin rate and pressure durin coolin. Althouh specific becomes larer as coolin rate increases, it. Althouh specific becomes relatively soon strives towards a limit larer value. as This coolin means rate that, increases, with it relatively standard soon coolin strives rates towards > a limit C/s value. that are This encountered means that, in with practice, a standard constant coolin increase rates in > can C/sbe that are encountered in practice, a C/s constant increase in can be d Mean coolin rate dt expected. G C/s In case semi-crystalline plastics, d a reater specific is similarly Fi. : Specific Mean as coolin a function rate dt coolin rate and pressure an G In seen case with hiher semi-crystalline coolin rates. plastics, Fi. The: Specific amorphous rmoplastic a function Source: IKV) coolin rate and pressure an a reater crystallisation specific conditions is deteriorate. similarly Fi. : Specific as a function coolin rate and pressure an amorphous rmoplastic Source: IKV) seen The with deree hiher crystallisation coolin rates. is The lower amorphous rmoplastic Source: IKV) crystallisation and specific conditions deteriorate. becomes slow isobaric coolin. C/s The larer. deree At an crystallisation elevated coolin is lower rate, rapid isobaric coolin. C/s and however, specific crystallisation becomes slow isobaric coolin. C/s At an remains elevated virtually coolin constant. rate,. larer. however, With se hih crystallisation coolin rates, it must rapid isobaric coolin. C/s bar be born remains mind virtually that post-crys- constant.. tallisation and hence a subsequent cm bar With se hih coolin rates, it must K be reduction born in mind that specific post-crystallisation can occur. This and is hence frequently a subsequent cause cm reduction warpae in and dimensional specific deviations can K occur. in moulded This is parts. frequently cause warpae and dimensional deviations in moulded Efficient, parts. uniform mould coolin is. thus essential in case semicrystalline 6 uniform plastics. mould The coolin properties is Efficient,. thus essential moulded in part are case determined semicrystalline 6 by processin plastics. The operation properties in mould. moulded If, part for instance, are determined identical by coolin processin rates are achieved operation in in all mould. areas If, for moulded instance, part, identical throuh coolin identical rates coolin are achieved conditions, in n all this.7 areas will mark a moulded major step part, in throuh direction identical identical coolin moulded conditions, part properties. n this.7 will mark a major step in direction identical moulded part properties. C Fi. : Comparison slow and rapid isobaric coolin a C semi-crystalline rmoplastic at two different Temperature pressures Source: IKV) Fi. : Comparison slow and rapid isobaric coolin a semi-crystalline Fi. : Comparison rmoplastic slow at two and different rapid isobaric pressures coolin Source: IKV) a semi-crystalline rmoplastic at two different pressures source: IKV) cm... isobaric heatin isobaric coolin meltin line d dt ) =. C/s G bar K C Fi. : Slow isobaric coolin and heatin a semi-crystalline rmoplastic Fi. : Slow isobaric Source: coolin IKV) and heatin a semi-crystalline rmoplastic source: IKV) bar erature K C solidification line meltin rane raw material producer). Melt It is clear from p-v- rmoplastics do not meltin point in sense at which t chanes its areate > solid). Thermoplastics in rane or a freezin rane. This transition, or s chane from molten solid phase, is known a transition or for amorph plastics. The value this is a function coolin ambient pressure see F In case semi-crysta plastics, reference is m crystallisation temperatu tallisation is pressure and is hardl coolin rate Fi. ) however, be differences and meltin semi-cryst plastics. Fiure shows di tween slow isobaric co heatin at ambient pres one hand, and at bar hand. It is only when established coolin test has been su considerable marin that line curve for melt is point contact charac tallite meltin and is de crystalline meltin point The hysteresis between coolin is due to suppr tallisation durin coolin pressed crystallisation o

7 The hysteresis between heatin and coolin is due to suppressed crystallization durin coolin. This suppressed crystallization occurs already at very low coolin rates []. In or words, crystallization sets in at lower s. With coolin rates encountered in practice >>. C/s) fall in crystallization is more or less constant Fi. ). State curve durin injection moldin Usin p-v- diarams that have been presented, it is possible to show rmodynamic state curve prevailin durin injection moldin for three process staes molded part fillin, holdin pressure phase and residual coolin phase. C Fi. : Slow isobaric coolin and heatin a semi-crystalline rmoplastic Source: IKV) Crystallisation K C 6 meltin rane raw material producer) bar Fiure shows dif tween slow isobaric co heatin at ambient pres one hand, and at bar hand. It is only when established coolin test has been sur considerable marin that line curve for melt is a point contact charact tallite meltin and is de crystalline meltin point The hysteresis between coolin is due to suppr tallisation durin coolin pressed crystallisation oc low coolin rates already words, crystallisation set s. With coolin rates en practice >>. C/s crystallisation temperatu less constant Fi. ). This is done by transferrin pressures and s that prevail durin different process staes to a p-v- diaram, on an isochronous basis. Fiure shows a measured pressure prile close to ate and a computed mean prile inside moldin in course injection moldin cycle. The numbered points are transferred to material s p-v- diaram Fi. ). mouldin The state points plotted on Fis. and indicate followin: mouldin Start mold fillin melt touches pressure sensor) Mold is trically full End compression phase Switchover to holdin pressure partial dischare cavity with melt flowin into melt antechamber) Holdin pressure level 6 Gate has frozen 7 Pressure has sunk to atmospheric pressure start shrinkae) Mean melt has attained freezin Demoldin Fi. ). Molded part has reached room Based on state curves like this, it is possible to make meaninful statements on course shrinkae and follows: on Start mould fillin movement melt at each stae process. Point 7 Start mould fillin on Fiures attainment atmospheric pressure) is important for start shrinkae. This point can occur at different s with different holdin pressure melt flowin priles into melt and coolin conditions. It is possible to influence antechamber) shrinkae in Holdin pressure level this way. melt flowin into melt C/s d Mean coolin rate dt ) K Fi. : Influence coolin rate on crystallisation Source: IKV) Fi. : Influence coolin rate on crystallization source: IKV). State curve durin injection bar Usin. State p-v- curve diarams durin injection that have C been presented, it is possible to bar mean moldin compound portray rmodynamic state curve in mold T M prevailin Usin durin p-v- diarams injection mouldin that have C for been three presented, process it staes is possible moulded portray part fillin, rmodynamic holdin pressure state phase curve in mold T M to mean moldin compound and prevailin residual durin coolin injection phase. mouldin for three process staes moulded part is done fillin, by holdin transferrin pressure phase This pressures and residual and coolin s phase. that prevail durin different process staes This is to done a p-v- by transferrin diaram, on an mould pressure isochronous pressures basis. and s Fiure shows thata 6 start shrinkae 7 measured prevail durin pressure prile different close process to ate staes and to a a computed p-v- diaram, mean isochronous prile basis. inside Fiure mouldin shows ina 6 start shrinkae on an mould pressure s Time 7 t measured course pressure injection prile close mouldin to cycle. ate The and numbered a computed points mean are to prile material s inside p-v- mouldin diaram Fi. : in Pressure cycle and [] prile Time durin t injection moldin transferred Fi. : Pressure and prile durin injection mouldin s course injection mouldin cycle [] cycle. The numbered points are transferred meanins to material s state p-v- points diaram cycle [] Fi. : Pressure and prile durin injection mouldin The plotted Fi. ). on Fis. and are as. follows: cm Material: polystyrene The meanins state points plotted on Fis. and are as.. melt touches pressure sensor) cm Material: polystyrene Mould is trically full 6. 7 End melt touches compression pressure phasensor). Switchover to holdin pressure Mould is trically full ~ tric partial dischare cavity with shrinkae 7 6 End compression phase. V 6 Switchover to holdin pressure. ~ tric partial dischare cavity with shrinkae V 6. 6 Gate antechamber) has frozen Pressure Holdin pressure has sunk level to atmospheric. 6 Gate has pressure frozen C start shrinkae) Pressure has sunk to atmospheric pressure Temperature T Mean melt has. attained freezin Fi. : State curve durin injection mouldin C start shrinkae) Temperature T Demouldin Mean melt has Moulded attained part freezin has reached room Fi. : State Fi. : curve State durin curve durin injection moldin mouldin[] Demouldin Takin Moulded state curves part has like reached this, it is room possible to make meaninful statements on course shrinkae and on movement Takin state curves melt like at each this, it stae is possible process. to make Point meaninful 7 on statements Fiures on attainment course shrinkae atmospheric and pressure) movement is important melt for at each start stae on shrinkae. process. This Point point 7 can on occur Fiures at different attainment s atmospheric with different pressure) is pressure important priles for and start coolin holdin conditions. shrinkae. It This possible point can to occur influence at different s in this way. with different shrinkae holdin pressure priles and coolin conditions. It is possible to influence shrinkae in this way. Pressure Pressure p p Specific Specific v v Temperature Temperature T T COV76/Pae 7 Edition 6-

8 If taret a short cycle time is to mm be fulfilled, n it is essential for 6. Demouldin material-dependent demouldin tem- to be known. Mouldins are and coolin timeperature frequently left in mould for too s) mm lon, in order to be on safe side, An injection moulded althouh part cannot, coolin or time to should not be demoulded demouldin until it has has lon 6 E cooled C) to point since elapsed. where it is Demoldin dimensionally stable. The Knowlede ejector pins demouldin not be is allowed important on economic 6 mm Fi. : Influence demouldin 6. Demouldin on coolin and ir time holes should and coolin time rounds. Fiure shows influence demouldin to leave pronounced marks on s) mouldin. An injection moulded part cannot, or on expected coolin time. The should not be demoulded until it has lower demouldin is, t k cooled to point where If it is loner coolin time will be. taret a short cycle time is to E dimensionally stable. The ejector pins 6 mm mm and ir holes should not be be allowed fulfilled, n it is essential The demouldin for, by to leave pronounced marks material-dependent on demouldin definition, is to be known. Mouldins are that mouldin. prevails at a point moulded part t in central layer wall k If taret a short cycle frequently time is to left in thickness mould at for too time demouldin. mm be fulfilled, n it is essential mm lon, for in order to be on Fiure safe shows side, a prile material-dependent demouldin to be known. Mouldins althouh are coolin time to in a rmoplastic mouldin at time demouldin. frequently left in mould demouldin for too has lon mm lon, in order to be on safe side, 6 E C) since elapsed. Alonside this, a mean demouldin althouh coolin time to, demouldin has lon E, is frequently to be Demoldin found. This is interal mean value 6 E C) since elapsed. W Knowlede time will be. demouldin tem- is important demouldin. on economic prile at time Demoldin Fi. : Influence demouldin on x coolin timeknowlede demouldin Fi. Fi. : : Influence demouldin demoldin on coolin timeon coolin time perature is important on economic rounds. Fiure shows influence mouldin demouldin at time demouldin, Wall Wanddicke thickness rounds. s Fi. : Temperature prile in a rmoplastic Fiure shows influence demouldin on expected coolin time. on The expected demouldin coolin time. E in The centre lower demouldin lower is, demouldin is, loner coolin time will be. loner coolin time will be. E The demouldin, by E definition, is that The demouldin, by prevails at a point moulded part demoldin. in central layer definition, wall is that E thickness at time demouldin. prevails at a point moulded part Fiure shows a prile in a rmoplastic mouldin in at timecentral layer wall demouldin. thickness at time demouldin. Fiure shows a prile Alonside this, a mean demouldin, E, is frequently in a to rmoplastic be mouldin at time found. This is interal mean demouldin. value W prile at time W x demouldin. x Alonside this, a mean demouldin Wall Wanddicke thickness s Fi. : Temperature prile in a rmoplastic Fi. Wanddicke specific 6: Mean demouldin case mouldin at time demouldin,, E, is frequently be established? Wall thickness s to E be demouldin E in centre found. This is interal mean value prile at time Fi. W : Temperature prile in a rmoplastic x mold in at time demoldin, demoldin Wall Wanddicke thickness ^ θ E in scenter E t k Fi. 6: Mean demold in θ E 6 mm demouldin. Fi. : Temperature prile in a rmoplastic mouldin at time demouldin, demouldin E in centre dimensionally stable. The ejector pins and ir holes should not be allowed to leave pronounced marks on mouldin. 6 Demoldin and coolin time An injection molded part cannot, or should not be demolded until it has cooled to point where it is dimensionally stable. The ejector pins and ir holes should not be allowed to leave pronounced marks on moldin. If taret a short cycle time is to be fulfilled, n it is essential for material-dependent demoldin to be known. Moldins are frequently left in mold for too lon, in order to be on safe side, althouh coolin time to demoldin has lon since lapsed. Knowlede demoldin is important on economic rounds. Fi. shows influence demoldin on expected coolin time. The lower demoldin is, loner coolin The demoldin, by definition, is that prevails at a point molded part in central layer wall thickness at time demoldin. Fi. shows a prile in a rmoplastic moldin at time Alonside this, a mean demoldin, E, is frequent ly to be found. This is interal mean value prile at time demoldin. How can correct demoldin s for a First all, raw materials manufacturers issue recommendations as to mean demoldin s for ir products Fi. 7). If re is no recommended uide available for demoldin, it can be established from shear modulus curve material in question [6]: Abbreviations Thermoplastics Mean demoldin s C) Guide values)* W To ensure successful demoldin, mean x E PC-HT Apec HT E Fi. 6: Mean demouldin Wall Wanddicke thickness s E or in center molded part ^ E, must not lie within rane where plastic yields and is not able PC+ABS) Bayblend to absorb any force. It is possible to establish this from shear modulus curves. Fiure shows shear PC Makrolon modulus curve for an ABS. Above a some 6 C, shear modulus falls sharply, which means that dimensional stability is no loner uaranteed. The maximum * It may be necessary to deviate from values in table dependin on W product rade. x possible demoldin is thus approximately Fi. 6: Mean demouldin 6 C. Wall Wanddicke thickness s E Fi. 7: Recommended mean demoldin s for a number rmoplastics [] E max = 6 C If no shear modulus curves are available, n maximum permitted demoldin for a iven material can be determined from p-v- diarams described above. In case amorphous materials, this can be stenin or lass transition and, in case semi-crystalline materials, crystallization. For ABS shown in Fi. shear modulus curve), a approximately C is obtained as stenin from p-v- diaram. This tallies well with value from shear modulus curve. If no curves are available, n demoldin can be taken as bein equivalent to heat deflection Vicat ). COV76/Pae Edition 6-

9 ane where s not able to is possible to ure from shear shows for an ABS. f some 6 C, sharply, which l stability is no he maximum emperature is C. i curves are imum permitted re for a iven ined from ibed above. In materials this emperature or rature and, in lline materials, rature. For shear modulus f approximately stenin p-v- diaram. value from able, n e can be taken o heat deicat tempera- N ) mm. Shear modulus G C + solid = 6 C = E max Fi. : Determination maximum demouldin from a shear Fi. : Determination modulus curve maximum demoldin from a shear modulus curve, material ABS cm... mean coolin rate, slow isobaric coolin ABS bar 6 E max = C. C Fi. : Demoldin from p-v- diaram, material ABS Fi. : Demouldin from p-v- diaram, material ABS Temperature C.6 mm. mm Demoldin Centre s = mm Moldin material: polystyrene s = 6 mm M = C TM = C.6 mm Ede 7 s 7 Time Fi. : Temperature prile in a plastics mouldin before and after demouldin COV76/Pae Edition lo. dampin decrement Λ Measurement demoldin [7] As has already been mentioned, demoldin represents a key criterion for both requisite coolin time and dimensional stability demolded part. This should refore be verified as precisely as possible on a part that has just mean been coolin demolded. rate, slow cm After ejection, surface molded part rises fairly rapidly to reach a peak value and n falls radually Fi. ). This increase is due to equalization prile that developed durin coolin and is. particularly pronounced with larer wall thicknesses). The maximum value measured should be taken as demoldin, since this ultimately constitutes a measure mean molded part. Measurin demoldin. is important not only 6 for optimizin coolin time but also for monitorin mold. With an effective form mold control which presupposes no major differences in wall thickness over molded part), mean demoldin measured should be as constant as possible over 6. all different reions moldin. Any differences would suest that mold control has not been efficiently confiured. Measurement demouldin [7] Temperature-controllable contact sensors or noncontact As has already been mentioned, E max = C demouldin infra red. measurin represents cells a can suitably be used for measurin key criterion for both requisite C demoldin. coolin time and dimensional stability demoulded part. This Fi. : Demouldin from p-v- diaram, material ABS should refore be verified as precisely as possible on a part that has just been demoulded. After ejection, surface moulded Cpart rises fairly rapidly to reach a peak value and n falls radually Fi. ). This increase is due to equalisation prile that developed durin Demoldin Moldin material: polystyrene coolin and is particularly pronounced s = 6 mm with larer wall thicknesses). Centre s = mm M = C The maximum value measured should TM = C be taken as demouldin.6 mmtem- perature, since this ultimately constitutes a measure. mm mean moulded part. Measurin demouldin.6 mm is important not only for optimisin coolin time but also Ede for monitorin mould. With an effective form mould 7 s 7 control which presupposes no major Time differences in wall thickness over moulded Fi. part) : Temperature mean demouldin prile in a plastics mouldin before and after demouldin Fi. : measured Temperature should prile be as in a plastics moldin before and after constant as possible demoldin over all different reions mouldin. Any differences would suest that mould control has not Temperature 7. Coolin time been efficiently confiured. isobaric coolin ABS Temperature-controllable contact sensors or noncontact infrared measurin cells can suitably be used for measurin demouldin. bar Strictly speakin, coolin phase in injection moldin commences with injection sinal and ends with open mold sinal. This is because as soon as hot molten plastic comes into contact with cooler mold wall at any point in mold, coolin n commences in this reion. Measures should be taken, however, to prevent mold from freezin durin fillin phase. The loss heat to mold wall should be fset by flow heat. Most heat is released durin residence time holdin pressure phase and residual coolin phase). Measurem demouldin As has alread demouldin te key criterion coolin time stability th should re precisely as p just been dem After ejection, moulde to reach a pe radually Fi due to eq perature pri coolin and is with larer wa The maximum be taken as perature, sin stitutes a m moulded part demould portant not o coolin time b effective form control which differences in moulded part m constant as p ferent reion differences w mould tempe been efficientl Temperaturesors or nonco cells can suit urin dem

10 time, or time by which demouldin see above) will have been attained. In case a flat panel, where an exchane heat t K =.6.7 t K = s Simple coolin equations can be used to estimate coolin only time, takes or time place by which over demoldin panel nozzle side for a box-shaped molded part. The Fiure shows computed mold surface on see thickness, above) will have followin been attained. equation In can case a flat distribution shown is obtained as a result panel, where an exchane heat only takes place over be used to estimate coolin time Even if just an coolin estimate, channel this positions simple and or control panel thickness, followin equation can be used to conditions coolin medium, flow rate). The for furr coolin time equations see example serves to show that if too low estimate coolin time for furr coolin time equations control for top and lateral surfaces see ATI Technical e, Thermal Information Mould Optimized Desin, Mold by Temperature a demouldin molded part is not is selected, optimally confiured. Control ). same author): this will have a pronounced effect on coolin time. The In box has example a uniform iven, wall thickness yet, despite this, different coolin demouldin times result tem- for different reions on account s C lower t K = In M perature extends coolin time by π W dissimilar mold surface s. a eff π E W some %! t K = Coolin time The example already set out above will be used once aain s t = Wall K = coolin thickness to show how coolin time can be estimated for different wall s. time The lenth coolin time is influenced not only by demouldin a eff = Effective conductivity s = wall thickness M = Moldin compound at end fillin phase a eff = effective but also by mould wall W = Mean mold wall Example: Mold ^ E = Demoldin conductivity at center molded. part Wall For thickness: influence s = mm M = moldin compound wall thickness Effective s and rmal melt diffusivity tem-operature, also has a ABS: face s. a eff =. mm /s The fact that correct demoldin at end fillin Demoldin : and also influence E = C decisive influence phase on cost efficiency production mould has Melt after fillin: on quality M = C already Beispiel: been Entformunstemperatur mentioned in previous chapter. W = mean mold wall moulded A simple Wall Center top and ßen von parts see ATI e, Thermal example will be iven to illustrate this. lateral surfaces: WD C u enomnd endet Effektive Temperaturleitfähikeit Platte E mit = Wanddicke: demoldin at s Mould = mmdesin Wall by same author.) Ede top: WR C The recommended centre demoldin molded part für ABS: a for eff =, mm a molded /s öffnen. Massetemperatur nach der Füllun: part in ABS is approximately C. How is M coolin Fiure = C time shows Employin computed coolin mould time formula and conditions nststfeuwand Entformunstemperatur in der Formteilmitte: Mittlere Werkzeuwandtemperatur: affected The fact if that part is demolded correct demouldin at approximately W = C surface C specified, two on coolin nozzle times are obtained for two wall s: instead C? E = C zeu bereich von die fluence on cost efficiency pro- Example: Demoldin Demouldin Ede top: t WD Beispiel: Entformunstemperatur also has a decisive in- E side = C for a box-shaped moulded part. Center top and lateral surfaces: t WR s eßen s u enomund endet Panel Effektive with Temperaturleitfähikeit a wall thickness : für ABS: as mm in Effective Panel previous with rmal a wall thickness diffusivity chapter. : A ABS: simple ex- eff =, mm /s Kühlzeit Platte duction mit : has Wanddicke: already been mentioned in s = mm a eff, s mm = /s Since mm demoldin E = C applies to both, üllphase öffnen. Massetemperatur ces with Polymer Effective tample melt will rmal be iven diffusivity to after illustrate ABS: fillin: this. M a eff =. mm cycle /s time is increased by approximately % throuh e verhinrlust zur Entformunstemperatur wall : in der Formteilmitte: after fillin: W C M = Cloner coolin time that is required for center K = mm nach der Füllun: C C In π, mm / s with Mean Mouldin mold compound s M = C nststfeuwand Mittlere Werkzeuwandtemperatur: π C C W = C E = C kzeu ie because Fließdenreich Die die be- Demoldin Mean mould The recommended wall : at demouldin center molded part: Example: W = top Cand lateral surfaces. t Mold n plastic ^ Demouldin K =,6,766 E = C at centre moulded for a moulded part in ABS is part: E = E C = C e cooler ^ er Stand- approximately C. How is E = C E = C tkühlzeit Different mold wall s mean different coolin e mould, K = s : estkühl- zeit rlust bzw. zur C C rates and hence different properties, such as shrinkae, surface appearance, structure and warpae. Füllphase in this Coolin coolin time time : Kühlzeit : mm affected if C part C is t e verhin- demoulded K = In π, at approximately C instead mm mm at / s π C C C? however, K In π. mm These two examples have shown just how sensitively Entfor- K.6 In / s C C die Fließdenben) Die er- important control in mold and optimum t π C C freezin K =,6,766 π C C coolin time responds to processin conditions and how er e Abkühlrden. Restkühl- Für loss Stand- K t be fset K K =,6 s,7 processin conditions are for cost-efficient production. r uantity nur der K tkühlzeit residence K = s : /kstenk.cer BLOCK NUMBER: BLOCK TEMP [de. C].77 to 6.7 richtun e and recan be K.6 In C C.77 zeit olender bzw. 7. schätzen Entforben) siehe er- wenn es sich nur um eine Abschät- Lae der Kühlkanäle und der übrien Dieses Coolin t K =.6 einfache time : In Beispiel C C π C zeit auch C Formteil darestellt. Aufrund der.. erkzeuitfähikeit Abkühlrden. Für er Entformunstemperatur die Kühltemperatur, Strömunseschwindizun 6.77 t handelt, daß e coolin π sich bei zu niedri- Temperierverhältnisse Kühlmedium- K =,6,7 C C.. r nur debove) will K = s der zeit t K stark.6 ändert..7 Im Beispiel wird keit) eribt sich die darestellte Temperaturverteilun. Die Deckfläche und. nrichtun durch die um C niedriere Entformunstemperatur t K = s die Kühlzeit um die Seitenflächen des Kästchens wer-..67 folender case a e heat. schätzen ca. Dieses %!) einfache verlänert. Beispiel zeit auch den Formteil nicht optimal darestellt. temperiert. Aufrund der e panel. en siehe Even wenn if es just sich an estimate, nur um eine this simple Abschätzun if handelt too der low Entformunstemperatur, a demoldin daß sich bei zu niedri- hat Das Temperierverhältnisse is selected, Kästchen this besitzt will eine Kühlmedium- leichmäßi- /schl/kasten example Lae serves der Kühlkanäle to show und der übrien 6.7 ation erkzeuitfähikeit Autor) auch die Werkzeuwandtemperatur verschiedenen e Wanddicke, und Wandn trotzdem ereben can that Neben lin time Even if just an estimate, this simple The distribution shown is y z have auch er Entformunstemperatur a die pronounced Werkzeuwandtemperatur effect on die Kühlzeit coolin e temperatur, time. Wanddicke, In Strömunseschwindikeit) aufrund eribt example einen und trotzdem ereben tions see example serves to show that if too low obtained as a result coolin x Ende esin, by a demouldin iven, stark Einfluß ändert. auf C die lower Im Läne Beispiel demoldin der Kühlzeit. durch wird is selected, sich channel positions extends sich der die unterschiedlichen darestellte Temperaturverteilun. Die Deckfläche und MOLDFLOW and or this coolin Einfluß die um will have time der a pronounced by Wanddicke C some niedriere %! s und Entformunstemperatur sowie die Kühlzeit Einfluß der um unterschiedliche die Seitenflächen Kühlzeiten des Kästchens Fi. für : die Calculated wer- je- mold surface on nozzle der Werkzeuoberflächenn effect on control conditions Fi. : Computed coolin medium, Employin flow rate). coolin time formula. Cycle time mould surface on nozzle side a box-shaped moulded part - Massetemperatur coolin time. In example iven, Werkzeutemperatur ca. %!) verlänert. auf die Qualität weilien den nicht Bereiche. optimal temperiert. side a box-shaped molded part and conditions specified, two The lenth C lower coolin demouldin time is influenced extends coolin but also time by by and mold lateral wall tempera- surfaces moulded periodically repeated. It is made up The not only by control coolin for times are obtained top for two The cycle time is time interval at The cycle time can be shown in r in der der Formteile siehe ATI, Thermische Neben der Werkzeuausleun, Entformunstemperatur leicher hat Zur Das Abschätzun Kästchen besitzt der Kühlzeit eine leichmäßi- wall s: which production sequence is raphic form as below: demoldin Centre top bei and den lateral surfaces: from individual production steps The different times can be different ture some for %! influence wall thickness part s is and not optimally melt confiured. t WD s and ancillary time. lenths as a function processin conditions., and also influence mold Ede top: t WR s Cycle time = fillin time + holdin urde Endeer- einen Einfluß auf die Läne der Kühlzeit. Bild Einfluß ist der eine Wanddicke berechnete s und Werk- der riffen. Werkzeuoberflächenn wird sich das aufrund obie der Beispiel unterschiedlichen erneut aufe- pressure time + residence time residual coolin time) + ancillary time. or residual coolin time accounts for Normally, however, residence time on The lenth quality molded coolin parts, time see is influenced not Mold only Temperature by demouldin Control. yet, despite this, different E = C applies to both, cycle larest time span. Technical The box Information has a uniform wall Since thickness demouldin ormuns- dend d- die zeuoberflächentemperatur Massetemperatur sowie Einfluß auf der unterschiedliche Kühlzeiten für die je- Im Optimized coolin time is increased by approximately Openin and closin mould, % throuh loner coolin time ejection, switchover time and, where e but also by mould wall times result for different reions ktion behes in der Bei- der Formteile siehe ATI, Ther- Düsenseite Werkzeutemperatur für ein kastenförmies auf die Qualität weilien Bereiche. that is required for centre top appropriate, plasticisation time.) COV76/Pae. For influence account dissimilar and mould lateral surfaces. r surface s. Different mould wall s wall thickness s and melt, and also influence hence different properties, such as Edition mische 6- Werkzeuausleun, leicher Zur Abschätzun der Kühlzeit mean different bei coolin den rates and f fillin Beispiel: Autor) Werkzeutemperatur verschiedenen Wandn shrinkae, surface appearance, structure and out warpae. above Fillin time Holdin pressure time Residence time/residual coolin time Ancillary time mould on quality The example already set eine urde Ent- er- wird das obie Beispiel erneut aufe- perature moulded parts see ATI e, Thermal will be used once aain These to show two examples how have shown just The distribution shown obtained as a result cooli channel positions and oth control conditions co in medium, flow rat The control for t and lateral surfaces mould part is not optimally confiured. The box has a uniform wall thickne yet, despite this, different cooli times result for different reions account dissimilar mould s The example already set out abo will be used once aain to show h coolin time can be estimated different wall s. Wall thickness: s = m Effective rmal diffusivity ABS: a eff =. mm Demoldin : E = Melt after fillin: M = Wall Centre top and lateral surfaces: WD Wall Ede top WR

11 ime formula cified, two d for two surfaces: emperature th, cycle proximately coolin time tre top Cycle time surface on nozzle side a box-shaped moulded part /schl/kasten y z The cycle time is time interval at which production sequence. Cycle time is periodically repeated. It is made up from individual production steps and ancillary time. The cycle time is time interval at which production sequence is Cycle periodically time repeated. = fillin It time is made + holdin up pressure time + residence from individual production steps The different times can be different time and residual ancillary time. coolin time) + ancillary lenths as a time function openin processin and closin mold, ejection, switchover conditions. time and, where appropriate, Cycle time = fillin plasticization time + holdintime). pressure time + residence time residual coolin time) + ancillary time. The cycle time can be shown in raphic form as below: The cycle time can be shown in raphic larest time form span. as below: Openin and closin mould, The different times can be different lenths as a function ejection, switchover time and, where appropriate, processin plasticisation conditions. time.) Normally, however, residence time or residual coolin time accounts for larest time span. x Normally, however, residence time or residual coolin time accounts for Fillin time Holdin pressure time Residence time/residual coolin time Ancillary time Specific Specific enthalpy enthalpy h h number pressure dependence amorphous and specific semicrystalline enthalpy plays rmoplastics. only a minor Since role display a more or less stead time Whilst as amorphous ones. rmopla pressure by comparison dependence to its dependence plays order only a minor manitude role display a sharp a bend more in or less curve stead for specific Whilst crease in amorphous ir specific rmopla enthalpy, enthalpy by approximately comparison to %/ its dependence diarams measured order at p = manitude bar can crystallisation a sharp bend interval. curve for bar) crease crystalline ir rmoplastics specific enthalpy, in approximately suitably be applied in %/ practice. bar) crystalline rmoplastics in diarams measured at p = bar can crystallisation interval. suitably be applied in practice. HDPE mperatures rates and ies, such as rance, struce shown just olin time conditions emperature optimum for cost-. Coolin Heat time content for a specific point a in cavity. molten Heat content plastic a molten plastic Cycle time Before requisite coolin capacity The term specific enthalpy denotes A comparison two classes Before mould requisite coolin control capacity system mass-related The term specific heat enthalpy content denotes a material mass-related a function heat content a ma- and materials shows have a that considerably semi-crystalline hiher material A comparison shows that semi-crystalline two classes Heat can be content established, a molten it is plastic mould control necessary system to know can be established, heat content it is that necessary is released to pressure. terial as a function The enthalpy values and for heat materials content have than a considerably amorphous hiher materials heat content in molten than amorphous rane. Appro- ma- Before by a molten requisite plastic. coolin capacity mold control system can be established, it is necessary to know heat content that is released plastics pressure. are The frequently enthalpy found values in diaram plastics form, are with frequently enthalpy found plotted in diaximatelterials for by a molten plastic. Temperature in twice molten capacity rane. is required Approximately melt or twice cool semi-crystalline capacity is required mould- know heat content that is released by a molten plastic. Fi. : Specific enthalpy as a function for a number rmoplastics; p = bar The mean quantity heat to be ram over form,. with enthalpy Fiure plotted shows to eliminated per time unit is specific enthalpy The mean quantity heat to be over. Fi. diarams Fiure : Specific enthalpy shows for as aa function in compounds in same period The mean quantity heat to be eliminated per time unit is to melt or cool for semi-crystalline a number rmoplastics; mouldin a function compounds as amorphous in ones. for same a number period r- p = bar eliminated per time unit is specific number enthalpy amorphous Fi. diarams : Specific and enthalpy semicrystalline number rmoplastics. amorphous and Since semi- time as amorphous ones. for a as time moplastics; p = bar crystalline pressure dependence rmoplastics. Since specific Whilst amorphous rmoplastics enthalpy pressure dependence plays only a minor specific role display Whilst amorphous a more less rmoplastics steady decrease in a ir more specific or less enthalpy, steady re de- by enthalpy comparison plays to only its a dependence comparison order Summary minor role display by to its dependence order %/ manitude bar) crystalline is a sharp bend rmoplastics in curve for in semi- manitude crease is a sharp in ir bend specific in curve enthalpy, for semi- re approximately diarams approximately measured The %/ at rmoplastic p = bar) can bein crystalline crystallisation processed passes rmoplastics interval. throuh different in diarams suitably be measured applied in at practice. rmodynamic states in course injection p = bar can crystallisation interval. moldin process. Knowlede state curve durin processin makes it easier to selectively control processin suitably be applied in practice. sequence and exert a positive influence on it. The term specific enthalpy denotes mass-related heat content a material as a function and pressure. The enthalpy values for plastics are frequently found in diaram form, with enthalpy plotted as a function. Fiure shows specific enthalpy diarams for a number amorphous and semicrystalline rmoplastics. Since pressure dependence specific enthalpy plays only a minor role by comparison to its dependence order manitude approximately %/ bar), diarams measured at p = bar can suitably be applied in practice. Specific enthalpy h h A comparison two classes material shows that semi-crystalline materials have a considerably hiher heat content than amorphous materials in molten rane. Approxi mately twice capacity is required to melt or cool semi-crystalline moldin compounds in same period time as amorphous ones. COV76/Pae Edition 6- HDPE HDPE lpy h h Specific Specific enthalpy enthalpy h h heat to be eliminated heat to be eliminated HDPE The coolin behavior melt can be influenced to a pronounced extent by coolin in mold. Different mold surface s can lead to dissimilar coolin times inside molded part. The solidification behavior, i.e. level lass transition or crystallization, is a function ambient conditions pressure, coolin and heatin rate), where with amorphous and semi-crystalline rmoplastics, elevated coolin rates relatively soon lead to specific s that remain constant. The position coolin channels also has an influence here. If part is not cooled uniformly n a dissimilar structure can develop inside it, leadin to dissimilar shrinkae and warpae behavior. A carefully selected demoldin makes contributes to more cost-efficient production. While amorphous rmoplastics display a more or less Knowlede material s state curve durin processin steady decrease in ir specific enthalpy, re is a sharp and particularly durin coolin phase is especially bend in curve for semi-crystalline rmoplastics Temperature in important when enineerin rmoplastics are to be processed crystallization interval. into hihly-stressed, hih-rade molded parts.

12 References [] Thienel, P.: Der Formfüllvoran beim Spritzießen von Thermoplasten. Dissertation, RWTH Aachen, 77 [] Hirai, N./Eyrin, H. B.: Viscosity Polymeric Systems, Journal Appl. Phys., Vol., Nr. ), S. 6 [] Stuart, H. A.: Die Physik der Hochpolymeren. Bd.,, Sprinerverla, Berlin [] Thienel, P./Kemper, W./Schmidt, L.: Praktische Anwendunsbeispiele für die Benutzun von p-v--diarammen. Mitteilun aus dem Institut für Kunststfverarbeitun an der RWTH Aachen [] N.N.: Verarbeitunsdaten für den Spritzießer. Informationsschrift. Covestro, Leverkusen [6] Sarholz, R.: Rechnerische Abschätzun des Spritzieß - prozesses als Hilfsmittel zur Maschineneinstellun. Dissertation, RWTH Aachen, [7] N.N.: Spritzießen Verfahrensablauf, Verfahrensparameter, Prozessführun. Institut für Kunststfverarbeitun an der RWTH Aachen Typical value These values are typical values only. Unless explicitly areed in written form, y do not constitute a bindin material specification or warranted values. Values may be affected by desin mold/die, processin conditions and colorin/pimentation product. Unless specified to contrary, property values iven have been established on standardized test specimens at room. The manner in which you use and purpose to which you put and utilize our products, technical assistance and information wher verbal, written or by way production evaluations), includin any suested formulations and recommendations, are beyond our control. Therefore, it is imperative that you test our products, technical assistance, information and recommendations to determine to your own satisfaction wher our products, technical assistance and information are suitable for your intended uses and applications. This application-specific analysis must at least include testin to determine suitability from a technical as well as health, safety, and environmental standpoint. Such testin has not necessarily been done by Covestro. Unless we orwise aree in writin, all products are sold strictly pursuant to terms our standard conditions sale which are available upon request. All information and technical assistance is iven without warranty or uarantee and is subject to chane without notice. It is expressly understood and areed that you assume and hereby expressly release us from all liability, in tort, contract or orwise, incurred in connection with use our products, technical assistance, and information. Any statement or recommendation not contained herein is unauthorized and shall not bind us. Nothin herein shall be construed as a recommendation to use any product in conflict with any claim any patent relative to any material or its use. No license is implied or in fact ranted under claims any patent. With respect to health, safety and environment precautions, relevant Material Safety Data Sheets MSDS) and product labels must be observed prior to workin with our products. Covestro Germany AG Business Unit Polycarbonates D-6 Leverkusen, Germany [email protected] COV76/Pae Edition 6-