Highly Dynamic and Homogeneous Heating of Organo Sheets

Transcription

1 PR O D U C T I O N O r g a no Sh ts Highly Dynamic and Homognous Hating of Organo Shts Th infrard hating tchnology dvlopd by KraussMaffi with an intllignt hardwar and softwar solution nabls fast and homognous hating of fibr-rinforcd thrmoplastic smi-finishd products. To valuat th hating procss, th company has dvlopd a mthodical approach for dtrmining th hating quality of organo shts. Authors DR. MESUT CETIN orks in Tchnology w Dvlopmnt at KraussMaffi Automation GmbH in Obrding Schwaig (Grmany). CHRISTIAN HERRMANN i s Dvlopmnt Enginr for Lightwight Construction at KraussMaffi Automation GmbH in Obrding-Schwaig (Grmany). STEFAN SCHIERL i s Dvlopmnt Enginr at KraussMaffi Tchnologis GmbH in MünchnAllach (Grmany). 34 lightwight.dsign Componnts mad of fibr-rinforcd thrmoplastics ar vry much in fashion. Componnt manufacturrs ar placing incrasing importanc on thrmoforming continuous-fibr-rinforcd smifinishd products and on othr lightwight construction tchnologis, such as th Rsin Transfr Molding (RTM) procss, as wll as on shortfibr injction molding. High strngth valus with an xtrmly light wight and Th Fibr Form tchnology dvlopd by KraussMaffi combins th injction molding procss with thrmoforming continuous-fibr-rinforcd thrmoplastic smifinishd products, known as organo shts. Ths ar larg-format smifinishd products usually mad up of glass, carbon, aramid or composit fibr layrs mbddd in a thrmoplastic matrix, for xampl polyamid (PA) or polypropyln (PP). Dspit th many advantags of IR hating tchnology, hating organo shts is associatd with a coupl of challngs. short cycl tims ar among th chif rquirmnts for fibr-rinforcd thrmoplastic componnts. Injction molding of thrmoplastic plastics is particularly wll suitd with rgard to th rquirmnts mntiond abov bcaus it nabls high lvls of dsign frdom, short cycl tims as wll as th implmntation of continuous fibr structurs and mtallic insrts. Th manufacturing procss can b dividd chronologically into th procss stps for hating up, thrmoforming and ovr-molding. Th first procss stp of hating up th organo shts is of cntral importanc for th ntir procss. Th hating of organic shts abov th mlting tmpratur of th thrmoplastic matrix can b carrid out by contact hating, convctiv hat transfr in a convction ovn or by WORLDWIDE

2 Figur 1 Gnral structur of th vrtical KraussMaffi IR ovn ( KraussMaffi) infrard (IR) radiation. From a cost-ffctivnss standpoint and with rgard to high productivity, IR hating tchnology has provn its valu in both rsarch and industry. Th major advantags of IR tchnology compard to hating in th con vction ovn ar lowr invstmnt costs and a highr powr dnsity of th IR mittrs, which lads to significantly shortr hating tims. systm rquirs intllignt thrmal managmnt, bcaus th rpatd hating procsss fd thrmal nrgy cyclically not only to th organo sht, but also to th IR ovn. Th thrmal nrgy lads to a continuous tmpratur incras within th IR ovn, which prvnts hating oprations from bing static and thus rproducibl. During production, this can caus ovrhating of th ovn and thus scrap or vn bring production to a KraussMaffi uss an ovrriding control systm that can tak multipl pyromtrs into account. Dspit th many advantags of IR hating tchnology, hating organo shts is associatd with a coupl of challngs. Fast hating with convntional control systms frquntly lads to ovrhating and a non-uniform tmpratur distribution on th componnt surfac, bcaus th raction tims of standard controllrs ar too long for th highly dynamic hating bhaviour of th IR mittrs. In addition, using IR hating tchnology in a closd Volum 10 standstill. Thrfor, hating with IR mittrs rquirs an intllignt hardwar and softwar solution tailord to th FibrForm procss. Intllignt Hating of Organo Shts With th targt of fast and uniform hating of th organo sht, KraussMaffi has dvlopd an IR hating tchnology spcifically for th FibrForm procss. Its outstanding faturs includ intllignt hardwar and softwar solutions as wll as complt intgration into th MC6 control systm for injction molding machins. Compard to convntional, commrcially availabl IR hating tchnologis for fibr-rinforcd thrmoplastic smi-finishd products, KraussMaffi uss a closd IR ovn systm for this application. Rquirmnts-basd nrgy dissipation that compnsats for th high nrgy input via th IR mittrs nsurs a static nrgy stat of th systm bfor and during sris production, which brings about a rproducibl hating procss in a closd systm. Th gnral structur of th Krauss Maffi IR ovn for hating fibr-rinforcd thrmoplastic componnts is displayd in Figur 1. For vrtical positioning of th IR ovn abov th fixd (mold) platn (FP), th connction to th injction molding machin is mad using th standardisd Euromap 18 intrfac. This nabls th IR ovn to b rtrofittd into xisting injction molding machins. To incras nrgy fficincy and to comply with xisting safty rquirmnts, th IR ovn is compltly insulatd. In addition, vntilation flaps and othr patnt-pnding masurs nabl con lightwight.dsign 35

3 PR O D U C T I O N O r g a no Sh ts Figur 2 Commrcially availabl control systms for hating fibr-rinforcd thrmoplastic smi-finishd products ( KraussMaffi) trolld dissipation of nrgy from th IR ovn. Th listd advantags can b usd indpndntly of th componnt gomtry, bcaus th modular ovn concpt prmits th ovn siz to b adaptd to th componnt with grat flxibility. In addition, th numbr and positioning of th pyromtrs can b configurd asily, for xampl for a product chang. Thr ar two options for th transfr rout of th hatd organo sht from th IR ovn into th mold. Aftr th sliding door is opnd, th hatd organo sht can b passd from th IR ovn into th injction mold (from th front) or by opning a f lap at th bottom of th ovn housing (from th bottom). Th typ of ovn opning usd dpnds on th automation concpt. Th KraussMaffi control systm nsurs fast, uniform and synchronous hating up of th organo shts and rliably prvnts ovrhating of th organo sht surfac. Th diffrnc btwn this control systm and convntional ons is in th numbr and assignmnt of th controllrs as wll as in th control systm itslf, which is illustratd blow in th xampl of th IR ovn with a hating surfac siz of 750 x 750 mm (nin IR mittrs). Convntional IR hating panls with control usually hav only on pyromtr (Pi), which is mad availabl as a masuring lmnt for th controlld systm. For this purpos, th controlld systm combins all nin radiators to crat on hating zon (Zon 1). During th hating procss, th control variabl, th surfac tmpratur of th organo sht (TACT-P2), is masurd by pyromtr P2 and compard to th control variabl, th targt tmpratur (TTAR), Figur 2. Th comparison provids th control variation usd by th controllr and th actuator to calculat th control variabl, th output of th mittr. Pyromtrs 1, 3 and 4 ar usd solly for surfac tmpratur masurmnt and ar not considrd by th control systm. In contrast to commrcially availabl control systms, th KraussMaffi control systm can tak multipl pyromtrs into account and assign ths to multipl zons. With rgard to th xampl on th IR ovn with th hating surfac siz of 750 mm 750 mm (nin IR mittrs), all four pyromtr tmpraturs (P1 to P4) ar mad availabl as th control variabl for th controlld systm, whr diffrnt IR mittrs ar assignd to ach individual pyromtr. This rsults in a total of four zons, Figur 3, ach of which has its own control loop and is additionally incorporatd into an outr control loop. Through this systm (outr control loop and innr control loop), th zons ar not only controlld sparatly (own tmpratur in th innr control loop), but also tak into account th hating Figur 3 KraussMaffi control systm for hating fibr-rinforcd thrmoplastic smi-finishd products ( KraussMaffi) 36 lightwight.dsign WORLDWIDE

4 Figur 4 Comparison of th hating curv for an organo sht: top with a convntional control systm, bottom with th KraussMaffi control systm ( KraussMaffi) bhaviour of th othr zons (outr control loop). Th outr controllr taks th hating rats of all zons into account, rsulting in a synchronous incras in th ris of th tmpratur curvs. This synchronism causs all zons to rach thir stpoint tmpratur at th sam tim. If w compar th rsult of th hating procss of both control systms on a fibr-rinforcd smifinishd product with a siz of 670 x 490 mm, with a vrtical hanging organo sht and a hating stpoint tmpratur of 225 C, it bcoms vidnt that convntional control systms hav substantial shortcomings in both th hating tim and in th hating procss, Figur 4. Th tmpratur curvs masurd using pyromtrs 1 to 4 show strong dviation and diffrnt hating rats, rsulting in hating of th organo sht that is not uniform, Figur 4 (top). A synchronous and uniform hating bhaviour is providd by th KraussMaffi control systm Figur 4 (bottom). Th spcially dvlopd intllignt control of th individual zons, sparatly and rlativ to ach othr, calculats th control variabls for th diffrnt Volum 10 IR mittrs, nsuring that th matrial is hatd synchronously across all zons. Anothr advantag of th KraussMaffi control systm is vidnt in th hat-up tim, which is shortr than that of a convntional control systm. This has a positiv ffct on th ovrall cycl tim. Thrmographic masurmnts ar a grat way to valuat th hating quality of a organo sht. Thrmography is an imaging procss for displaying th surfac tmpratur of objcts. In this procss, th amount of hat mittd by an objct is dtctd by an IR camra and tmpratur valus for th objct in th camra s fild of viw ar calculatd taking into account th mission cofficint of th masurmnt objct surfac [1]. KraussMaffi dfins th hating quality of composit shts by using th homognity/htrognity of th tmpratur distribution on th surfac of th organo sht and th dviation of th tmpratur valus from th hating stpoint tmpratur. Th thrmographic masurmnt is carrid out aftr th hating procss, for xampl outsid th IR ovn, bfor th handovr to th mold. Du to basic principls of physics, valuation of th tmpratur distribution ovr th ntir surfac is not usful. Bordr aras or cutouts ar mor strongly xposd to natural convction. This lads to fastr cooling of th organo sht in ths aras compard to th cntral ara. In light of ths facts and bcaus no valuation mthods hav bn in plac to dat, KraussMaffi has dvlopd an asy-to-us valuation mthod that maks it possibl to valuat and compar th hating quality of composit shts of narly any gomtry and siz using ky figurs. In doing so, dpnding on th thicknss of th organo sht, th bor diamtr or th gomtry of cutouts, a masurmnt surfac is dfind on th organo sht that can b usd in th valuation of th hating quality. Individual masurmnt filds ar positiond on this masurmnt surfac. Th numbr and siz of th masurmnt filds rsults from th gomtry and siz of th composit sht. Subsquntly, th tmpratur distribution in th individual masurmnt filds is analysd and tstd to s whthr th tmpratur valus ar within th dfind tolr lightwight.dsign 37

5 PR O D U C T I O N O r g a no Sh ts Figur 5 Thrmographic masurmnt of organo shts; lft: KraussMaffi control, right: commrcial control ( KraussMaffi) Figur 6 38 Cooling bhaviour of th hatd composit sht with commrcial control ( KraussMaffi) lightwight.dsign anc rang. In th nxt stp, th avrag tmpratur valus of th individual masurmnt filds ar usd to dtrmin th ky figurs for valuating th hating quality. Firstly, common statistical mthods ar usd to analys th scattr of th avrag tmpratur valus of th individual masurmnt filds to valuat th homognity/htrognity of th tmpratur distribution ovr th ntir organo sht surfac. Scondly, th dviation of th avrag tmpratur valus of th masurmnt filds from th spcifid tmpratur st valu is considrd. In doing so, th tolranc rang dfins th rquirmnt for th hating quality. It is ncssary to considr that th dfind tmpratur st valu has to b corrctd according to th cooling rat and th tim of th masurmnt. Th lssr th tmpratur fluctuation btwn th individual masurmnt filds, for xampl th mor homognous th tmpratur distribution, and th lssr th diffrnc of th avrag tmpratur valus of th masurmnt filds to th tmpratur st valu within th tolranc rang, th bttr th hating quality. Th dimnsionlss ky figur for th hating quality Hq can b dfind according to Eq. 1. In doing so, th two ky figurs for homognity and th WORLDWIDE

6 Equation 1 Tabl 1 Comparison of th hating quality btwn - n1 ni=1 T i - ( T Stpoint - t EA v c) + n1 ni=1 ( T i - T ) 2 - q = H with T = n1 ni=1 T i T Tol max - T Stpoint n Numbr of masurmnt filds Ti Avrag tmpratur valu of th masurmnt fild i [ C] TStpoint Hating stpoint tmpratur in th IR ovn [ C] TTol max Maximum tmpratur tolranc valu [ C] rlativ to TStpoint tea Tim aftr th nd of th hating procss [s] vc Cooling rat [K/s] th KraussMaffi control and commrcial control for hating fibr-rinforcd thrmoplastic smi-finishd products (matrial: Tpx dynalit 104-RG600(x)/47 %, 0.5 mm) ( KraussMaffi) KraussMaffiControl Commrcial Control T T T T T T Stpoint T Stpoint, corrctd T5 dviation from tmpratur st valu ar considrd quivalnt. Dpnding on th rquirmnt, howvr, a wighting of th ky figurs can b carrid out. To nabl comparisons of th hating quality of various composit shts, th two ky figurs ar st in rlation to th rspctiv spcifid tolranc rang. Thrfor, a lowr ky figur stands for bttr hating quality. Th hating quality of th KraussMaffi hardwar and softwar solutions for IR hating tchnology can b dtrmind in accordanc with Figur 5, Tabl 1 and Tabl 2, in accordanc with Eq. 1. At a spcifid hating stpoint tmpratur of 225 C, a dfind tmpratur tolranc rang of ± 5 % (T Tol max = C), a cooling rat of 6 K/s and a tmpratur masurmnt 4 s aftr th nd of hating, w hav a ky figur for th hating quality of 0.36 for th KraussMaffi control and of 1.02 for th commrcial control systm. Control of th hating mittrs using a singl pyromtr Figur 4 (top) has bn provn to rsult in lowr hating quality. Th thrmographic masurmnt shows a highly inhomognous hating pattrn, Figur 5 with a maximum tmpratur diffrnc of th masuring rangs of 14.3 C. Compard to this, th maximum tmpratur diffrnc with th KraussMaffi hardwar and softwar solution is just 5.1 C. Th hating quality is vry important for th forming and injction molding procss, as is shown by th cooling-off curvs in Figur 6 and Figur 7. Ths show that th Volum 10 cooling has a narly linar curv at a cooling rat of 6 K/s and th tmpraturs of th individual aras do not qualis during cooling. Howvr, a homognous tmpratur distribution is indispnsibl for good thrmal forming and a good positiv plastic bond. From this, w can infr that th hating procss is of fundamntal importanc for th quality of th ovrall procss. An inhomognous tmpratur distribution on th organo sht surfac (poor hating quality) can no longr b corrctd (linar cooling bhaviour) and can hav a ngativ ffct on componnt quality in th forming or injction molding procss. Summary Th hating procss of composit sht is cntral procss stp of FibrForm tchnology. Th lack of commrcially availabl ovn solutions and th lack of valuation mthods for th hating quality wr rasons for dvloping th KraussMaffi IR hating tchnology. Th spcially dvlopd IR hating tchnology is charactrisd by intllignt hardwar and softwar solutions and has bn provn to dmonstrat fast, homognous and synchronous hating of composit shts, Figur 5. Th KraussMaffi IR hating tchnology is a major componnt of product-orintd manufacturing solutions for sris production of fibr-rinforcd componnts [2] and is fully intgratd into th KraussMaffi MC6 injction molding [ C] T Tol max t EA [s] 4 4 v [K/s] c Hq Tabl 2 Paramtrs of th tst stup ( KraussMaffi) Paramtrs Valu / data Width of th organo sht [mm] 490 Hight of th organo sht [mm] 670 Thicknss of th organo sht [mm] 0.5 Matrial of th organo sht Tpx dynalit 104-RG600/47% Thrmographic camra Optris PI 400 (62 objctiv) Distanc to th masurmnt objct [mm] 1300 Ambint tmpratur [ C] 23 Emission valu 0.97 Hating st tmpratur [ C] lightwight.dsign 39

7 PR O D U C T I O N O r g a no Sh ts control systm. This prmits connction to Plastics 4.0 products from KraussMaffi, such as DataXplorr. This givs th usr a mans of not only simpl adjustmnt and monitoring of th hating procss on th machin, but also transparnt documntation and analysis of all quality-orintd procss data, such as hating curvs of th composit shts, using DataXplorr. On application xampl was introducd at K 2016: Th data of DataXplorr ar assignd to ach spcific componnt using a QR cod this nabls samlss tracking of all product and procss data for ach componnt. No lss importantly, th hating zons can b assignd flxibly to th xisting pyromtrs Figur 4 (bottom) to implmnt simpl adaptation of th ovn for anothr product or a changd gomtry. All hating paramtrs ar stord along with th injction molding paramtrs, nabling simpl startup aftr a product chang. Rfrncs [1] Brnhard, F. (Ed.): Handbuch dr Tchnischn Tmpraturmssung (Handbook of Tchnical Tmpratur Masurmnt). VDI-Buch, Brlin: Springr Viwg, 2014 Figur 7 Cooling bhaviour of th hatd composit sht with KraussMaffi control ( KraussMaffi) 40 lightwight.dsign [2] Ctin, M.; Hrrmann, C.; Fnsk, S.: Automatisirungskonzpt zur Hrstllung fasrvrstärktr Thrmoplastbautil (Automation concpts for manufacturing fibr-rinforcd thrmoplastic componnts). In: lightwight.dsign 10 (2017), No. 2, pp WORLDWIDE

8 NEW: Top Magazin for Lightwight Construction harg: c f o r f 3 0 d ay s sign r d t o f h g i n i z w a / l i g ht M ag m h o t c. w o g n d t Ts - k n ow l d z i l a i c -sp w w w.my Th consistnt application of innovativ lightwight construction concpts today plays a ky rol in rducing wight and saving nrgy. lightwight.dsign worldwid provids you with all th practical information you nd for implmnting lightwight construction principls in dvloping and manufacturing nw products across th ntir valu Volum 10 chain from th matrial to construction tchnology, simulation and optimization procdurs up to production tchnology, quality assuranc and rcycling. Tst now th Magazin for 30 days fr of charg! lightwight.dsign 41