Simulation of Die Casting Process in an Industrial Helical Gearbox Flange Die

Transcription

1 Simultion of Die Csting Process in n Industril Helicl Gerbox Flnge Die Mehdi Modbberifr, Behrouz Rd, Bhmn Mirzkhni Abstrct Flnges re widely used for connecting vlves, pipes nd other industril devices such s gerboxes. Method of producing flnge hs considerble impct on the mnner of their involvement with the industril engines nd gerboxes. By Using die csting insted of snd csting nd mchining for mnufcturing flnges, production speed nd dimensionl ccurcy of the prts increses. Also, in die csting, obtined dimensions re close to finl dimensions nd hence the need for mchining flnges fter die csting process decreses which mkes significnt svings in rw mterils nd improves the mechnicl properties of flnges. In this pper, typicl die of n industril helicl gerbox flnge (size ISO 50) ws designed nd die csting process for producing this type of flnge ws simulted using ProCAST softwre. The results of simultion were used for optimizing die design. Finlly, using the results of the nlysis, optimized die ws built. Keywords Die csting, finite element, flnge. I. INTRODUCTION ITH the growth of technology, vrious methods of W csting hve been introduced nd used in industries. One of these methods is die csting. Die-csting cn be done using cold chmber (high pressure) or hot chmber (low pressure) process. In high pressure csting process, molten metl is injected into die under high pressure of psi. However, typicl injection pressures for hot chmber die csting mchine re between 1000 nd 5000 psi. The procedure for filling die cvity in die csting is similr to permnent mold csting except tht the metl is injected into the mold under high pressure. This results in more uniform prt, generlly good surfce finish nd good dimensionl ccurcy. For mny prts, post-mchining cn be totlly eliminted, or very light mchining my be required to bring dimensions to size. The dies re typiclly composed of two hlves - the cover die, which is mounted onto sttionry plten, nd the ejector die, which is mounted onto movble plten. This design llows the die to open nd close long its prting line. Once closed, the two die hlves form n internl prt cvity which is filled with the molten metl to form the csting. This cvity is formed by two inserts, the cvity insert nd the core insert, Mehdi Modbberifr is with Mechnicl Engineering Deprtment, Fculty of Engineering, Ark University, Ark , Irn (phone: ; fx: ; e-mil: m-modbberifr@ rku.c.ir). Behrouz Rd ws with Mechnic Deprtment of Science nd Reserch brnch, Islmic Azd university, Ark, Irn (e-mil: behrouz.rd66@gmil.com). Bhmn Mirzkhni is with Metllurgy Engineering Deprtment, Fculty of Engineering, Ark University, Ark , Irn (phone: ; fx: ; e-mil: b-mirzkhni@ rku.c.ir). which re inserted into the cover die nd ejector die, respectively. The cover die llows the molten metl to flow from the injection system, through n opening, nd into the prt cvity. The ejector die includes support plte nd the ejector box, which is mounted onto the plten nd inside contins the ejection system. When the clmping unit seprtes the die hlves, the clmping br pushes the ejector plte forwrd inside the ejector box which pushes the ejector pins into the molded prt, ejecting it from the core insert. Multiple-cvity dies re sometimes used, in which the two die hlves form severl identicl prt cvities (Fig. 1). Fig. 1 Die ssembly nd components (cold chmber) [1] The first theoreticl explntion bout the cvity filling in Die csting ws given by Frommer nd Brndt. Frommer explined the filling the die cvity with lloy s hydrodynmic streming without losses by friction. In Frommer nlysis, the lloy strem psses through the die cvity nd disperses on the wll of the die cvity opposite the gte nd fills the die cvity from here. According to studies by Brndt the lloy strem with lower speed widens fter entrnce into the die cvity nd touches wlls of the die cvity [1]. Kopf proved tht both frommer nd brndt theory re correct. If the kinetic energy in injection gte is greter thn the die cvity resistnce to molten metl flow, then die filling will be bsed on Frommer theory. Also, if the kinetic energy in injection gte is lesser thn the die cvity resistnce to molten metl flow then die filling will be bsed on brndt theory [2]. In 1991 the therml field simultion in die csting dies ws developed by computer softwre. This softwre solves two-dimensionl model of het conduction in the die csting dies using boundry element method (BEM). In recent 1371

2 yers, by developing simultion softwre, it is possible to predict defects such s shrinkge porosities in csting prts [3]-[5]. In this pper, n industril helicl gerbox flnge (size ISO 50) die csting die is designed nd die csting process is simulted. By using simultion results, die design is optimized nd by using CAD / CAM technology, finl die is produced. II. DESIGN OF HELICAL GEARBOX FLANGE DIE CASTING DIE There re mny design issues tht must be considered in the design of the dies. Firstly, the min die cvity must be sme s the flnge nd llows the molten metl to flow esily into ll of the cvities. Eqully importnt is the removl of the solidified csting from the die, so drft ngle must be pplied to the wlls of the prt cvity. In ddition, other fctors such s molten metl flow rte nd pressure, solidifiction shrinkge, size nd loction of overflows nd feeding system should be considered. On the other hnd the loction of the min cvity depends on prting line. Fig. 2 Model nd dimensions of the helicl gerbox flnge (ll dimensions re in mm) The first step for designing the die is computer modeling of the flnge. Fig. 2 shows three-dimensionl model nd dimensions of the flnge. Next step is defining prting surfce which seprtes two hlves of the die (core nd cvity). Prting surfce hs direct effect on mteril flow nd die filling. The best prting surfce for helicl gerbox flnge is flt type (Fig. 2). Wlls drft ngle ws selected 1 degree. The mount of over size for compensting solidifiction shrinkge ws selected mm/m bsed on the selected mteril (here ALSI9CU3). Cvity hlf die is the min prt of the die nd included runner, injection nozzle, feeder chnnels nd gte. Sectionl re of injection nozzle cn be clculted with the following eqution: s Q = (1) r In this eqution, Q is flow (m 3 /s) nd r is flow velocity (m/s). Injection time depends on the thinnest flnge wll nd mteril nd for wll thickness of 10 mm; rnge of injection time is between 0.65 to 0.8 seconds. The injection time for filling die cvity cn be written s: v t = ( ) v (2) s In this eqution, t is the injection time (s), s is crosssectionl re of gte (m 2 ) nd v is the volume of flnge (m 3 ). v is flow velocity in injection nozzle nd cn be clculted using following eqution: 2 p v = (3) ρ where p nd ρ re injection pressure (p) nd density of the metl (kg/ m 2 ). Injection pressure is determined bsed on injection mchine (here Model 08). Molten metl flow velocity is selected 25 (m/s) bsed on experience nd the verge thickness of the csting prt. In ddition, the crosssectionl re of the injection nozzle is 15.5 (mm 2 ). Finlly, bsed on the bove clcultions, the core nd cvity were modeled which re shown Fig. 3. III. SIMULATION AND ANALYSIS OF HELICAL GEARBOX FLANGE CASTING PROCESS In order to nlyze the process of die csting, ProCAST ws used. To do this, firstly, the die ws modeled in CATIA softwre, then the model dt files imported to ProCAST nd die csting process ws simulted. At first stge of the simultion, ll die prts including the runner, feeding system overflows, nd so on were meshed nd then boundry conditions were pplied to the meshed model. 1372

3 Fig. 3 Model of core nd cvity Fig. 4 shows the meshed model with boundry conditions. As the die csting die shpe is sme s the shpe of the flnge (with considering design considertions such s contrction nd drft ngle etc.), in simultion of die csting process, the most importnt vribles re runner nd feeding systems. Proper design of these prts reduces costs nd improves the qulity of csting prts. In this study, injection pressure nd temperture re Mp nd 700 C respectively. Also, the mbient temperture nd preheting temperture of the die re nd C respectively. Fig. 4 Meshed model with boundry conditions Fig. 5 Contour of filling time of the die cvity Fig. 6 Contour of solidifiction time Bsed on the type of injection mchine (Model 08), rdius of gte nd injection pressure ws chosen. Fig. 5 illustrtes the Contour of filling time of the die cvity, the totl time of filling nd the filling procedure in different prts of the die. This figure shows tht this die is filled in less thn 1 second. Fig. 6 shows the contour of solidifiction time. As cn be seen in this figure, the totl solidifiction time is 24 second nd runner is the lst solidified point. Fig. 7 depicts the contour of temperture distribution 7.31 seconds fter injection. By using this contour t different times, it is possible to determine the best time for ejecting the flnge. Another importnt prmeter is flow lines during filling of the die. In this stge of design, the feeder chnnel nd injection nozzle should be designed to reduce the possibility of turbulence in molten metl flow. 1373

4 cross-sectionl re of 225 mm 2, injection nozzle crosssectionl re of 13.5 mm 2 nd the gte rdius of 22.5 mm. Fig. 7 Contour of temperture distribution 7.31 seconds fter injection Turbulence in molten metl flow increses the gs porosities in the flnge. The effect of chnging injection pressure, gte rdius, nd re of feeder chnnel on flow lines investigted in this die nd it ws found tht by reducing pressure inside the die nd injection nozzle rdius, the mechnicl strength of the prt decreses. Fig. 8 shows the flow lines in injection pressure of 15 MP, feeder chnnel Fig. 8 Flow lines in die cvity Another importnt prmeter in designing the die is shrinkge porosities. The min fctors ffecting the shrinkge porosity re injection pressure, feeder chnnel crosssectionl re, injection nozzle cross-sectionl re, gte rdius nd overflows cross section. Here, by considering different scenrios (bsed on experience) for these prmeters, the lowest number of shrinkge porosity is obtined. Selected conditions hve been shown in Tble І. TABLE I SELECTED CONDITIONS FOR INVESTIGATING THE EFFECT OF VARIOUS PARAMETERS ON THE NUMBER OF SHRINKAGE POROSITY IN FINAL PART 6 th Conditions 5 th Conditions 4 th Conditions 3 rd Conditions 2 nd Conditions 1 st Conditions Prmeter Figs. 9 -(d) illustrte shrinkge porosities within the prt in the first to fourth condition. These figures show tht the fourth stte hs fewer holes thn the other scenrios. In ddition, the depths of the cvities in the first nd second condition re more thn other sttes. (In Figs. 9 depth of cvities decreses from green to blue nd then violet) After reching the best condition for gte rdius, feeder chnnel cross-sectionl re, injection nozzle cross-sectionl re nd injection pressure in the die, the effect of overflows size (scenrios V nd VI) on shrinkge porosity ws investigted. The results were shown in Figs. 10,. As shown in Fig. 10 it cn be seen tht by incresing overflows size compred to 4 previous conditions, there re no significnt chnges in the rte of shrinkge porosities, but the chnge cuses more rw mteril nd thereby increses the cost of process. Fig. 10 shows tht by reducing the overflow size, shrinkge porosities drmticlly increses nd thus the finl prt will reject injection pressure (MP) feeder chnnel cross-sectionl re(mm 2 ) injection nozzle cross-sectionl re (mm 2 ) gte rdius(mm) overflow cross-sectionl re(mm 2 ) 1374

5 (c) Fig. 10, Shrinkge porosity in the prt for conditions 5 nd 6 in Tble I respectively IV. MANUFACTURING HELICAL GEARBOX FLANGE DIE By finliztion of the die dimensions from simultion results, the die ws built using CAD/CAM technology. Die ws built from steel (H13) X40 CrMov51 nd lso got hrdened. Core nd cvity were mchined using CNC mchined nd other prts mchined by universl mchine tools. Figs. 11 -(c) show the core (top), cvity (middle) nd the finl prt (bottom). (d) Fig. 9 -(d) Shrinkge porosity in the prt for conditions 1-4 in Tble I respectively 1375

6 REFERENCES [1] E. Brunhuber, Moderne Druckgussfertigung, Berlin. Fchverlg Schiele & Schon GMBH, [2] G. Br-Meir, Fundmentls of Die Csting Design, Potto Project, [3] H. Yn, W. Zhung, Y. Hu, Q. Zhng, H. Jin, Numericl simultion of AZ91D lloy utomobile plug in pressure die csting process, Journl of Mterils Processing Technology, Volumes , Pges , 07. [4] K. Domkin, J.H. Httel, J. Thorborg, Modeling of high temperture- nd diffusion-controlled die soldering in luminum high pressure die csting, Journl of Mterils Processing Technology, Volumes 9, Pges , 09. [5] B.H Hu, K.K Tong, X.P Niu, I Pinwill, Design nd optimistion of runner nd gting systems for the die csting of thin-wlled mgnesium telecommuniction prts through numericl simultion,, Journl of Mterils Processing Technology, Volumes 105, Pges , 00. (c) Fig. 11, Mnufctured die nd (c) the finl prt V. CONCLUSION In this pper, design, process simultion nd production of n industril helicl gerbox flnge die csting die were presented. The simultion results showed tht by incresing molten metl injection pressure nd decresing Injection nozzle cross-sectionl re the mechnicl strength of finl prt increses. Also, by reducing overflows size, number of shrinkge porosity increses. 1376