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Abstract no Uni w and streets and process K 1. last process as ne of w engineering”). ture some Uni has plastics hundreds household-electric, URL: 0924-0136/$ doi:10.1016/j.jmatprotec.2005.04.006 Journal of Materials Processing Technology 175 (2006) 1519 An example of simulation tools use for large injection moulds design: The CONTENUR TM 2400 l solid waste container J. Aisa a, , C. Javierre a , J.A. De la Serna b a T.I.I.P., C.S.I.C. Associated Unit, Department of Mechanical Engineering, University of Zaragoza, Spain b CONTENUR ESPA NA, S.L., Polgono Industrial Los Angeles, Getafe, Madrid, Spain Large containers with volumes above 1100 l are usually produced using procedures such as rotomoulding process. These techniques have part weight or dimensional limits. T.I.I.P., injection moulding plastic group of the Department of Mechanical Engineering of the Zaragoza versity, developed with CONTENUR TM a new product under European norms for solid waste containers up to 2000 l volume; the result as a new main body up to 60 kg weight in one part. The design process combined several CAE tools (aesthetical design, mechanical design rheological simulation) and, in last June, showed final result and passed different tests. Nowadays, more than 5000 samples are on the without basic modifications in the mould (more than 100 tonnes weight). The paper focuses on the methodology used to integrate tool process design with product definition (i.e. injection pressure and clamp force versus thickness and part shape). Some parameters about control in this particular mould (injection rate, temperature, viscosity, gate location, .) are detailed. 2005 Elsevier B.V. All rights reserved. eywords: CAE design; Container; Injection moulding Introduction CAE tools have constituted an authentic revolution in the years within injection of thermoplastics. The sequential until the final solution (including several setups such development, test of prototypes, modification of figures, w test, .) has been replaced by a faster one consisting a procedure with the designer, transformer and final client orking together on the same computer files (“concurrent Therefore, the timing for mould manufac- and completion has been reduced enormously; however, interesting advices about CAE use are described in 1. The Workshop of Injection of the Plastics Industry of the versity of Zaragoza (T.I.I.P.), C.S.I.C. Associated Unit, been working with CAE tools on injection of thermo- for more than 15 years, with enormous advantage for of projects made in different sectors (automotive, packaging, toys, etc.). T.I.I.P. activities Corresponding author. E-mail address: tiipunizar.es (J. Aisa). . included tion, dif the uf collaborated Association try injection technological or ish research cascade techniques 2. the see front matter 2005 Elsevier B.V. All rights reserved. several research projects (rheological characteriza- semiautomatic mould design, .) working together with ferent European companies. Nevertheless, this group has always been conscious of necessity to arrange simulation with procedure of man- acture next to the machine, of such a form that has been and directed by the constitution of the Research of the Workshop of Injection of the Plastic Indus- (a.i.T.I.I.P.) foundation, which provides services to the companies without a profit spirit (Fig. 1). This center has been supported by various national ganizations such as the Aragons Government and Span- Department of Industry through different programs and lines (new processes like gas-assisted techniques or injection moulding, new designs, process-measuring using pressure and temperature devices .). The CONTENUR Project When, in 1999, the first Spanish company involved in manufacture of containers for the collection of urban 16 Processing solid T pieces testing of with plastic of all the ples big mould mak and to and minimum material), J. Aisa et al. / Journal of Materials Fig. 1. a.i.T.I.I.P. injection moulding area, general view. remainders (CONTENUR SPAIN, S.L.) went to the .I.I.P.a.i.T.I.I.P. Group to work jointly on the design of of great size in injection, then arrived the moment for the real possibilities of these programs in this field. The main objective of the project was the fast manufacture containers of great capacity (2400 l and more) to compete market products with welded metallic plate solutions or ones made by rotational moulding with the inclusion expensive reinforcement structures. Obviously, between the pieces that constituted the set, the main challenge was manufacture of a single part bucket. The literature shows several part and mould design exam- and failure advices 2,3, but it is not possible to find plastic parts up to 40 kg weight and a mistake in this size will have no easy solution (tool transport to mould ers manufacturing plant will be too expensive, and trial error method is not available). For the design of this element, the following aspects had be considered: basic dimensions agreed with the European Norm EN 12574 4; unloading resistance (discharge sides) (Fig. 2); high impact resistance for functional conditions and loca- tion (parking areas, for example); easily cleaning surfaces; friendly aspect, aesthetical design; minimum cost (not only for processing and assembly but also for on-street maintenance); restriction of the clamping force imposed by the installed press machine (big special machines with limited clamping range between 5000 and 10,000 tonnes); prepared for labelling, that is to say, with visible free and flat spaces; material restrictions: same materials used for other CON- TENUR designs. Special mention requires two limitations: minimum cost maximum clamping force under mentioned limits. For a cost, thickness is fundamental (by the cost of raw inasmuch as the time of manufacture; therefore, Fig. model, the the jected strongly a force not techniques (a) (b) T Results Main (mm)/weight Technology 175 (2006) 1519 2. Boundary conditions for unloading operation, nonlinear material finite element model. cost of the machine derived approximately depends on square of the thickness 5. On the other hand, to reduce the closing force, the pro- area of the piece and the distribution of pressures are related with part thickness (narrow sections caused high injection pressure, which could as well suppose a high of closing). The methodology applied, developed by Castany et al., only for injection moulding but also for other similar 68, is as given below: Determination of the feasibility of the product: clamping force evaluation and thickness part on an agreed basic geometry to adjust dimensions with the European norm. Only general design lines, and not functional details, were included in this step. Some basic results are shown in Table 1. These analyses were made with basic param- eters for generic material family, high-density polyethy- lene (Table 2). For advanced steps, calculations were made using several temperature conditions. Material selection, combining melt flow index (MFI) and mechanical behaviour, and injection point locations were simulated, without even knowing the final geometry of the component. Best results were found for several injec- tion points arranged around the bottom area in the main able 1 for simple plastic model, first analysis using simulation tools body thickness (kg) Maximum injection pressure (MPa) Required clamping force (kN) 6/52 96 166,000 7/60 71 122,000 8/68 55 94,000 9/76 44 74,000 10/84 35 59,000 Processing T Computing Melt Injection Mould Fig. ments. (c) (d) J. Aisa et al. / Journal of Materials able 2 parameters for basic simulations temperature ( C) 240 time at constant ram speed In seconds 20 In percent 50 temperature ( C) 40 3. Basic line, Pro-Engineer software, before final moulding arrange- body of the container. This criteria was also imposed by mould structure and part shape. Analysis of the body form and thickness of the part comparing constructive alternatives: its sidewall shapes, metallic elements of reinforcement and, if necessary, inclusion of the tubes injected with gas-assisted tech- niques to increase inertia of the sections, etc., were con- sidered. Obviously, mould dimensions and the presence of under- cuts supposed a problem added for the design of piece and mould. In this way, semicircular shape of the border T Basic Height W Length (e) the geometry settling sories set w Compan (other trial 1. 2. 3. Fig. 4. Software C-Mold: plastic temperature Technology 175 (2006) 1519 17 able 3 dimensions for 2400 l main body (mm) 1600 idth 1480 1600 of the upper container was a hard design problem; it was required for functional use but supposed an undercut area involving slides in the mould. Part volume was adapted and different aesthetic forms appearedfeasible conjunction of the possible thick- ness by manufacture with the thickness and forms by mechanical resistance. In this step, finite analysis, solid 3D design and filling simulation were made simultane- ously (Figs. 3 and 4). The final part dimensions are shown in Table 3. With these basic magnitudes calculated in these four steps, design team had an initial point for the final drawing of and the inclusion of the elements of details like down of output angles, radios, position of acces- of the set (cork, skid, etc.). Industrial flow analysis was in definitive way, fixing optimum positions for manifold orking together with the mould maker, Kyowa Industrial y with mould plants in the USA, Japan and Mexico. The main aspects of the process and their simulations details cannot be presented in order to protect indus- know-how) are: Model of the figure with geometries type 2.5D. Location of the entry points to the cavity. The use of race tracks for a better control of the filling was considered, following rheological design rule for simultaneous end of filling at the end of the cavity (avoiding over-pack effect), especially considering the border shape with semicircular areas. Optimal conditions of process: the selection of temper- ature and its relation with thickness and cycle strongly conditioned the permissible values for the design. Values between 210 and 250 C were evaluated. at ejection and cooling lines layout. 18 Processing Fig. mould. 4. tests ( is lated because gradients could 5. J. Aisa et al. / Journal of Materials 5. Real container model used for testing industrial conditions in 2400 l The adjustment of the filling form by means of the cor- rect programming of speeds became essential. At constant speed profile, the increase of pressure-supposed values of inadmissible force of closing by the limitation imposed to the dimensions of the machine. In the final arrange- ment for container mould, several ram speed stages were recommended. This procedure was experimentally validated with real using already existing smaller dimension container Fig. 5). Typical ram speed profile calculated with CAE techniques shown in Fig. 6, but this “function” cannot be trans- to the injection machine without practical arrangements, hydraulic systems are not able to follow all those exactly. Anyway, around 15% less clamping force be achieved after this optimisation procedure. After the filling possibilities were fixed, this was verified with a new numerical model by the mould maker from the initial ideas sent by the design equipment and with the final hot runner system data necessary for the mould. Fig. 6. Theoretical ram speed profile from computer results. 6. detecting of cessing (2025 ously Technology 175 (2006) 1519 Fig. 7. Real sample in CONTENUR assembly plant. The sequential technology was considered as a possibil- ity with the purpose of reducing filling pressure, but the practical arrangement, the maintenance and possible shut- downs underestimated their use. Finally, the analyses of cooling of the mould, packing and warpage induced by the process were developed. In this way, different constructive materials were used according to their thermal conductivity, adjusting cooling layout pro- vided by Kyowa Industrial Company. Final mould weight was higher than 150,000 kg (up to 150 metric tonnes). Actually, more than 6000 pieces were made without any problem in the injection, expulsion or the life the component in good condition (Figs. 7 and 8), and pro- rates are similar with other existing 1000 l containers parts per hour). Other components were simultane- designed and, in fact, it was more complicated to get Fig. 8. Complete 2400 l waste container, including all components. J. Aisa et al. / Journal of Materials Processing Technology 175 (2006) 1519 19 fine results, for example, in container lids, obviously smaller than the body. For the authors, the final conclusion is that CAE tools were basic in design process, and also compared with knowledge and real test using similar moulds. Acknowledgements The authors want to extend their gratitude to T.I.I.P. a.i.T.I.I.P. Group and CONTENUR Technical Staff, for their support and facilities to reach this final goal and very special thanks to Dr. Castany for all their “know-how” on plastic injection moulding process and design, exposed in many training References 1 C. Austin, Lean moulding: faster = cheaper = better, in: J.F. Stevenson (Ed.), Innovation in Polymer Processing Moulding, Hanser, 1996. 2 H. Gastrow, Injection Moulds: 102 Proven Designs, Hanser, 1983. 3 M. Ezrin, Plastics Failure Guide: Cause and Prevention, Hanser, 1996. 4 European Norm EN 12574: stationary waste containers: containers with a capacity from 1700 l to 5000 l, CEN/TC 183/WG1, 2000. 5 G. Menges, P. Mohren, How to Make Injection Moulds, Hanser, 1996. 6 J. Fuentelsaz, Metodologa para el diseno de componentes de plastico inyectados, Doctoral Thesis, University of Zaragoza, Spain, June, 1993. 7 F.J. Castany, F. Serraller, I. Clavera, C. Javierre, Methodology in gas assisted moulding of plastics, J. Mater. Process. Technol. 143144 (2003) 214218. 8 F.J. Castany, J. Fuentelsaz, F. Serraller, J. Llado, F. Martnez, Sim- ulacion aplicada al diseno y produccion de componentes inyectados, courses and seminars around the world. Plasticos Universales, 35, num. 11, September, 1991.