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Metal Casting Technologies : March 2006
Structural integration of the casting simulation Data and information are increasingly valuable once they are used in praxis. In the foundry, technologies like charge material calculation, thermal analysis, spectral analysis, analysis of the gas concentration, x-ray, or CT provide information, whose flow and use is determined by QA-processes. In the same way it needs to be dealt with data generated by the casting simulation, that only gain in value when implemented into design and manufacturing (A. Schroth, D. Schemme, 2002). There are no standardized rules in respect to the integra- tion of casting simulation into design and manufacturing processes. However, companies with good experience in casting simulation exercise binding rules regarding the integration of simulations into existing QA-structures. Generally, the following is determined: ● Projects, where a casting simulation needs to be carried out, ● Point in time of the simulation, ● Charged cost centers, ● Documentation and back-up of the simulation results, ● Responsibility for optimization measures based on the simulation, and ● Verification of the optimization measures. A steady improvement of development and manufacturing with the use of casting simula- tion can only be assured where work processes strictly follow such binding agreements. Use and restrictions Commercial programs for simulation of casting processes have been on the market for nearly 20 years now. Performance and cred- ibility of software and available hardware have been drastically expanded and improved in this time. In some casting applications, like steel casting, the use of simulation had been evolved very quickly and reached a high level ten years ago. Today, there is hardly any steel casting with corresponding casting process that has not been extensively optimized with the help of casting simulation. On the contrary, the utilization of casting simulation in the design of high pressure die castings and die casting processes is much less than in steel casting. In the light of the global competition, especially by Asian foundries that are producing with drastic cost advantages and rapidly improving technology and equipment, as well as increasing know-how, the following perceptions exist in the western countries: The cost of the simulation is too high. The costs of a high pressure casting die in rela- tion to the costs of a pattern for a sand casting shows a huge potential to save costs if one succeeds in avoiding tool changes, in increas- ing tool lifetime, and in producing the desired quality of the casting at the first go. In many cases, costs for failed sample runs or for error correction and for rework are not consequently added to the unit costs. This results in high overhead costs that are considered as inevi- table. Engineers and technicians are not exactly aware of these costs in detail and sometimes do not feel responsible for them. On the one hand, the management tolerates significant cost variances for single products, but on the other hand, the management avoids to either pay in advance for simulation or to approve expenses for improvements that assure cost re- ductions. The result is a declining competitive- ness of the company. There is hardly a casting process, where effective and professionally used simulation is as beneficial as in high pressure die casting. Up to now, solutions have been found without the help of simulation. Foundries with a conventional and little changing range of products will find satisfac- tory solutions without the help of simulations. However, in this case simulations could help to reach improvements in a quicker and more methodical way. As the automotive industry requires a yearly price reduction for repetition parts due to constant operational optimization, room for improvement needs to be detected by simulation, and effectiveness of these improve- ments need to be evaluated by calculation. Ev- erything can be tried in a simulation, including variants that are finally not implemented into the real process. For sophisticated castings, it is important that provider as well as customer know as early as possible about the reliability of the planned casting technique. The simulation doesn't present the exact reality. The validity of the physical-mathematical models as basis for the simulation has been proven in many successful projects. It is often difficult to find the exact manufacturing process conditions of a casting. In this case assumptions need to be met, where the detec- tion of useful variations finally leads to a good agreement between the real conditions of the casting and the simulation values. This is the basis for the improvements achieved by the implemented changes. The experimentation is carried out in computerized manner. Due to the high number of parameters in high pressure die casting there are phenomena that appear in reality but are not part of the simulation model. Based on simulations, many companies have significantly improved the accuracies of new parts so that already in the first sample line high-quality parts are produced followed by a consistently top-quality serial production. With simulation, knowledge can easily be transferred and know-how based on experience has less value. It is difficult to defend the competitiveness of a company based on the specific knowledge of certain employees. There is probably a higher loss of this knowledge due to employee turnover than due to the transfer of simula- tion results between designer, foundryman, toolmaker and end user. The work of casting service providers is based on confidentiality. It is proved that simulation in one's own com- pany leads in any case to increasing know-how rather than to the loss of technical expertise. Knowledge can be stored and internally trans- ferred by using documentation and archiving processes. In this way, personal knowledge is much better processed and actually made available to other employees. The quality of the calculated results is significantly improved when considering know-how based on experi- ence in the simulation. Now and in the future, the foundry specialist is needed. There is no use of simulation in my area of responsibility. No question, some casting engineers gave up hope. The casting is designed by the design engineer without specific consideration of the manufacturing process. The toolmaker prioritizes on his own process. All problems of the whole manufacturing process are passed on to the foundryman. This applies to designing heavy sections in the casting as well as to not systematically elaborating the position of the ingates, the cooling channels, or the overflows. If the foundryman accepts those conditions without objection, he decreases to a simple metal pourer. Chances arise by the endeavor of great automotive companies to create an integrated development and manufacturing chain. This includes integral cost awareness, i.e., also the designer needs to contribute to a cost effec- tive production. It is understandable that the designer doesn't want to perform the casting simulation by himself, especially as he doesn't profit from the cost reductions in the further course of the manufacturing chain. This is the chance for the foundryman to provide prompt and capable input with the use of simulation and also to point out requirements in respect to the production of new designs. This kind of assistance can also be offered by service provid- ers. In their own interest, foundryman should be involved in and pro-actively work on the processes as early as possible. Alfred T. Spada, editor of 'Modern Casting', writes regarding the reservation towards the simulation in an editorial of 'Modern Casting' (A. T. Spada, 2004): 'If you are still waiting for casting process modeling/simulation to prove itself, I'd say that your are at least a decade behind the times. If you still argue that you can't justify the cost for the technology/manpower, I'd say that you haven't done a true time or cost analysis as to what this software can save your operation. The proof is in the success that every metal- caster using the technology has had.' METAL Casting Technologies March 2006 ADVERTORIAL