System Efficiency
In looking at cutting energy, we always need to be mindful of the efficiency of the system. Much like the widely accept- ed casting process simulation, modeling of the core making process can result in fewer shop floor hours spent develop- ing and optimizing tooling. The efficient placement of blow tubes and vents may result in lower binder levels, by reduc- ing the compensation used to make up for inefficiencies in current methods.
These examples are not used to endorse any product or sys- tem, but to show how simple ideas can significantly con- tribute to going greener, enhance the process, and become beneficial quality control tools.
What Else Can Be Done?
Energy reductions in the molding process represent a big- ger challenge for going greener. The easiest savings are in the efficient use of power. Utilizing high-efficiency motors should be the first consideration. High-efficiency motors or even ultra-high-efficiency motors can save 2–5% on oper- ating energy. When considering the cost of high-efficiency motors, remember that the original purchase price will prob- ably be no more than 5% of the operating cost of the motor over its lifespan, and the cost of electricity will be more than 95% of the cost of operation. As a general note on motors, a foundry needs to have a very specific procedure on the rewinding of motors. In most cases, the rebuilding of motors should not be done except in the case of very unique motors or a long leadtime for a new motor. Studies have shown that rewinding motors nearly always results in a motor that is not as efficient as the originally purchased motor. If rewinding must be done, a carefully written set of engineering instruc- tions and procedures, as well as an approved source for car- rying out the work, must be in place. Another consideration is using variable frequency motors for operations that have widely varying loads throughout a cycle, for example, mull- ing of sand.
In the nonferrous foundry, industry conservation of water in diecasting operations offers opportunities for significant savings. Far too often, cooling water is used once and passed down the drain. This hot or warm water has heating value for many applications. As discussed previously, BTU con-
tent can be pulled from any liquid. Creative use of this heat recovery is a matter of looking for the best use for the heat.
Additionally, water of varying temperatures may be suitable for reuse. One fallacy is that cold water draws more heat out of a mold. Temperature pickup is uniform over a very wide range of incoming water temperatures. Going greener often requires some research to break a paradigm and change a popular belief.
What technical barriers exist in the foundry process that prevents us from becoming much greener? Are there some areas of the foundry process that have technical challenges, for which we have no current solution? The fact is there are technical barriers to the casting process that have yet to be broken, and these barriers are preventing us from achieving really significant energy savings or waste reductions.
One example of a technical barrier is the lack of a rapid prototyping system for green sand molded iron castings. There are no complete systems to make a casting in a day’s time that will replicate a production casting. There are some programs that will replicate the geometry of a mold, but usually not in a binder system suitable for iron pour- ing. Duplicating the surface finish, draft, ingate and riser locations, and mold pouring and shakeout conditions are also considerations. The other major component of a rapid prototyping system must be the duplication of iron proper- ties from a small furnace, where chemistry can be varied to tailor casting properties.
Conclusion
Many of these ideas are not so new and we have all talked about implementing them. However, time passes and maybe we have not pursued these ideas due to other current con- cerns, or we have done so only in an inconsistent manner. Reaching the point of determined action and embracing the possibilities of sustainability may prove to be one of our greatest challenges. Once we have achieved the focus to think green in all aspects of our industry, we are open to the possibilities that were only waiting for us to seize them. This focus, along with the pragmatic application of exist- ing technology, will guarantee that the foundry industry is recognized as a sustainability leader by other industries and the public.
International Journal of Metalcasting/Summer 10
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