Make Your Testing Matter M


A proper testing plan will ensure your testing results have some meaning. Shannon Wetzel, Senior Editor


ost metalcasting facilities have testing and inspection procedures in place for their molding, melting and quality control operations, but the


time and effort put into a facility’s test- ing plans can be wasted if there is little meaning behind the data or the wrong data is collected. One of the main aims of process


or quality control testing is to detect variation from the established range. Variation can indicate a below-quality casting or an inefficient process. But care must be taken to establish timely and regular tests that are read and recorded in-process. “The more consistent the properties


of all the individual components of the process, the more consistent the overall quality of the finished casting,” said Eugene Murator, senior foundry met- allurgist, Rio Tinto Iron and Titanium America, Chicago.


Sand Molding Pointers Mold sand tests help ensure casting


properties and avoid defects, and per- forming them is a key step in a sand casting facility’s quality assurance plan. One of the keys to a good sand testing plan is the frequency with which your tests are performed. Some textbooks and research papers


provide a regimented view, calling for testing once an hour or once a shift, depending on production rates and the quantity of sand that moves through the system. According to Vic LaFay, research and technical development manager, S&B Industrial Minerals North America, Niagara Falls, N.Y., another way to set frequency is by turns of the sand system. LaFay said the properties of the sand should not change until a new batch is added to the system, so multiple tests taken in the same day on the same sand cycle are irrelevant. “If you over-test or over-control, the data means nothing,” he said. Typically in a casting facility, mold


MODERN CASTING / July 2010


samples are sent to the sand lab for full testing. But a few tests can be performed on the molding line for an immediate look at how the process is running. “The optimum use for inspection or monitoring data is to have it close and immediate so we have a short feedback loop,” said Ted Schorn, general man- ager, Enkei America, Columbus, Ind. “If anything lengthens that time, even if it makes it prettier or a little more accurate, I’d rather have [the results] right away.” On the sand line, LaFay recommends


three tests be performed while standing on the shop floor, rather than back in a lab. Mold hardness and mold strength can be tested with handheld devices, such as a B-scale electronic mold hard- ness tester. A simple thermometer can test a mold’s temperature, which affects the casting surface and proper filling and cooling in the mold. “Temperature is critical to mold quality,” LaFay said. “And you can use


a simple $2 thermometer that fits in your pocket.” Record the quick shop-floor tests in


order to map out trends in the molding area, and perform them with regular- ity, such as with each turn of the sand system, LaFay said. “Ninety-five percent of metalcasters


use data as a post-moratorium, after the defect has occurred,” he said. “But you can utilize the data for prevention. It’s important to put the data in front of the operator.” Many shops employ an automatic


sand testing system that continuously tracks the properties of the sand, such as compressive strength, temperature and shear strength, and controls the ingredients and temperature in the muller or mixer to achieve the proper mix. However, LaFay still recommends performing the three online molding tests to verify the results from the green sand control system. When performing the separate tests, don’t get hung up on


The chemical characteristics of metal poured in your casting facility should be checked while the metal is still molten, rather than verified after the castings are poured, according to Ted Schorn, general manager at Enkei America.


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