Denison Industries can produce cores up to 600 lbs. with a binder percentage of 0.4-0.45%.
Walker said. “But really, we were trying to find the best binder for our prod- uct. In turn, that meant dealing with our variables that we had never really addressed before to understand them fully. We challenged ourselves to bring our binders down, for our benefit and for the environment.” Denison invited three binder suppliers to provide a solution to its requirements but eventually settled on a mixture of its own design with a lower binder percentage. Te met- alcaster watched every aspect of the process both in the lab and on the plant floor, running tests for strength and core quality and studying how the binder held up over time and per- formed at shakeout. “We started out trying to get to at least 0.7% binder and then see what we could do,” said Tim Purcell, Porter Warner Industries, Arlington, Texas, who consulted with Denison Industries during the testing. “Ten we said we’ll keep going until we can’t go any longer.” Operators were consulted to be sure no variables were missed in the testing.
Denison performed tests in the lab on test bars and tests in the shop on 600- lb. (272-kg) core assemblies. “By testing on the floor, we were
able to start working with the high temperatures and moisture ranges that we would see,” Walker said. “All of that has an impact on how the mold sets up and the strength built into the mold.” Based on the results of a round of
tests, Denison separated the chemi- cals in the binder mixture, weighed them, and mixed a new trial binder by increasing or decreasing the percent- age of a chemical. “We repeated the process over and
over, and I charted out the variables from the data to see what was tak- ing place in the process,” Walker said. “After a week’s worth of collection, I’d look back and see how each variable correlated. From there we started devel- oping what the next mix should be.”
Bringing Down the Binder In each test conducted, the casting
company purposely learned where failure occurred to establish a nominal
We’re so comfortable with [our binder] now, operators hardly ask questions about it.”—Mike Walker, Denison Industries
38 | MODERN CASTING July 2011
operating range. Tests for failure were conducted offline so shop personnel would remain unbiased toward the various binder mixtures being tested. As Denison passed through round
after round of tests, ratcheting down the amount of binder chemical, it discovered the plant could operate at a high level with much less binder than it had been using. Eventually, the plant was producing 600-lb. cores in the summer with 0.4-0.45% binder— down from 0.65%—resulting in cast- ings with C60 surface finish or better. “I didn’t know what to expect,”
Walker said. “We were standing on the edge of a cliff. But we took the data and remained unbiased about what the process could do.” Walker said Denison has suc-
cessfully produced cores with binder percentages as low as 0.38 but holds at 0.4% to manage at a comfortable level. “If someone would have told me
they would be able to make a core at 0.38% binder, I would have said they were crazy,” Purcell said. According to Purcell, most aluminum nobake casting facilities use binder levels from 0.7 to 1%. Te lower binder level means
both decreased VOCs in the casting facility and an increase in the two- part binder’s flash points (the point at which chemical vapors will ignite) to 389.98F (198.9C) for Part 2 and 200.1F (93.4C) for Part 1.
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