How
Low
Denison Industries reduced its nobake binder percentage from 0.75 to 0.4 while achieving more consistent production. SHANNON WETZEL, SENIOR EDITOR
Denison Industries, Denison, Texas, sits down to dinner at home, he no longer dreads a phone call from the off-shift with sand molding prob- lems. Following a comprehensive and methodical 18-month investiga- tion into its nobake sand molding operation, the aluminum metalcaster is producing 20-lb. to 30-ton molds with 0.4 to 0.65% binder (down from 0.65 to 0.75%) like clockwork, and Walker can eat in peace. “We are very comfortable with [our
W
binder],” Walker said. “I never thought I would say that. We’re so comfortable with it now, operators hardly ask questions about it. We don’t have the common problems from the process.” Previously, Denison experienced occasional soft spots on cores or poor mixes that produced a failed mold on the line. Te failures caused backups in the entire operation. According to Walker, Deni-
son’s main problem areas were related to moisture and sand
hen Mike Walker, main foundry superintendent,
temperature. In the Texas summers, days start at 70F (21C) with 20% humidity, but by the afternoon, ambi- ent temperatures can reach 90-100F (32-38C) with humidity close to 100%. Actual sand temperatures range from 40F (4C) in the winter to 102F (39C) in the summer. “At each level of temperature or
moisture [change], we saw an effect on the way molds were setting up, work time and strip time,” Walker said. “Trough extensive testing and trying different methods of application, we now understand when and how to adjust to the variables. We are operat-
“If someone would have
ing with low to high sand tempera- tures now with no negative effects on the sand mold or casting quality.” At the same time, Denison Indus-
tries reduced the costs associated with binder material and reworked castings and lowered the amount of volatile organic compounds (VOCs) produced in its nobake operations.
Charting the Variables
Denison gained confidence in its molding operations by first taking a magnifying glass to it. Te metalcaster performed a
told me they would be able to make a core at 0.38% binder, I would have said
they were crazy.”—Tim Purcell, Porter Warner Industries
complete documentation of its nobake process, examining and testing individual equipment capabili- ties and improvements, resin binders, core release agents and their compatibility with resin binders, shakeout properties, calibration methods, and long- and short-term core strength values. “When we first started test-
ing, we were trying to improve the nobake line itself because of its issue of releasing cores and molds out of the boxes and erosion and burn-in defects,”
July 2011 MODERN CASTING | 37
Can It Go?
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