Denison Industries tested each binder mixture across a wide range of variables, including how long a core or mold sits before pouring.


Sand Plays a Role According to Purcell, mixing


equipment also plays a role in binder performance. Wil Tinker, president of Tinker Omega, said a mixer’s perfor- mance is based on the diameter vs. length of the chamber (where the sand is mixed) and the overall tip speed of the mixing blades. Te accuracy of the pumping system, design and type of pump and spin control yield accuracy of delivery. Accuracy in the pump- ing system allows for a lower overall binder percentage, Tinker said. “Once you get to a certain binder


percentage, [going lower] depends on how good of a mixer you have,” Purcell said. “So we started learning how far we could push Denison’s mixers and went as low as the mixer would let us go.” During testing, Denison discov- ered each mixer had different capabili- ties, but all of them have been able to manage 0.4% binder levels. “It’s important to know that your


sand level is consistent and the mixer keeps the sand-to-binder ratio that was set,” Walker said. Denison uses 98% thermally


reclaimed sand with 2% Oklahoma 75GFN sand. Te high quality Oklahoma sand is an advantage for running at low binder levels, according to Purcell, because it is a pure, round grain silica sand. Termal reclamation burns the binders off the sand grains,


Mixer equipment performance affects how low binder level can be reduced.


so Denison Industries can remove the dust fines through a collection system, producing a better quality of sand grain to which the binder adheres. “What is happening at Denison


is a trifecta—they’ve got a good resin system, as well as a good sand system,” Tinker said. “Plus, the sand they are bringing to it is good.” Denison keeps its sand stored outside in a silo. “We’re not heating or cooling sand


down except with a cooler classifier on the thermal reclamation unit,” Walker said. “Te moisture from humidity is still there. We haven’t done anything to control the environment on the shop floor. We just adapted our process to run effectively with lower binders. We fully understand what percentages to run for various temperatures and set up times based on the data [from the testing].”


Chemical Compatibility Denison’s investigation led to total


knowledge of its nobake operations, from how a unique batch of new sand will affect the molding line to which chemicals are present and active in its release agent. Armed with this data, Walker says he knows how to adjust the system for cores that may be setting up and sitting for two weeks or are being produced on a humid day. He can calculate the cost going into each mold or core in the shop,


and opportunities for improvement become more apparent with better understanding of all the variables. Case in point: Denison had been


experiencing difficulty removing molds from one of its larger nobake lines. After making sure the box was level and the shaker to remove the mold was operating properly, the metalcaster studied the release agent and its com- patibility with the binder. It discovered the solvents in the release agent were some of the same chemicals used in the binder, and the combination was acting like a thinner, reducing the effect of the release agent. Te casting facility stopped using binder with similar chemicals, and the erosion of chemicals was eliminated. Once the binder was no longer negatively react- ing with the release agent, Denison found it could use less of the agent on its molds. It now uses 12.5 gallons of release agent a year, compared to 250 to 275 gallons prior to the testing. “We never thought in our wildest


dreams we could do that,” Walker said. “It came along with looking at the process. And now the molds nearly fall out of the boxes.”


ONLINE RESOURCE Visit www.moderncasting.com for an article on low emissions binders.


July 2011 MODERN CASTING | 39


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60