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St. Paul Foundry

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Airset Molding Basics for Non-Ferrous Castings


Airset molding is sometimes referred to as no-bake or dry sand molding. It is a chemically bonded process. There are many different chemical systems that can be used to make molds. The capabilities of the systems are similar, but the costs can vary widely.


Cost drivers include the binder chemicals, time to make a mold, time for the mold to set, ease of workability, requirements for coating the mold cavity, resistance to mold metal reactions, how much sand can be reclaimed, resin requirements as a percent of sand used, requirements for temperature control of the sand - either heating or cooling, and the amount of finishing labor necessary to make the castings meet the customer's requirements.


Our airset molding is a phenolic urethane bonded catalyst, resin and accelerator system. The resin is coated evenly on the sand grains in a mixer. Sand and resin flow into a tubular chamber. Inside the chamber is an armature with spinning paddles that rapidly coat the sand. Mixers vary in size.


In a typical, horizontally parted mold the coated sand flows from the mixer into either a flask or a flaskless box at the bottom of which is the pattern. The cope and drag are made separately. The sand is packed as it fills. It is vibrated on a compaction table. When filled the mold half is conveyed to a curing line. Mold cure time can be managed by catalyst and accelerator levels. Strip time is managed so that the sand is workable for a short time then becomes hard enough to strip the pattern. When the mold has cured enough that it cannot be deformed the pattern is pulled from the sand or "stripped".


If necessary, coatings are applied to the inner surfaces of the mold cavity. Cores are set. Filters are placed. The mold is blown clean. The cope must now be rolled over so that it can be placed on the drag. This is done with a mold manipulator. Once the mold is assembled it is ready to go to the pouring line. Large molds may be allowed to cure for additional time. Airset chemicals can continue to gain strength for up to 24 hours.


Airset is a more precise process than greensand. The molds are extremely strong to handle the pressures of large castings. Because the mold is fully set before close over, complex core assemblies and multi-part molds can be assembled with precision.

St. Paul Foundry
954 Minnehaha Avenue West
Saint Paul, Minnesota 55104
(651) 488-5567  Fax: (651) 488-0908
Sales: (651) 312-4734 email

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