Dry ice blasting: a new technology for corebox cleaning.

In the past few years, there have been great strides made in corebox technology, particularly in the area of corebox cleaning.

Ten years ago, when coreboxes became caked with deposits and gas vents were plugged, an assortment of cleaning methods

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Thorough cleaning of vents was virtually impossible. Cleaning was performed by the tedious method of pulling boxes out of the machines and knifing the vents out, one slot at a time.

Now, with shorter runs, faster turn-arounds and flexible approaches to manufacturing, new corebox techniques have emerged, and optimizations prevail. At Saginaw Malleable Iron/ Central Foundry Div.- General Motors (GM), one process that was analyzed was the use and cleaning of coreboxes, especially those made of newer materials. The traditional metal cleaner used on the tooling during molding combined with the new resins in coreboxes, producing a heavy, clay-like deposit. These deposits could not be blown out, making it necessary to revert back to sand blasting and the tedious knifing process. Project Parameters

The entire core production process was reviewed during a six-month project at GM. The project focused on the most efficient way to maintain urethane coreboxes in the new coldbox process.These coreboxes are softer than the older metal boxes, and grit blasting would wear and change the box dimensions.

The initial survey of various plants in the foundry division at GM turned up a variety of methods used for cleaning coreboxes. The optimum method appeared to be a combination of chemical dipping and grit blasting with glass beads.

Simultaneously, a unique cleaning technology (CO[sub.2]Cleanblast[TM] was developed at Lockheed for aerospace applications and had been licensed to Alpheus Cleaning Technologies for general industrial use. Through joint experimentation and trials with Alpheus, a new technique evolved for cleaning coreboxes and tooling, which has dramatically improved production at GM. Dry ice Blasting Process

This new process involves the production of dry ice (solid CO[sub.2]) pellets that can be sprayed from a nozzle at high velocity as the cleaning agent. Although the process is similar in nature to grit blasting, there are two significant differences: * The dry ice pellets do not clean by