Summary:

Researchers at the Ohio State University have discovered a novel and inexpensive ways to detect density gradient in materials. A variety of industries use compaction as means of shaping material, most notably the manufacture of metal and ceramic parts. However, density gradients in the mold, or changes in density in different parts of the material, are inevitable in all of these processes and cause a host of downstream problems. A common element of these problems involves the cost of further processing of these compacted parts. If these gradients are severe enough in the compacted part, the least costly solution would be to reject/recycle the part prior to a particular thermal process. Unfortunately, density gradients are currently invisible to the naked eye, so many parts with unacceptably high density gradients go on to costly further processing only to be discarded later on. Only by the use of sophisticated and expensive techniques not suited to the production environment can they be visualized.

Scientists at OSU have developed a method to detect the presence or absence of density gradients in sand molds. This method uses elements that are readily available in the typical production environment and does not add significantly to total production costs. This detection method is able to identify density gradients, allowing for early rejection of out-of-spec molds. Further, the detecting chemical is added in such low concentrations that there is no detectable change the physical properties of the sand mold.

This detection chemical (a readily available commercial material) is dissolved in one part of a two-part binding system that cures at room temperature following mold formation. The remainder of the processing to sand molds occurs in a normal fashion. No untoward effects of the presence of the dye on the mold formation process have been observed. High and low density defects on the surface of these sand molds can be readily observed using equipment that is common to the production environment.

Potential Applications:

• Reduction of waste and cost for mold manufacturers
• Reduction of waste and cost for biner/resin manufacturers

Advantages:

• Does not add significantly to production cost
• Use elements available in typical production environments
• No detectable change in physical properties of mold
• Allows for early rejection of bad molds