Method of making gas curable resin-coated sand cores

Abstract

A method of making sand cores to obtain optimum mechanical properties and particularly to obtain accurate adjustment of the gas curing cycle for making optimum resin-coated sand cores. The method comprises blowing, into a core box cavity, mixture of core making particulated sand and gas curable liquid resin having a first level of pH, such mixture containing a uniform distribution of a pH indicating dye additive that changes color in response to a change in pH level, in contact therewith, such blowing being continued to fill the cavity to a desired density and form an uncured sand core shape with a predetermined porosity, (b) introducing a catalyst gas having a second level of pH, through the pores of the core shape to cure the resin and contact the dye additive, (c) concurrently, or subsequent to step (b), sensing the degree of color change of any part of the core shape that is or has taken place as a result of exposure to the flow front of the catalyst gas, and (d) responding to such color sensing to modify the parameters of catalyst gas introduction (i.e. exposure time, gas pressure, gas concentration or gas inlet/out location) to ensure the desired degree of catalyst reaction in the desired time period.