Joe, his wife Nancy, and their golden retriever Tequila reside in Universal City, Texas. This month we feature a question about cracks in ring-less investment molds. Should you want more information about a particular topic, please contact the individual whose name follows the specific answer in which you are interested. If you have a question about a topic not discussed in this issue, feel free to call DIS at DSN 240-3502. The castings still fit well and there is no finning.
Several factors cause cracks in investment molds.
Since there is no finning, the cracks are not very deep. This leads me to believe there is rapid steam expansion on the surface of the investment. You are probably rinsing the mold after scraping the top of the mold or, you are wet trimming the mold. Dampening the mold introduces water on to the surface that causes rapid steam expansion and cracks. Carefully scrape the top and then inspect the sprue area.