24 be foundry specific, I suggest 85% within +/-1, and 95% within +/-3. Evaluating the percentage of the time the sand was within +/-3 this month compared to last month can be a quick check. This is an easy metric to share daily, weekly, and monthly to communicate the sand performance with molding and maintenance teams. If the metric is 10% lower today than yesterday, it should signal that something is off. Start evaluating what else was happening during that time, such as temperature fluctuations, clay to water ratio, or operation of the compactability controller. Most often, the temperature fluctuates during times of lack of control. The quickest and easiest check is ensuring you are using the full amount of your return sand storage. Another item that can affect the sand temperature is changes in the sand-to-metal ratio. However, this is much less controllable. The most dependable way to reduce variation in temperature and moisture is a sand cooler. Temperature Control Compactability (TCC) functions on compactability controllers optimize water additions based on temperature. Ideally the water added is the exact amount needed to activate the clay. When the sand is hot, some water will be used to cool the sand, and the remainder to activate the clay; therefore, more water is required when the sand is hot than if at ambient temperature. To account for moisture loss as the sand travels from the muller discharge to the molding line, the TCC can be programmed to add additional water at elevated temperatures. The foundry can adjust the TCC offsets if it is deemed the moisture loss is having greater or lesser impact on compactability. If there is a lot of fluctuation at specific temperature ranges, it may help to evaluate these settings. There is a possibility that the offset is too great or too low for the temperature range. CONDUCTIVITY Conductivity is used as a relative measure of moisture in the return sand coming into the muller; typically, a wetter sand mixture will result in a higher conductivity measurement. Multiple conductivity measurements are taken and averaged together to report a single value. Plotting time by conductivity can highlight concerns that should TCC offsets can be adjusted to optimize sand properties When tracking conductivity values over time, look for repeating 0.35 readings. Continued on page 26
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