Excerpt from the Foundry Management & Technology January 2021 article
Proactively monitoring sand temperature, compactability, moisture content, green compressive strength, and permeability will eliminate green sand variation at the molding location.
A common problem for metalcasters is proper green sand preparation. Even when the sand is prepared correctly, how can the foundry operators determine the accuracy of the formulation? How are the results recorded for repeatability purposes? How are changes implemented at the muller? Many foundries monitor sand by how the molding is performing. Proactive preparation of the green sand, accurately and consistently, will eliminate green-sand variation at the molding location.
Removing unwanted variations from the green sand properties is critical to producing consistent castings and running a successful foundry. Many factors contribute to variations in the way that green sand is prepared and delivered. Foundries usually have equipment from different manufacturers and perform different types of molding processes, which means they prepare the green sand from various recipes. It's important to determine what type of sand works best for each molding system.
To determine what green sand recipe is right for a foundry, establish what type of sand is to be used and how much clay content is needed. On a daily basis, green-sand preparation has five critical factors that need to be monitored closely for proper molding: sand temperature, compactability, moisture content, green compressive strength, and permeability.
It is understood that measurement can be performed at the muller but to get an accurate reading of these five components, it would best to take a reading at the point that the green sand is used with a digital sand testing unit.
The features of digital sand testing units include self-calibration and repeatable, accurate readings. It can be interfaced with the muller controls to adjust for variability between muller and molding machine. A load cell is used to is used to conform test sample height, which eliminates variance introduced by manually sampling, resulting in highly accurate results. Measurement data can be exported via USB, for easy data transfer to a quality-control database.
Accurate green-sand testing provides foundries with immediate return on investment for a small investment. The sand testing unit solutions can be implemented at a reasonable cost, and the ROI can be calculated by the signification reduction in scrap due to sand defects, as well as scrapped molds.Read more
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