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.
Many foundries will batch mull sand for each molding line; which is delivered and stored in the small sand hopper at the machine. This process is a simple solution for individual sand properties at each molding location. If you do not have the means to batch-mull green sand, then sand must be prepared in a manner that will provide best properties for all equipment. Due to the narrow window of variation of the sand parameters, close monitoring of the sand will be required.
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. The Sinto DST-II series allows foundry operators to take readings of the sand make-up at any point in the system because it is a portable testing unit. Unlike the fixed sand-testing systems that fixed in one place, the DST-II can be used anywhere, such as at a jolt squeeze line or molding machine.
Sinto has provided DST-II units to smaller foundries that do not have in house established testing procedures: foundries can process real-time data of the sand they are using and receive the results within 90 seconds for results.
Sinto has successfully used the testing unit for customers installing new automated molding line, accurately analyzing the sand and removing any variable from the start-up procedure when launching new projects. With accurate data, the new machinery can be launched quickly and reliably.
The features of the DST-II in-line digital sand testing unit 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 DST-II is a solution that 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.
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