This is true, real-time compactability control. The sample feeder, a direct drive screw feed device, begins taking a continuous sample of sand through the mixer wall, aerating it and dropping it on the vibratory feeder trough of the compactability tester. If the sand is exceptionally dry, it falls through an adjustable slot in the trough into a lower catch basin. Its presence there is detected by a photocell that signals the moisture addition system to quickly add water to the batch. The initial water charge is determined by the batch recipe and incoming sand temperature.
Excess sand is removed by a strike-off blade before it passes under a compaction wheel.
A smaller compaction wheel, mounted on a pivoting armature, applies a fixed load to the sand sample that is in the larger mold wheel. The PID loop compares the measured value to the selected set-point value and continuously makes the required adjustments to maintain precise control over the system. The system captures the data that triggered the alarm, making it easy to trace the problem to its source. Otherwise, the system operates without any operator intervention. Special systems are also available where a single control panel can provide control and reporting over multiple mixers and testers.