Pulsed compaction

State-of-the-art molding technique used for the manufacture of flasked molds made of bentonite-bonded mold materials. It uses compressed air as the pressure medium; the gas-based pulsed compaction used in the past is no longer applied.

Pulsed compaction counts among the dynamic compaction processes in which force is applied for a time of no more than 0.01 to 0.02s. The compressive stresses acting to compact the mold material increase rapidly to then decrease as quickly. The compaction principle of the molding machine is based on the acceleration of the mold material and subsequent deceleration at the pattern plate. A high pressure gradient of the compressed air pressure medium over the mold material column is the critical factor in pulsed compaction.

The generation of the necessary pressure gradient is achieved by briefly opening a valve. The pre-metered mold material mass is then subjected to a compressed air blast, accelerated from the direction of the back of the mold and compacted on the pattern when stopped. The maximum air pressure for compaction is 6 bars. The degree of compaction can be controlled by changing the pressure.

Additional references:
Mold material compaction
Compaction testing