Sponge Slabstock Foaming Machine--Overflow Trough Method Flat-Top Foaming Machine

The overflow trough method (Maxfoam method) is a process developed in the 1970s. Unlike traditional foaming machines, which foam from bottom to top, this method ingeniously combines an overflow trough with a drop plate. The emulsified foam overflows from the trough onto the drop plate, and by adjusting the angle of the drop plate, the foam forms from top to bottom. This design eliminates the obstruction caused by sidewalls and results in a flat-top foam block (Figure 1). Since the foam does not need to overcome its own weight as in bottom-up foaming, the Maxfoam method produces foam blocks with thinner bottom skins and lower overall density.

Figure 1: Schematic Diagram of the Overflow Trough Method

From the characteristics of the overflow trough method, it is evident that the foam flowing onto the drop plate paper mold is in an emulsified state. If air bubbles are trapped inside, they cannot float to the surface in a slurry clearing zone like in conveyor-type foaming machines. Instead, they remain within the foam, leading to uneven pore distribution and defects. Therefore, in overflow trough foaming machine production, factors such as mixing head stirring speed, air intake, and foaming speed adjustment are crucial. Due to these challenges, using an overflow trough foaming machine to produce industrial foam plastics requiring high uniformity in pore distribution is relatively difficult.