Vacuum Forming and Dewatering: How Suction Builds the Molded Pulp Wall

In molded pulp forming, vacuum does two jobs at once: it pulls suspended fiber onto the screen mold and draws water through the forming layer, compacting it into a wet wall. The vacuum profile — timing, level, and distribution — decides how thick, dense, and uniform that wall becomes before pressing and drying.

The Scenario: A wall built by suction

Vacuum forming faces three challenges:

Pain Points

• Weak or uneven vacuum leaves thin, low-density patches in the wall;
• Excessive vacuum can pull fiber through the screen or over-densify surfaces;
• Timing errors — vacuum on too early or late — misbuild the wet web.

The Solution: Three vacuum solutions

Three controls build a uniform wall:

1. Profiled vacuum timing Stage vacuum application so fiber deposits evenly before dewatering compacts the web.

2. Balanced suction level Set vacuum level to compact without pulling fiber through the screen or over-densifying.

3. Screen condition control Maintain clean, uniform screens so suction distributes consistently across the mold.

The Result: A uniform wet web

The wet wall forms even, dense, and consistent — the foundation for pressing and drying.