Fig 1. Heavy-duty multi-cylinder thermal wood pallet press
The Moisture Threshold in Molded Wood Packaging
One of the most frequent errors in molded fiber production is attempting to compress raw, wet sawdust directly into the hydraulic press. Hydraulic pallet presses operate using extreme pressure (up to 1000T) and thermal oil heating (around 200°C). When sawdust containing more than 15% moisture is introduced, the rapid heating causes water to vaporize instantly within the mold. This steam pressure creates internal air pockets, leading to pallet delamination, blowouts, and failed dynamic load capacity.
The 8-12% Golden Rule
To achieve a seamless ISPM-15 exempt pallet, the raw material matrix must hover precisely between 8% and 12% moisture. Below 8%, the natural lignin within the wood fiber fails to plasticize, leading to brittle pallet corners. Above 12%, the excessive steam prevents the urea-formaldehyde resin from curing correctly.
Implementation Boundaries
Unprocessed Green Wood: Direct from the sawmill, green sawdust often holds 40-60% moisture. You cannot feed this into a pallet press. A rotary drum dryer is an absolute prerequisite to bring this material down to the pressing threshold.
Internal Linking to Core Assets
To establish a defect-free continuous line, the interaction between your dryer and the high-capacity pallet machine must be synchronized via Siemens PLC.