How long does plywood need to be cold pressed in a cold press machine
The cold pressing time of plywood in a cold press machine needs to be flexibly adjusted according to the type of adhesive, thickness of the board, and process requirements, usually fluctuating within the range of 15 minutes to 12 hours.
Based on the type of adhesive, when using casein glue, the moisture content of the plywood should be controlled at 7% -10%, and the pressure time should be 3-5 hours; If cold setting resin adhesive is used, the moisture content needs to be reduced to 4% -6%, and the pressurization time is also 3-5 hours. For specific substrates such as eucalyptus veneer, cold pressing for 60 minutes can achieve adhesive penetration saturation, but exceeding this time can easily cause excessive compression of the veneer, leading to rebound after unloading and reducing bonding strength.
From the perspective of the process flow, in conventional operations, the slab needs to be continuously pressurized in the cold press for 4-12 hours and synchronously subjected to pressure stabilization treatment. If it involves a composite process of hot pressing and cold pressing, such as transferring to a cold press machine for secondary shaping after hot pressing, it can be shortened to 15 minutes (as in the case of post-treatment of lignin based adhesives). In addition, if the 19mm thick board is bonded by cold pressing with urea formaldehyde resin, the unit pressure needs to reach 1.2 megapascals, and the bonding time needs to be extended to 6-8 hours.
In actual production, operators need to strictly follow the process documents to set the holding time, such as placing pads at fixed heights during slab stacking to ensure uniform force distribution. In low temperature environments during winter, the cold pressing time needs to be extended by an additional hour to compensate for the decrease in adhesive curing rate.
