Views: 9 Author: Site Editor Publish Time: 2020-06-30 Origin: Site
The veneer after rotary cutting is dried, and then repaired to form the plywood production molding stage. At this stage, the veneer undergoes sizing, forming, cold press, and finally enters hot press to form plywood. The amount of sizing and the result of cold press are related to the process of hot press and the quality of the product, and are an important link in the production of plywood to determine the quality of the product.
Before the plywood is cold pressed, the glued plywood needs to be left for a period of time. The purpose of this is to allow some of the water in the glue to evaporate or penetrate into the veneer, which can reduce the water in the glue layer, increase the viscosity, and increase the degree of glue. It is easy to form a uniform and continuous glue layer during cold press, to avoid excessive glue from infiltrating into the wood, thereby improving the strength of the glue. If the storage time is not enough, the glue layer has too much water, the glue will dry out and lose its activity to reduce the adhesion, or it will open the glue.
The function of cold press is to allow the veneers in the plywood to be bonded to each other, so that the plywood is firm and the surface is flat. In this way, it is easy to install the board by mechanical board without pad during hot pressing. The use of cold press can also shorten the time of hot pressing, improve production efficiency, reduce heat consumption, and ensure the quality of plywood.
In order to adapt to the cold press process requirements, the adhesive must have a certain initial viscosity, otherwise the veneers cannot be well bonded together. The cold pressing process differs depending on the properties of the tree species and gum. Make adjustments according to your own production.
When cold pressing, put the glued plywood into the cold press to apply pressure. The plywood stomp height is determined by the hot press. Generally about 1 m, the plate pressure adopted is 0.8 ~ 1.0 MPa, and the cold pressing time is 15 ~ 20 min. To check the effect of cold pressing, you need to see whether the adhesion between the various layers of boards is good. For plywood with good adhesion, when the veneer is lifted, you can see that the glue layer is slightly drawn (note that there can be no wire drawing when applying glue).
The cold press equipment generally adopts the upper pressing type, so that the plywood slab will be more convenient when entering the cold pressing machine. The number of one-time cold pressing plywood slabs cannot be too large, otherwise the effect of cold-pressing is not good, and the thickness of each cold-pressed plywood slab does not exceed 60 cm. If one cold press can not meet the output of the hot press, you can buy two to use together.