How to solve the common problems of blistering, delamination, warping and hot pressing of plywood

How to solve the common problems of blistering, delamination, warping and hot pressing of plywood?

Plywood production process, hot pressing plays a very important role, today to share with you hot pressing problems and solutions.

How to solve the common problems of blistering, degumming, warping and hot pressing of plywood?

1、 Blistering and local degumming

The causes are as follows:

1. The moisture content of veneer is too high or the drying is uneven

2. Too much glue

3. The pressure drop speed is too fast or the hot pressing temperature is too high

4. Insufficient condensation degree of resin

5. Insufficient hot pressing time

Solutions:

1. The moisture content of veneer should be controlled in the range of 8-12%

2. Control the amount of glue to meet the process requirements

3. The speed of the second stage of depressurization should be slow, and the hot pressing temperature should be appropriately reduced

4. Check resin quality

5. Prolonging the hot pressing time properly

2、 Low bonding strength or degumming

The causes are as follows:

1. Poor glue quality

2. Insufficient or uneven glue application

3. If the aging time is too long, the glue solution has dried or the aging time is too short, the glue does not form a continuous film

4. The pressure is insufficient, or the temperature is too low, or the hot pressing time is too short

5. The burr and groove mark of veneer are too deep and the quality of rotary cutting is poor

6. The moisture content of veneer is too high

Solutions:

1. Check the glue quality

2. Pay attention to the moderate and uniform amount of glue

3. The aging time is mainly controlled

4. Increase the pressure and temperature properly, or extend the hot pressing time

5. Improving the quality of veneer rotary cutting

6. The moisture content of veneer should not exceed the specified range

3、 Penetration

The causes are as follows:

1. The quality of veneer is too poor, and the back crack is too large

2. The glue solution is too thin or too large, and the aging time is too short

3. The temperature of hot pressing is too high or the pressure is too high

Solutions:

1. Improve veneer quality and reduce back crack depth

2. Increase the concentration of glue, reduce the amount of glue, prolong the aging time

3. Reduce the hot pressing temperature or the unit pressure of hot pressing

4、 Core plate lamination gap

The causes are as follows:

1. The core plate is not integrated, and the manual core clearance is not controlled

2. The movement and dislocation of core plate during plate installation

3. The edge of the core plate is uneven

4. The edge of the core plate has a lotus leaf edge or a crack

Solutions:

1. The core is arranged after the core plate is whole sheet or glued and aged

2. Prevention of core plate dislocation during plate installation

3. The edge of the core plate is sheared straight

4. Improve the quality of core board rotary cutting and drying, prevent lotus leaf edge and crack

5、 Warpage

The causes are as follows:

1. Plywood structure and processing technology do not conform to the principle of symmetry

2. The moisture content of veneer is not uniform

3. Too high temperature and pressure

Solutions:

1. Observe the principle of symmetry

2. Improving drying quality of veneer

3. Reduce temperature and pressure properly

6、 Tolerance range of plywood

Causes

1. Too many hot pressing sheets in each interval

2. Veneers vary in thickness

3. Platen tilt or plunger tilt

4. The thickness calculation of plywood blank is not correct or the pressure is too high and the temperature is too high in the hot pressing process

Solutions:

1. As far as possible, the hot pressing process of one sheet and one press should be adopted

2. Improve veneer quality

3. Press installation and calibration to level

4. Adjust the thickness of blank, pressure and temperature

7、 Plate indentation

The causes are as follows:

1. The backing plate shows unevenness

2. There are rubber blocks or foreign matters on the surface of the base plate

3. Splinters or sundries are sandwiched between layers of veneer

Solutions:

1. Check and replace the base plate

2. Check and clean the base plate

3. Be careful when matching embryos

For the defects of plywood such as low bonding strength, blistering and partial degumming during hot pressing, the following three points are summarized: 1. The veneer quality should be good and the moisture content should be low; 2. The hot pressing process should be reasonable; 3. The quality and use of adhesive should be good.

How to solve the common problems of blistering, degumming, warping and hot pressing of plywood?

However, due to the backwardness of formulation and technology of some glue factories, as well as the fact that in order to reduce production costs and obtain higher profits, many glue factories use less or no organic modifiers equivalent to polyvinyl alcohol and melamine, especially those without plywood base, resulting in poor quality of urea formaldehyde adhesive, i.e., thin glue, slow film-forming, long prepressing time, poor bonding strength, low heat resistance and wear resistance Formaldehyde content is high.

Plywood factories only use a lot of flour to eliminate the above disadvantages, which is not only poor quality, but also high cost. What are the good strategies for some advanced plywood factories?

Some choose to use modifiers or additives to modify in the factory and glue. As for the modification, there are only organic and inorganic modification, organic modification is the most commonly used, although the effect is the best, but the cost is too high, and it can not be popularized and applied. At present, although there is a certain threshold for inorganic modification, the price is relatively low, so it has great potential for promotion and application. Of course, if you do high-grade plywood, it is better to give priority to organic and inorganic as auxiliary This not only improves the board grade, but also reduces the board cost!

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