Professional training would be good for most of the Plywood QC/QA Parts 47: Plywood defects easy to produce when hot pressing and and solution

Plywood defects easy to produce when hot pressing and and solution

Defects are easy to proce and solving methods in hot pressing of plywood

First, the bubble and core inside local delamination /local unglued
Cause of production:
1, veneer moisture content is too high or dry
2, the large amount of glue /Excessive glue
3, the pressure is too fast or too hot./Buck too fast or hot pressing temperature is too high.
4, the degree of resin condensation is not enough
5, lack of hot pressing time /Insufficient hot pressing time

Solution method:
1, Control the moisture content in the range of 8 ~ 12%
2, gelatinize control according to the technological requirements /Controlling the amount of glue meet the technical requirements

3, the second stage of the speed should be slow, hot pressing temperature should be appropriate to reduce /The second phase should slow down the speed of pressing temperature should be appropriately reduced
4, check the quality of resin
5, the appropriate extension of hot pressing time /Appropriate to extend the pressing time

Two, low bonding strength /Bonding strength is low or unglued
Cause of production:
1, poor quality glue

2, amount of glue is insufficient or uneven glue /insufficient amount of glue or uneven coating
3,the aging time is too long, the glue is dry or aging time is too short, not a continuous plastic film is formed
4, low pressure, or temperature is too low, or the pressing time is too short

5, grooves deep burr veneer, peeling poor quality
6, veneer moisture content is too high
Solution method:
1, check the quality of rubber liquid
2, pay attention to moderate and uniform amount of glue
3, the main control of the aging time
4, the appropriate increase in pressure or temperature, or the extension of hot pressing time
5, improve the quality of veneer
6, veneer moisture content is too high

Three, adhesive through /Glue bleeding
Cause of production:
1, the single core veneer quality is too poor, the crack of the back is too large
2, glue coating is too thin or too large, the aging time is too short
3, hot pressing temperature is too high or too much pressure

Solution method:

  the solution:

     1, to improve the quality of the veneer , reducing the back of the crack depth

     2, increase the concentration of glue, to reduce the amount of glue, extended aging time

     3, reduce the temperature or lower the hot pressing unit pressure

Four, the core voids and overlaps

Cause of production:
1, the core veneer is not whole piece , hand made core lay-up are not skilful ,Clearance is too large or too small.
2, When fill out the platform to the hot pressing machine ,the core veneer are displaced .

3, the edge of the core veneer is not neat
4, the edge of the core veneer has a gap

Solution approach:
1, one-whole-piece core veneer or glue aging then make the core lay-up
2, when the vener core platform is installed to the hot pressing and take measures to prevent the core veneer dislocation
3, veneer core edge shear and veneer straight
4, improve the quality of the core veneer rotary cutting and drying, to prevent the edges and cracks of the lotus leaf shape and gaps

Five, warp
Cause of production:
1, plywood structure and processing technology is not consistent with the principle of symmetry /plywood structure and process does not comply with the principle of symmetry
2, veneer moisture content is not uniform
3, temperature, pressure is too high
the solution:

     1, observe the principle of symmetry

     2, to improve the quality of veneer dried

3, appropriate to reduce the temperature and pressure

Six, plywood of varying thickness or outside the permissible tolerance range
Cause of production:
1, the number of hot pressed in each interval is too large
   2, varying thickness veneer
3, the pressure plate tilt or plunger tilt
4, the thickness of the plywood is incorrect or the pressure is too large, and the temperature is too high.

Solution method:
1, as far as possible one piece of core veneer platform for only one hot pressing plates .
2, improve the quality of veneer
   3, correcting the press installation level

     4, adjust the thickness of the plate with embryos, adjust the pressure and temperature
Seven, the surface indentation
Cause of production:
1, the hot pressing plates are showed uneven
2,the surface of the pad sticky buns or debris
3, the veneer debris or debris layer sandwiched between the hot pressing plates

Solution approach:
1, check ,replace the hot pressing plates
2, check and clean the hot pressing plates
3, pay attention when clear with embryos

For bonding strength occurs when the lower plywood hot pressing, bubbling unglued and local defects, mainly summarized the following three points: 1, the board is better quality, and lower moisture content; 2, hot-pressing process must be reasonable; 3, adhesive and the use of better quality.

Check Also

CARB /EPA certified E0 plywood production HOt pressing control

As The chinese Linyi and Xuzhou temperature is higher so much ,when making E0 GLUE …

Leave a Reply

Your email address will not be published. Required fields are marked *