Gluing process usually often give results that are inadequate or failure is generally caused by finir conditions (moisture content and porosity) and the adhesive itself, in addition to the gluing process. Kagagalan are:
o BGJ = Bleeding Joint Glue, the adhesion failure caused by excess adhesive in the gluing process, so that the adhesive becomes overflowing. This is because given the excessive adhesive, adhesive too thin or because the water content finir / timber is too high.
o SGJ = Starved Joint Glue, namely the failure of adhesion, which is caused due to a lack of adhesive in the gluing process, so that the surface finir / timber is not terlabur adhesive evenly. This is because the amount of adhesive dilaburkan less, porosity finir / timber high or because the moisture content finir / wood are bonded very low.
o The water content finir to be bonded should be at 6-8%, or do not exceed 10%.
Compression Plywood
Compression can be done in cold plywood (plain), heat or a combination of both, which is cold and heat compression. When used in combination will result pres efficiency fairly high heat for smoothing the adhesive has been done on cold pressed. The combination is very suitable compression applied to the use of synthetic adhesives such as UF and PF. Adhesion conditions can be given as follows:
Cold pressed: – the time over 5 minutes
Pressure above 15 kg / cm2 (above 200 psi)
– Cold compression is done once for each of the candidate pile plywood (up to 100 sheets) of each of the tools of cold press.
Pres heat: – more than 1 downloading it
Pressure above 10 kg / cm2 (above 100 psi)
– The temperature of 82-176 ° C (for UF 100 o -130 o Cdan PF 130-170) hot compression is done by inserting one by one sheet of plywood candidate into the space between the hot plates of the press or opening. Each of the tools can heat up to 50 press opening.
The amount of a given compression pressure is calculated by the following formula:
In psi or kpc, where:
G = total compression (psi, kpc)
P = specific pressure (psi, kpc)
J = The total area of the piston press (¶2, in in2 or cm2)
PSI = pounds per square inch kpc = kg per cm2
The amount of total granted pres influenced by factors:
o density finir / wood origin
o The thickness of the plywood produced
Wood with higher density and thickness of the thicker coating should use pres pressure and higher total compression time is longer on the finir sheet. To finir the outside, for example for the F / B is not cut out but dried first in a new dryer continues then cut. Finir cores obtained is then dried in a drying mill roll (roll dryer) (110 -175 ° C, 10-25 minutes) until the moisture content 5-10%.
Finir drying can be done before finirnya cut, especially for finir F / B. Furthermore, the pieces are sorted finir quality with attention to the scraps, holes and others. If there should be filling (closing) or tapping and connection-splicing or jointing, so finir be whole and well. Tapping is done by patching using similar finir, being jointing can be done with two finir glue, connecting with gumtape or by sewing (with nylon). Just kind finir core and or back which should be no connection.