The production process of laminated glass

Laminated glass is a glass product made of two or more pieces of glass, which are glued and sandwiched between the two layers of glass, and then heated and pressed. In the production process of laminated glass, the lamination process, the glass preheating and pre-pressing process, and the operation of the glass in the autoclave are the most difficult processes in the production process!
1. The operation process of lamination
When laminating the glass, first select the PVB film suitable for the width of the glass, and keep the film clean, avoid touching the film and the glass directly by hand, flatten the PVB film naturally, do not stretch it, and align the inside and outside of the glass. There should be no sense of unevenness, and it is necessary to check whether the reserved marks overlap.
Then cut off the excess film. During the cutting operation, keep the blade inclined, and leave 0.5mm-2mm film at the edge of the film to avoid shrinkage caused by film shrinkage.
After the film and the glass are combined, put a vacuum rubber ring and check the sealing strip. The tensile force around the glass should be uniform, and then cold-pump the glass to remove the air between the pieces, and the cold-pumping time should not be short. in 5 minutes.

2. Glass preheating and prepressing process
The glass is sandwiched with the PVB film, and after the air is evacuated, the combined glass is preheated and pre-pressed.
There are three kinds of equipment for preheating and preloading operation. One is the preheating and preloading box, which is favored by many manufacturers because of its simple equipment, small investment and low energy consumption. However, the disadvantage of the preheating and pre-pressing box is that the efficiency is low and cannot be adapted to industrial production; the transmission-type vertical and horizontal pre-heating and pre-pressing machines have high production efficiency and are suitable for large-scale production.
The difference between the two is that when the glass is placed to complete the preheating and pre-pressing work, the way of placing the glass is that one is placed vertically and the other is placed flat. When the vertical preheating and pre-pressing machine performs the air evacuation operation on the glass, the influence on the curvature of the glass is small.
When the horizontal preheating hot press performs the air evacuation operation on the glass, due to the flat laying of the glass, the curvature of the glass will be affected under the influence of its own gravity and vacuuming pressure. Therefore, the horizontal preheating and pre-pressing machine is more suitable for the production of large-scale glass.

3. The operation process of glass in the autoclave
The production process in the autoclave is the last process in the production of laminated glass. In order to better bond the PVB film and the glass laminate together, the glass that has been preheated and pre-pressed must be treated with constant temperature and high pressure before it can be used.
The constant temperature and high pressure treatment should be operated in an autoclave. First, the semi-finished products of laminated glass that are bonded together are isolated between each piece, placed on the special stand of the autoclave, and made firm, and then the autoclave door is tightly closed, and the Pressurize and inflate in the kettle. When the air pressure in the kettle reaches about 0.75MPa, stop inflating the kettle. This is because the edge of the laminated glass is not firmly bonded, so that the space in the middle of the glass interlayer overflows under the action of pressure, so as to prevent air from entering the interlayer from the edge. When the temperature in the kettle reaches about 130°C, the heating is stopped immediately and this temperature is maintained.
At this time, the laminated glass has been able to be bonded, and the kettle is pressurized for a second time. Since the glass has reached the bonding temperature, this pressurization will not allow air to enter the interlayer. When the pressure reaches 1.2MPa, stop the pressurization. And keep the pressure balance, after 1h ~ 1.5h, when the temperature in the kettle is lowered to 50 ℃, start to exhaust and reduce the pressure in the kettle, until the air is completely discharged, open the kettle door to push out the glass.
At this point in the production of laminated glass, there is still the finishing work, that is, the glass is inspected one by one, and the qualified products are trimmed. Cut off the excess film around; select and repair the glass containing bubbles and degumming, and re-enter the kettle for pressure heating.
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