Vacuum Laminators for Glass Lamination
Vacuum lamination is the method of choice in the solar industry for over 30 years. SM InnoTech did not invent this technology but brought the vacuum laminator into the 21 century by redesigning virtually all aspects of the machine making it more versatile.
The laminator is an inline system consisting of an input conveyor, the lamination unit and an output conveyor. The evacuation takes place in the heated vacuum chamber. The base pressure is less than 1 mbar and is reached in less than a minute. During evacuation the laminate is not compressed. Hence, the longer the laminate stays in the vacuum chamber, the more air is removed from in between the layers of the laminate. After a few minutes of evacuation, the laminate is compressed by means of a diaphragm (= silicone blanket), which is controlled by air pressure. The diaphragm wraps around the laminate and forms a vacuum bag. The force exerted on the laminate is uniform across its entire surface and the pressure is 1 bar. After a few minutes of heating, the lamination is completed and the finished laminate can leave the machine. In a production unit, a cooling press would cool down the laminate quickly. When done right, the laminate would be bubble free.
Vacuum bags are used to remove air from inside the laminate. But compression sets in right when the evacuation begins. The layers of the laminate are pressed together, more and more as the pressure decreases. The air inside the laminate gets trapped rather than removed no matter how long the pump works. The lowest achievable pressure in a vacuum bag is about 300 times higher than in the vacuum laminator. On top of the inherent difficulty to remove trapped air from inside a laminate, it is time consuming and labor intensive to put the laminate into the bag.
A nip roller can be used to remove the bulk of air from in between the layers of a laminate by squeezing the lites together. There are many problems with this kind of machine. Wavy tempered glass for instance can break because the thickness of the laminate is not uniform. The nip roller does not remove all the air but leaves a fair amount in the laminate. As a result the laminate is opaque when it leaves the nip roller due to a layer of tiny air bubbles.
The autoclave makes trapped air inside of a laminate invisible. The temperature is set to 140 - 160°C, the pressure to 12 - 14 bars. At this temperature the captured air in the laminate would remain in the gaseous state forming bubbles when cooled down. But at that pressure, the air dissolves in the liquified interlayer material, which becomes gradually transparent. This can take up to 10 hours. Cooling it in a controlled manner under pressure at the appropriate rate solidifies the interlayer material and it remains transparent at room temperature and atmosphere pressure. If the cooling parameters are off, the laminate hazes over and becomes opaque again. This would constitute a production loss.
SM InnoTech is working with interlayer manufacturers to develop the lamination process with their material. The company Kuraray is confirming that the SM InnoTech vacuum laminator is suitable for the lamination of their Trosifol PVB and SentryGlas®. The following tests have been carried out and passed: (i) moisture content measured, (ii) bake test until bubbles appear, (iii) boil test to see if bubbles appear, (iv) pummel adhesion, (v) ball drop impact.
SM InnoTech vacuum laminators open the path to true inline fabrication. Together with a partner company, SM InnoTech offers a combined layup station with climatized interlayer storage and feed, and a vacuum laminator. The input coveyor of the laminator is a staging work table where workers arrange laminates coming from the layup station. All laminates on the input table are fed into the laminator when the current batch is finished. The machines are designed for 24/7 operation.
Where is SM InnoTech located? SM InnoTech is located in the town of Bocholt in the north-west of Germany, close to the Dutch border. The next international airport is Düsseldorf (DUS). From there it is a 1 hour ride by car - depending on traffic. Amsterdam and its airport (AMS) can be reached in about 2 hours.