GANA Event Introduces Fabricators to Laminating, Tempering and IG Production
May 5, 2011
The Glass Association of North America’s (GANA) Glass Fabrication Educational Event finished yesterday in Kansas City, Mo., with a cross-section of presentations geared toward better understanding of the glass fabrication process.
Philip Bradbourne of DuPont provided tips on “Troubleshooting Laminating Glass Manufacturing,” noting as he opened his presentation that producing good quality laminated glass is “important to have that edge over your competition.”
Bradbourne noted, “A number of different things can cause delamination.” Among them, he said, “High moisture can cause problems with delamination; PVB likes to absorb moisture.” He added, “The good thing is it sucks it up but you can also recondition it back.”
Other causes of delamination can include rippled or dirty glass, having the wrong adhesion grade and pinch points in the autoclave, among other factors. As far as solutions to delamination, Bradbourne advised seeking lab analysis to know the exact cause.
Bradbourne also reviewed problems such as PVB blocking; where the PVB interlayer sticks to itself. He noted this can be caused when the interlayer storage temperature is too warm, and that suppliers must be sure the interlayer is transported in a refrigerated truck on the way to customers. The problem also can occur if the roll is wound too tightly by the supplier or is too old.
He also discussed causes of bubbles, gas pockets in the interlayer or between the glass and interlayer. A large number of small bubbles along the edges could mean the autoclave pressure releases at too high a temperature. Glass imperfections, such as caliper variations, can cause a large number of bubbles at the glass-PVB interface.
Like other speakers, Bradbourne also stressed the importance of maintaining a clean glass washer, as well as keeping the lay-up or clean room clean is well. He suggested using filtered air condition, and making sure employees use special lint free hats and clothing to prevent static or contamination - and only allowing authorized personnel entry into the lay-up room.
To prevent many problems, Bradbourne advised having clear written directions, a troubleshooting model and experienced employees handling their laminating. He also noted, it is very important to understand and document your process.
Chuck Wencl of Viracon addressed an audience interested in tempering on the topic of “Roll Wave Distortion.”
He opened by noting there are a number of different definitions for this problem, but GANA’s roller wave subcommittee offers this one of roller wave: a repetitive wave-like departure from flatness related to the heat-treated process, excluding edge effects, distortion influenced by assembly or installation.
Wencl also showed images of glass installations with severe distortion, including one project that won an award (for energy efficiency he pointedly added). “If this is what the market will take, this is what the market gets,” he commented. However, today many fabricators are seeing requests for thicker lites of glass in an attempt to get flatter glass. Wencl reviewed a number of tools available today to indicate when this distortion is present and notify the operator that it’s time to check the performance of or maintain the rollers or tempering furnace itself.
Wencl went through a list beginning with the zebra board, a subjective test for monitoring roller wave, to the various options available in flat bottom gauges. He called the 3-point gauge “very effective,” noting for this particular device, “it doesn’t matter what kind of a surface you put them on they target that wave only.” In recent years, he noted, digital grid photography has been introduced. This method uses a grid board and if “you look at the reflection in a piece of glass you’ll see the variation.” In addition, a number of automated solutions are available to provide on-line visual inspection for optical distortion.
Edgetech’s Mike Burk introduced the group to “Triple Glazed IGUs” or, as he suggested calling it “multiple cavity IGUs.” As Burk pointed out, it’s not the glass that provides the performance boost, since more glass means more conductive surfaces - what’s really important is the extra number of cavities. “It might be better to talk about cavities rather than the layers of glass,” Burk suggested. He pointed out the Insulating Glass Manufacturers Alliance forthcoming TR-1300 document adopts this view, as its current title is Design Considerations for Multiple Cavity IGUs.
Whatever it’s called, Burk could safely say of this product segment, “I think everyone in the industry believes this is going to grow.”
Burk noted that there are people who say triples aren’t the answer to improving the energy efficiency of window products. He points to concerns about decreased light transmittance, acknowledging that by adding an additional lite there may be some decrease, although typically it’s a clear center lite that is added. He agreed, too, that there could be some extra weight by adding an extra lite and producing frames that fit (although products such as suspended film negate that argument). And, Burk agreed that the concern for a higher risk of glass seal failure on a triple than a double-lite unit makes some sense, since the product is going from two to four seals. But that solution, he added, “comes down to workmanship and training and building good IG.”
Overall, Burk said the three main advantages of triples – thermal performance, condensation resistance and sound dampening – can outweigh the negatives, when produced appropriately. As Burk said, there’s a lot more going on in manufacturing triple-glazed units than “just adding a third lite of glass.” He advised his audience to carefully consider the steps of determining what type of gas to use and in which cavities, the impact of selecting an appropriate glass type and coatings on light transmittance, and considering structural components to be sure the frame can handle the added weight. He also recommended looking at the changes that will be made to the customer order entry system and machinery interface software, as well as training operators on changes to the manufacturing sequencing process. For example, operators not familiar with how to handle coated glass will need to review, for example, the sequence and operation of glass washing and accommodations that will need to be made for adjusting brushes for different glass thicknesses or using a detergent that can be used on coated glass or ensuring that the middle lite is properly cleaned on both sides.