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Flexible and creative design that meets high performance without sacrificing style, curved insulating glass is used in the design of many buildings today (both exterior and interior). As we all know, the production of curved arc glass and curved insulating glass has always been extremely challenging. In the past 10 years, the market has been constantly summarizing successful experiences and failure lessons, and the emergence of new technologies is making the application of curved insulating glass more and more Easy and able to meet innovative design styles without compromising quality and structural performance. This article will analyze typical engineering cases to show the difficulties and challenges in the application of curved insulating glass in glass curtain wall buildings, and what methods can avoid or reduce the hidden dangers in the design and assembly of curved insulating glass.
Then, as a glass deep processing practitioner, what is the biggest challenge in using curved insulating glass to build glass curtain wall buildings? Regulation makers and energy-saving assessment standards in various countries and regions are constantly putting forward higher requirements for the door and window industry. The traditional flat glass industry uses warm edge technology and high-performance coated glass to meet energy-saving indicators; while curved glass has also been applied to unique designs in commercial and residential buildings to achieve compelling ideas that designers and developers expect. The shapes and styles of single-piece curved glass are almost varied, see an example in the following image:

Both options also have similar consequences:

The requirements for thermal performance and energy efficiency also present challenges for curved glass that have never been seen in the flat glass market. Curved insulating glass is now to bend two, three, or even more pieces of glass with a film structure into a consistent shape and separate them with the same air spacer, as shown in the figure below. There is a huge challenge here. How to minimize the deviation in curvature fit and deal with potential defects during processing, Jinan LIJIANG Glass will discuss several feasible methods.
Today's new technologies and processes allow designers to design curved or curved insulating glass without losing the properties of flat insulating glass.

Challenge 1: Durability of curved insulating glass

Traditional flat glass has different test standards in different countries. Until a few years ago, European insulating glass processors had to do durability tests according to the standards of the countries where the products were exported. Through the efforts of industry insiders, the durability test standard has finally been unified into one standard (EN1279). The purpose of the test is to review the processing technology of insulating glass processors, and whether it is possible to continuously and repeatably produce products that meet the requirements of the standard.

The North American market has also experienced a period of coexistence of many test standards, including ASTM773/774 and CGSB12.8, and the final standard is unified to ASTM2190, which combines the standards of the United States and Canada.

Again, the purpose is to use a test standard to give manufacturers the confidence that if they can pass this standard test, they are producing a durable and reliable hollow product.
The functional design of the edge seal plays a very important role in the durability of the insulating glass. It should be noted that just passing a standardized test does not mean that the sealing system you choose is the best choice. Intermediate processing links, with the necessary flexibility and energy-saving features, achieve the repeatable durability you expect.

It is well known that edge seals of curved glass are subject to greater and more dynamic stress changes than conventional flat glass. For this reason, processors and designers need to be very careful in selecting and using a suitable edge seal Insulating glass failure loss caused by improper.

The edge durability of curved insulating glass also affects the selection of other related components, including coated glass, ammonia filling, and spacers, which will ultimately determine whether you can achieve the energy-saving requirements you want to achieve.

If you want to lower the U value to 0.2, we can do the following:

1. Fill nitrogen;

2. *Replace rigid metal spacers with flexible warm edge spacers;

3. Replace the online Low-E Glass with the offline Low-E Glass.

Each of these options will lead to the following results:

1. Filling nitrogen will improve the thermal insulation performance, but it will increase the cost and one more process. Customers will also question the long-term retention rate of nitrogen. The inert gas is colorless and odorless. How can we ensure that it can be maintained in the hollow cavity for a long time?

2. The flexible spacer reduces the processing procedure and improves thermal performance. The practice has proved that it also has long-term durability, and you can see and identify it with the naked eye.

3. Offline Low-E Glass improves thermal performance, but because the film is very fragile, it is easily scratched and damaged by handling.

If you want to reduce the U value to 0.4, you can take a combination of two solutions:

1. Fill with ammonia gas and adopt offline Low-E Glass;

2. *Adopt flexible warm edge spacer + offline Low-E Glass.

Both options also produce similar consequences:

1. Customers still have doubts about filling with argon gas, and using offline Low-E Glass needs to be handled carefully to avoid damage to the film.

2. *The flexible spacer reduces the processing steps and improves thermal performance. The practice has proved that it also has long-term durability; Off-line Low-E Glass improves thermal performance, but because the film layer is very fragile, it is easily scratched and handles damage.

Both of the above solutions can reduce the U value, but which one can bring more cost reduction and processing convenience?

Plans marked with an asterisk can achieve the greatest thermal performance improvement and significantly reduce complaints and claims due to manufacturing defects.

Challenge 2: How to choose suitable spacers to produce curved insulating glass

The selection of spacers is crucial to improving the overall thermal performance of insulating glass. From a global perspective, customers are willing to use warm edge spacers to improve the energy-saving index of the hollow curtain wall, but not all spacers have the same thermal performance and processing convenience, they also have different durability performance, especially It is when applied under high-stress conditions, such as curved insulating glass. Below we will specifically discuss the advantages and disadvantages of various spacer options in the production of curved Insulating glass. These principles are also applicable to flat insulating glass.

Various rigid and flexible spacers can be seen on the market today. With the increasing requirements for thermal conductivity, the market tends to choose spacers with low thermal conductivity. At the same time, when producing curved insulating glass, designers are reluctant to choose rigid spacers, because their characteristics will be distorted and deformed during the bending process, resulting in the uneven size of glue on the edge, and the need for a long time. time to make precise bends.

For this reason, we mainly discuss the characteristics of the flexible spacer here, because it is not affected by the above problems.

How to choose a suitable spacer is very important to consider the process and application. For example, flexible silicone foam spacers have suitable products for different assembly processes and surfaces.

Assembly Process Considerations:

The production of curved insulating glass requires a different process from that of flat glass. The specific details of the assembly and laying of spacers, the type of secondary glue, and the glue depth of the secondary glue are not discussed in detail here; the installation of a single product The application needs to be carried out under the guidance of the specific product manufacturer, and the assembly of the insulating glass also needs to take into account the structural bonding that is the most insufferable.
1.1 Choose the right spacer and sealant system
Structural sealants are generally not required for IG if it is installed in a frame. Frameless or hidden-frame curtain walls are hollowed out to be bonded to structural members through structural adhesives. Due to the lack of direct connection with the structural parts of the outer glass, a structural silicone sealant is required to ensure the overall structural strength of the insulating glass.
Not all spacers are compatible with structural adhesives, so pay special attention to the requirements of the installation method.
The choice of structural adhesive must be made by designers or experts, not by hollow processors. The matching of spacers and sealants must also be fully communicated with professional organizations to confirm.

1.2 Advantages and limitations of using flexible spacers to produce curved insulating glass
The flexible spacer can be laid directly with the curved outline of the curved glass. The curvature of the two pieces of glass should have a deviation of no more than 1mm within the range of 1 extension meter to ensure good bonding.
Special attention should be paid to the insulating glass laminates with the spacer layer exceeding 12mm, and the spacer strips cannot have inclined skins. At this time, the craftsmanship of the laminates will be very important.
1.3 Hollow production stage
1.3.1 Preparation of glassBecause of the curved surface of curved glass, the glass needs to be cleaned manually before production. Pay special attention not to scratch the coating surface.
1.3.2 Laying of spacersTo ensure accurate positioning and good bonding of the flexible spacer strips, the best way is to lay the spacer strips on the raised surface of the glass.
For multi-curved or concurrently oppositely-curved glass, the spacers shall be laid on the surface with the smallest raised radius.
1.3.3 CompositeDifferent from the ordinary flat glass lamination method, it is best to start lamination from one corner of the glass, and then slowly extend to other positions; curved glass is difficult to lace successfully at one time. In many cases, horizontal lamination is difficult. Sheets are not practical, so the laying and lamination of spacers, including spacers, need to be carried out vertically.
In the hot bending process, the corner of the glass is usually the final temperature required for the hot bending, resulting in the curvature of the two pieces of glass at the corners not matching as well as the middle position, to shackle the first part to produce sealing holes, additional strips of butyl tape are required at the corners to fill potential voids.
Most of the corner sags can be resolved through a lot of trial and error before production can begin.
1.3.4 Press fit
For curved glass, it is impossible to press the machine, usually use "C" pliers to press along the four sides of the glass to ensure good wetting of the adhesive and butyl glue; During the process, special attention should be paid not to scratch the glass or cause other damage.
Another method is to use a hand-held spoke press tool to perform the press.
1.3.5 Filling with ammonia gas
Special attention should be paid to the reasonable placement of the inflation tube, and the control of the inflation flow rate to ensure that the filling concentration of the complex shape is sufficient and the air can be quickly expelled.
When inflating a hollow with a large surface, it takes a longer time. If the inflation is excessive, it may be necessary to depressurize the hollow.
1.3.6 Apply secondary glue
Depending on the size, weight, and structural configuration of the hollow, it may be necessary to apply a second coat of glue in the vertical state.
In vertical conditions, wooden blocks or other similar blocks may be used to support the glass off the ground. When gluing, especially when it reaches the supporting position, the glass will easily slide or dislocate, but still Pay attention to taking measures to ensure that the hollow is glued at the same time.
The quality inspection and requirements for surfacer glue are no different from those for flat glass.
1.3.7 Handling of new finished products
During the curing of the surfacer glue, both the upper and lower pieces of glass need to be effectively and completely supported by wooden blocks or similar blocks. During the handling process, vacuum suction cups or rope sets are required to protect the insulating glass from being squeezed, especially if the edges of the glass cannot be squeezed.
2. Conclusion
As the design of curved insulating glass becomes more complex, its manufacturing becomes more and more difficult, but as long as the right components and materials are selected and the proper process is applied, the chance of defective products should be minimized; in the past few years, the door and window industry has greatly improved the quality and performance of coated glass, spacer materials, profiles, and other related components. Architectural designers now have more choices to realize their creative designs; the development of flexible warm edge technology has also given the industry Bringing new possibilities for more applications of curved insulating glass to achieve creative designs without sacrificing structural integrity and energy-saving performance.
Global insulating glass manufacturers can now supply the building market with more high-quality, energy-efficient insulating glass without design constraints.

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