Real-time Ratio Monitoring Critical for Adhesives in the Glass Industry

Producing insulated glass and curtain wall incorporates bonding and sealing steps that use adhesives and sealants with multiple components. The success of these bonding and sealing steps depends on using a proportioner to achieve accurate mixing and on-ratio dispensing of the adhesive components.

New proportioner systems coming on the market, like the Graco ExactaBlend Advanced Glazing Proportioner (AGP), prevents off-ratio material from being dispensed onto the curtain wall or insulating glass product. Material is correctly mixed and dispensed on-ratio and glass manufacturers can be more confident in the end quality of their products.

Two-component adhesive material is widely used for manufacturing curtain walls and insulated glass windows. In curtain walls, the sealant is used to seal and bond glass panels to metal frames. In commercial insulated window applications, a spacer bar is sealed between two panels of glass; the space between the panels is usually filled with a gas. The assembly allows the window to provide a thermal barrier to help reduce conducted heat loss through the window.

For both applications, achieving the proper sealant mix ratio is vital to the quality of the final product. Typically, glass industry adhesive and sealing proportioners are used to achieve accurate mixing and on-ratio dispensing of the individual components. These proportioners usually use hydraulic or pneumatic mechanically linked pumps and rocker arms. Unfortunately, the mixing and dispensing methods used have serious drawbacks that can have a negative effect on final product quality, material costs, and production time.

In North America, most companies use static mixing technologies in the proportioner, in which an element in a tube folds the two materials over and over again, eventually blending them. Another option available is dynamic mixing, which uses a rotating mixing blade that turns inside a mixing chamber to blend components into a homogeneous mixture. While dynamic mixing blends better, it is a more expensive option and is not used as widely in North America.

Existing static proportioner technology offers many challenges for operators, especially as far as ratio settings are concerned. With current systems, operators must manually adjust ratio settings. They have to start each day with a validation measurement and then perform checks throughout the day by physically measuring the material ratio.

To ensure accuracy, they have to take samples in the morning, running strips with a bead of sealant on a piece of wax paper. When folded, the strips may show a blotch of material; this sampling process allows operators to observe striations if the ratio is not quite right. The samples also help them identify a lead/lag condition, in which the catalyst material is ahead of the base material, or vice versa, due to equipment pressure changes.

Unfortunately, when producing panels for window applications, it can be difficult to spot mix issues, since the material is black. Only towards the end of the process can an operator spot the tell-tale softness in the seal, in which case they catch the error and may have to deglaze the panel and start over, or even scrap the panel.

Unlike proportioners with mechanically linked pumps or gear pumps with no real-time ratio monitoring to mix materials, the Graco ExactaBlend™ AGP (Advanced Glazing Proportioner) constantly monitors material ratios. If an off-ratio condition occurs, failsafe measures automatically shut down the system to prevent dispensing of any off-ratio material onto the curtainwall or insulating glass product. This automatic shutdown prevents defects in production that can lead to scrap or long down times that can reduce production during a shift.

The new ExactaBlend AGP technology can be used with two different applicator options – the MD2 dispense gun paired with a disposable mixer and the Ultra-Lite 6000 pistol grip flow gun paired with a hose mixer. Each has advantages and disadvantages. The availability of two options gives operators choices, so they can select the applicator they find most comfortable. The ultimate decision will be based on both operator comfort and economic and cost considerations.

MD2 dispense gun with a disposable static mixer

The first option is pairing an MD2 dispense gun with a disposable static mixer. With this option, catalyst and base materials are blended together in the disposable mixer – apart from the applicator. Using a disposable static mixer eliminates the need for complex purging operations that can end up wasting mounds of material.

This waste material can add up to thousands of dollars per year – plus the costs for disposal – so this option can result in significant savings. For example, if purge and load operations are conducted twice a day for a one-shift operation 250 days a year, operators could save about 1600 kilograms of material per year, which may be as much as $6,000 per year. The 2-step base purge is fast, clean and easy, requiring only the touch of a button to open and close the valve.

In addition, using the MD2 helps prevent damaging the applicator and hoses with cured material. Also, if the system locks up during operation, the cost of a new disposable mixer is only a few dollars, compared to $2,000-$3,000 worth of hardware with the older technology.

Hose mixer attached to an ultra-light gun with an ergonomically designed head

The second option uses a hose mixer attached to an ultra-light gun with an ergonomically designed head, called the Ultra-Lite 6000. This option uses a hose that is three times as long as other systems, making it much easier to maneuver around a curtain wall assembly. This pistol grip flow gun is lightweight and comfortable with an operator-friendly ergonomic design combined with high-operating pressure. While more ergonomic, this option requires purging more material and there is a potential for the mechanical flow gun to lock up at the end.

The MD2 is larger and bulkier and the tip of the mixer extends further from the gun than the Ultra-Lite 6000. However, newer versions of the MD2 have additional ergonomic features, including angled adapter kits that make the MD2 dispense more comfortable.

Digital systems like those used in the ExactaBlend AGP change the way operators interact with the proportioner and vastly improve system control. Operators can set up the system and make ratio changes with the touch of a button. They can easily change the system’s mixing ratio, verify the proper calibration, and review system diagnostics. New proportioners can also be programmed so that only those with proper authorization can make ratio changes.

New technology improves quality and reduces waste

The accuracy and reliability of new proportioners provides positive ratio assurance and on-ratio mixing. The new technology prevents the production of inferior products that must be deglazed or scrapped, costing valuable time and money. Final product quality is improved and material costs and production time is decreased.