How to Make Insulated Glass Units: Part 1

Insulated glass (IG) is a combination of two or more sheets of glass spaced apart with a spacer bar and sealed to form a single unit with one or more air spaces in between. It is commonly called double pane or double glazing glass as well. Insulated glass is an evolution from older technologies known as double-hung windows and storm windows. Traditional double-hung windows used a single pane of glass to separate the interior and exterior spaces.

The major manufacturing process for creating insulated glass includes glass cutting, glass edging, glass washing assembly, gas filling, glazing and packaging.

Glass Cutting

The two panes of glass that will be used to make the sealed unit are measured and cut to size either by hand or using an automatic cutting table. An important part of any glass cutting line is an air float table (sometimes called a free fall table), which are ideal for dropping, moving and cutting sheets of glass. There are also a variety of automated solutions to reduce costly mistakes, waste and improve overall efficiency when it comes to cutting glass. From saws to transfer tables, Wakefield has the best-in-breed tools needed to get the job done.

Glass Edging

Once cut, the insulated glass layers must be sealed using sealants so that the two separate sheets become one single unit of glass. In order for the sealants to adhere to glass, any moisture-sensitive coatings need to be fully removed, or edge-deleted. Edge deletion is the removal of a narrow strip of coating around the perimeter of a sheet of glass that has been cut to size so that the sealants can bond directly to the glass. This can be a very time consuming process.

Fortunately for window manufacturers, there are a variety of cost effective machines available to achieve edge deletion and eliminate costly edge deletion failures. Wakefield Equipment offers both a single edge deletion table and a twin edge deletion table designed to increase both productivity and operator safety at the same time.

The next step in the process is that the glass units are fed through a glass washer. There might not be any more critical piece of equipment than the washer to ensure that glass is completely free of debris. Wakefield offers glass washers in 60” and 84” capacity and can custom build to suit the needs of a manufacturer. Tilt caster tables are often used to transport fragile glass across the production floor to the glass washing station. After being washed they are thoroughly inspected by the operator for quality and are then fed through an oven to temper the glass using an automated conveyor system.

Spacer Assembly

Once the glass is prepared, it’s time to join the single panes into one using a spacer bar as quickly as possible to keep out any contaminants. Window and glass spacers are the seals that sit between panes of glass in a window. Over the years, the window manufacturing industry has seen advances in the materials used. Historically, spacers were made primarily of metal and fiber, which manufacturers thought provided more durability. Metal conducts heat, however, so manufacturers are turning to other types of materials and technology, such as the intercept spacer and the flexible spacer. Intercept spacers are considered to be much more energy-efficient, with a greater ability to lock in desired temperatures. They also can cause quite a bit of noise to echo through the windows, which makes them a poor choice for certain applications.

The flexible spacer is one of the newest and most energy-efficient types of insulated glass spacers on the market today. Depending on the materials used when it’s manufactured, it is often considered to be better at insulating than aluminum or intercept spacers. A flexible spacer is a type of swiggle spacer, which in addition to its environmentally-friendly profile, is also a quieter type of seal than aluminum or intercept seals.

Wakefield offers a variety of tables that are designed to assist in the flexible spacer assembly. For added productivity, grid application tables with air float are combined with pneumatic tilt to ensure large glass pieces can be securely and safely moved.

Assembling the IG Unit

Once the glass pieces and the spacer pieces are created, the components are ready to be put together and turned into an IG unit. The glass and spacers are sandwiched together.

To further increase an IG unit’s thermal efficiency, gas filling is used. Gas filling equipment for windows work by filling the space between planes with either argon or krypton, which reduces the window’s U-factor rating. Moisture is also removed from the air trapped between the panels of glass to ensure that condensation does not take place.

IG Units typically consist of:

• Polysulfide (standard) Primary seal
• Butyl Secondary seal
• Two or more lites of glass
• Argon gas-fill (Optional when Low E Used)
• Aluminum Spacer with integral desiccant
• Unit thickness from 1/2″ inches to 1 1/2″ inches

Stay tuned for Part 2 of our informative series on how insulated glass units are created with the final steps of cutting, glazing and packaging.