Glass Tempering Evolution Brings Improvements in Efficiency and Quality

By Ellen Rogers

The first tempering ovens from the 1970s were a lot like the early cars of the 1900s: they were great at the time, but look at how far we’ve come. Tempering ovens and cars today make a pretty good comparison: many of the best are slick, fast and efficient; they can even warn you about errors and troubleshoot the solution. Maybe you’re even slightly envious when your neighbor gets a new one. The tempering evolution has brought massive changes to the glass strengthening process. Furnace sizes have increased to accommodate the demand for oversized glass lites. They’ve become more efficient in controlling heating and cooling, helping to improve glass quality, and they’re more automated than ever, helping to improve throughput and safety, among other benefits. Even with such tremendous advances, experts agree, the evolution isn’t over yet.

“Skilled operators are a scarce resource in many places, and demands in production efficiency and quality increase the pressure on continuous development in both machinery and process know-how,” says Kimmo Kuusela, vice president of strategic accounts and innovation for Glaston Corp., based in Tampere, Finland. “As a result, increased know-how in glass processing technology and glass processing has contributed to developing the glass processing industry overall, enabling innovations in end-user design, too.”

Driving Change

Many changes to tempering furnaces happened because of customer requests.

“Architectural demands for increased quality, energy efficiency standards, glass sizes and coatings have continuously evolved, so glass processing and the furnace have evolved, too,” says Kuusela.

Nancy Mammaro, CEO of Mappi, an Italian machinery company, says the continual evolution of tempering equipment and the process is essential because glass and the perception of quality also evolve. “Glass still seems to be the same material,” she says, “but the needs of glaziers, builders and architects are becoming more and more refined.”

Mike Synon, president/owner of HHH Equipment Resources, has worked in glass tempering since the 1970s and has seen significant changes and developments.

“Some of the biggest changes in tempering have been the insulation of the furnace to retain heat and energy,” he says. “You could lean against a furnace today and wouldn’t even feel the warmth. Also, the inspection process and the thermal efficiency of the heating zone have increased.”

Focus on Quality

Many fabricators will remember the zebra board as one of their earliest means of inspection for roller wave and other types of distortion. Zebra boards haven’t gone away but are often used with other high-tech online inspection equipment.

“It only takes one high-rise project to go south,” says Synon of the increasing demand for these tools. No one, he explains, wants to have to remove the poor-quality glass, re-make it and then put it back in. He says investing in the online inspection equipment upfront can help avoid some of these issues.

Synon adds that the push for quality drives manufacturers to continue innovating and improving their furnaces.

“Going ten stories up on a building with ten pieces of bad glass is a problem,” he says. “What keeps pushing us forward is the ability to have quality glass the first time through. We’re constantly improving the furnace. We’re working on less human touching of the glass and software updates to make the process more efficient.”

“The challenge we face every morning is to help the glass industry temper glass that has excellent and consistent quality, even though the process is difficult to standardize and new varieties of glass are produced every year,” says Mammaro. “The support offered by electronics, research into new materials, construction technologies, and rapid and consistent support over time helps the glassmaker manage each temper to the best of their ability. Perfect tempering comes from the combination of an excellent machine and the know-how of a glazier and baker.”

Efficient Fueling

Tempering furnaces also have evolved to help companies ensure energy-efficient operations. Mammaro says electronic controls, improved software and advanced materials have changed the rules of the game regarding energy efficiency in operations.

Kuusela adds that efficient convection in pre-heating, sophisticated cooling and blower control also help minimize energy used.

“Maximizing bed load is key to making the most in saving energy, as it decreases the energy used per processed glass surface … Maximizing the bed utilization is important in making the most of the furnace capacity needed for processing the needed amount of glass. Combined with optimizing the cooling, these are the ingredients improving energy use,” he says.

Kuusela adds that the latest technology innovations enable customers to utilize full bed capacity on a tempering line without sacrificing quality. “Some systems allow targeted heating that can process different sizes and shapes of glass simultaneously within the same loading, without delay between loads and without adjusting parameters or temperatures. These new systems can follow the glass through the heating cycle, releasing only as much heat as needed for any specific load. This means even with low bed utilization rates energy savings are high.”

Synon says his company’s furnaces include variable frequency drives. This allows the operator to gradually increase the furnace’s electrical output, avoiding a significant electrical demand for power immediately.

Terry Hessom, vice president of operations/owner of HHH, adds there are several cost-effective benefits in using variable frequency drives.

“Whether it is actual energy savings or the longevity of equipment performance directly affected from the ability to smooth movements reducing wear on motors, gearboxes and really any moving parts within their control.”

He notes that variable frequency drives can help reduce peak energy demand and the associated additional charges from the energy provider. Also, speeds are fully adjustable as are the acceleration and deceleration parameters to provide a smooth transition from one speed to another.

Support Crew

While quality glass and an efficient production process are important, there’s something else fabricators want: reliable support.

“The number-one thing is after sales and service. That has become the keyword in the industry because fabricators no longer have maintenance staff or, if they do, they’re limited in experience,” says Synon. “Now, we can communicate with the furnace remotely. We can dial in and see what changes [to the system] a fabricator made. We can dial in, see the glass, and monitor their entire operating screen.”

Providing technical support also ties into the importance of training.

“It’s vital to train [new employees], so they know what is good glass and what is bad glass,” says Synon. Though the equipment is becoming increasingly automated, Synon says there will continue to be a place for people. “Humans will always be involved,” he says, “but we are working to make them less responsible.”

Ellen Rogers is the editorial director of USGlass magazine. Email her at and connect with her on LinkedIn.

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